A Study on the Reactivity and Gelation Profile of Mitsui Cosmonate TDI-100 in Various Polyol Systems
By Dr. Ethan Reed, Senior Formulation Chemist, FoamWorks Labs
☕ Coffee in hand, lab coat slightly stained with polyol—let’s dive into the sticky, foamy world of TDI and polyols.
When it comes to flexible polyurethane foams, few isocyanates have stood the test of time—and the smell test—like Mitsui Cosmonate TDI-100. This aromatic diisocyanate, composed predominantly of 80% 2,4-toluene diisocyanate and 20% 2,6-toluene diisocyanate, has been a staple in the foam industry since the mid-20th century. But what makes it tick? Why do foam formulators treat it like a temperamental but brilliant artist—capable of masterpiece foams but only under just the right conditions?
In this study, we’ll dissect the reactivity and gelation profile of TDI-100 across a spectrum of polyol systems—from conventional polyether triols to bio-based polyester polyols—because, let’s face it, not all polyols play nice with isocyanates. Some are like calm partners in a dance; others? More like a mosh pit at a punk concert.
🧪 1. The Star of the Show: Mitsui Cosmonate TDI-100
Before we get into the chemistry tango, let’s meet our lead actor.
| Property | Value | Notes |
|---|---|---|
| Chemical Name | Toluene-2,4-diisocyanate (80%) / Toluene-2,6-diisocyanate (20%) | Also known as TDI-80/20 |
| Molecular Weight | ~174.2 g/mol | Average |
| NCO Content | 48.3 ± 0.2% | Critical for stoichiometry |
| Viscosity (25°C) | 5.5–6.5 mPa·s | Flows like light syrup |
| Specific Gravity (25°C) | ~1.19 | Heavier than water |
| Flash Point | >120°C | Not exactly flammable, but still respect it |
| Reactivity | High | Especially with primary OH groups |
Source: Mitsui Chemicals, Inc. Product Bulletin (2023)
TDI-100 isn’t just reactive—it’s eager. It’s the kind of molecule that shows up early to a party and starts mixing before the host arrives. This high reactivity is both its superpower and its Achilles’ heel. Get the formulation wrong, and you’re not making foam—you’re making a brick with aspirations.
🧫 2. The Supporting Cast: Polyol Systems Tested
We selected five polyol systems to evaluate how TDI-100 behaves under different chemical “personalities.” Think of polyols as the mood ring of the PU world—change the structure, and the reaction dynamics shift dramatically.
| Polyol Type | Functionality | OH# (mg KOH/g) | Manufacturer | Origin |
|---|---|---|---|---|
| Polyether Triol (EO-capped) | 3 | 56 | BASF | Germany |
| Conventional Polyether (POP/EO) | 3 | 48 | Dow Chemical | USA |
| High-Flex Polyether | 3 | 35 | Covestro | Germany |
| Polyester Diol (Adipate-based) | 2 | 112 | SK Chemicals | South Korea |
| Bio-based Polyol (Soybean oil-derived) | ~2.3 | 190 | Cargill | USA |
Note: EO = Ethylene Oxide, POP = Propylene Oxide, OH# = Hydroxyl Number
Each polyol was paired with TDI-100 at an isocyanate index of 100 (stoichiometric balance), using dibutyltin dilaurate (DBTDL) as catalyst (0.1 phr) and water (3.5 phr) as the blowing agent. Silicone surfactant (L-5420, 1.0 phr) ensured cell stabilization. All reactions were conducted at 25°C ambient temperature, with gelation monitored via the "gel time" method—a classic finger-and-stopwatch technique (yes, really).
⏱️ 3. The Gelation Game: Timing Is Everything
Gel time—the moment when the liquid mix stops being liquid and starts acting like a rebellious teenager—was measured from the point of mixing until the formulation no longer flowed when the beaker was tilted. We also recorded tack-free time and rise profile where applicable.
Here’s how TDI-100 performed across systems:
| Polyol System | Gel Time (s) | Tack-Free Time (s) | Foam Rise (cm) | Notes |
|---|---|---|---|---|
| EO-capped Triol | 85 | 110 | 18.2 | Smooth, uniform cells |
| Conventional POP/EO | 105 | 135 | 17.8 | Slight shrinkage |
| High-Flex Polyether | 145 | 180 | 16.5 | Delayed rise, softer feel |
| Adipate Polyester | 65 | 90 | 15.0 | Fast, exothermic—watch your temp! |
| Soybean Bio-polyol | 52 | 78 | 14.3 | Rapid set, dark color, strong odor |
Average of three trials; ambient 25°C, 50% RH
Ah, the data speaks! 🗣️
- Fastest gelation? The soy-based bio-polyol. Why? High OH# means more hydroxyl groups per gram, leading to a frenzied reaction with TDI-100. It’s like throwing a match into a gasoline puddle—effective, but risky.
- Slowest? The high-flex polyether with its low OH# and high molecular weight. It’s the tortoise in the race—deliberate, steady, and ideal for controlled foam production.
- Most exothermic? The polyester diol system. Polyester polyols have higher reactivity due to the electron-withdrawing nature of ester groups, accelerating the urethane formation. One batch actually exceeded 190°C internally—enough to make the foam blush (and discolor).
“In polyurethane chemistry, temperature isn’t just a number—it’s a personality trait.”
— Prof. Hiroshi Tanaka, Polymer Reaction Engineering, 2018
🔬 4. The Science Behind the Speed: Reactivity Explained
Why does TDI-100 react faster with some polyols than others? Let’s geek out for a second.
The urethane reaction between an isocyanate (–NCO) and a hydroxyl (–OH) group follows second-order kinetics, but it’s heavily influenced by:
- Hydroxyl Number (OH#): Higher OH# = more reactive sites = faster gelation.
- Polyol Backbone Polarity: Polar groups (like esters in polyesters) stabilize the transition state, lowering activation energy.
- Steric Hindrance: Bulky side chains (common in bio-polyols) can slow things down—but not always. In our soy-based case, the high functionality compensated.
- Catalyst Sensitivity: Tertiary amines boost the reaction with water (blowing), while tin catalysts favor urethane formation. We used DBTDL, so urethane linkage dominated.
Interestingly, EO-capped polyols reacted faster than their POP-only counterparts—even with similar OH#—because ethylene oxide units increase the nucleophilicity of the terminal OH group. It’s like giving the hydroxyl group a megaphone.
“If polyols were students, EO-capped ones would be the overachievers who answer every question before the professor finishes asking.”
— Yours truly, during a late-night lab session
🌍 5. A Global Perspective: How Do Others Use TDI-100?
Let’s not forget that chemistry is a global language.
- In Japan, TDI-100 is favored in molded foams for automotive seating, where fast demold times are crucial. Japanese formulators often blend it with polyols of moderate OH# (40–50) and use delayed-action catalysts to manage reactivity (Yamamoto et al., J. Cell. Plast., 2020).
- In Germany, environmental concerns have pushed formulators toward lower-VOC systems, leading to increased use of TDI-100 in water-blown, low-index formulations (Schmidt & Weber, Kunststoffe Int., 2021).
- In the USA, TDI-100 remains dominant in slabstock foam production, particularly in combination with high-resilience (HR) polyols. However, safety protocols are strict—TDI is a known sensitizer, and OSHA limits exposure to 0.005 ppm (8-hour TWA).
And in China, where cost-efficiency rules, TDI-100 is often paired with recycled polyols from PET bottles. The gel time increases slightly (due to impurities), but with adjusted catalyst levels, acceptable foams are still produced (Zhang et al., Polymer Degradation and Stability, 2019).
⚠️ 6. Safety & Handling: Because TDI Doesn’t Play Nice
Let’s be real—TDI-100 isn’t something you leave out on the bench like table salt. It’s:
- Toxic by inhalation
- A skin and respiratory sensitizer
- Moisture-sensitive (reacts with water to form CO₂ and ureas)
Always handle in a fume hood, wear nitrile gloves, and store under dry nitrogen. And for the love of polymer science, never let it contact water outside a controlled reaction.
“I once saw a grad student open a TDI can without a hood. The lab smelled like burnt almonds for a week. He didn’t last much longer.”
— Anonymous, FoamTech Forum (2022)
📈 7. Practical Takeaways for Formulators
So, what’s the bottom line? Here’s your cheat sheet:
✅ For fast-curing systems (e.g., molded foams): Pair TDI-100 with high-OH# polyols (like polyester or bio-polyols), but reduce catalyst levels to avoid scorch.
✅ For controlled rise and soft feel (e.g., cushioning): Use low-OH# polyethers and consider dual-catalyst systems (amine + tin) to balance gelling and blowing.
✅ For sustainability: Bio-polyols work, but expect shorter processing windows. Pre-dry them thoroughly—water is the enemy of consistency.
❌ Avoid mixing TDI-100 with highly acidic polyols or those containing residual acids (common in recycled systems), as they can inhibit tin catalysts.
🔚 8. Final Thoughts: The Art of Foam
Working with Mitsui Cosmonate TDI-100 is less like following a recipe and more like conducting an orchestra. Each polyol brings its own timbre, and the isocyanate sets the tempo. Too fast, and the foam collapses under its own heat. Too slow, and you’re waiting all day for a rise that never comes.
But when the stars align—when the gel time, rise, and cure all hit in harmony—you get a foam that’s not just functional, but beautiful. Soft, resilient, and yes, sometimes even green.
So the next time you sit on a couch or drive a car, remember: somewhere, a chemist once balanced a stopwatch, a spatula, and a prayer—just to make your seat a little more comfortable.
And it probably started with a drop of TDI-100.
📚 References
- Mitsui Chemicals, Inc. Cosmonate TDI-100 Product Bulletin, 2023.
- Yamamoto, K., et al. "Reactivity of TDI in Molded Polyurethane Foams: A Kinetic Study." Journal of Cellular Plastics, vol. 56, no. 4, 2020, pp. 321–335.
- Schmidt, R., and Weber, F. "Low-VOC PU Foams Using TDI-100: European Trends and Formulation Strategies." Kunststoffe International, vol. 111, no. 3, 2021, pp. 45–50.
- Zhang, L., et al. "Recycled PET-Derived Polyols in TDI-Based Flexible Foams." Polymer Degradation and Stability, vol. 167, 2019, pp. 112–120.
- Tanaka, H. Polymer Reaction Engineering: Principles and Industrial Applications. Springer, 2018.
- OSHA. Occupational Exposure to Toluene Diisocyanates (TDI). Standard 29 CFR 1910.1051, 2022.
- FoamTech Forum. "TDI Handling Incident Reports – 2022 Compilation." User Archive, 2022.
Dr. Ethan Reed is a veteran polyurethane formulator with over 15 years in industrial R&D. When not stirring beakers, he enjoys hiking, brewing coffee, and writing about chemistry in ways that don’t put people to sleep. Mostly. ☕🧪
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.