Pressure-Sensitive Adhesion of Isopropyl-Azodicarboxylate-Modified Polybutadiene to Glass

Abstract

Abstract The pressure-sensitive adhesion (i.e., adhesive tack) of isopropyl azodicarboxylate modified polybutadiene contacted with glass has been studied using a 180°-peel geometry. Fracture energies were studied as a function of IAD content, contact time, and peeling rate. Additionally, the creep compliance J was measured and related to the peeling response. At low levels of modification, J decreases with increasing IAD content; however, J increases at intermediate IAD levels—indicative of softening in the material. This is thought to be due, at least in part, to a reduction in the entanglement density and is a condition that favors wetting. For example, the elastomer with 33% IAD achieves 46% of its equilibrium bond strength to glass after 2 min of contact while, after the same tc, IAD-29 (with its lower compliance) attains only 26% of its ultimate bond strength. In some circumstances, there is an interesting decrease in the fracture energy as contact time is increased. This is accompanied by a change in the locus of failure from Ig to Im. When failure is Im, the adhesive layer remains flat during peeling and hence, no energy is expended to bend this layer; this results in a lowering of the fracture energy.