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

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 5mol% with various crosslinking degrees. Tack was measured using a probe tack test with probe rates of 1 and 10mm/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 10mm/s, while the tendency was opposite for 1mm/s. The temperature dependency of tack was measured with a contact time of 30s. 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 10mm/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 1mm/s and high crosslinking degree, then peeled out. C: After B, fibrillation occurred at 1mm/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.