Effect of Molecular Weight of Rubber on Tack and Peel Strength of SMR L-Based Pressure-Sensitive Adhesives using Gum Rosin and Petroresin as Tackifiers

Abstract

Loop tack and peel strength of natural rubber (SMR L)-based pressure-sensitive adhesive were studied using five different molecular weights of SMR L. Gum rosin and petroresin were used as tackifiers, whereas toluene was chosen as the solvent throughout the experiment. A SHEEN hand coater was used to coat the adhesive on a polyethylene terephthalate (PET) substrate at a coating thickness of 30, 60, 90 and 120 μ m. Loop tack and peel strength were determined by a Llyod Adhesion Tester operating at 30 cm/min. Results show that maximum values of loop tack and peel strength were obtained at a molecular weight of 8.5 × 10⁴, an observation which is attributed to maximum wettability of adhesive on the substrate. Loop tack and peel strength increases with coating thickness for all molecular weight of rubber and tackifiers studied.