Reaction injection molding of mica reinforced polyurethane

Abstract Reaction injection molded polyurethanes are reinforced with inorganic materials to improve stiffness and structural integrity at elevated temperatures and to reduce the coefficient of thermal expansion. This work describes the reinforcement obtained with an experimental grade of mica designed to achieve low viscosity of mica suspensions in polyol. The effect of mica on properties is essentially identical to that of glass flake (i.e., improved stiffness at the cost of reduced impact strength). Compared to hammer milled glass fiber, mica and glass flakes yield more isotropic, albeit weaker, materials. The study of unreinforced polyurethane shows that mechanical properties (tensile and impact strength, flexural modulus) are approximately proportional to the square of foam density.