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Low-viscosity liquid trimer based on toluene diisocyanate (TDI), enabling easy handling and homogeneous mixing with polyol components.
Excellent compatibility with polyester and polyether polyols, supporting broad formulation flexibility in two-component polyurethane systems.
Provides fast room-temperature curing kinetics while maintaining sufficient pot life for industrial processing.
Delivers high crosslink density, resulting in superior chemical resistance, hardness, and abrasion resistance in cured films.
Free of solvents and monomeric TDI, meeting stringent VOC and occupational health requirements for industrial coatings and adhesives.
Industrial maintenance coatings for metal substrates requiring corrosion protection and mechanical durability.
Automotive refinish clearcoats and basecoat/clearcoat systems demanding high gloss and weather resistance.
High-performance wood coatings for furniture and flooring, where rapid throughput and surface hardness are critical.
Flexible and rigid polyurethane adhesives for bonding composites, plastics, and metals in transportation and construction.
Roller coating and coil coating formulations for pre-finished metal applications.
| Chemical Type | TDI-based isocyanurate trimer |
| Product Form | Clear to pale yellow liquid |
| Appearance | Homogeneous, low-viscosity liquid at 25 °C |
| NCO Content (wt %) | 13.5 – 14.5 |
| Viscosity (mPa·s at 25 °C) | 800 – 1,200 |
| Density (g/cm³ at 20 °C) | 1.18 – 1.22 |
| Flash Point (°C, closed cup) | 190 – 210 |
| Primary Applications | 2K PU coatings, adhesives, sealants, and elastomers |
Q1: What is the primary chemical nature and functionality of Desmodur L 75 C?
A: Desmodur L 75 C is a low-viscosity, trifunctional aromatic polyisocyanate based on toluene diisocyanate (TDI) trimer chemistry. It contains predominantly isocyanurate ring structures, offering enhanced thermal and hydrolytic stability compared to monomeric or uretdione-based systems.
Q2: How does Desmodur L 75 C differ from standard TDI-based prepolymers or monomeric TDI in coating and adhesive applications?
A: Unlike monomeric TDI, Desmodur L 75 C exhibits significantly lower volatility and reduced health hazards during handling. Its trimeric structure provides higher crosslink density, improved hardness development, and better resistance to solvents and elevated temperatures—making it especially suitable for high-performance two-component polyurethane coatings and reactive adhesives.
Q3: What types of resins or polyols are commonly compatible with Desmodur L 75 C?
A: Desmodur L 75 C demonstrates broad compatibility with hydroxyl-functional resins including polyester polyols, acrylic polyols, and polyether polyols. It is frequently used in solventborne and high-solids formulations where rapid cure, excellent film integrity, and gloss retention are required.
Q4: Is Desmodur L 75 C suitable for ambient-cure applications, or does it require heat activation?
A: Desmodur L 75 C is formulated to support both ambient- and forced-dry curing, depending on the co-reactant and catalyst system. While it reacts readily at room temperature with active hydrogen compounds, full property development—especially hardness and chemical resistance—is typically accelerated by mild thermal treatment (e.g., 60–80 °C).
Q5: How should Desmodur L 75 C be stored and handled to maintain stability and performance?
A: Store in tightly sealed containers under dry, inert conditions (e.g., nitrogen blanket) at temperatures between 15 °C and 30 °C. Prolonged exposure to moisture, humidity, or elevated temperatures may lead to viscosity increase or gelation due to isocyanate group reactivity. Always follow Covestro’s safety data sheet for handling precautions.
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