Epoxidized Natural Rubber for Adhesive Applications

Abstract

ENR-based adhesives were prepared under the concepts of (i) crosslinking at epoxirane rings and/or (ii) curing at α-carbon positions along the rubber chain. The crosslinking at epoxirane rings was accomplished when two crosslinking agent/catalyst systems, i.e., diamine/bisphenol A and anhydride/imidazole were used. However, the crosslinking efficiency of the anhydride/imidazole crosslink system was higher than that of the diamine/bisphenol A crosslink system. The curing of ENR at the α-carbon positions was carried out by conventional vulcanization (CV). The mechanical testing of three formulations of ENR-toluene based adhesives, i.e., (i) ENR-PA adhesive, (ii) ENR-S adhesive, and (iii) sulfur cured ENR-PA adhesive showed that ENR-S adhesive gave the highest tensile strength. The fourth formulation of adhesive was, hence, prepared by adding tackifier (resin PX1150) to the ENR-S adhesive (ENR-S-resin PX1150 adhesive). The effect of resin PX1150 on the mechanical properties of ENR-S-resin PX1150 adhesives was studied to find that when the amount of tackifier increased the tensile strength and tensile modulus of the adhesive also increased, while the %elongation at break decreased.