Abstract
Tack properties of poly(methyl methacrylate)-block-poly(n-butylacrylate)-block-poly(methy methacrylate) triblock copolymer (MAM) and a 1/1 blend with a diblock copolymer consisting of the same components (MA) were used asbase polymers, and tackifier added systems in amounts ranging from 10 to 30 wt% wereinvestigated in order to clarify the role of MA and tackifier. The temperature dependence of tack was measured by a probe tack test. The tack of MAM/MA at room temperaturewas significantly higher than that of MAM, and the improvement of MAM/MA upon the addition of the tackifier was greater than that of MAM. The peeling process at the probe/adhesive interface during the probe tack test was observed using a high speed microscope. It was found that for MAM/MA, cavitation wascausedin the entire adhesive layer, and peeling initiation was delayed by the absorption of strain energy due to deformation of the adhesive layer. In contrast, for MAM. peeling progressed linearly from the edge to the center of the probe. The greater flexibility of the chain in the diblock copolymer resulted in improved interfacial adhesion. 'H pulse nuclear magnetic resonance analysis showed that the presence of the tackifier reduced the molecular mobility of the base polymers and improved the cohesive strength of the adhesive. Adhesion strength is affected by two factors:the development of interfacial adhesion, and cohesive strength. In the MAM/MA/tackifier system, the presence of MA and the tackifier improved the interfacial adhesion and cohesive strength, respectively. This synergistic effect brought the higher adhesion strength
