Durability of Rubber Modified SMC

A carboxylated butadiene-styrene elastomer has been developed as a low profile modifier for polyester resins used in sheet molding compounds. The elastomeric modifier will provide Class A surfaces with low long-term wavi-ness, energy absorbing characteristics and zero shrinkage. Especially outstanding results are obtained when molding large, thin, flat panels such as roof, door, hood and tailgate panels from rubber modified SMC. Surface appearance properties are subjective, but properties such as radial bend, tension testing, high impact and reverse impact tests are shown to demonstrate the energy absorbing and toughening characteristics imparted by the modifier.