Effects of Rubber Addition to an Epoxy Resin and Its Fiber Glass-Reinforced Composite

Epoxy resins are considered as one of the most important class of thermosetting polymers and find extensive use in various fields. However, these materials are characterized by a relatively low toughness. In this respect, many efforts have been made to improve the toughness of cured epoxy resins. In this work, samples of epoxy resin diglycidyl ether of bisphenol-A and fiber glass-reinforced composite of this polymer with and without liquid carboxyl-terminated butadiene acrylonitrile (CTBN) copolymer were prepared to assess the effect of CTBN rubber on the properties of polymeric and composite laminate specimens. The addition of CTBN into the polymeric specimens led to a decrease in the glass transition temperature, fracture stress (from 70.39 to 56.34 MPa), and tensile elasticity modulus (from about 3.51 to 2.65 GPa), accompanied by an increase in elongation (from 2.47 to 5.64%). However, the degradation temperature of the polymeric system was not modified. Infrared analysis evidenced the occurrence of chemical reaction between the two components, and scanning electron microscopy results suggested rubber particles deformation as the prevailing toughening mechanism. The rubber addition in the composite specimens, promoted an increase simultaneous in fracture stress and in elongation at fracture. The elasticity tensile modulus has not changed. This probably results from the increased deformation capacity of the matrix, which prevents its premature cracking, and better adhesion between fibers and matrix observed in the CTBN-modified composite laminates. POLYM. COMPOS., 2012. (c) 2011 Society of Plastics Engineers