Controlling the Physical Properties of RIM Urethanes with Non-Organic Reinforcement

Milled fiberglass or mica flake reinforcement can be used to control the physical properties of RIM urethanes. The addition of these reinforcements results in increased flexural modulus, decreased coefficient of linear thermal expansion, decreased elongation and decreased impact strength. Milled fiberglass is shown to orient during injection into the mold causing anisotropic behavior in the physical properties. Mica flake reinforced urethanes do not show the orientation effects found with milled fiberglass, but mica flake, causes a greater reduction in elongation and impact than does milled fiberglass.

Several urethane systems are examined and the general effects of mica flake or milled fiberglass are found to be reasonably independent of the base urethane system.