Influence of the interfacial adhesion on the stringiness of crosslinked polyacrylic pressure‐sensitive adhesives

ABSTRACT The stringiness of crosslinked polyacrylic pressure‐sensitive adhesives (PSA) was observed during 90° peeling under a constant peel rate with various adherends in order to clarify the influence of interfacial adhesion on the stringiness behavior. The crosslinked random copolymer of butyl acrylate with 5 wt % acrylic acid was used as a representative PSA. Poly(methyl methacrylate) (PMMA), polycarbonate (PC), poly(vinyl chloride) (PVC), fused quartz plates and some surface‐modified poly(ethylene terephthalate) films were used as adherends. The films were pasted on a glass plate using a cyanoacrylate adhesive. The 180° peel strength was higher in the order of PVC >> PMMA ≈ PC > other adherends. All observed stringiness was sawtooth‐shaped, but the stringiness width and length were longer in the same order. The number of sub‐branches formed at the tips of the strings was much more for the PVC, PMMA and PC adherends. Frames formed at the front end of the strings in the case of PVC adherend. Sufficient interfacial adhesion generates large internal deformation of the PSA layer. Internal deformation occurred preferentially over peeling as a result of front frame formation. The string length and the peel load required for the constant peel rate have good correlation with the peel strength. The estimation of generated inner stress in the fibrils of the strings was possible by analysis using the string length for various adherends and the stress–strain curve of pure PSA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40869.