Retardation of Peeling by Cavitation in Pressure Sensitive Adhesive Layer

Abstract

Peeling behavior of polyacrylic block copolymer and crosslinked polyacrylic copolymer containing acrylic acid during probe tack test was observed using a high speed microscope. As a result, three different peeling patterns were observed: Peeling progressed linearly from the edge to the center of the probe without cavitation（A）, peeling progressed from the edge to the center of the probe with cavitation（B）and cavitation occurred in the entire adhesive layer, and peeling initiation was delayed （C）. Tack was higher in the order of C＞B＞A. The stringiness during 90°peel test was observed for crosslinked polyacrylic copolymer with various crosslinking degrees. All observed stringiness were sawtooth shaped, however the frame formed at the peeling front in the case of middle crosslinking degree. When the front frame formed, the peel strength was higher. It was found that the cavity formation and the sawtooth shaped stringiness with front frame are caused by the internal deformation of adhesive layer preferentially over peeling. Then these phenomena delayed peeling by the strain energy dissipation with the deformation of adhesive layer.