The dependence of peel strength and shear strength of epoxidized natural rubber (ENR 25)-based
pressure-sensitive adhesive on molecular weight and rate of testing was investigated using coumarone-
indene as the tackifying resin. Toluene and polyethylene 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 at a coating thickness of 120 lm. All the adhesion properties were determined by a Llyod
Adhesion Tester operating at different rates of testing. Result shows that peel strength and shear strength
increases up to an optimum molecular weight of 6.5 104 of ENR 25. For peel strength, the observation is
attributed to the combined effects of wettability and mechanical strength of rubber at the optimum
molecular weight, whereas for the shear strength, it is ascribed to the increasing amount of adhesive
present in the coating layer which enhances the shear resistance of the adhesive. Peel strength and shear
strength also increases with increase in rate of testing, an observation which is associated to the viscoeslastic
response of the adhesive. Differential scanning calorimetry (DSC) and Fourier transform infrared
spectroscopy (FTIR) study confirms the miscibility of tackifier and the ENR 25.