Effect of cross-linking on adhesion property of benzoyl-peroxide-cured epoxidized natural rubber (ENR 50) adhesives

Abstract

The loop tack, shear and peel strength of cross-linked epoxidized natural rubber (ENR 50)-based adhesive were investigated. Coumarone–indene resin and toluene were used as the tackifier and solvent, respectively, throughout the study. Benzoyl peroxide was used to cross-link the ENR 50 adhesive at 80°C for 30 min. The dosage of benzoyl peroxide was varied from 1 to 5 parts per hundred parts of rubber (phr). The adhesive was coated on the polyethylene terephthalate substrate at various coating thickness using a SHEEN hand coater. Loop tack, shear and peel strength were determined by a Llyod adhesion tester operating at 30 cm min−1. The result shows that loop tack and peel strength of the ENR 50 adhesives indicate a maximum value at 2 phr of benzoyl peroxide dosage. This observation is attributed to the effect of optimum cross-linking of rubber chains that enhances the cohesive strength of the adhesive system. However, shear strength increases with increasing dosage of benzoyl peroxide, an observation that is associated with the steady increase in the cohesive strength resulting from increasing cross-linking of rubber chains. In all cases, the adhesion properties increase with increasing coating thickness.