Pressure-sensitive adhesive (PSA) sheets having a thin filmy PSA layer (1 µm thickness) were prepared from polyurethane or acrylic copolymer and their adhesive properties were investigated. In the polyurethane-based adhesive sheets, an increase of probe tack energy and peel strength was attributed to the improvement of the wettability to the uneven adherend surface as well as the cohesive strength of the adhesives. On the other hand, the peel strength in the acrylic adhesive sheets increased as interactions between the adhesive surface and the adherend surface increased. Furthermore, the adhesive properties of the adhesive sheet laminates which were prepared using the polyurethane-based adhesive and the acrylic adhesives were also examined. The highest peel strength in these sheet laminates was 5.1N/25mm, which was significantly higher than that of single layer PSA sheets. This result is probably owing to the synergistic effects of the improvement of the wettability to the uneven adherend surface and the surface interaction among the sheet laminates.
In this present report, the surface color of adhesion was studied to be related to the strength of adhesive as the non-destructive test of the adhesive structures under high temperature circumstances. In other word, the deformation and the strength under tensile test of the adhesive joint which had been under high temperature circumstance was related to the surface color of adhesion. One liquid curing epoxy resin and roll steel for general structure SS400 were used for the adhesion and the adherend, respectively. Firstly, the thin film bulk test piece and the adhesive single lap joint were fabricated to investigate the mechanical properties of epoxy resin and the strength of adhesive joint under high temperature circumstance. Next, the relationship between the surface color of adhesive and the adhesive strength under high temperature circumstance was investigated. Moreover, the experimental result revealed that the strength of adhesive joint under the same circumstance as the experimental condition was able to be evaluated and predicted by measuring the surface color of adhesion quantitatively.