PROPERTIES ENHANCEMENT OF FLUOROSILICONE ELASTOMERS WITH COMPATIBILISED CRYSTALLINE VINYLIDENE FLUORIDE POLYMERS

An experimental investigation was carried out to explore the possibili ty of using crystalline vinylidene fluoride copolymers as reinforcing agents for fluorosilicone elastomers. To achieve a fine dispersion of the fluoropolymer in the fluoroelastomer matrix, and to develop a stro ng adhesion between the two polymer phases, a compatibilisation proced ure was used involving the pre-grafting of multi-functional free-radic al crosslinking agents on the fluoropolymer chains before being blende d with the fluorosilicone gum. Mixtures of Triallyl isocyanurate and D iallyl phthalate were found to be particularly useful for this purpose using gamma-radiation to promote grafting reactions, which were enhan ced by the addition of a small amount of benzoyl peroxide paste in the subsequent melt blending operation. The efficacy of this procedure wa s confirmed by differential scanning calorimetry and dynamic mechanica l tests, showing a reduction in the degree of crystallinity and a depr ession of the melting point of the fluoropolymer phase and a small inc rease in glass transition temperature of the fluoroelastomer matrix. T he peroxide cured blends exhibited large improvements in mechanical pr operties, both at room temperature and at 140 degrees C, and in large reductions in solvent absorption.