Effects of liquid rubber modification on the behaviour of epoxy resin

The aim of this study was to investigate the behaviour of brittle epoxy res in when modified by liquid rubber for toughening purposes. The changes in m echanical and thermal properties of diglycidyl ether of bisphenol-A based e poxy resin with hydroxyl terminated polybutadiene (HTPB) (1% and 1.5%) have been studied. A silane coupling agent (SCA) was also utilized to improve t he compatibility of HTPB and epoxy matrix. Four groups of specimens were pr epared by using different orders of mixing of HTPB with SCA and hardener. Tension and impact tests were performed in order to observe the effect of r ubber modification, SCA and mixing processes on the mechanical properties. Tensile strength and impact toughness values were increased in the specimen s containing 1% HTPB and 2% SCA. Furthermore. it was found that rubber modi fication markedly increased the plastic strain at failure due to the possib le decrease in crosslinking density with the change in path of the reaction s. The changes in storage modulus and glass transition temperatures of all specimens were also evaluated by dynamic mechanical analysis. Fracture surf aces of all specimens were examined by scanning electron microscope. Use of SCA and different mixing orders improved the interaction between HTPB and epoxy matrix. The deformed rubber domains and higher amounts of deformation lines in some specimens indicated the improvement in toughness. (C) 2001 E lsevier Science Ltd. All rights reserved.