Effects of the compatibility of a polyacrylic block copolymer/tackifier blend on the phase structure and tack of a pressure‐sensitive adhesive

Adhesion and viscoelastic properties and morphology of a polyacrylic block copolymer/tackifier blend were investigated. Special rosin ester resins with different weight average molecular weights of 650, 710, 890, and 2160 were used as the tackifier and blended with a polyacrylic block copolymer consisting of poly(methyl methacrylate) and poly(n‐butyl acrylate) blocks at tackifier content levels of 10, 30, and 50 wt %. The compatibility decreased with an increase in molecular weight. From TEM observation, the number of formed agglomerates of the tackifier with sizes on the order of several tens of nanometers increased with increasing tackifier content and molecular weight of the tackifier in the range from 650 to 890. For the tackifier with a molecular weight of 2160, micrometer‐sized agglomerates were observed. The storage modulus at low temperature and the glass transition temperature of adhesive measured by a dynamic mechanical analysis increased dependent on the number of formed nanometer sized agglomerates. Tack was measured using a rolling cylinder tack tester over wide temperature and rolling rate ranges, and master curves were prepared in accordance with the time‐temperature superposition law. Tack and peel strength were optimum at a blend combination of intermediate compatibility, i.e., the molecular weight of 890. These optimum properties were correlated to maximal values of the storage modulus at room temperature and the glass transition temperature. Therefore, it was found that these features of blend properties are strongly affected by the nanometer sized agglomerates of tackifier. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012