2011 Volume 47 Issue 9 Pages 344-353
Influences of the compatibility of apolyacrylic block copolymer/tackifier blend on the phase structure of the tackifier and adhesion properties of the blend were investigated. For this purpose,special rosin ester resins with different weight average molecular weights of 650,710,890 and 2160 were used as the tackifier and blended with apolyacrylic 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. It was confirmed by transmission electron microscopic observation that agglomerates of the tackifier of several tens ofnanometers in size formed,with the number of agglomerates increasing with increasing molecular weight of the tackifier (in the range from 650 to 890) and tackifier content. For a molecular weight of 2160, micrometer-sized agglomerates were observed. Dynamic mechanical analysis indicated that both the glass transition temperature and the storage modulus at low temperature increased with addition of the tackifier,and these effects became more pronounced with an increase in the molecular weight of the tackifier and tackifier content in the molecular weight range from 650 to 890. These effects were lower, however,when the molecular weight was 2160. 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 superpositionlaw. The rolling rate at which tack began to appear shifted to a lower rate with an increase in molecular weight of the tackifier and was lowest for amolecular weight of 890. The effect was again reduced,however,for the tackifier with a molecular weight of 2160. It was found that the formation of agglomerates of the tackifier of several tens of nanometers in size aided in development of the storage modulus of the adhesive, and as a result the tack at lower rolling rates increased.
