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A series of ethylene vinyl acetate copolymers (EVA) were blended with some tackifier resins that are made from wood extracts, and possible relations between their miscibility and properties as hot-melt adhesives (HMA) were investigated. From our previous report on miscibility of various EVA-based HMAs, we chose some blends that represent some of typical miscibility types and measured their adhesive tensile strengths. When the blends were miscible at testing temperatures, the temperature at which the maximum value of adhesive tensile strength was recorded tended to move toward higher temperature as tackifier content of blends increased. This result corresponds to the glass transition temperature (T g ) of the blends that became higher as tackifier content of blends increased when blend components were miscible. In terms of HMA performances, we suggest that factors other than miscibility affect absolute values of adhesive tensile strength more directly than miscibility; this idea has to be investigated further in a future study.

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Natural rubber (NR) was blended in various ratios with 29 kinds of tackifier resins, which were prepared from rosin, terpenes, and petroleum. Miscibilities of all the blend systems were illustrated as phase diagrams. From these blend systems, we selected 7 systems having typical phase diagrams [completely miscible, completely immiscible, and lower critical solution temperature (LCST) types] and carried out measurements of peel strength. Peel strength was measured at the angle of 180°at 20°C over the wide range of pulling rates. In the case of pressure-sensitive adhesives (PSAs), which showed phase diagrams of the completely miscible or LCST type, the peak positions in the pulling rate-peel strength curves shifted to the lower velocity as the tackifier content increased. On the contrary, completely immiscible PSAs had a smaller peel strength than miscible ones and did not give manifest shift of peaks. In most of the adhesives, the fracture mode changed from cohesive failure to interfacial failure (between adhesive and adherend), slip-stick failure, and glassy failure (between the tape and adhesive) as the pulling rate increased.