Urethane-modified isocyanurate, fiber

Urethane-Modified Isocyanurate Foams. Urethane-modified isocyanurate foams are prepared by the trimerization of a polyisocyanate in the presence of a polyol, a trimerization catalyst, a blowing agent, and a surfactant. The foams have high flame and temperature resistance. The combined use of an isocyanurate foam and glass fiber not only improves the physical properties, e.g., flexural strength, friability, etc. but it also improves the flame resistance because the char formed from the foam acts as thermal barrier and protects it from flame and heat. This type of composite, therefore, is widely used for buUding applications in the U.S.A. Urethane-modified isocyanurate foam systems have also been used in the SRIM process (26, 36, 37). 

Examples of the matrix resins employed for SRIM include rigid polyurethane (7,15, 16), or urethane-modified isocyanurate foam (9, 26, 35, 36). The matrix resins for foamed composites are required to have low viscosity and relatively slow cream time for better impregnation into fiber mat and fast-cure cycle time for higher j oductivity. 

Kuyzin et al discussed a low-density SRIM made by using glass-fiber reinforcement and a urethane-modified isocyanurate foam system (26), or by using polyamide-coated polyester fibers and a urethane-modified isocyanurate-foam system (36). 

Table XI demonstrates the effect of fiber length on properties for a type of RIM processable material - the urethane modified isocyanurate which has low impact. Table XI ccnpares milled glass fibers with 1/8" chapped strand. The longer aspect length chopped strand provides for true reinforcement. However, it cannot be used in current RRIM equipment.

---