Influence of crosslinking and peeling rate on tack properties of polyacrylic pressure-sensitive adhesives

Abstract Tack properties and peeling behavior of crosslinked polyacrylic pressure-sensitive adhesives were investigated. The model adhesive was a crosslinked poly(n-butyl acrylate-acrylic acid) random copolymer with an acrylic acid content of 5 mol% with various crosslinking degrees. Tack was measured using a probe tack test with probe rates of 1 and 10 mm/s and various contact time. The tack increased with contact time. The degree of tack rising with contact time decreased with an increase in crosslinking degree for 10 mm/s, while the tendency was opposite for 1 mm/s. The temperature dependency of tack was measured with a contact time of 30 s. The tack peak shifted to higher temperatures with an increase in crosslinking degree and probe rate. Peeling behavior was observed using high-speed microscopy. The peeling behavior changed from A to C with the decrease of peeling rate and crosslinking degree. A: Cavitation and peeling progressed simultaneously at maximum stress at 10 mm/s independent on the crosslinking degree. B: Cavitation occurred at the edge of the probe at low stress and spread to the center of the probe at maximum stress at 1 mm/s and high crosslinking degree, then peeled out. C: After B, fibrillation occurred at 1 mm/s with low crosslinking degree. The change of peeling behavior was caused by the following: the interfacial adhesion increased, while the cohesive strength decreased as crosslinking degree and probe rate decreased. Keywords: pressure-sensitive adhesiveadhesion strengthtackfracture energycrosslinkingcavitation Acknowledgments The authors are grateful to Toagosei Co., Ltd (Tokyo, Japan) for the polyacrylic polymer preparations and to Mitsubishi Gas Chemical Company, Inc., (Tokyo, Japan) for the kind donation of the crosslinking agent.