Influence of curative, filler, compatibilizer, domain size, and blend ratio on the dynamic mechanical properties of silicone–EPDM blends

Abstract

Abstract Dynamic property measurements show two loss tangent peaks for silicone rubber at about −95°C and −20°C, and one peak for EPDM at about −30°C. DSC studies confirm that the first loss tangent peak of silicone rubber is caused by its glass transition and the other is caused by crystalline melting of silicone. Measurements with blends reveal the individual characters of the components in the blends. Large differences in the solubility parameter between them also explains the incompatible nature. The effects of curative, blend ratio, and ageing are found on the glass‐transition temperature and also on the storage modulus and loss tangent. Although filler does not change the glass‐transition temperature, it changes the dynamic properties. Silane‐grafted EPR shows an optimum concentration as a compatibiliser, resulting in improved mechanical properties of the blends. The domain size of the blends also reduces with the introduction of the compatibilizer. Imposition of restriction on the domains by partial curing during mixing results in materials with higher storage modulus. The morphology study indicates an interpenetrating network structure for these restricted domain blends. © 1993 John Wiley & Sons, Inc.