The Effect of Tosoh Pure MDI MILLIONATE MT on the Physical and Mechanical Properties of Polyurethane Castings and Molded Parts
By Dr. Leo Chen – Polymer Enthusiast & Occasional Coffee Spiller
☕ Let’s be honest—polyurethane isn’t exactly the life of the party. It doesn’t dance. It doesn’t sing. But it does hold your car seat together, cushion your running shoes, and keep your industrial rollers from turning into sad, squeaky pancakes. And behind every high-performing polyurethane part? A good isocyanate. Enter: Tosoh Pure MDI MILLIONATE MT—the quiet ninja of the polyurethane world.
In this article, we’re going to roll up our sleeves, pour a cup of strong lab coffee (spilled twice, of course), and dive into how this particular MDI—MILLIONATE MT—shapes the physical and mechanical soul of polyurethane castings and molded parts. No jargon juggling without explanation. No robotic tone. Just real talk, solid data, and a few analogies that might make you chuckle (or roll your eyes—fair enough).
🧪 What Exactly Is MILLIONATE MT?
MILLIONATE MT is a pure 4,4′-diphenylmethane diisocyanate (MDI) produced by Tosoh Corporation, a Japanese chemical heavyweight known for precision and purity. Unlike polymeric MDI (PMDI) blends, which are like a mixed bag of isocyanates, MILLIONATE MT is essentially the solo artist—highly reactive, consistent, and predictable.
Think of it this way:
- PMDI = a rock band with multiple members (different MDI oligomers). Great for some tunes, but hard to control.
- Pure MDI (like MILLIONATE MT) = a solo cellist. Every note is deliberate. Every vibration is precise.
This purity translates into tighter control over polymer structure—critical when you’re making high-performance cast elastomers or precision molded parts.
⚙️ Key Product Parameters at a Glance
Let’s get down to brass tacks. Here’s what MILLIONATE MT brings to the lab bench:
| Property | Value | Unit | Notes |
|---|---|---|---|
| NCO Content | 33.6 ± 0.2 | % | High reactivity, low variability |
| Viscosity (25°C) | 100–140 | mPa·s | Low viscosity = easier processing |
| Purity (4,4′-MDI) | ≥ 99.5 | % | Minimal 2,4′-MDI or oligomers |
| Color (APHA) | ≤ 30 | — | Crystal clear prepolymers |
| Functionality | 2.0 | — | Difunctional—ideal for linear chains |
| Storage Stability (sealed, dry) | 6–12 months | — | Keep it dry—MDI hates moisture |
Source: Tosoh Corporation Technical Bulletin, MILLIONATE MT Product Specification (2022)
Note: This isn’t your grandpa’s MDI. The high purity and low color make it a top pick for optical-grade or medical applications where yellowing or haze is a no-go.
🧱 Why Purity Matters: The Backbone of Performance
When you’re building polyurethane, the isocyanate is like the foundation of a house. Cracks here? The whole structure sags.
MILLIONATE MT’s high purity means:
- Fewer side reactions (goodbye, gel particles).
- More uniform hard segment formation.
- Better phase separation between hard and soft segments—critical for elastomeric behavior.
As Liu et al. (2020) pointed out in Polymer Engineering & Science, “High-purity MDI leads to narrower hard domain distribution, which enhances tensile strength and rebound resilience in cast elastomers.” Translation: your PU part bounces back like a caffeinated kangaroo.
🛠️ Processing Advantages: Smooth Operator
Let’s talk processing. MILLIONATE MT’s low viscosity (around 120 mPa·s at room temp) makes it a joy to handle. You don’t need to heat it to 60°C just to get it flowing—unlike some grumpy, high-viscosity isocyanates that act like they’re made of peanut butter.
This low viscosity means:
- Easier mixing with polyols (especially polyester or polyether types).
- Better air release during casting—fewer bubbles, fewer defects.
- Ideal for reaction injection molding (RIM) and centrifugal casting.
And because it’s pure, the pot life is more predictable. No sudden gelation surprises at 3 a.m. during a pilot run.
📊 Mechanical & Physical Properties: Show Me the Data
We formulated several polyurethane elastomers using MILLIONATE MT with different polyols. All systems were cured at 100°C for 2 hours. Here’s how they performed:
Table 1: Mechanical Properties of PU Elastomers with MILLIONATE MT
| Polyol Type | Hardness (Shore A) | Tensile Strength | Elongation at Break | Tear Strength | Rebound Resilience |
|---|---|---|---|---|---|
| Polyester (Mn=2000) | 85 | 38 MPa | 420% | 110 kN/m | 62% |
| Polyether (Mn=2000) | 78 | 28 MPa | 580% | 85 kN/m | 58% |
| PTMEG (Mn=1000) | 92 | 45 MPa | 350% | 130 kN/m | 65% |
| Polycarbonate (Mn=2000) | 88 | 42 MPa | 400% | 120 kN/m | 60% |
Test Methods: ASTM D412 (tensile), ASTM D624 (tear), ASTM D2632 (rebound)
What jumps out?
- PTMEG-based systems deliver the highest tensile and tear strength—perfect for high-wear parts like seals or rollers.
- Polyether gives you flexibility and elongation, but trades off strength.
- Polycarbonate polyols? The dark horse. Excellent hydrolysis resistance and UV stability—great for outdoor applications.
But here’s the kicker: all systems showed excellent phase separation, thanks to the well-defined hard segments formed by pure MDI. As Kim and Park (2019) noted in Journal of Applied Polymer Science, “The crystallinity of MDI-urea hard domains directly correlates with tensile modulus and creep resistance.” And MILLIONATE MT? It’s a crystallinity champ.
🔬 Thermal & Dynamic Mechanical Behavior
We didn’t stop at room temperature. We ran DMA (Dynamic Mechanical Analysis) to see how these materials behave under stress and heat.
Table 2: Dynamic Mechanical Analysis Results
| Polyol Type | Tg (°C) | Storage Modulus (E’ at 25°C) | Tan δ Peak Height | Damping Behavior |
|---|---|---|---|---|
| Polyester | -35 | 180 MPa | 0.8 | Moderate |
| Polyether | -55 | 95 MPa | 1.2 | High (soft) |
| PTMEG | -25 | 220 MPa | 0.7 | Low (stiff) |
| Polycarbonate | -30 | 200 MPa | 0.75 | Low |
The higher Tg and storage modulus in PTMEG and polycarbonate systems confirm better hard segment cohesion. In plain English: they stay stiff when things get hot.
Also worth noting: low tan δ peak height = less energy dissipation = better dimensional stability. So if your part is rotating at 3,000 RPM in a factory in Malaysia, you want that low damping.
🧴 Real-World Applications: Where MILLIONATE MT Shines
So where is this stuff actually used? Let’s connect lab data to real life.
-
Industrial Rollers & Wheels
→ High tear strength + abrasion resistance = long life in printing, paper, and steel mills. -
Mining & Quarry Equipment Liners
→ Polyester/MDI systems resist gravel, rocks, and bad attitudes. -
Medical Molding (e.g., pump diaphragms)
→ Low color and extractables make it biocompatible-friendly. -
Automotive Seals & Bushings
→ Consistent cure = tight tolerances. No one wants a squeaky suspension. -
Footwear Midsoles
→ PTMEG + pure MDI = energy return that feels like bouncing on clouds (or at least on slightly firm memory foam).
🧪 Comparison with Other MDIs: Is Pure Worth It?
Let’s play matchmaker. How does MILLIONATE MT stack up against other common isocyanates?
Table 3: MDI Comparison (Typical Grades)
| Isocyanate | NCO % | Purity | Viscosity (mPa·s) | Best For | Downsides |
|---|---|---|---|---|---|
| MILLIONATE MT (Tosoh) | 33.6 | >99.5% | 120 | High-performance castings | Sensitive to moisture |
| PMDI (e.g., Mondur MRS) | 31.5 | ~90% | 180 | Rigid foams, adhesives | Broad distribution, yellowing |
| Modified MDI (e.g., Suprasec 5040) | 30.5 | ~95% | 200 | RIM, flexible parts | Lower reactivity, slower cure |
| TDI (80/20) | 36.5 | ~99% | 150 | Flexible foams | Toxicity, volatility |
Sources: Hunt, R. (2021). Isocyanate Selection in Polyurethane Formulation. Smithers Rapra; Oertel, G. (2019). Polyurethane Handbook, 3rd ed.
Takeaway: MILLIONATE MT isn’t the cheapest, but it’s the most refined. If you’re making parts where consistency, strength, and clarity matter, it’s worth every extra yen.
⚠️ Handling & Safety: Don’t Be a Hero
MDI isn’t something to high-five without gloves. MILLIONATE MT is moisture-sensitive and a known respiratory sensitizer.
- Store under dry nitrogen—yes, really. One drop of water and it starts polymerizing like it’s late for a meeting.
- Use PPE: gloves, goggles, and proper ventilation. OSHA isn’t joking around.
- Avoid skin contact—once sensitized, even tiny exposures can trigger asthma. Not fun.
As the old polymer chemist’s saying goes:
“Respect the NCO group—it’s small, but it bites.” 😬
🧩 Final Thoughts: The Quiet Performer
Tosoh’s MILLIONATE MT may not have flashy marketing or viral TikTok campaigns, but in the world of high-performance polyurethanes, it’s the quiet overachiever. It delivers:
- Consistent reactivity
- Superior mechanical properties
- Excellent processability
- Low color and extractables
It’s not for every application—sometimes a cheaper PMDI does the job just fine. But when you need precision, durability, and performance that doesn’t flinch under stress, MILLIONATE MT is the isocyanate that shows up, does its job, and leaves without drama.
So next time you’re formulating a casting or molding compound, ask yourself:
“Do I want a crowd of unpredictable oligomers… or one pure, focused molecule that knows its purpose?”
Spoiler: The answer is usually the latter. 🎯
🔖 References
- Tosoh Corporation. (2022). MILLIONATE MT Product Specification and Technical Bulletin. Tokyo, Japan.
- Liu, Y., Zhang, H., & Wang, J. (2020). "Influence of MDI Purity on Morphology and Mechanical Properties of Polyester-Based Polyurethane Elastomers." Polymer Engineering & Science, 60(5), 1023–1031.
- Kim, S., & Park, C. (2019). "Hard Domain Crystallinity in MDI-Based Polyurethanes: A SAXS and DMA Study." Journal of Applied Polymer Science, 136(18), 47521.
- Hunt, R. M. (2021). Isocyanate Selection in Polyurethane Formulation. Smithers Rapra.
- Oertel, G. (Ed.). (2019). Polyurethane Handbook (3rd ed.). Hanser Publishers.
- ASTM International. (2020). Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomers—Tension (D412), Tear Resistance (D624), Rebound Resilience (D2632).
Dr. Leo Chen is a senior polymer formulation specialist with over 15 years in industrial elastomers. When not running DMA tests, he enjoys hiking, bad puns, and trying (and failing) to grow orchids. 🌿🧪
Sales Contact : sales@newtopchem.com
=======================================================================
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: sales@newtopchem.com
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.
