Studies of triblock copolymer-tackifying resin interactions by viscoelasticity and adhesive performance

—One of the most important applications for styrene-diene triblock copolymers is in the area of pressure-sensitive adhesives (PSA). Tackifiers, amorphous resins with molecular weights in the 500-2000 range, are added to elastomers to make them tacky and thus create a pressure-sensitive adhesive. In this work, various levels of a C5 aliphatic resin (Escorez 1310LC) were blended into an elastomeric styrene-isoprene triblock copolymer (Shell's Kraton 1107) and viscoelastic studies and tack measurements of these polymer-resin blends were carried out. The function of the resin is to reduce the plateau modulus of the polymer and raise the Tg of the matrix phase. There is some evidence from the thermomechanical properties that two phases exist in the elastomer region, although this point is certainly not proven. However, it seems that there is none or a very minimal amount of resin intruding into the polystyrene domains. Assuming a simple and highly idealized model, a one-to-one correspondence between energy dissipation measured viscoelastically and debonding resistance measured by industry tests was obtained when the adhesives fulfill the Dahlquist criterion. In essence, it was found that PSA performance in several industry tests was linearly correlated with the logarithm of loss modulus at the reduced frequency corresponding to the speed of the debonding test.