Mechanical properties of epoxy/rubber blends

Abstract

Highly cross-linked epoxies that are susceptible to brittle failure can be effec-tively toughened by blending them with various types of rubber. Initially, a small amount of a miscible liquid rubber is incorporated into the matrix of the curing agent-incorporated epoxy resin, and then the whole mass is subjected to curing. The phase separation depends upon the formulation, processing, and curing conditions. The improvement in fracture toughness occurs due to the dissipation of mechanical energy by cavitation of the rubber particles, followed by shear yielding of the matrix. A few factors such as the size of the rubber particles, curing agent, cross-linking density, etc. play an important role in succeeding or failing to improve the toughness. This chapter provides an overview of the toughening mechanism of rubber-modified epoxies. The effects of a few major factors (i.e., the size of the rubber particles, curing agent, curing time and temperature, etc.) on the mechanical properties of rubber-modified blends were studied. The effect of the varieties of synthetic and natural liquid rubber on the impact, flexural, and tensile properties of the epoxy blend is compared and studied.