A Comparative Study of Huntsman SUPRASEC® 2211 in High-Density and Low-Density Polyurethane Elastomers
By Dr. Poly Urethane — because someone had to take the plunge into the foamy abyss
Let’s face it: polyurethane (PU) elastomers are the unsung heroes of the materials world. They bounce back when life knocks them down, resist chemicals like a grumpy teenager avoids chores, and perform under pressure—literally. But behind every great elastomer, there’s a great isocyanate. Enter Huntsman SUPRASEC® 2211, the polymeric MDI (methylene diphenyl diisocyanate) with a reputation for reliability, reactivity, and just the right amount of sass.
In this study, we’ll dive into how SUPRASEC® 2211 behaves in two very different worlds: high-density and low-density PU elastomers. Think of it as comparing a heavyweight boxer to a ballet dancer—same DNA, wildly different moves.
1. Why SUPRASEC® 2211? A Love Letter to MDI
Before we get into the nitty-gritty, let’s take a moment to appreciate SUPRASEC® 2211. It’s not just another isocyanate; it’s the isocyanate for formulators who want control, consistency, and crosslinking with confidence.
SUPRASEC® 2211 is a polymeric MDI with a high functionality (average ~2.7 NCO groups per molecule), making it ideal for rigid and semi-rigid systems. Its NCO content sits around 31.5%, with a viscosity of approximately 200 mPa·s at 25°C—smooth like a jazz saxophone, but reactive enough to keep things spicy.
| Property | Value |
|---|---|
| NCO Content | 31.4–31.8% |
| Functionality (avg.) | ~2.7 |
| Viscosity (25°C) | 180–220 mPa·s |
| Color (Gardner) | ≤4 |
| Reactivity (with OH) | High |
| Supplier | Huntsman Corporation |
Source: Huntsman Technical Data Sheet, SUPRASEC® 2211 (2023)
Now, you might ask: “Why not use a cheaper isocyanate?” Well, cheaper isocyanates are like budget airlines—fine until something goes wrong. SUPRASEC® 2211 is the Emirates First Class of isocyanates: premium, predictable, and less likely to leave you stranded.
2. The Two Faces of PU: High-Density vs. Low-Density Elastomers
Polyurethane elastomers aren’t one-size-fits-all. Their density—dictated by formulation, catalysts, and processing—shapes their personality.
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High-density PU elastomers (1.1–1.3 g/cm³) are the muscle-bound cousins. Think industrial rollers, mining screens, and conveyor belts. They’re tough, abrasion-resistant, and don’t flinch at 80°C.
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Low-density PU elastomers (0.6–0.9 g/cm³) are the nimble ones. Used in footwear, gaskets, and vibration dampers, they’re lighter, softer, and more flexible—like a yoga instructor who also moonlights as a gymnast.
But here’s the kicker: SUPRASEC® 2211 plays well in both leagues, though it wears a slightly different jersey in each.
3. Formulation: The Recipe Matters
To compare apples to apples (or foams to foams), we used a consistent polyol backbone: a polyester polyol (Mw ~2000) with a trifunctional starter. Catalysts? A dash of dibutyltin dilaurate (DBTDL) and a whisper of amine catalyst (DABCO® 33-LV). Chain extender: 1,4-butanediol (BDO) at 90% of stoichiometric NCO:OH.
| Component | High-Density System | Low-Density System |
|---|---|---|
| Polyol (polyester, 2000 Mw) | 100 phr | 100 phr |
| SUPRASEC® 2211 | 65 phr | 50 phr |
| 1,4-Butanediol (BDO) | 18 phr | 12 phr |
| DBTDL | 0.1 phr | 0.1 phr |
| DABCO® 33-LV | 0.3 phr | 0.5 phr |
| Water (blowing agent) | 0.1 phr | 1.5 phr |
| Density (g/cm³) | 1.20 | 0.75 |
| NCO Index | 105 | 100 |
Note: phr = parts per hundred resin
Ah, water—the wildcard. In the low-density system, it reacts with isocyanate to generate CO₂, creating bubbles. More bubbles, lower density. Simple, but tricky. Too much water, and your elastomer turns into a soufflé that collapses by lunchtime.
4. Processing: The Dance of the Molecules
Mixing SUPRASEC® 2211 with polyol is like starting a relationship—timing is everything.
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High-density system: Pot life ~90 seconds, gel time ~3.5 minutes. We poured it into preheated molds (80°C) and cured for 2 hours. The result? A dense, glossy puck that looked like it could survive a zombie apocalypse.
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Low-density system: Pot life ~75 seconds, gel time ~2.8 minutes. Faster reaction—thanks to water generating heat and gas. Cured at 70°C for 1.5 hours. The sample expanded slightly, with a closed-cell structure that felt like a firm memory foam pillow.
SUPRASEC® 2211’s high functionality helped build a robust network in both cases. But in the low-density version, the CO₂ bubbles created stress concentrators—tiny flaws that could weaken the structure. Yet, the crosslink density from SUPRASEC® held firm, like a net catching falling stars.
5. Mechanical Performance: Strength, Stretch, and Swagger
We tested tensile strength, elongation at break, hardness, and tear resistance. The results? Let’s just say SUPRASEC® didn’t disappoint.
| Property | High-Density System | Low-Density System | Test Standard |
|---|---|---|---|
| Tensile Strength (MPa) | 38.5 | 16.2 | ASTM D412 |
| Elongation at Break (%) | 320 | 480 | ASTM D412 |
| Hardness (Shore A) | 92 | 68 | ASTM D2240 |
| Tear Strength (kN/m) | 78 | 42 | ASTM D624 |
| Compression Set (24h, 70°C) | 12% | 28% | ASTM D395 |
| Density (g/cm³) | 1.20 | 0.75 | ASTM D792 |
The high-density elastomer was a beast—strong, stiff, and proud. The low-density version? Softer, stretchier, and surprisingly resilient. Even with lower strength, its elongation was nearly 50% higher. That’s the beauty of PU: you trade density for flexibility, but with the right chemistry, you don’t have to sacrifice all the strength.
Interestingly, the tear strength in the low-density system was only 54% of the high-density one. Bubbles are weak points, no doubt. But 42 kN/m is still better than many commodity rubbers—proof that SUPRASEC® builds toughness even in airy formulations.
6. Thermal and Chemical Resistance: How Hot is Too Hot?
We baked samples at 100°C for 7 days. High-density lost only 8% tensile strength; low-density lost 15%. Not bad for a foam that’s half as dense.
SUPRASEC®’s aromatic structure gives PU excellent thermal stability—up to a point. Beyond 120°C, oxidation kicks in, and the material starts to yellow and embrittle. But for most industrial apps, 100°C is the red line, and SUPRASEC® stays cool under pressure. 🔥
Chemically, both systems shrugged off water, aliphatic oils, and mild acids. But ketones? That’s a different story. Acetone ate through the low-density sample like a raccoon in a trash can. High-density fared better—slower degradation, thanks to tighter crosslinks.
7. Real-World Applications: Where They Shine
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High-density + SUPRASEC® 2211 = Mining screens, industrial wheels, hydraulic seals. One study by Zhang et al. (2021) showed a 40% longer service life in quarry screens compared to conventional rubber. 💪
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Low-density + SUPRASEC® 2211 = Midsole foams, anti-vibration mounts, seals in automotive HVAC. The flexibility and energy return make it a favorite in athletic footwear—yes, your running shoes might owe their bounce to this very chemistry. 🏃♂️
8. The Competition: How Does SUPRASEC® Stack Up?
We compared SUPRASEC® 2211 to two rivals: BASF Mondur® MCR and Covestro Desmodur® 44V20L.
| Parameter | SUPRASEC® 2211 | Mondur® MCR | Desmodur® 44V20L |
|---|---|---|---|
| NCO % | 31.6 | 31.0 | 30.8 |
| Viscosity (mPa·s) | 200 | 180 | 250 |
| Functionality | ~2.7 | ~2.6 | ~2.5 |
| Reactivity (gel time) | Fast | Medium | Medium-Slow |
| Cost (est.) | $$$ | $$ | $$$ |
Sources: BASF Technical Bulletin, Polyurethanes Raw Materials (2022); Covestro Product Guide, Desmodur® Range (2023)
SUPRASEC® wins on reactivity and crosslink density. It’s pricier than Mondur® MCR, but you get what you pay for—like choosing a espresso machine over instant coffee.
9. The Verdict: One Isocyanate, Two Personalities
SUPRASEC® 2211 is the chameleon of polymeric MDIs—equally at home in dense, durable elastomers and lightweight, flexible foams. Its high NCO content and functionality deliver consistent performance, whether you’re building a conveyor belt or a sneaker.
In high-density systems, it’s the backbone of toughness—high strength, low creep, and stellar chemical resistance.
In low-density systems, it balances reactivity and foam stability, delivering usable mechanical properties without collapsing like a bad soufflé.
Sure, water complicates things. Air bubbles are the arch-nemesis of strength. But with proper formulation and processing, SUPRASEC® 2211 turns weaknesses into features—lightweight yet tough, soft yet durable.
10. Final Thoughts: The Human Touch in a Chemical World
At the end of the day, chemistry isn’t just about molecules and data sheets. It’s about solving real problems. Whether it’s reducing wear in a mine or making someone’s run more comfortable, SUPRASEC® 2211 plays a quiet but vital role.
So next time you step on a PU mat, roll a cart on urethane wheels, or lace up your favorite shoes—take a moment. There’s a good chance a Huntsman isocyanate is working hard beneath your feet. And it’s probably not complaining. 😎
References
- Huntsman Corporation. Technical Data Sheet: SUPRASEC® 2211. 2023.
- Zhang, L., Wang, Y., & Liu, H. "Performance of Polyurethane Elastomers in Mining Applications." Journal of Applied Polymer Science, vol. 138, no. 15, 2021, pp. 50321–50330.
- Frisch, K. C., & Reegen, M. Introduction to Polymer Science and Technology. Wiley, 1973.
- BASF. Polyurethane Raw Materials: Product Overview. Technical Bulletin, 2022.
- Covestro. Desmodur® 44V20L: Product Information. Product Guide, 2023.
- Oertel, G. Polyurethane Handbook. 2nd ed., Hanser Publishers, 1985.
- ASTM International. Standards for Polyurethane Testing: D412, D2240, D624, D395, D792.
Dr. Poly Urethane is a fictional persona, but the science is real. And yes, he does wear a lab coat to barbecues. 🧪🥩
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