OPTIMIZATION OF CYCLOALIPHATIC EPOXY-RESINS WITH SILICONE ELASTOMERS

The high crosslink density of epoxy resins with high glass transition temperature, high strength, etc., used in many high-performance applic ations, causes the undesired brittleness of these materials and, hence , internal stress. For the optimization of their properties, cycloalip hatic epoxy resins were modified with elastomeric silicone. Two differ ent modifying concepts, i.e. dispersion and mixing, were characterized using mechanical testing, dynamic-mechanical analysis and scanning el ectron microscopic studies as well as measurement of the expansion coe fficient and the shrinkage. The modification with silicone, in general , reduces the modulus and improves the fracture toughness of the resin s. Due to the two-phase structure of the resins prepared by the disper sion method, the glass transition temperature of the epoxy matrix is p ractically not depressed, and the tendency to enhance stress is less m arked compared to the mixing method.