Effect of test rate on adhesion properties of SMR L, ENR-25 and ENR-50-based pressure-sensitive adhesives

The dependence of loop tack, peel strength and shear strength of SMR L and Epoxidized Natural Rubber (ENR-25 and ENR-50)-based pressure sensitive adhesives on the rate of testing was investigated using coumarone-indene as the tackifying resin. Toluene and poly(ethylene terephthalate) (PET) were used as the solvent and substrate respectively throughout the study. A SHEEN hand coater was used to coat the adhesive on the substrate. All adhesion properties were determined with a Llyod Adhesion Tester operating at different rates of testing. Results show that loop tack, peel strength and shear strength all increase with increase in rate of testing, an observation which is attributed to the viscoelastic response of the adhesive which results in cohesive and adhesion failures at low and high test rates, respectively. Except for shear strength, the other adhesion properties increase with adhesive coating thickness. ENR-25-based adhesive consistently exhibits higher value compared to ENR-50 and SMR L. For shear strength, the largest value measured is for ENR-50 adhesive system.