Effect of Hybrid Tackifiers on Viscosity, Peel Strength and Shear Resistance of Natural Rubber and Epoxidized Natural Rubber-Based Pressure Sensitive Adhesives

Abstract

Natural rubber (SMR L grade), epoxidized natural rubber (ENR) 25 and 50 were loaded with hybrid tackifiers consisting of a mixture of coumarone-indene and gum rosin. The coumarone-indene was fixed at 40 parts per hundred of rubber (phr) while the concentration of gum rosin was varied from 20 to 80 phr. The viscosity, peel and shear strength of the adhesives prepared from the elastomers was studied. Results show that peel strength exhibits a maximum value at 60 phr gum rosin for SMR L-based adhesive while for ENR 25 and ENR 50 based adhesives a maximum value is observed at 40 phr gum rosin which was attributed to the occurrence of optimum wettability and compatibility at this tackifier loading. Meanwhile, viscosity and shear strength decreases with increasing gum rosin concentration. SMR L-based adhesive consistently exhibits higher viscosity and shear strength whereas ENR 25-based adhesive steadily shows higher value for all modes of peel tests.