Abstract
The effect of zinc oxide and testing rate on shear strength of natural rubber-based pressure-sensitive adhesives was studied using coumarone-indene resin and toluene as the tackifier resin and solvent, respectively. The range of zinc oxide concentration varied from 0 to 60 parts per hundred parts (phr) of rubber, whereas the testing rate was from 10 to 50 cm/min. Viscosity and shear strength of adhesive were determined using a Brookfield viscometer and a Lloyd Adhesion Tester, respectively. Results show that the viscosity of adhesive increases gradually with the increase in zinc oxide concentration. For a fixed coating thickness, shear strength increases with zinc oxide loading up to 20 phr, after which it drops with further addition of zinc oxide, an observation that is attributed to varying degree of cohesive strength of adhesive. Shear strength increases with coating thickness and testing rate, suggesting that the shear strength is both thickness- and rate-dependent.
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