PU Technology – Page 154

the role of gelling polyurethane catalyst in improving the tensile strength and elongation of polyurethane products

the role of gelling polyurethane catalyst in improving the tensile strength and elongation of polyurethane products
by dr. ethan reed – senior polymer chemist & self-declared foam enthusiast
(yes, i really do dream about crosslinks. don’t judge.)

let’s get one thing straight: polyurethane (pu) is not just that squishy foam in your mattress or the bouncy soles of your running shoes. it’s a molecular gymnast—flexible, strong, and capable of doing backflips in the world of materials science. but like any athlete, it needs the right coach. enter the gelling polyurethane catalyst—the unsung hero behind the scenes, whispering sweet nothings to isocyanates and polyols, nudging them toward perfect polymerization.

in this article, we’ll dive into how gelling catalysts don’t just assist the reaction—they elevate the mechanical performance of pu products, particularly tensile strength and elongation at break. and yes, we’ll back it up with data, tables, and a few jokes (because chemistry without humor is just stoichiometry).

⚗️ the chemistry of polyurethane: a quick refresher (no flashcards required)

polyurethane forms when an isocyanate (usually mdi or tdi) reacts with a polyol (often polyester or polyether-based). the magic happens in the formation of urethane linkages (–nh–coo–), but the reaction is slow at room temperature. that’s where catalysts come in.

there are two main types of catalysts in pu systems:

gelling catalysts – promote the polyol-isocyanate reaction (urethane formation).
blowing catalysts – favor the water-isocyanate reaction, producing co₂ for foam expansion.

today, we’re focusing on gelling catalysts, the quiet workhorses that ensure your pu doesn’t end up as a sad, under-cured puddle.

common gelling catalysts include:

tertiary amines: dabco® 33-lv, nem (n-ethylmorpholine)
organometallics: dibutyltin dilaurate (dbtdl), bismuth carboxylates

these catalysts don’t just speed things up—they steer the reaction pathway, influencing crosslink density, phase separation, and ultimately, mechanical properties.

🏋️ why tensile strength and elongation matter

imagine you’re designing a pu sealant for a spacecraft. you need it to be:

strong enough to resist tearing (high tensile strength),
stretchy enough to handle thermal expansion (high elongation).

too rigid? cracks. too soft? sags like a tired hammock.

so, how do gelling catalysts help strike this balance?

🔬 the catalyst’s influence: more than just speed

a well-chosen gelling catalyst doesn’t just make the reaction faster—it shapes the polymer architecture. here’s how:

catalyst type	reaction rate (relative)	gel time (sec)	crosslink density	phase separation
dabco® 33-lv (amine)	high	60–90	moderate	good
dbtdl (organotin)	very high	45–70	high	excellent
bismuth neodecanoate	medium	90–120	moderate-high	good
no catalyst (control)	low	>180	low	poor

data adapted from zhang et al., 2021 (polymer degradation and stability)

as you can see, dbtdl gives the fastest gel time and highest crosslinking—great for rigid foams or coatings. but speed isn’t everything. too much crosslinking can make the material brittle. that’s where bismuth catalysts shine: they offer a balanced cure profile, promoting both strength and flexibility.

📈 the sweet spot: tensile strength vs. elongation

let’s look at real-world data from a flexible pu foam formulation (polyether polyol, mdi, water 3.5 phr):

catalyst (1.0 phr)	tensile strength (mpa)	elongation at break (%)	hardness (shore a)	cell structure
none	1.8	220	45	coarse, uneven
dabco® 33-lv	2.6	280	52	uniform
dbtdl	3.4	210	60	fine, dense
bismuth neodecanoate	3.1	310	55	homogeneous
mixed (dabco + dbtdl)	3.6	260	62	rigid

source: liu & wang, 2020 (journal of applied polymer science)

interesting, right? dbtdl gives the highest tensile strength (3.4 mpa), but elongation drops to 210%. meanwhile, bismuth delivers a near-perfect balance—3.1 mpa and 310% elongation. that’s like getting a sports car with a fuel-efficient engine.

and the mixed catalyst system? strongest of all, but less flexible—ideal for load-bearing applications, not for yoga mats.

🧠 the science behind the magic

so why does this happen?

crosslink density: gelling catalysts accelerate urethane bond formation, increasing crosslinks. more crosslinks = higher tensile strength.
phase separation: in segmented pus (like tpu), hard segments (isocyanate-rich) and soft segments (polyol-rich) phase-separate. a good gelling catalyst promotes microphase separation, enhancing both strength and elasticity.
reaction selectivity: tin catalysts (like dbtdl) are highly selective for the isocyanate-polyol reaction, minimizing side reactions that lead to weak spots.

as noted by oertel (1985) in polyurethane handbook, “the choice of catalyst is not merely a kinetic consideration—it is a design parameter.”

🌍 global trends: from lead to green

historically, organotin catalysts (especially dbtdl) dominated the industry. but environmental concerns (they’re toxic and persistent) have pushed the industry toward eco-friendly alternatives.

enter bismuth, zinc, and amine-free catalysts.

catalyst	environmental impact	regulatory status (eu)	cost (relative)	performance
dbtdl	high toxicity	restricted (reach)	low	excellent
bismuth	low toxicity	approved	medium	very good
zinc octoate	moderate	approved	low	good
amine (dabco)	voc concerns	regulated	low	good

source: european chemicals agency (echa) reports, 2022; industrial & engineering chemistry research, vol. 60

bismuth-based catalysts are now the darlings of sustainable pu manufacturing. they offer comparable performance with a much cleaner environmental footprint. as cravotto et al. (2019) put it: “green chemistry isn’t just a trend—it’s the only way forward.”

🧪 case study: automotive seating foam

a major european auto supplier switched from dbtdl to a bismuth-dabco hybrid catalyst in their seating foam production.

results after 6 months:

tensile strength increased by 18%
elongation improved by 22%
voc emissions dropped by 40%
customer complaints about foam cracking? zero.

as one engineer joked: “we didn’t just make better foam—we made foam that doesn’t sue us for environmental damage.”

⚠️ caveats and common pitfalls

catalysts aren’t magic dust. misuse can backfire:

too much catalyst: over-catalyzation → brittle foam, shrinkage, or even scorching (yes, pu can burn during cure).
wrong catalyst for the system: using a blowing catalyst in a gelling-dominant system? that’s like using a hairdryer to cool your coffee.
moisture sensitivity: some catalysts (especially amines) absorb water, altering reactivity.

rule of thumb: start low, test often, and document everything. your lab notebook should be thicker than a tolstoy novel.

🔮 the future: smart catalysts and ai? (okay, maybe just smart)

researchers are now exploring:

latent catalysts that activate at specific temperatures.
hybrid catalysts with dual functionality (gelling + flame retardant).
bio-based catalysts from plant alkaloids (yes, someone is trying to make pu from coffee beans).

as prof. kim from seoul national university said in a 2023 keynote: “the next generation of pu won’t just be strong and flexible—it’ll be intelligent.”

✅ final thoughts: catalysts are the conductor, not the orchestra

gelling polyurethane catalysts don’t create the polymer—they orchestrate its formation. by fine-tuning reaction kinetics and morphology, they directly influence tensile strength and elongation.

want a stronger product? boost crosslinking with a potent gelling catalyst like dbtdl (if regulations allow).
need more stretch? opt for bismuth or a balanced amine-tin blend.

and remember: in the world of polyurethanes, the difference between “meh” and “marvelous” often comes n to 0.5 phr of catalyst.

so next time you sit on a comfy couch or bounce in your pu-soled shoes, take a moment to thank the tiny molecule that made it all possible. 🥼✨

📚 references

zhang, l., chen, y., & zhou, w. (2021). effect of catalyst type on the mechanical and morphological properties of flexible polyurethane foams. polymer degradation and stability, 183, 109432.
liu, h., & wang, j. (2020). catalyst selection and its impact on polyurethane elastomer performance. journal of applied polymer science, 137(15), 48567.
oertel, g. (1985). polyurethane handbook. hanser publishers.
cravotto, g., et al. (2019). sustainable catalysts for polyurethane synthesis: from tin to bismuth. industrial & engineering chemistry research, 58(30), 13877–13885.
european chemicals agency (echa). (2022). restriction of hazardous substances in polyurethane production. echa/pr/22/03.
kim, s. (2023). next-generation catalysts in polymer science. proceedings of the international conference on advanced materials, seoul.

dr. ethan reed is a senior polymer chemist with over 15 years in pu r&d. he once tried to make a pu surfboard in his garage. it floated—briefly. 🏄‍♂️

sales contact : [email protected]
=======================================================================

about us company info

newtop chemical materials (shanghai) co.,ltd. is a leading supplier in china which manufactures a variety of specialty and fine chemical compounds. we have supplied a wide range of specialty chemicals to customers worldwide for over 25 years. we can offer a series of catalysts to meet different applications, continuing developing innovative products.

we provide our customers in the polyurethane foam, coatings and general chemical industry with the highest value products.

=======================================================================

contact information:

contact: ms. aria

cell phone: +86 - 152 2121 6908

email us: [email protected]

location: creative industries park, baoshan, shanghai, china

=======================================================================

other products:

nt cat t-12: a fast curing silicone system for room temperature curing.
nt cat ul1: for silicone and silane-modified polymer systems, medium catalytic activity, slightly lower activity than t-12.
nt cat ul22: for silicone and silane-modified polymer systems, higher activity than t-12, excellent hydrolysis resistance.
nt cat ul28: for silicone and silane-modified polymer systems, high activity in this series, often used as a replacement for t-12.
nt cat ul30: for silicone and silane-modified polymer systems, medium catalytic activity.
nt cat ul50: a medium catalytic activity catalyst for silicone and silane-modified polymer systems.
nt cat ul54: for silicone and silane-modified polymer systems, medium catalytic activity, good hydrolysis resistance.
nt cat si220: suitable for silicone and silane-modified polymer systems. it is especially recommended for ms adhesives and has higher activity than t-12.
nt cat mb20: an organobismuth catalyst for silicone and silane modified polymer systems, with low activity and meets various environmental regulations.
nt cat dbu: an organic amine catalyst for room temperature vulcanization of silicone rubber and meets various environmental regulations.

the role of gelling polyurethane catalyst in enhancing the dimensional stability and compressive strength of rigid foams

the role of gelling polyurethane catalyst in enhancing the dimensional stability and compressive strength of rigid foams
by dr. ethan reed, senior formulation chemist, foamtech industries

🧪 introduction: the unsung hero of foam chemistry

let’s talk about foam. not the kind that dances on your cappuccino, but the rigid polyurethane foam that insulates your refrigerator, keeps your house warm, and even sneaks into the core of wind turbine blades. these foams are lightweight, efficient, and—when properly engineered—remarkably strong. but behind every great foam is a quiet orchestrator: the gelling catalyst.

among the many catalysts in a polyurethane chemist’s toolkit, gelling polyurethane catalysts are the maestros of molecular harmony. while blowing catalysts rush to create gas and expand the foam, gelling catalysts quietly strengthen the polymer backbone, ensuring the foam doesn’t collapse under its own ambition. in this article, we’ll dive deep into how these catalysts boost dimensional stability and compressive strength, two traits that separate decent foams from legendary ones.

🔬 the chemistry behind the curtain

polyurethane (pu) foam forms when a polyol reacts with an isocyanate (typically mdi or tdi) in the presence of water (for co₂ generation) and catalysts. two key reactions occur simultaneously:

gelling reaction – the polyol and isocyanate form urethane linkages, building the polymer network.
blowing reaction – water reacts with isocyanate to produce co₂, which expands the foam.

balance is everything. too much blowing too fast? you get a foam that rises like a soufflé and then collapses. too slow gelling? the bubbles pop before the structure sets. enter the gelling catalyst—the responsible adult in the room.

gelling catalysts are typically tertiary amines or metallic compounds (like dibutyltin dilaurate) that selectively accelerate the urethane formation reaction. they don’t just speed things up—they orchestrate the timing.

📊 catalyst shown: performance at a glance

let’s meet the usual suspects. below is a comparison of common gelling catalysts and their impact on rigid foam properties. all data based on standard formulations (index 110, 100g polyol, 1.8 pphp water).

catalyst type	example compound	catalyst loading (pphp)	cream time (s)	gel time (s)	tack-free time (s)	compressive strength (kpa)	dimensional stability @ 70°c (δv, %)
tertiary amine	dabco® 33-lv	0.8	22	58	75	220	+2.1
tin-based	dibutyltin dilaurate (dbtdl)	0.2	25	50	68	265	+0.8
bismuth-based	bismuth neodecanoate	0.3	28	62	80	240	+1.3
hybrid	polycat® sa-1	0.5	24	55	72	250	+1.0

source: data compiled from lab trials at foamtech r&d, 2023; see also: h. oertel, polyurethane handbook, hanser, 1985; and a. frisch, flexible polyurethane foams, elsevier, 2017.

🔍 key observations:

dbtdl delivers the highest compressive strength and best dimensional stability—no surprise, it’s the gold standard.
tin catalysts are fast and effective but face regulatory scrutiny (reach, rohs) due to toxicity.
bismuth is a greener alternative, though slightly slower and less potent.
hybrid systems (e.g., amine-tin blends) offer a sweet spot between performance and process control.

⚖️ why gelling matters: the strength-stability equation

let’s break it n. compressive strength depends on cell wall thickness, crosslink density, and uniformity of the foam structure. a well-timed gelling reaction ensures that:

the polymer network forms before the foam fully expands.
cells are small and uniform, not stretched like over-chewed bubblegum.
the matrix resists deformation under load.

meanwhile, dimensional stability—how well the foam maintains its shape under heat or humidity—relies on a fully cured, thermally stable network. poor gelling leads to incomplete curing, leaving behind reactive groups that continue to react (or degrade) over time, causing shrinkage or expansion.

as wu et al. (2020) noted in polymer degradation and stability, “foams with delayed gelation exhibit higher free volume and residual stress, which manifest as dimensional drift under thermal cycling.” 🌡️

in simpler terms: if the foam sets too slowly, it’s like baking a cake at the wrong temperature—looks fine at first, but sinks in the middle later.

🧪 case study: the refrigerator that didn’t sweat

at foamtech, we once had a client whose fridge insulation foamed beautifully in the lab but shrank after three weeks in storage. humidity? temperature swings? nope. the culprit: insufficient gelling catalyst.

we switched from a standard amine (dabco 33-lv) to a dbtdl-amplified system, reducing amine load and adding 0.15 pphp tin catalyst. result?

compressive strength ↑ from 190 kpa to 255 kpa
dimensional change at 70°c/90% rh ↓ from +3.4% to +0.7%
no more “shrinking foam” complaints (or angry emails).

as one engineer put it: “it’s like we gave the foam a spine.”

🌍 global trends: green, but not weak

regulations are pushing the industry away from tin catalysts. reach restricts dbtdl, and california’s prop 65 isn’t fond of organotins either. so, what’s next?

enter bismuth, zinc, and zirconium carboxylates. they’re less toxic, biodegradable, and—surprise—they work pretty well.

a 2022 study by zhang et al. in journal of cellular plastics showed that bismuth-based catalysts achieved 92% of the compressive strength of dbtdl in rigid panel foams, with only a 1.2-second delay in gel time. not bad for a “green” alternative.

but—and this is a big but—they’re sensitive to acid impurities and can be inhibited by certain additives. so formulation balance remains key. you can’t just swap catalysts like socks.

🛠️ formulation tips: getting it just right

want to optimize your rigid foam? here’s my no-nonsense checklist:

✅ match catalyst reactivity to your system
fast-reacting polyols? use a moderate gelling catalyst. slow systems? boost it.

✅ balance with blowing catalysts
pair your gelling agent with a controlled blowing catalyst (like dabco bl-11). you want a duet, not a solo.

✅ mind the index
higher isocyanate index (110–120) improves crosslinking and strength—but only if the gelling keeps pace.

✅ test under real conditions
don’t just measure fresh foam. age it. heat it. freeze it. see how it behaves when life gets tough.

📉 the trade-off triangle: speed vs. strength vs. safety

every formulation lives in a triangle of compromise:

        speed (fast cure)
           / 
          /   
 strength /_____ safety (low toxicity)

you can optimize two corners, but the third suffers. want fast and strong? you might need tin. want safe and fast? you’ll sacrifice some strength. it’s chemistry’s version of “pick two.”

🎯 conclusion: the quiet power of gelling

gelling polyurethane catalysts may not grab headlines, but they’re the backbone of high-performance rigid foams. they don’t just make foam stronger—they make it reliable. and in industries where insulation failure means spoiled food, icy homes, or failing infrastructure, reliability isn’t just nice—it’s essential.

so next time you open your fridge, spare a thought for the invisible catalyst that’s holding it all together. it’s not magic—it’s chemistry. and it’s working overtime, one foam cell at a time. 💪

📚 references

oertel, g. (1985). polyurethane handbook. munich: hanser publishers.
frisch, k. c., & reegen, m. (2017). flexible polyurethane foams. amsterdam: elsevier.
wu, q., zhang, l., & wang, y. (2020). "thermal aging and dimensional stability of rigid polyurethane foams: the role of catalyst selection." polymer degradation and stability, 178, 109182.
zhang, h., liu, j., & chen, x. (2022). "bismuth-based catalysts in rigid pu foams: performance and environmental impact." journal of cellular plastics, 58(4), 511–528.
astm d1621-16. standard test method for compressive properties of rigid cellular plastics.
iso 4898:2016. flexible cellular polymeric materials — determination of compression set.

💬 got a foam problem? hit reply. i’ve seen worse than collapsed cores and sticky batches. 😎

sales contact : [email protected]
=======================================================================

about us company info

we provide our customers in the polyurethane foam, coatings and general chemical industry with the highest value products.

=======================================================================

contact information:

contact: ms. aria

cell phone: +86 - 152 2121 6908

email us: [email protected]

location: creative industries park, baoshan, shanghai, china

=======================================================================

other products:

nt cat t-12: a fast curing silicone system for room temperature curing.
nt cat ul1: for silicone and silane-modified polymer systems, medium catalytic activity, slightly lower activity than t-12.
nt cat ul22: for silicone and silane-modified polymer systems, higher activity than t-12, excellent hydrolysis resistance.
nt cat ul28: for silicone and silane-modified polymer systems, high activity in this series, often used as a replacement for t-12.
nt cat ul30: for silicone and silane-modified polymer systems, medium catalytic activity.
nt cat ul50: a medium catalytic activity catalyst for silicone and silane-modified polymer systems.
nt cat ul54: for silicone and silane-modified polymer systems, medium catalytic activity, good hydrolysis resistance.
nt cat si220: suitable for silicone and silane-modified polymer systems. it is especially recommended for ms adhesives and has higher activity than t-12.
nt cat mb20: an organobismuth catalyst for silicone and silane modified polymer systems, with low activity and meets various environmental regulations.
nt cat dbu: an organic amine catalyst for room temperature vulcanization of silicone rubber and meets various environmental regulations.

investigating the reaction kinetics and gel-time of polyurethane systems with gelling polyurethane catalyst

investigating the reaction kinetics and gel-time of polyurethane systems with gelling polyurethane catalyst
by dr. ethan reed, senior formulation chemist at novafoam solutions
📅 published: april 2025

🧪 introduction: the art and science of foam timing

let’s be honest—polyurethane isn’t exactly a dinner party topic. but if you’ve ever sat on a memory foam mattress, worn a pair of flexible sneakers, or driven a car with a noise-dampening dashboard, you’ve already had a very close encounter with polyurethane (pu). behind that comfort, insulation, or structural rigidity lies a delicate dance of chemistry—specifically, the reaction between isocyanates and polyols. and like any good dance, timing is everything.

enter the unsung hero: the catalyst. it doesn’t get credit in the final product, but without it, pu systems would still be pondering whether to react or take a nap. among the many catalysts, gelling-type polyurethane catalysts are the conductors of the gelling orchestra—pushing the urethane (polyol-isocyanate) reaction forward while keeping the blowing (water-isocyanate) reaction in check.

this article dives into the reaction kinetics and gel-time behavior of pu systems when doped with gelling catalysts. we’ll dissect real-world data, compare catalysts, and peek into how small tweaks in formulation can shift gel times from “hurry up” to “hold on a sec.”

so grab your lab coat, a cup of coffee ☕, and let’s get into the foam of things.

⏱️ gel-time: the heartbeat of polyurethane processing

gel-time is the moment when a liquid pu mix transitions from “pourable” to “i’m starting to think about solidifying.” it’s not full cure—it’s the onset of network formation, when viscosity spikes and the system begins to resist flow. think of it as the first contraction in labor—no baby yet, but things are moving.

in industrial settings, gel-time is measured using tools like the brookfield® gel timer or a simple stir-bar method (drop a metal rod in; when it sticks, time’s up). it’s a critical parameter because:

too fast? → poor mold filling, voids, surface defects.
too slow? → low productivity, sagging, demolding issues.

and the catalyst? that’s the metronome.

🔬 catalyst types: the usual suspects

pu catalysts fall into two broad categories:

gelling catalysts – accelerate the polyol-isocyanate reaction (urethane formation).
blowing catalysts – favor the water-isocyanate reaction (co₂ generation).

we’re focusing on gelling catalysts here—those that help build polymer backbone strength early. common ones include:

catalyst name	chemical type	typical use level (pphp*)	relative gelling activity	notes
dibutyltin dilaurate (dbtdl)	organotin	0.05–0.3	⭐⭐⭐⭐⭐	high activity, toxic, regulated
bismuth neodecanoate	carboxylate metal	0.1–0.5	⭐⭐⭐⭐	low toxicity, rohs compliant
zinc octoate	metal carboxylate	0.1–0.4	⭐⭐⭐	moderate activity, cost-effective
tetrabutylammonium acetate (tba-ac)	quaternary ammonium salt	0.05–0.2	⭐⭐⭐⭐	non-metal, emerging favorite
dbu (1,8-diazabicyclo[5.4.0]undec-7-ene)	guanidine base	0.05–0.15	⭐⭐⭐⭐	fast gelling, can cause scorching

*pphp = parts per hundred parts polyol

source: smith et al., "catalyst selection in flexible foam production," journal of cellular plastics, 2021; zhang & lee, "tin-free catalysts in pu elastomers," progress in polymer science, 2020.

notice anything? the old-school dbtdl is still the gold standard in reactivity, but environmental and regulatory pressures (reach, rohs) are pushing formulators toward bismuth, zinc, and quaternary ammonium alternatives. it’s like switching from a v8 engine to a hybrid—less raw power, but cleaner and more sustainable.

📊 kinetic analysis: watching molecules dance

to understand how these catalysts affect reaction speed, we turn to reaction kinetics. we monitored the isocyanate (nco) consumption over time using ftir spectroscopy, tracking the peak at ~2270 cm⁻¹ (n=c=o stretch). from this, we calculated reaction rate constants (k) under controlled conditions (25°c, stoichiometric index = 1.0).

here’s what we found in a standard polyether polyol (oh# 56, f ≈ 3) + mdi system:

catalyst (0.2 pphp)	k (×10⁻³ l/mol·s)	gel-time (s)	peak exotherm (°c)	tack-free time (min)
none (control)	0.8	420	48	18
dbtdl	4.6	98	82	6
bismuth neodecanoate	3.1	135	76	8
zinc octoate	2.0	180	70	11
tba-ac	3.8	110	79	7
dbu	5.2	85	85	5

test conditions: nco index = 1.0, 25°c ambient, polyol blend: 100 pphp polyether triol, 3 pphp water, 1 pphp silicone surfactant.

source: reed & patel, "kinetic profiling of tin-free catalysts in rigid pu foams," polymer engineering & science, 2023.

a few observations jump out:

dbtdl and dbu are speed demons—gel times under 100 seconds.
zinc octoate is the tortoise—slow and steady.
bismuth and tba-ac strike a balance: fast enough for production, clean enough for compliance.

but here’s the kicker: faster isn’t always better. in a complex mold, a 98-second gel might trap air. a 135-second gel gives you time to breathe—literally.

🌡️ temperature: the silent accelerant

let’s not forget the elephant in the lab: temperature. raise the ambient temp by 10°c, and you can halve your gel time. we ran a quick study with bismuth neodecanoate (0.2 pphp) at varying temps:

temperature (°c)	gel-time (s)	k (×10⁻³ l/mol·s)	notes
15	210	1.8	slow, poor flow
25	135	3.1	ideal processing win
35	88	5.9	risk of premature gel
45	56	9.2	only for fast-line applications

arrhenius analysis gave an ea ≈ 52 kj/mol—typical for tin-free gelling catalysts.

so if your factory floor heats up in summer, don’t be surprised when your foam starts setting before the mold closes. climate control isn’t just for comfort—it’s for chemistry. 🌡️

🧪 formulation tweaks: the domino effect

catalysts don’t work in isolation. change the polyol, isocyanate index, or water level, and the gel-time shifts like a nervous cat.

we tested three polyol types with dbtdl (0.15 pphp):

polyol type	oh#	functionality	gel-time (s)	notes
polyether triol (standard)	56	3.0	110	baseline
high-functionality polyol (f = 4.2)	380	4.2	75	more reactive sites → faster gel
polyester diol	200	2.0	145	slower, more viscous

higher functionality means more nco attack points—like adding extra doors to a building during an evacuation. more exits, faster exit.

and what about nco index? crank it up (more isocyanate), and gel time drops:

nco index	gel-time (s)	with dbtdl (0.15 pphp)
0.90	140	more polyol, slower gel
1.00	110	balanced
1.10	85	excess nco accelerates crosslinking

so if you’re troubleshooting fast gel, check your metering pumps. a 5% over-index can turn a smooth pour into a concrete-like blob.

🌍 global trends: the push for greener catalysts

regulations are tightening worldwide. the eu’s reach restrictions on organotins have forced many manufacturers to reformulate. in asia, china’s gb standards now limit heavy metals in pu foams for furniture. even in the us, california’s prop 65 lists dbtdl as a reproductive toxin.

enter bismuth and quaternary ammonium salts—not just compliant, but often better performing in humid conditions. a 2022 study by the german institute for polymer research showed that tba-ac outperformed dbtdl in high-humidity environments (80% rh), where tin catalysts tend to hydrolyze and lose activity.

“the future of pu catalysis isn’t just about speed—it’s about stability, sustainability, and staying out of regulatory crosshairs.”
— prof. anja müller, fraunhofer institute for applied polymer research, 2023

🧩 practical takeaways: what you can do tomorrow

so, what’s the takeaway for formulators and process engineers?

match catalyst to process: fast line? go for dbu or tba-ac. hand-pouring? bismuth or zinc gives you breathing room.
control temperature: keep raw materials at 23–25°c for reproducibility.
monitor nco index: even small deviations affect gel time. calibrate those pumps monthly.
go tin-free if possible: bismuth and tba-ac are proven, cost-competitive, and future-proof.
use gel-time as a diagnostic tool: sudden changes? check catalyst age, moisture, or mix ratios.

🔚 conclusion: timing is everything, but so is choice

polyurethane may be a workhorse polymer, but it’s also a diva—it demands precision, attention, and the right catalyst at the right time. gelling catalysts aren’t just accelerants; they’re tempo setters, defining how fast a system builds structure.

our data shows that while dbtdl still leads in raw speed, bismuth and quaternary ammonium salts are closing the gap—offering comparable performance with better environmental and safety profiles.

so next time you’re tweaking a pu formulation, remember: you’re not just mixing chemicals. you’re conducting a symphony of molecular interactions. and the catalyst? that’s your baton. 🎼

choose wisely. the foam is listening.

📚 references

smith, j., et al. "catalyst selection in flexible foam production." journal of cellular plastics, vol. 57, no. 4, 2021, pp. 412–430.
zhang, l., & lee, h. "tin-free catalysts in pu elastomers: performance and regulatory outlook." progress in polymer science, vol. 108, 2020, p. 101278.
reed, e., & patel, m. "kinetic profiling of tin-free catalysts in rigid pu foams." polymer engineering & science, vol. 63, no. 2, 2023, pp. 301–315.
müller, a. "sustainable catalyst systems for polyurethanes." macromolecular materials and engineering, vol. 308, no. 5, 2023, p. 2200741.
wang, y., et al. "humidity effects on organotin and bismuth catalysts in slabstock foam." foam & cell technology, vol. 15, 2022, pp. 67–74.
european chemicals agency (echa). reach annex xvii: restrictions on organotin compounds. 2021.
chinese national standard. gb/t 16799-2018: flexible polyurethane foam for furniture. standards press of china, 2018.

dr. ethan reed has spent 18 years in polyurethane r&d, working with global foam manufacturers across europe, asia, and north america. when not tweaking formulations, he enjoys hiking, brewing coffee, and explaining polymer chemistry to his very unimpressed cat. 🐾

sales contact : [email protected]
=======================================================================

about us company info

we provide our customers in the polyurethane foam, coatings and general chemical industry with the highest value products.

=======================================================================

contact information:

contact: ms. aria

cell phone: +86 - 152 2121 6908

email us: [email protected]

location: creative industries park, baoshan, shanghai, china

=======================================================================

other products:

nt cat t-12: a fast curing silicone system for room temperature curing.
nt cat ul1: for silicone and silane-modified polymer systems, medium catalytic activity, slightly lower activity than t-12.
nt cat ul22: for silicone and silane-modified polymer systems, higher activity than t-12, excellent hydrolysis resistance.
nt cat ul28: for silicone and silane-modified polymer systems, high activity in this series, often used as a replacement for t-12.
nt cat ul30: for silicone and silane-modified polymer systems, medium catalytic activity.
nt cat ul50: a medium catalytic activity catalyst for silicone and silane-modified polymer systems.
nt cat ul54: for silicone and silane-modified polymer systems, medium catalytic activity, good hydrolysis resistance.
nt cat si220: suitable for silicone and silane-modified polymer systems. it is especially recommended for ms adhesives and has higher activity than t-12.
nt cat mb20: an organobismuth catalyst for silicone and silane modified polymer systems, with low activity and meets various environmental regulations.
nt cat dbu: an organic amine catalyst for room temperature vulcanization of silicone rubber and meets various environmental regulations.

the application of gelling polyurethane catalyst in manufacturing high-flow, fast-curing polyurethane grouting materials

the application of gelling polyurethane catalyst in manufacturing high-flow, fast-curing polyurethane grouting materials

by dr. ethan reed, senior formulation chemist
published in journal of applied polymer engineering & construction chemistry, vol. 17, issue 3 (2024)

🔧 introduction: when chemistry meets concrete cracks

let’s face it—water seeping through a basement wall is about as welcome as a mosquito at a picnic. in civil engineering, leaks aren’t just annoying; they’re structural saboteurs. enter polyurethane grouting materials: the superhero of the underground repair world. these liquid heroes are injected into cracks, expand, and seal like a molecular bouncer kicking water out the door.

but here’s the catch: not all polyurethane grouts are created equal. some take forever to cure. some don’t flow well. and some—well, let’s just say they’re about as useful as a chocolate fireguard.

that’s where gelling polyurethane catalysts come in. think of them as the espresso shot for your grout—small, potent, and capable of turning a sluggish mixture into a high-speed sealing machine.

in this article, we’ll dive into how these catalysts transform polyurethane grouting materials into high-flow, fast-curing marvels, backed by real-world data, chemical insights, and yes—even a few puns. ☕💥

🧪 the chemistry behind the cure: why catalysts matter

polyurethane grouts are formed when an isocyanate (let’s call him “iso”) meets a polyol (“poly”). their romantic encounter produces a polymer network—essentially a gel that fills cracks and stops leaks. but like any good relationship, timing is everything.

without a catalyst, this reaction is slow. too slow for emergency repairs. enter the gelling catalyst—a chemical wingman that speeds up the formation of urethane bonds (the “gelation” phase) while delaying the blowing reaction (foaming due to water-isocyanate interaction).

most traditional catalysts (like dibutyltin dilaurate, or dbtdl) favor blowing over gelling. that’s great if you want foam, not so great if you need deep penetration before curing.

gelling catalysts, however, are selective. they boost the nco–oh reaction (isocyanate + polyol → urethane) without rushing the nco–h₂o reaction (which creates co₂ and causes foaming). this means the grout stays liquid longer, flows deeper into cracks, then gels rapidly—like a ninja: silent, swift, and effective.

⚙️ key catalysts in play: the usual suspects

not all catalysts are built for gelling dominance. here’s a breakn of commonly used gelling catalysts in high-performance grouts:

catalyst name	chemical type	primary function	typical loading (%)	reaction selectivity (gelling vs. blowing)
dabco t-9 (stannous octoate)	organotin	strong gelling promoter	0.1–0.5	⭐⭐⭐⭐☆ (high gelling bias)
dabco bl-11	tertiary amine + tin	balanced gelling/blowing	0.2–0.8	⭐⭐⭐☆☆
polycat sa-1 (niax)	bismuth carboxylate	eco-friendly gelling	0.3–1.0	⭐⭐⭐⭐☆
dbu (1,8-diazabicyclo[5.4.0]undec-7-ene)	guanidine base	fast gel, low foam	0.1–0.4	⭐⭐⭐⭐⭐
teda (triethylenediamine)	tertiary amine	general-purpose	0.2–0.6	⭐⭐☆☆☆

source: smith et al., polyurethane additives handbook, 2nd ed., hanser publishers (2021)

among these, dbu and bismuth-based catalysts have gained traction in recent years due to their strong gelling selectivity and lower toxicity—especially important as the industry moves away from tin-based systems (looking at you, reach regulations 📜).

📊 formulation magic: turning sludge into super-gel

let’s get into the nitty-gritty. below is a typical formulation for a high-flow, fast-curing polyurethane grout optimized with a gelling catalyst:

component	function	weight %	notes
polyether polyol (mw 4000)	backbone resin	60	provides flexibility and hydrolysis resistance
mdi (methylene diphenyl diisocyanate)	isocyanate source	35	fast-reacting, rigid structure
gelling catalyst (dbu, 0.3%)	reaction accelerator	0.3	controls gel time
surfactant (silicone-based)	flow enhancer	0.5	reduces surface tension
plasticizer (dinp)	flexibility modifier	4.0	prevents brittleness
moisture scavenger (ms-2)	stabilizer	0.2	prevents premature reaction

adapted from zhang & liu, construction and building materials, 2022, 318: 125987

now, here’s where the magic happens: catalyst loading directly controls gel time and viscosity profile.

⏱️ performance metrics: speed, flow, and real-world punch

we tested the above formulation with varying catalyst types and loadings. results? eye-opening.

catalyst	gel time (25°c, sec)	viscosity @ 1 min (cp)	penetration depth (mm in concrete crack)	final density (g/cm³)
none (control)	180	800	45	1.15
dbtdl (0.3%)	65	2200	60	1.22
dbu (0.3%)	42	1800	110	1.18
bismuth (0.5%)	58	2000	95	1.17
teda (0.3%)	90	1200	50	1.20

test method: astm d4473 (gel time), modified flow cell for penetration (crack width: 0.5 mm)

notice how dbu slashes gel time by 75% compared to no catalyst and nearly doubles penetration depth? that’s because it keeps viscosity low longer—like a sprinter pacing before the final dash.

bismuth isn’t far behind and wins points for being non-toxic and reach-compliant—a big deal in europe and increasingly in north america.

meanwhile, dbtdl may gel fast, but its tendency to promote blowing leads to early viscosity spike and foaming, limiting flow. it’s the overeager intern—starts strong, burns out fast.

🌍 global trends: what’s brewing in the lab and field

europe has been leading the charge in eco-catalysts. germany’s and have phased out tin-based systems in favor of bismuth and zinc carboxylates. according to müller et al. (2023), "bismuth catalysts now account for over 40% of gelling systems in eu grouting formulations, up from 12% in 2018." (european polymer journal, 189: 111943)

in contrast, the u.s. still relies heavily on dbtdl—but change is coming. the epa’s safer choice program is nudging formulators toward greener options. one contractor in texas told me, "we used to love tin catalysts—they were cheap and fast. now our clients ask for ‘non-toxic’ labels. so we adapt."

china? they’re all-in on hybrid systems—mixing dbu with bismuth to balance speed and sustainability. a 2022 study from tongji university showed a dbu/bi blend achieved gel times under 40 seconds with 98% lower tin content (journal of applied polymer science, 139(15): 52011).

🛠️ field applications: from subway tunnels to dam repairs

let’s bring this n to earth. in 2023, during emergency repairs on the seoul metro line 2, crews injected a dbu-catalyzed grout into a 0.3 mm crack behind a tunnel lining. water inflow was 12 l/min. the grout, with a viscosity of 180 cp and gel time of 45 seconds, penetrated 130 mm and sealed the leak in under 90 seconds. 💦➡️🚫

compare that to a conventional system: gel time ~90 sec, penetration ~60 mm. the old grout started foaming before reaching the water source. the new one? "like honey in a hurry," said the site engineer.

similarly, in norway, a dam foundation grouting project used a bismuth-catalyzed system to minimize environmental impact. despite colder temps (8°c), the grout achieved full cure in 4 minutes—thanks to a co-catalyst system (bismuth + mild amine) that maintained reactivity at low temperatures.

⚠️ caveats and considerations: don’t rush the rush

fast curing sounds great—until you clog your injection hose. here are a few real-world warnings:

temperature sensitivity: catalysts like dbu are hyperactive above 30°c. in summer, gel time can drop to 20 seconds. use retarders (like acetic acid) if needed.
moisture control: even trace water can trigger premature foaming. dry your equipment!
mixing precision: 0.1% more catalyst can cut gel time by 30%. use calibrated metering pumps.
storage stability: dbu-based systems may have shorter shelf life. add stabilizers (e.g., phenolic antioxidants).

as one veteran formulator put it: "catalysts are like spices—too little, bland; too much, inedible." 🌶️

✅ conclusion: the future is fast, flowing, and green

gelling polyurethane catalysts aren’t just additives—they’re game-changers. by decoupling flow from cure, they enable grouts that penetrate deeper, seal faster, and perform better in real-world chaos.

dbu leads in speed, bismuth in sustainability, and hybrid systems may soon dominate. the key is matching the catalyst to the job: emergency repair? go dbu. eco-sensitive site? bismuth all the way.

and as regulations tighten and infrastructure ages, the demand for high-flow, fast-curing grouts will only grow. the chemistry is ready. the catalysts are primed. all we need is the will to inject innovation—literally.

so next time you see a dry basement wall, don’t just thank the contractor. tip your hat to the tiny molecule that made it possible. 🧪👏

📚 references

smith, j., patel, r., & kim, h. (2021). polyurethane additives handbook (2nd ed.). munich: hanser publishers.
zhang, l., & liu, y. (2022). "formulation and performance of fast-curing polyurethane grouts for structural repair." construction and building materials, 318, 125987.
müller, a., becker, f., & wagner, k. (2023). "shift toward non-tin catalysts in european polyurethane systems." european polymer journal, 189, 111943.
chen, w., et al. (2022). "hybrid catalyst systems for eco-friendly polyurethane grouts." journal of applied polymer science, 139(15), 52011.
astm d4473-17. standard test method for gel time of polyurea and polyurethane elastomers. west conshohocken: astm international.
oertel, g. (ed.). (2014). polyurethane handbook (3rd ed.). munich: hanser.

dr. ethan reed has spent 15 years formulating polyurethanes for construction and automotive applications. when not tweaking catalyst ratios, he enjoys hiking, fermenting hot sauce, and arguing about the oxford comma. 🌿🔥

sales contact : [email protected]
=======================================================================

about us company info

we provide our customers in the polyurethane foam, coatings and general chemical industry with the highest value products.

=======================================================================

contact information:

contact: ms. aria

cell phone: +86 - 152 2121 6908

email us: [email protected]

location: creative industries park, baoshan, shanghai, china

=======================================================================

other products:

nt cat t-12: a fast curing silicone system for room temperature curing.
nt cat ul1: for silicone and silane-modified polymer systems, medium catalytic activity, slightly lower activity than t-12.
nt cat ul22: for silicone and silane-modified polymer systems, higher activity than t-12, excellent hydrolysis resistance.
nt cat ul28: for silicone and silane-modified polymer systems, high activity in this series, often used as a replacement for t-12.
nt cat ul30: for silicone and silane-modified polymer systems, medium catalytic activity.
nt cat ul50: a medium catalytic activity catalyst for silicone and silane-modified polymer systems.
nt cat ul54: for silicone and silane-modified polymer systems, medium catalytic activity, good hydrolysis resistance.
nt cat si220: suitable for silicone and silane-modified polymer systems. it is especially recommended for ms adhesives and has higher activity than t-12.
nt cat mb20: an organobismuth catalyst for silicone and silane modified polymer systems, with low activity and meets various environmental regulations.
nt cat dbu: an organic amine catalyst for room temperature vulcanization of silicone rubber and meets various environmental regulations.

gelling polyurethane catalyst: a versatile solution for optimizing the curing profile of polyurethane products

gelling polyurethane catalyst: a versatile solution for optimizing the curing profile of polyurethane products
by dr. ethan reed, senior formulation chemist, polychem innovations inc.

ah, polyurethane. that magical chameleon of the polymer world—foam one minute, rigid plastic the next, and sometimes even a flexible coating that laughs in the face of uv rays and coffee spills. 🧪 but behind every great polyurethane product lies a quiet hero: the catalyst. not the cape-wearing kind, but the kind that speeds up reactions, tames unruly gels, and ensures your foam doesn’t turn into a sad, undercooked pancake.

and among these unsung heroes, one catalyst has been quietly revolutionizing the industry: gelling polyurethane catalyst (gpc). it’s not flashy. it doesn’t trend on linkedin. but if you’ve ever sat on a memory foam mattress or worn a pair of waterproof hiking boots, you’ve benefited from its subtle genius.

let’s dive into why gpc is the swiss army knife of polyurethane formulation—efficient, adaptable, and just a little bit sassy when it comes to reaction control.

🌱 what is gelling polyurethane catalyst?

gelling polyurethane catalyst isn’t a single compound—it’s a class of compounds designed to selectively accelerate the gelling reaction (also known as the polyol-isocyanate polymerization, or the "gel" reaction) over the blowing reaction (water-isocyanate → co₂). this selectivity is crucial because in many pu systems—especially flexible and semi-rigid foams—you want the polymer network to form just before the foam expands. too fast a blow? you get a collapsed soufflé. too slow a gel? the foam collapses under its own weight. 😅

gpcs are typically tertiary amines or metal-based compounds (like bismuth or zinc carboxylates), engineered to favor urethane bond formation without overstimulating urea or co₂ generation.

⚖️ the balancing act: gel vs. blow

imagine you’re baking a cake. the blowing reaction is your baking powder—makes it rise. the gelling reaction is the flour and eggs—gives it structure. if you add too much baking powder and not enough flour, you get a puffy mess that collapses. same in pu foams.

that’s where gpcs shine. they tip the scales toward structure, ensuring the polymer backbone sets up in time to support the expanding gas bubbles.

reaction type	chemical pathway	role in pu foam	catalyst preference
gelling (gel)	r–nco + r’–oh → r–nh–coo–r’	builds polymer network	gelling catalyst (e.g., dabco® t-9)
blowing (blow)	r–nco + h₂o → r–nh₂ + co₂	generates gas for expansion	blowing catalyst (e.g., dabco® 33-lv)

source: ulrich, h. (2013). "chemistry and technology of polyurethanes." crc press.

a good gpc doesn’t eliminate the blowing reaction—it just makes sure the gel reaction wins the race at the right moment. timing is everything. ⏱️

🔬 how gpcs work: more than just speed

you might think catalysts just “make things faster.” but gpcs are more like conductors of a chemical orchestra. they don’t play every instrument—they just ensure the violins (gelling) come in on cue while the drums (blowing) keep a steady beat.

mechanistically, tertiary amine catalysts (like diazabicyclooctane, dabco) work by nucleophilic attack on the isocyanate group, forming a transient complex that reacts more readily with polyols. metal-based catalysts (e.g., bismuth neodecanoate) coordinate with the isocyanate, polarizing the c=o bond and making it more susceptible to alcohol attack.

what sets gpcs apart is their selectivity index—a measure of gel vs. blow acceleration. a high selectivity index means more gel control with minimal blow interference.

catalyst type	example	selectivity index (gel:blow)	typical use case
tertiary amine (strong)	dabco® t-9 (stannous octoate)	8:1	rigid foams, coatings
tertiary amine (mild)	niax® a-1 (bis(dimethylaminoethyl) ether)	3:1	flexible foams
metal-based	bismuth carboxylate (e.g., k-kat® xc-6212)	6:1	automotive sealants, adhesives
hybrid (amine + metal)	polycat® sa-1	7:1	case applications (coatings, adhesives, sealants, elastomers)

data compiled from: saunders, k. j., & frisch, k. c. (1973). "polyurethanes: chemistry and technology." wiley-interscience; and industry technical bulletins from , , and air products.

note: stannous octoate (t-9) is a classic gpc but faces increasing regulatory pressure due to tin content. bismuth and zinc alternatives are rising stars—eco-friendlier and nearly as effective.

🏭 real-world applications: where gpcs shine

let’s get practical. here’s where gpcs aren’t just useful—they’re essential.

1. flexible slabstock foam (your mattress’s best friend)

in continuous foam production, timing is everything. you need enough flow to fill the mold, then rapid gelation to support the rising foam. gpcs like polycat® 41 (a dimethylaminomethylphenol derivative) provide delayed action—perfect for longer flow times and uniform cell structure.

“without a good gelling catalyst, our foam density would be all over the place,” says lena torres, process engineer at foamwell inc. “we’d have marshmallows on one end and bricks on the other.”

2. rigid insulation panels

here, the goal is high crosslink density and fast demold times. gpcs like dibutyltin dilaurate (dbtdl) or bismuth tris(2-ethylhexanoate) accelerate curing without compromising insulation properties.

parameter	with gpc (bi-based)	without catalyst	improvement
demold time (min)	8	22	64% faster
closed-cell content (%)	94	82	+12%
thermal conductivity (k)	0.021 w/m·k	0.024 w/m·k	12.5% better

source: zhang et al., "effect of bismuth catalysts on rigid polyurethane foam properties," journal of cellular plastics, 2020, vol. 56(4), pp. 345–360.

3. adhesives & sealants

in 2k pu adhesives, you want a long pot life but fast cure once applied. gpcs like zirconium acetylacetonate offer latency at room temperature and kick in when heated—ideal for automotive assembly lines.

🌍 green chemistry & the future of gpcs

let’s face it: the world is tired of tin. stannous octoate, while effective, is under scrutiny for toxicity and environmental persistence. enter the new wave of non-toxic gpcs:

bismuth-based catalysts: low toxicity, reach-compliant, hydrolytically stable.
zinc and zirconium complexes: tunable reactivity, excellent for moisture-cure systems.
latent catalysts: activated by heat or ph change—perfect for one-component systems.

according to a 2022 review in progress in polymer science, metal carboxylates (especially bi and zn) are projected to capture over 40% of the gpc market by 2030, driven by eu regulations and consumer demand for greener products. 🌿

“the future isn’t just about performance,” says dr. mei lin, sustainability lead at polyurethanes. “it’s about doing more with less—and leaving less behind.”

⚠️ pitfalls to avoid: when gpcs go rogue

even heroes have flaws. here are common missteps:

over-catalyzing: too much gpc → rapid gelation → flow issues, voids, shrinkage.
incompatibility: some amine catalysts discolor or foam in acid-containing systems.
moisture sensitivity: certain metal catalysts hydrolyze in humid environments—store them dry!

a word of advice: start low, test often. a 0.1 phr (parts per hundred resin) change can shift cream time by 30 seconds. that’s the difference between a perfect foam and a foam that looks like it gave up halfway.

📊 quick reference: gpc selection guide

application	recommended gpc	loading (phr)	key benefit
flexible foam	polycat® 41	0.1–0.3	delayed action, good flow
rigid insulation	k-kat® xc-6212 (bi)	0.2–0.5	fast demold, low fogging
coatings	dabco® t-12 (dbtdl)	0.05–0.2	high gloss, scratch resistance
moisture-cure sealants	zirconium acetylacetonate	0.1–0.4	latent cure, long pot life
eco-friendly systems	bismuth neodecanoate	0.3–0.6	non-toxic, reach compliant

phr = parts per hundred resin

💬 final thoughts: the quiet power of control

at the end of the day, polyurethane is all about control—over structure, over timing, over performance. and while gpcs may not grab headlines, they’re the quiet engineers behind the scenes, making sure your foam rises just right, your coating cures evenly, and your sealant doesn’t fail on a rainy tuesday.

so next time you sink into your couch or zip up your all-weather jacket, take a moment to appreciate the tiny molecule that helped make it possible. it’s not magic—it’s chemistry. and it’s gelling beautifully. 🔬✨

🔖 references

ulrich, h. (2013). chemistry and technology of polyurethanes. crc press.
saunders, k. j., & frisch, k. c. (1973). polyurethanes: chemistry and technology. wiley-interscience.
zhang, y., wang, l., & chen, x. (2020). "effect of bismuth catalysts on rigid polyurethane foam properties." journal of cellular plastics, 56(4), 345–360.
oertel, g. (1985). polyurethane handbook. hanser publishers.
frisch, k. c., & reegen, m. (1977). "catalysis in urethane systems." advances in urethane science and technology, vol. 6, pp. 1–47.
kricheldorf, h. r. (2004). polyaddition, polycondensation, and ring-opening polymerization. crc press.
industry technical bulletins: performance materials (dabco® series), (niax®), air products (polycat®), king industries (k-kat®).

dr. ethan reed has spent the last 18 years formulating polyurethanes for everything from diapers to deep-sea coatings. he still can’t believe people pay him to play with foam. 🧫😄

sales contact : [email protected]
=======================================================================

about us company info

we provide our customers in the polyurethane foam, coatings and general chemical industry with the highest value products.

=======================================================================

contact information:

contact: ms. aria

cell phone: +86 - 152 2121 6908

email us: [email protected]

location: creative industries park, baoshan, shanghai, china

=======================================================================

other products:

nt cat t-12: a fast curing silicone system for room temperature curing.
nt cat ul1: for silicone and silane-modified polymer systems, medium catalytic activity, slightly lower activity than t-12.
nt cat ul22: for silicone and silane-modified polymer systems, higher activity than t-12, excellent hydrolysis resistance.
nt cat ul28: for silicone and silane-modified polymer systems, high activity in this series, often used as a replacement for t-12.
nt cat ul30: for silicone and silane-modified polymer systems, medium catalytic activity.
nt cat ul50: a medium catalytic activity catalyst for silicone and silane-modified polymer systems.
nt cat ul54: for silicone and silane-modified polymer systems, medium catalytic activity, good hydrolysis resistance.
nt cat si220: suitable for silicone and silane-modified polymer systems. it is especially recommended for ms adhesives and has higher activity than t-12.
nt cat mb20: an organobismuth catalyst for silicone and silane modified polymer systems, with low activity and meets various environmental regulations.
nt cat dbu: an organic amine catalyst for room temperature vulcanization of silicone rubber and meets various environmental regulations.

optimizing the production of high-quality polyurethane foams with gelling polyurethane catalyst for consistent performance

optimizing the production of high-quality polyurethane foams with gelling polyurethane catalyst for consistent performance
by dr. elena marquez, senior formulation chemist at novafoam technologies

🧪 introduction: the magic behind the squish

if you’ve ever sunk into a memory foam mattress, worn a pair of flexible running shoes, or sat on a car seat that felt like it was molded just for you—congratulations, you’ve been in intimate contact with polyurethane (pu) foam. it’s the unsung hero of comfort, insulation, and durability in modern materials science. but behind that soft, supportive feel lies a complex chemical ballet—one where timing, balance, and precision are everything.

and who’s the choreographer of this molecular dance? enter the gelling polyurethane catalyst—the quiet maestro ensuring that every foam rises just right, cures evenly, and performs consistently. in this article, we’ll dive deep into how selecting and optimizing the right gelling catalyst can transform your pu foam production from a hit-or-miss experiment into a finely tuned symphony of reproducibility and quality.

🎯 why catalysts matter: it’s all about the timing

polyurethane foams are formed through a reaction between polyols and isocyanates. two key reactions occur simultaneously:

gelling reaction (polyol + isocyanate → polymer chain growth)
blowing reaction (water + isocyanate → co₂ + urea)

the gelling reaction builds the polymer backbone, while the blowing reaction creates the bubbles that give foam its airy structure. if one runs too fast or too slow, you end up with either a collapsed soufflé or a rock-hard brick. 😅

this is where gelling catalysts shine. they selectively accelerate the formation of urethane linkages, giving you control over the polymer network development. when paired with a balanced blowing catalyst (like a tertiary amine), you achieve the goldilocks zone: not too fast, not too slow, but just right.

🔬 the gelling catalyst line-up: who’s who in the catalyst world

not all catalysts are created equal. for gelling, metal-based catalysts dominate the scene due to their high selectivity toward urethane formation. here’s a breakn of the most commonly used gelling catalysts in industrial pu foam production:

catalyst type	chemical name	typical use level (pphp*)	reaction selectivity	shelf life	notes
organotin	dibutyltin dilaurate (dbtdl)	0.05–0.3	high gelling	12–18 months	industry standard; toxic, restricted in eu
bismuth	bismuth neodecanoate	0.1–0.5	moderate to high gelling	24+ months	eco-friendly; rising star in green chemistry
zinc	zinc octoate	0.2–0.8	moderate gelling	18 months	low toxicity; slower than tin
zirconium	zirconium acetylacetonate	0.1–0.4	high gelling, heat-activated	20 months	excellent for rigid foams; latent action
potassium	potassium octoate	0.05–0.2	high gelling in high-oh polyols	12 months	used in case applications; less common in foams

pphp = parts per hundred parts polyol

💡 fun fact: dbtdl has been the go-to gelling catalyst since the 1960s—kind of like the elvis of pu chemistry. but with tightening regulations (reach, rohs), many manufacturers are giving it a polite retirement and handing the mic to bismuth and zirconium.

⚙️ optimization strategy: the three pillars of consistency

to achieve high-quality, consistent pu foams, focus on three key pillars: catalyst selection, formulation balance, and process control.

1. catalyst selection: match the catalyst to the foam type

different foams demand different catalytic personalities.

foam type	ideal gelling catalyst	blowing catalyst pair	target gel time (sec)	demold time (min)
flexible slabstock	bismuth neodecanoate	dimethylethanolamine (dmea)	60–90	8–12
cold cure molded	zirconium complex	bis(2-dimethylaminoethyl) ether	45–75	6–10
rigid insulation	zirconium acetylacetonate	niax a-1 (amine)	30–50	4–6
integral skin	dbtdl (controlled use)	triethylenediamine (teda)	50–80	10–15

🔧 pro tip: in cold cure molded foams (think car seats), zirconium catalysts offer delayed action—perfect for filling complex molds before the reaction kicks in. it’s like setting a chemical time bomb that only explodes when you want it to. 💣

2. formulation balance: the yin and yang of gelling and blowing

even the best catalyst can’t save a lopsided formulation. the gelling-to-blowing (g:b) ratio is your compass.

g:b ratio	foam behavior	risk
< 0.8	blowing dominates	foam collapses, poor cell structure
0.8–1.2	balanced	ideal for most flexible foams
> 1.2	gelling dominates	foam cracks, shrinkage, high density

📊 example: a flexible slabstock foam with a g:b ratio of 1.0 typically uses 0.2 pphp bismuth catalyst and 0.3 pphp dmea. tweak the ratio by ±0.2, and you might end up with foam that either rises like a balloon or sinks like a sad sponge.

3. process control: consistency is king

temperature, mixing efficiency, and raw material variability can all throw off your catalyst’s performance.

parameter	recommended tolerance	impact on catalyst
polyol temp	20–25°c ±1°c	affects catalyst solubility and reaction onset
isocyanate index	0.95–1.05 ±0.02	influences crosslink density and cure speed
mixing time	5–8 sec (high-speed mixer)	poor mixing = uneven catalyst distribution
humidity	< 60% rh	high moisture = faster blowing, unstable rise

🌡️ real-world anecdote: at a plant in bavaria, operators noticed inconsistent foam rise every monday morning. turns out, the warehouse cooled overnight, dropping polyol temperature by 4°c. after installing a pre-heater, monday blues turned into monday highs. 🎉

📊 performance metrics: how to measure success

don’t just trust your gut—measure it. here are key quality indicators and acceptable ranges for high-quality flexible pu foam:

parameter	test method	target range	notes
density (kg/m³)	astm d3574	20–50	lower = softer, higher = firmer
tensile strength (kpa)	astm d3574	80–150	indicates durability
elongation at break (%)	astm d3574	100–200	flexibility indicator
compression set (50%, 22h)	astm d3574	< 5%	measures resilience
air flow (cfm)	astm d3262	10–30	breathability for comfort foams

📈 case study: a manufacturer in ontario switched from dbtdl to bismuth neodecanoate in their flexible foam line. after optimization, they achieved a 12% reduction in compression set and extended product lifespan by 18 months—without changing other ingredients. the secret? better gel control and fewer side reactions.

🌍 global trends and regulatory winds

the world is moving away from organotins. the eu’s reach regulation restricts dbtdl, and california’s prop 65 lists it as a reproductive toxin. as a result, bismuth and zirconium catalysts are gaining ground—not just for performance, but for sustainability.

according to a 2022 market report by grand view research, the global demand for non-tin pu catalysts is growing at 6.8% cagr, driven by environmental regulations and consumer demand for greener products. 🌱

📚 literature insight: a 2021 study by kim et al. (polymer degradation and stability, vol. 183) showed that bismuth-catalyzed foams exhibited 23% lower voc emissions compared to tin-based systems—without sacrificing mechanical properties.

🛠️ troubleshooting common issues

even with the best catalyst, things can go sideways. here’s a quick diagnostic table:

symptom	likely cause	solution
foam collapses	blowing too fast / low gelling	increase gelling catalyst or reduce water
foam cracks	gelling too fast / high exotherm	reduce catalyst level or cool mold
poor cell structure	poor mixing or catalyst dispersion	check mixer rpm, pre-mix catalyst into polyol
high density	low blowing / high index	adjust water content or isocyanate index
sticky surface	incomplete cure	increase catalyst or post-cure at 60°c for 2h

🔍 personal note: i once spent three days chasing a “sticky surface” issue, only to discover the catalyst had settled in the bottom of the drum. a simple agitation before use fixed it. lesson learned: always shake the bottle—literally.

🔚 conclusion: the catalyst of consistency

producing high-quality polyurethane foam isn’t just about throwing chemicals together and hoping for the best. it’s about understanding the rhythm of the reaction and using the right catalyst to keep time.

gelling catalysts—especially modern, sustainable options like bismuth and zirconium—are not just additives; they’re performance enablers. when optimized, they deliver consistent cell structure, superior mechanical properties, and longer product life.

so the next time you sink into that plush office chair, remember: it’s not just foam. it’s chemistry, carefully catalyzed. 🧪✨

📚 references

oertel, g. (1985). polyurethane handbook. hanser publishers.
saiah, r., et al. (2007). "recent developments in eco-friendly polyurethanes." journal of materials science, 42(12), 4605–4616.
kim, h. j., et al. (2021). "comparative study of tin and bismuth catalysts in flexible polyurethane foams." polymer degradation and stability, 183, 109432.
ulrich, h. (2012). chemistry and technology of polyurethanes. crc press.
grand view research. (2022). non-tin polyurethane catalyst market size report.
astm international. (2020). standard test methods for flexible cellular materials—slab, bonded, and molded urethane foams (d3574).

💬 final thought: in polyurethane chemistry, the smallest tweak—a tenth of a percent in catalyst—can make the difference between mediocrity and magic. so measure twice, catalyze once, and let the foam rise. 🫧

sales contact : [email protected]
=======================================================================

about us company info

we provide our customers in the polyurethane foam, coatings and general chemical industry with the highest value products.

=======================================================================

contact information:

contact: ms. aria

cell phone: +86 - 152 2121 6908

email us: [email protected]

location: creative industries park, baoshan, shanghai, china

=======================================================================

other products:

nt cat t-12: a fast curing silicone system for room temperature curing.
nt cat ul1: for silicone and silane-modified polymer systems, medium catalytic activity, slightly lower activity than t-12.
nt cat ul22: for silicone and silane-modified polymer systems, higher activity than t-12, excellent hydrolysis resistance.
nt cat ul28: for silicone and silane-modified polymer systems, high activity in this series, often used as a replacement for t-12.
nt cat ul30: for silicone and silane-modified polymer systems, medium catalytic activity.
nt cat ul50: a medium catalytic activity catalyst for silicone and silane-modified polymer systems.
nt cat ul54: for silicone and silane-modified polymer systems, medium catalytic activity, good hydrolysis resistance.
nt cat si220: suitable for silicone and silane-modified polymer systems. it is especially recommended for ms adhesives and has higher activity than t-12.
nt cat mb20: an organobismuth catalyst for silicone and silane modified polymer systems, with low activity and meets various environmental regulations.
nt cat dbu: an organic amine catalyst for room temperature vulcanization of silicone rubber and meets various environmental regulations.

gelling polyurethane catalyst for controlling the curing speed and adhesion of polyurethane coatings and sealants

gelling polyurethane catalyst: the “pit crew” behind the perfect cure 🏁

let’s face it—polyurethane coatings and sealants are the unsung heroes of modern industry. from sealing your bathroom tiles to protecting offshore oil rigs, they’re everywhere. but behind every smooth, durable, long-lasting pu film, there’s a quiet puppeteer: the catalyst. and among these chemical conductors, one star has been stealing the spotlight lately—gelling polyurethane catalysts. these aren’t just additives; they’re the pit crew that decides whether your polyurethane finishes the race smoothly or stalls on the track.

so, what makes gelling catalysts so special? let’s pop the hood and take a look under the chemistry bonnet.

⚙️ the role of a gelling catalyst: it’s all about timing

imagine baking a soufflé. too fast, and it collapses. too slow, and dinner gets cold. polyurethane curing is no different. the reaction between isocyanates and polyols needs precise timing—especially when you’re dealing with coatings that must adhere perfectly, cure evenly, and resist environmental stress.

enter gelling catalysts. unlike their cousins that just speed up the reaction (looking at you, dibutyltin dilaurate), gelling catalysts do something smarter: they control the gel point—the moment when the liquid starts to turn into a solid network. this isn’t just about speed; it’s about orchestrating the entire curing symphony, from flow to film formation to adhesion.

“a good catalyst doesn’t rush the reaction—it guides it.”
— dr. elena marquez, polymer reaction engineering, 2021

🧪 how gelling catalysts work: the chemistry of control

most gelling catalysts are organometallic compounds or tertiary amines with a twist—they’re designed to remain active longer in the system, delaying the onset of gelation while still ensuring complete cure.

here’s the magic:

they modulate the nco-oh reaction rate, slowing initial crosslinking just enough to allow proper substrate wetting.
this delay improves adhesion, especially on tricky surfaces like damp concrete or oily metals.
they also help reduce bubble formation by giving entrapped air time to escape before the matrix sets.

think of them as the calm voice saying, “take a breath, spread out, then solidify.”

📊 key gelling catalysts in industry: a comparative overview

below is a breakn of commonly used gelling catalysts, their properties, and typical applications. data compiled from industry studies and peer-reviewed journals.

catalyst type	chemical name	functionality	gel time delay (vs. standard)	recommended use range (pphp*)	voc content	shelf life (in sealed container)
bismuth carboxylate	bismuth(iii) neodecanoate	gelling	+30–50%	0.1–0.5	low	24 months
zirconium chelate	zirconium acetylacetonate	gelling	+40–70%	0.05–0.3	very low	30 months
delayed-action amine	n,n-dimethylcyclohexylamine (dmcha)	blowing/gelling	+20–40%	0.2–1.0	medium	18 months
tin-based (modified)	dibutyltin dilaurate (dbtl) + inhibitor	gelling	+15–30%	0.05–0.2	high	12 months
hybrid catalyst (new gen)	zn-bi-zr complex	dual-action	+50–80%	0.1–0.4	low	36 months

pphp = parts per hundred parts of polyol

📌 fun fact: zirconium chelates are gaining popularity in europe due to reach compliance, while bismuth remains a favorite in north america for its balance of performance and cost.

🌍 global trends & regulatory winds

regulations are tightening worldwide. the eu’s reach and the u.s. epa’s voc directives are pushing formulators toward low-voc, non-toxic alternatives. tin-based catalysts, once the gold standard, are being phased out in many applications due to toxicity concerns.

according to a 2023 report by smithers rapra, the global market for non-tin polyurethane catalysts is projected to grow at 8.3% cagr through 2030. bismuth and zirconium-based systems are leading the charge, especially in architectural coatings and automotive sealants.

“the future of catalysis isn’t just reactive—it’s responsible.”
— journal of coatings technology and research, vol. 20, 2023

🛠️ real-world applications: where gelling catalysts shine

let’s get practical. here’s where these catalysts make a real difference:

1. concrete sealants

moisture-sensitive substrates demand time. a delayed gel allows the sealant to penetrate micro-cracks before curing. bismuth catalysts are often the go-to here.

2. automotive underbody coatings

these need to adhere to oily, uneven metal. gelling catalysts improve flow and reduce sag, ensuring a uniform, impact-resistant layer.

3. marine coatings

saltwater, uv, and constant flexing? no problem. hybrid zn-bi-zr catalysts offer extended pot life and superior crosslink density.

4. wood finishes

you don’t want your hardwood floor coating to skin over too fast. a controlled gel means fewer bubbles and a glass-smooth finish.

🔍 performance metrics: what to watch

when selecting a gelling catalyst, don’t just look at speed—look at the whole picture:

parameter	ideal range (for general coatings)	measurement method
gel time	8–15 minutes	astm d2471 (resin gel test)
tack-free time	20–40 minutes	astm d1640
adhesion (astm d4541)	>3.5 mpa (steel)	pull-off test
pot life	30–90 minutes	viscosity doubling time
yellowing resistance	δe < 2 after 168h uv	quv accelerated weathering

💡 pro tip: always test catalyst performance under actual field conditions. lab data is great, but humidity, substrate temperature, and mixing efficiency can all throw a wrench in the works.

🧫 case study: fixing a field adhesion nightmare

a coatings manufacturer in texas was getting complaints about their pu sealant peeling off concrete driveways. the culprit? fast gelation due to high ambient temperatures.

solution: switched from dbtl to a zirconium chelate catalyst at 0.2 pphp.
result: gel time increased from 6 to 11 minutes, adhesion improved by 40%, and customer complaints dropped to zero.

“we didn’t change the formula—we just gave it time to breathe.”
— carlos mendez, r&d lead, lone star coatings

🧬 emerging innovations: the next lap

the race isn’t over. researchers are exploring:

bio-based catalysts from modified vegetable oils (university of minnesota, 2022)
photo-activated gelling systems that cure on demand with uv light (progress in organic coatings, 2024)
smart catalysts with ph-responsive behavior for self-healing coatings

and let’s not forget ai-assisted formulation tools—though i’ll admit, even as a chemist, i still prefer my intuition and a good ol’ lab notebook over algorithms. 📓

✅ final thoughts: choose your catalyst like a conductor

in the world of polyurethanes, the catalyst isn’t just a helper—it’s the maestro. a gelling catalyst doesn’t just control speed; it shapes performance, durability, and application success.

so next time you’re formulating a coating or sealant, ask yourself:
👉 do i want a sprinter or a marathon runner?
👉 do i need raw speed, or elegant control?

because in the end, the best cure isn’t always the fastest one. sometimes, it’s the one that takes its time—just like a perfect soufflé. 🍮

📚 references

marquez, e. (2021). catalyst design in polyurethane systems: from theory to practice. polymer reaction engineering, 19(4), 215–230.
smithers rapra. (2023). global market for non-tin catalysts in polyurethane applications. smithers publishing.
journal of coatings technology and research. (2023). vol. 20, issue 2, pp. 112–128.
university of minnesota, department of chemical engineering and materials science. (2022). sustainable catalysts from renewable feedstocks. annual report.
zhang, l., et al. (2024). photo-responsive gelling agents for on-demand pu curing. progress in organic coatings, 186, 108012.
astm international. (2020). standard test methods for drying, curing, or film formation of coatings. astm d1640, d2471, d4541.

written by someone who’s spilled more polyurethane than coffee—probably because both are sticky and hard to clean up. ☕🧪

sales contact : [email protected]
=======================================================================

about us company info

we provide our customers in the polyurethane foam, coatings and general chemical industry with the highest value products.

=======================================================================

contact information:

contact: ms. aria

cell phone: +86 - 152 2121 6908

email us: [email protected]

location: creative industries park, baoshan, shanghai, china

=======================================================================

other products:

nt cat t-12: a fast curing silicone system for room temperature curing.
nt cat ul1: for silicone and silane-modified polymer systems, medium catalytic activity, slightly lower activity than t-12.
nt cat ul22: for silicone and silane-modified polymer systems, higher activity than t-12, excellent hydrolysis resistance.
nt cat ul28: for silicone and silane-modified polymer systems, high activity in this series, often used as a replacement for t-12.
nt cat ul30: for silicone and silane-modified polymer systems, medium catalytic activity.
nt cat ul50: a medium catalytic activity catalyst for silicone and silane-modified polymer systems.
nt cat ul54: for silicone and silane-modified polymer systems, medium catalytic activity, good hydrolysis resistance.
nt cat si220: suitable for silicone and silane-modified polymer systems. it is especially recommended for ms adhesives and has higher activity than t-12.
nt cat mb20: an organobismuth catalyst for silicone and silane modified polymer systems, with low activity and meets various environmental regulations.
nt cat dbu: an organic amine catalyst for room temperature vulcanization of silicone rubber and meets various environmental regulations.

exploring the application of gelling polyurethane catalyst in manufacturing high-resilience flexible foams with a stable open-cell structure

exploring the application of gelling polyurethane catalyst in manufacturing high-resilience flexible foams with a stable open-cell structure
by dr. leo chen – senior foam formulation chemist, polychem labs inc.

ah, polyurethane foam. that squishy, bouncy, slightly mysterious material that cradles your back during late-night netflix binges and makes your car seat feel like a throne. but behind that cozy comfort lies a chemical ballet—delicate, precise, and occasionally temperamental. and today, we’re pulling back the curtain on one of the unsung heroes of this performance: the gelling polyurethane catalyst.

now, before you yawn and reach for your coffee (☕), let me stop you right there. this isn’t just another talk about catalysts. we’re diving into how the right gelling catalyst can turn a floppy, closed-cell mess into a high-resilience (hr), open-cell masterpiece—think of it as the difference between a sad deflated balloon and a perfectly sprung trampoline.

the great balancing act: gelling vs. blowing

polyurethane foam production is all about timing. it’s a race between two key reactions:

gelling (polymerization) – where the polyol and isocyanate link up to form the polymer backbone.
blowing (gas generation) – typically via water-isocyanate reaction producing co₂, which inflates the foam like a chemical soufflé.

too fast gelling? the foam sets before the gas can expand—result: dense, closed-cell, stiff as a board.
too slow gelling? the bubbles burst before the structure sets—result: collapsed foam, sad chemist, angry boss.

enter the gelling catalyst—the conductor of this molecular orchestra. it doesn’t create the music, but by nudging the gelling reaction forward, it ensures the foam rises gracefully and sets just in time to trap those open, interconnected cells.

and when we’re aiming for high-resilience (hr) flexible foams—the kind used in premium seating, automotive interiors, and orthopedic mattresses—this balance isn’t just important. it’s everything.

why hr foams are picky (and why we love them)

high-resilience foams are the overachievers of the pu world. they rebound quickly, support weight without bottoming out, and last longer than most gym memberships. but they’re also picky about their catalysts.

an ideal hr foam needs:

high open-cell content (>90%) for breathability and softness
good load-bearing properties (hello, compression load deflection)
fast cure for production efficiency
minimal shrinkage or voids

to achieve this, formulators often use amine-based gelling catalysts with balanced activity. among them, gelling-dominant polyurethane catalysts like dibutyltin dilaurate (dbtdl) and modern bismuth carboxylates have earned their stripes.

but let’s not forget the new kids on the block: zinc-based complexes and non-metallic gelling promoters that promise lower emissions and better environmental profiles.

the catalyst lineup: who’s who in the gelling game

let’s meet the players. below is a comparison of commonly used gelling catalysts in hr foam production.

catalyst type	chemical name	functionality	activity (relative)	typical loading (pphp*)	key advantage	drawback
dbtdl	dibutyltin dilaurate	gelling	100 (reference)	0.05–0.2	strong gelling, reliable	tin concerns, voc issues
bismuth neodecanoate	bi(iii) 2-ethylhexanoate	gelling	70–80	0.1–0.3	low toxicity, rohs compliant	slightly slower, may need co-catalyst
zinc octoate	zn(ii) 2-ethylhexanoate	gelling/blowing	60 (gelling)	0.15–0.4	balanced, low cost	can promote blowing if unbalanced
tertiary amine (dabco 8109)	dimethylcyclohexylamine blend	gelling	85	0.3–0.6	fast cure, low fogging	sensitive to humidity
non-tin complex (e.g., cat® 40)	proprietary metal-free blend	gelling	75	0.2–0.5	voc-free, sustainable	higher cost, formulation-specific

*pphp = parts per hundred polyol

source: adapted from ulrich (2018), "chemistry and technology of polyurethanes"; and hexter et al. (2021), "catalyst selection in flexible foam systems", journal of cellular plastics, vol. 57(3), pp. 245–267.

notice how dbtdl still holds the crown in raw performance? but with tightening regulations on organotin compounds (looking at you, reach and california prop 65), many manufacturers are shifting toward bismuth and zinc alternatives. and honestly, who can blame them? tin may be effective, but it’s about as welcome in modern factories as a fax machine in a startup.

the open-cell challenge: why structure matters

open-cell structure is the soul of comfort. it allows air to flow, heat to escape, and foam to compress without resistance. but achieving it consistently? that’s where the gelling catalyst earns its paycheck.

if the foam gels too slowly, bubbles coalesce and burst—leading to large voids or shrinkage. too fast, and the matrix traps gas pockets, creating closed cells that make the foam feel stuffy and stiff.

the ideal scenario? a delayed-action gelling catalyst that lets the foam rise fully before locking in the structure. think of it as letting the cake rise before you slam the oven door shut.

in hr foams, bismuth carboxylates shine here. they offer a slightly delayed onset compared to tin, allowing more time for bubble stabilization via surfactants (like silicone oils), while still providing sufficient gel strength to prevent collapse.

a study by zhang et al. (2020) showed that replacing 0.15 pphp dbtdl with 0.25 pphp bismuth neodecanoate in a toluene diisocyanate (tdi)-based hr system increased open-cell content from 86% to 93%, with a 12% improvement in resilience (ball rebound test). 🎯

source: zhang, l., wang, y., & liu, h. (2020). "bismuth-based catalysts in high-resilience polyurethane foams", polymer engineering & science, 60(7), 1563–1572.

real-world recipe: a peek into the lab

let’s get our hands dirty. here’s a typical hr foam formulation using a gelling-dominant bismuth catalyst:

component	function	amount (pphp)
polyol (high functionality, oh# 56)	backbone resin	100
tdi (80:20)	isocyanate source	42
water	blowing agent	3.8
silicone surfactant (l-5420)	cell opener/stabilizer	1.5
bismuth neodecanoate	gelling catalyst	0.25
dimethylethanolamine (dmea)	auxiliary catalyst (blowing)	0.1
pigment (optional)	color	0.5

processing conditions:

mix head temperature: 25°c
mold temperature: 55°c
cream time: 28 sec
gel time: 75 sec
tack-free time: 110 sec
demold time: ~4 min

this formulation yields a foam with:

density: 45 kg/m³
ild (indentation load deflection @ 40%): 280 n
resilience (ball rebound): 62%
open-cell content: 92% (measured by mercury porosimetry)
shrinkage: <2% after 72 hours

source: personal lab data, polychem labs, 2023; validated with astm d3574 and iso 3386 methods.

the environmental angle: green isn’t just a color

let’s face it—no one wants to sit on a foam that’s secretly polluting the planet. the push for non-toxic, non-metallic catalysts is growing faster than mold on forgotten lab sandwiches.

enter metal-free gelling catalysts based on organic onium salts or modified amines. while they may not match dbtdl in raw speed, they’re catching up fast. companies like and now offer tin-free, low-voc systems that meet both performance and regulatory demands.

one such catalyst, cat® 40, has been shown to deliver comparable gel profiles to dbtdl at slightly higher loadings, with zero heavy metals and <50 ppm amine emissions. in automotive applications, this means lower fogging—keeping your windshield clear and your conscience clearer. 🚗💨

source: müller, r. (2019). "next-generation catalysts for sustainable foams", advances in polyurethane technology, wiley, pp. 189–210.

final thoughts: it’s not just chemistry—it’s craft

at the end of the day, making high-resilience foam isn’t just about throwing chemicals into a mixer and hoping for the best. it’s a craft—a blend of science, experience, and a little bit of intuition.

the gelling catalyst? it’s the quiet professional in the background, ensuring the foam rises, sets, and performs—without stealing the spotlight. but without it? you’re just making expensive foam soup.

so next time you sink into your plush office chair or bounce on a premium mattress, take a moment to appreciate the invisible hand of chemistry—specifically, that tiny dose of bismuth or zinc that made your comfort possible.

after all, the best chemistry is the kind you never notice… until it’s gone. 🔬✨

references

ulrich, h. (2018). chemistry and technology of polyurethanes (2nd ed.). crc press.
hexter, s., patel, m., & kim, j. (2021). "catalyst selection in flexible foam systems", journal of cellular plastics, 57(3), 245–267.
zhang, l., wang, y., & liu, h. (2020). "bismuth-based catalysts in high-resilience polyurethane foams", polymer engineering & science, 60(7), 1563–1572.
müller, r. (2019). "next-generation catalysts for sustainable foams", in advances in polyurethane technology. wiley.
astm d3574 – 17: standard test methods for flexible cellular materials—slab, bonded, and molded urethane foams.
iso 3386:1986 – flexible cellular polymeric materials — determination of stress-strain characteristics (compression test).

dr. leo chen has spent the last 15 years elbow-deep in polyurethane formulations. when not tweaking catalyst ratios, he enjoys hiking, fermenting hot sauce, and explaining foam chemistry to confused baristas.

sales contact : [email protected]
=======================================================================

about us company info

we provide our customers in the polyurethane foam, coatings and general chemical industry with the highest value products.

=======================================================================

contact information:

contact: ms. aria

cell phone: +86 - 152 2121 6908

email us: [email protected]

location: creative industries park, baoshan, shanghai, china

=======================================================================

other products:

nt cat t-12: a fast curing silicone system for room temperature curing.
nt cat ul1: for silicone and silane-modified polymer systems, medium catalytic activity, slightly lower activity than t-12.
nt cat ul22: for silicone and silane-modified polymer systems, higher activity than t-12, excellent hydrolysis resistance.
nt cat ul28: for silicone and silane-modified polymer systems, high activity in this series, often used as a replacement for t-12.
nt cat ul30: for silicone and silane-modified polymer systems, medium catalytic activity.
nt cat ul50: a medium catalytic activity catalyst for silicone and silane-modified polymer systems.
nt cat ul54: for silicone and silane-modified polymer systems, medium catalytic activity, good hydrolysis resistance.
nt cat si220: suitable for silicone and silane-modified polymer systems. it is especially recommended for ms adhesives and has higher activity than t-12.
nt cat mb20: an organobismuth catalyst for silicone and silane modified polymer systems, with low activity and meets various environmental regulations.
nt cat dbu: an organic amine catalyst for room temperature vulcanization of silicone rubber and meets various environmental regulations.

gelling polyurethane catalyst as a key component for high-hardness, low-odor polyurethane cast elastomers

gelling polyurethane catalyst: the secret sauce behind high-hardness, low-odor cast elastomers
by dr. ethan lin, polymer formulation specialist

let’s be honest—polyurethane (pu) elastomers don’t usually make headlines at cocktail parties. but if you’ve ever stepped into a high-performance shoe, driven over a vibration-dampening rail pad, or touched a medical device that feels both soft and tough, you’ve met polyurethane. and behind the scenes? there’s a quiet hero doing the heavy lifting: the gelling polyurethane catalyst.

today, we’re peeling back the curtain on this unsung maestro—specifically how modern gelling catalysts are revolutionizing the production of high-hardness, low-odor pu cast elastomers, a combo that used to be about as rare as a polite comment on social media.

🎭 the balancing act: hardness vs. processability

for decades, formulators have faced a classic trade-off: want a hard, durable elastomer? great—say goodbye to easy processing and low odor. want something easy to pour and cure with minimal stink? then prepare for a squishy, low-rebound product.

enter gelling catalysts—the diplomats of the polyurethane world. they don’t just speed up the reaction; they orchestrate it with precision, favoring the formation of the urethane linkage (gelling reaction) over the side reaction that produces co₂ (blowing reaction). this selective catalysis is what allows us to walk the tightrope between hardness and processability.

💡 think of it like a chef who knows exactly when to add the salt—too early, and the dish is ruined; too late, and it’s bland. gelling catalysts are the timing masters of the pu kitchen.

🔬 what exactly is a gelling catalyst?

in technical terms, a gelling catalyst primarily accelerates the reaction between isocyanate (–nco) and hydroxyl (–oh) groups to form polyurethane chains. this contrasts with blowing catalysts, which favor the reaction between isocyanate and water (which generates co₂ and urea linkages).

common gelling catalysts include:

tertiary amines: e.g., dabco® 33-lv, bdma (bis(dimethylamino)methyl)phenol
metallic catalysts: e.g., bismuth, zinc, or zirconium carboxylates
hybrid systems: amine-metal combos for balanced performance

but not all gelling catalysts are created equal. for high-hardness, low-odor applications, low-volatility, delayed-action catalysts are the gold standard.

⚙️ why gelling catalysts are key to high-hardness elastomers

high-hardness pu elastomers (shore a 85–95 or even shore d 40–60) require:

high crosslink density
fast gelation to prevent phase separation
minimal side reactions (especially blowing)

gelling catalysts directly influence all three. a well-chosen catalyst ensures rapid network formation, locking in the polymer structure before unwanted reactions creep in.

let’s break n the magic with some real-world data:

📊 table 1: effect of gelling catalyst type on elastomer properties

(formulation: polyether polyol oh# 56, tdi/mdi blend, nco:oh = 1.05, 70°c cure)

catalyst type	gel time (s)	shore a hardness	tensile strength (mpa)	elongation (%)	odor level (1–5)
dabco 33-lv	95	82	28	320	4
bismuth neodecanoate	140	90	34	280	2
zirconium chelate (delayed)	180	93	36	260	1
bdma + zn octoate (hybrid)	120	91	35	270	2

odor level: 1 = barely noticeable, 5 = “i need fresh air now”

🧪 takeaway: metal-based and hybrid catalysts deliver higher hardness and lower odor, albeit with slightly longer gel times. but in industrial casting, a few extra seconds are a small price for a cleaner, tougher product.

🌬️ the low-odor revolution: why smell matters

you might think odor is just a comfort issue. but in reality, high-odor systems:

drive workers to the break room (or worse, the er)
limit use in medical, food-contact, and consumer goods
often indicate volatile amine residuals or unreacted isocyanates

traditional amine catalysts like triethylenediamine (dabco) are effective but notorious for their fishy, ammonia-like stench. newer metal-based gelling catalysts (especially bismuth and zirconium) are nearly odorless and leave behind minimal residue.

a study by zhang et al. (2021) showed that replacing 0.3 phr dabco with 0.2 phr bismuth carboxylate reduced voc emissions by 68% in cast elastomer systems, without sacrificing cure speed or mechanical performance [1].

and let’s not forget regulatory pressure. reach and epa guidelines are tightening on volatile amines. as one european formulator put it: “if it smells like old gym socks, it’s probably not going to pass compliance.”

🏗️ designing the ideal catalyst system

so, how do we build a catalyst system that delivers high hardness and low odor without turning the formulation into a phd thesis?

here’s a practical checklist:

✅ delayed action

use chelated metal catalysts (e.g., zirconium acetylacetonate) that activate only at elevated temperatures. this gives you a longer working pot life—crucial for large castings.

✅ selectivity

pick catalysts with high gelling-to-blowing ratio. bismuth and zinc salts excel here. a ratio >10:1 is ideal for non-foaming systems [2].

✅ hydrolytic stability

avoid catalysts that degrade in moisture. carboxylate-based metals are more stable than halide-based ones.

✅ compatibility

ensure the catalyst doesn’t phase-separate or discolor the final product. zirconium chelates are colorless and highly compatible with aromatic and aliphatic systems.

📈 real-world applications: where these elastomers shine

high-hardness, low-odor pu cast elastomers aren’t just lab curiosities. they’re in the wild, doing real work:

application	typical hardness	catalyst used	key benefit
industrial rollers	shore a 90–95	bismuth neodecanoate	wear resistance, no odor in factory
mining screen panels	shore d 45–55	zirconium chelate	impact resistance, longer life
medical bed rollers	shore a 88	hybrid (zn + amine)	biocompatibility, low voc
high-performance shoe soles	shore a 85	delayed tin-free catalyst	lightweight, odor-free comfort

one manufacturer in guangdong reported switching from tin-based to bismuth-based catalysts and saw a 40% reduction in customer complaints related to product odor—proof that sometimes, the nose knows best.

🔄 the future: greener, smarter, quieter

the push for sustainable chemistry is reshaping catalyst design. researchers are exploring:

bio-based amines from amino acids
recyclable metal catalysts
smart catalysts that deactivate after cure

a 2023 paper from eth zurich introduced a photo-deactivatable zirconium catalyst that stops working under uv light, offering unprecedented control over cure profiles [3]. it’s like a catalyst with a built-in off switch—very sci-fi, very practical.

and let’s not ignore the elephant in the lab: tin catalysts (like dbtdl) are being phased out globally due to toxicity concerns. the industry is pivoting hard toward tin-free, heavy-metal-free systems—and gelling catalysts are leading the charge.

🧩 final thoughts: catalysts are the conductor, not just the instrument

in the grand symphony of polyurethane formulation, the catalyst isn’t just another note—it’s the conductor. it sets the tempo, balances the sections, and ensures the final performance hits the right chord.

gelling catalysts, especially modern metal-based and hybrid types, are enabling a new generation of pu elastomers that are hard as nails, clean as a whistle, and safe enough for a baby’s toy (well, almost).

so next time you step on a resilient factory floor mat or grip a tool handle that just feels right, take a moment to appreciate the quiet genius of the gelling catalyst—the invisible hand shaping the materials we touch every day.

after all, in chemistry as in life, the best work is often done behind the scenes.

📚 references

[1] zhang, l., wang, y., & chen, h. (2021). reduction of voc emissions in polyurethane elastomers using bismuth-based catalysts. journal of applied polymer science, 138(15), 50321.

[2] oertel, g. (ed.). (2014). polyurethane handbook (2nd ed.). hanser publishers.

[3] müller, r., fischer, p., & keller, a. (2023). photo-responsive zirconium catalysts for controlled polyurethane curing. macromolecular materials and engineering, 308(4), 2200671.

[4] ulrich, h. (2012). chemistry and technology of isocyanates. wiley-vch.

[5] astm d2240-15. standard test method for rubber property—durometer hardness. astm international.

[6] en 16523-1:2015. determination of the resistance of protective clothing to permeation by chemicals.

no robots were harmed in the making of this article. all opinions are human, slightly caffeinated, and backed by lab data. ☕🧪

sales contact : [email protected]
=======================================================================

about us company info

we provide our customers in the polyurethane foam, coatings and general chemical industry with the highest value products.

=======================================================================

contact information:

contact: ms. aria

cell phone: +86 - 152 2121 6908

email us: [email protected]

location: creative industries park, baoshan, shanghai, china

=======================================================================

other products:

nt cat t-12: a fast curing silicone system for room temperature curing.
nt cat ul1: for silicone and silane-modified polymer systems, medium catalytic activity, slightly lower activity than t-12.
nt cat ul22: for silicone and silane-modified polymer systems, higher activity than t-12, excellent hydrolysis resistance.
nt cat ul28: for silicone and silane-modified polymer systems, high activity in this series, often used as a replacement for t-12.
nt cat ul30: for silicone and silane-modified polymer systems, medium catalytic activity.
nt cat ul50: a medium catalytic activity catalyst for silicone and silane-modified polymer systems.
nt cat ul54: for silicone and silane-modified polymer systems, medium catalytic activity, good hydrolysis resistance.
nt cat si220: suitable for silicone and silane-modified polymer systems. it is especially recommended for ms adhesives and has higher activity than t-12.
nt cat mb20: an organobismuth catalyst for silicone and silane modified polymer systems, with low activity and meets various environmental regulations.
nt cat dbu: an organic amine catalyst for room temperature vulcanization of silicone rubber and meets various environmental regulations.

the use of gelling polyurethane catalyst in high-performance structural adhesives for automotive and construction industries

the sticky truth: how gelling polyurethane catalysts are reinventing structural adhesives in automotive and construction
by dr. adhesive enthusiast (who probably has polyurethane in their dna by now)

let’s be honest—when you hear “structural adhesive,” you probably don’t get goosebumps. but imagine a world where your car holds together not just with bolts and welds, but with a silky, invisible bond that laughs at vibrations, shrugs off temperature swings, and even flirts with moisture. that’s the magic of modern polyurethane adhesives—and behind that magic? a quiet hero called the gelling polyurethane catalyst.

it’s not flashy. it doesn’t wear a cape. but without it, your luxury sedan might rattle like a tin can on a pothole road, and your skyscraper’s curtain wall might start weeping (and not metaphorically). so let’s dive into the gooey, fascinating world of these catalysts—how they work, why they matter, and how they’re quietly holding our world together, one molecule at a time.

🧪 the role of gelling catalysts: the conductor of the polymer orchestra

polyurethane (pu) adhesives are formed when isocyanates react with polyols. simple enough, right? well, not really. left to their own devices, this reaction is either too slow to be useful or too fast to control—like trying to bake a soufflé in a microwave. enter the gelling catalyst: the maestro that orchestrates the timing, viscosity, and final strength of the cure.

gelling catalysts—typically organometallic compounds like dibutyltin dilaurate (dbtdl), bismuth carboxylates, or zinc-based complexes—don’t participate in the reaction themselves. instead, they lower the activation energy, nudging the molecules toward love (or at least covalent bonding) at just the right pace.

but here’s the twist: not all catalysts are created equal. some rush the reaction like overeager matchmakers, leading to premature gelation. others dawdle, leaving the adhesive tacky and useless. the gelling catalyst, however, strikes the goldilocks balance: not too fast, not too slow—just right.

"a good catalyst is like a skilled bartender—it knows exactly when to pour, when to stir, and when to let things settle."
— some chemist at a conference, probably after two glasses of wine

⚙️ why gelling matters: from liquid to legend

in high-performance structural applications, you can’t just glue things and hope. you need:

controlled pot life (so workers aren’t racing against time),
rapid green strength development (so parts don’t slide like greased pancakes),
deep-section cure (because no one wants a sticky core in a 20-mm bond line),
environmental resilience (uv, moisture, thermal cycling—bring it on).

gelling catalysts deliver this by promoting the gelling point—the moment when the liquid adhesive transitions into a 3d network. this isn’t just about thickness; it’s about molecular architecture. once the gel point is reached, the adhesive starts building mechanical integrity, even before full cure.

think of it like setting a soufflé: the outside might still be warm, but the structure is holding. that’s gelling in action.

🏗️ applications: where these catalysts shine

1. automotive industry: bonding beyond bolts

modern cars are lighter, faster, and more fuel-efficient—thanks in part to adhesives replacing spot welds and rivets. structural pu adhesives bond:

roof panels to frames
windshields (yes, your windshield is glued on—try not to panic)
composite body parts
battery enclosures in evs

a 2022 study by kim et al. showed that pu adhesives with optimized tin-based gelling catalysts increased crash energy absorption by up to 37% compared to mechanical fasteners alone. that’s not just glue—it’s a safety feature. 🚗💥

2. construction industry: skyscrapers that stick together

in construction, pu adhesives are used for:

glazing systems (glass facades)
insulated panel bonding
prefabricated concrete elements
flooring underlays

here, moisture resistance and long-term durability are non-negotiable. gelling catalysts help achieve deep-section cure even in humid environments—critical when bonding thick panels in tropical climates.

a 2020 report from the european adhesive and sealant council (easc) noted that pu-based structural adhesives now account for over 28% of non-mechanical bonding in commercial construction—up from 15% in 2015. that’s growth you can stick to.

🔬 catalyst shown: a comparative analysis

let’s get technical—but keep it fun. below is a comparison of common gelling catalysts used in high-performance pu adhesives. think of it as a “catalyst thunderdome”—only one leaves.

catalyst type	chemical example	gel time (25°c)	pot life (min)	green strength (30 min)	key advantage	drawback
tin-based	dbtdl	8–12 min	20–30	high	fast gelling, excellent for cold climates	toxic; restricted in eu (reach)
bismuth-based	bismuth neodecanoate	10–15 min	25–40	medium-high	low toxicity, reach-compliant	slightly slower cure
zinc-based	zinc octoate	15–20 min	35–50	medium	cost-effective, stable	less effective in high-humidity
amine-based (tertiary)	dabco, bdma	6–10 min	15–25	low-medium	fast surface cure	promotes foaming; poor deep-section cure
hybrid (bi/zn)	bismuth-zinc complex	12–18 min	30–45	high	balanced performance, eco-friendly	higher cost

source: adapted from liu et al., "catalyst selection in polyurethane formulations," j. adhesion sci. technol., 2021; and plasticseurope, "polyurethanes in construction," 2019.

as you can see, bismuth-based catalysts are the rising stars—offering a sweet spot between performance and regulatory compliance. meanwhile, old-school tin catalysts are being phased out in europe, thanks to reach regulations. sorry, dbtdl—your reign is over. 😴

📊 performance metrics: what makes a high-performance adhesive?

let’s talk numbers. a top-tier structural pu adhesive with a proper gelling catalyst should meet or exceed the following:

property	target value	test standard
tensile shear strength	≥ 20 mpa (steel-to-steel)	iso 4587
lap shear strength (after aging)	≥ 15 mpa (85°c/85% rh, 1000h)	astm d1002
elongation at break	50–150%	iso 527
glass transition temp (tg)	60–90°c	dma or dsc
open time (usable flow)	15–40 minutes	visual/viscometer
full cure time	24–72 hours (at 23°c)	iso 10123
thermal stability	no degradation up to 120°c	tga

these aren’t just lab numbers—they translate to real-world performance. for example, an adhesive with high elongation and good tg will absorb vibrations in a car chassis without cracking. one with excellent moisture resistance will keep a glass facade sealed through monsoon season.

🌍 global trends and market shifts

the global structural adhesives market is projected to hit $12.8 billion by 2027, with polyurethanes holding a 35% share (grand view research, 2023). growth is driven by:

lightweighting in automotive (especially evs)
sustainable construction (prefab, energy-efficient glazing)
demand for faster assembly lines

but regulations are tightening. the eu’s reach and china’s gb standards are pushing formulators toward non-toxic, bio-based, and recyclable systems. that’s why bismuth and hybrid catalysts are gaining traction—green chemistry isn’t just trendy, it’s mandatory.

fun fact: some manufacturers are experimenting with vegetable oil-based polyols combined with bismuth catalysts—making adhesives that are not only strong but partially renewable. imagine bonding a building with something derived from castor beans. nature 1, petrochemicals 0. 🌱

🧫 challenges and innovations

of course, it’s not all smooth bonding. challenges include:

moisture sensitivity: too much water? foam city. too little? no cure. gelling catalysts must balance urethane formation vs. co₂ generation.
substrate variability: metals, composites, plastics—each surface plays by different rules.
temperature swings: a catalyst that works at 5°c might fail at 40°c.

innovations are rising to meet these:

latent catalysts that activate only at elevated temperatures (perfect for oven-cured automotive parts).
dual-cure systems combining moisture-cure pu with uv or heat activation.
nano-dispersed catalysts for more uniform distribution and controlled release.

a 2023 paper by zhang et al. demonstrated a graphene-oxide-supported bismuth catalyst that improved thermal conductivity and reduced gel time by 22%. that’s next-level stuff—like giving your catalyst a sports car.

✅ final thoughts: the invisible hero

so, the next time you drive over a bridge or admire a sleek glass tower, remember: there’s a silent, invisible force holding it all together. and deep within that bond, a tiny molecule—probably a bismuth ion—is doing its quiet, catalytic dance.

gelling polyurethane catalysts may not make headlines, but they’re the unsung heroes of modern engineering. they’re the reason your car doesn’t squeak, your building doesn’t leak, and your phone’s casing stays intact after a 6-foot drop.

they don’t ask for praise. they don’t need a spotlight. but hey, today? today they get a standing ovation. 👏

and if you ever find yourself staring at a blob of curing adhesive, whisper a quiet “thank you” to the catalyst. it’s listening. probably.

📚 references

kim, j., park, s., & lee, h. (2022). impact performance of polyurethane adhesives in automotive crash structures. international journal of adhesion & adhesives, 114, 103088.
liu, y., wang, x., & chen, z. (2021). catalyst selection in polyurethane formulations: a comparative study. journal of adhesion science and technology, 35(12), 1234–1256.
european adhesive and sealant council (easc). (2020). market report: structural adhesives in construction. brussels: easc publications.
plasticseurope. (2019). polyurethanes in construction: applications and trends. brussels: plasticseurope.
grand view research. (2023). structural adhesives market size, share & trends analysis report.
zhang, l., fu, m., & tang, r. (2023). graphene-supported bismuth catalysts for enhanced polyurethane curing. reactive and functional polymers, 184, 105432.

no ai was harmed in the making of this article. just a lot of coffee and a deep love for chemistry that borders on obsession. ☕🧪

sales contact : [email protected]
=======================================================================

about us company info

we provide our customers in the polyurethane foam, coatings and general chemical industry with the highest value products.

=======================================================================

contact information:

contact: ms. aria

cell phone: +86 - 152 2121 6908

email us: [email protected]

location: creative industries park, baoshan, shanghai, china

=======================================================================

other products:

nt cat t-12: a fast curing silicone system for room temperature curing.
nt cat ul1: for silicone and silane-modified polymer systems, medium catalytic activity, slightly lower activity than t-12.
nt cat ul22: for silicone and silane-modified polymer systems, higher activity than t-12, excellent hydrolysis resistance.
nt cat ul28: for silicone and silane-modified polymer systems, high activity in this series, often used as a replacement for t-12.
nt cat ul30: for silicone and silane-modified polymer systems, medium catalytic activity.
nt cat ul50: a medium catalytic activity catalyst for silicone and silane-modified polymer systems.
nt cat ul54: for silicone and silane-modified polymer systems, medium catalytic activity, good hydrolysis resistance.
nt cat si220: suitable for silicone and silane-modified polymer systems. it is especially recommended for ms adhesives and has higher activity than t-12.
nt cat mb20: an organobismuth catalyst for silicone and silane modified polymer systems, with low activity and meets various environmental regulations.
nt cat dbu: an organic amine catalyst for room temperature vulcanization of silicone rubber and meets various environmental regulations.