Studys on the modification of epoxy resin with polydimethylsioxane

Abstract

Epoxy resins are widely used as packaging and insulating materials in the fields of electric and electronic industries because of their excellent heat, moisture, solvent and chemical resistance, superior electrical and mechanical properties, and good adhesion to many substrates. Recently, tetramethyl biphenol diglycidyl ether (TMBPDGE) is commonly used as a base material for the encapsulation of microelectronic devices. However, it is relatively brittle and has poor impact resistance. It is also known that when epoxy resins are cured, they can contract and develop internal stresses. These shrinkage and internal stress cause reduced durability, such as moisture and heat-cycle resistance of electric and electronic parts. The overall objectives of this study are to investigate the influence of particle size and particle size distribution on toughness of cured epoxy systems in relation to the compositions of amino-terminated polydimethylsiloxane (ATPDMS) differing in molecular weight and the degree of the preliminary reaction conditions in the melt state, and to investigate the effect of the morphological parameters on internal stress relaxation and volume relaxation by studying physical aging behavior of polysiloxane modified epoxy systems. The solubility parameter of polydimethylsiloxane is much lower than that of the epoxy resin. Polydimethylsiloxane is, therefore, not compatible with epoxy resin unless it has functional groups that react with epoxy groups. The degree of preliminary reaction between epoxy and polysiloxane increased with the decrease of the molecular weight of polysiloxane in the melt state. The reaction in the melt state is conducted in the restricted interfacial region of polysiloxane and epoxy resin. When the low molecular weight polysiloxane is mixed with high molecular weight polysiloxane, the low molecular weight polysiloxane compatibilizes epoxy resin and high molecular weight polysiloxane and small particle size and narrower distributio...