Poly(butylene terephthalate) (PBT) , which is a typical engineering plastic, has been widely used for electrical components and also automobile parts due to its heat resistance and dimensional stability. In general, PBT should be annealed to obtain high dimensional stability at a temperature above the glass transition temperature prior to practical use. In this study, influence of annealing treatment on adhesion behavior of PBT with epoxy adhesive was studied. The tensile adhesion strength decreased after the annealing treatment of PBT. In the case of the untreated PBT, the failure depth after the failure was nearly 0nm. Once the PBT was annealed, the average failure depth became 4 nm. The above results imply that the failure mechanism for the system transformed from interfacial failure to cohesive fracture upon annealing treatment. This can be easily understood by taking into account that a mechanically weak layer is formed in the surface region of PBT after the annealing. Presence of such a weak boundary layer was evaluated by grazing incidence X-ray diffraction measurement and by scanning viscoelasticity microscopy. Improvement of adhesive property was attained by surface treatment.

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This paper dealt with a two-dimensional stress analysis of adhesive butt joints filled with elastic circular fillers in an adhesive subjected to external tensile loadings. Similar adherends and an adhesive including elastic circular fillers were replaced with finite strips in the analyses. Stress distributions in the adhesive joints were analyzed exactly using the two-dimensional theory of elasticity and the iteration method. The effects of stiffness, location of fillers and number of fillers on the interfaces stress distributions and around the fillers are shown in the numerical computations. It was seen that as an amount of number of fillers increased, stiffness of filler increased and location of filler got near the edge of interface, the strength of joints was more improved. For verification of the analyses, experiments were carried out to measure the strains. The analytical results were in fairly good agreements with the experimental ones. In addition, the analytical results are also compared with those obtained from the two-dimensional and three-dimensional FEM calculations. Fairly good agreements were seen between the analytical and the two-dimensional FEM results. However, the result from the present analysis was different from that of the three-dimensional FEM. Rupture tests were conducted, and joint strengths were seen to be improved by adding fillers.

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The bond quality of structural glued laminated timber bonded with one-component moisture curable polyurethane (PU) adhesive was investigated. Resorcinol formaldehyde (RF) and water-based polymer isocyanate (API) adhesives were also used for comparison. Two-ply laminations of Hinoki (Chamaecypalis obtuse Endl),Sugi (Cryptomeria japonica. D.don), Beimatsu (Pseudotsuga taxifolia Menziesii Franco) and Makamba (Betula maximowicziana REGEL) wood species were prepared using those adhesives. In order to estimate the bonding performance, the block shear test was applied according to the Japanese Agricultural Standard (JAS) for structural glued laminated timber under normal conditions and after accelerated-aging treatments. The curing time dependence of the relative amount of residual NCO groups in PU adhesive was also measured. The results showed that in Hinoki and Sugi laminations, the bond quality of PU adhesive was almost similar with that of RF and API adhesives. In Beimatsu and Makamba laminations, the bond quality of PU adhesive was almost similar with that of API adhesive, while the bond quality of RF adhesive was far better than that of PU adhesive. In the delamination test of PU adhesive we found that five-ply laminations of Hinoki wood species was satisfied the criterion of JAS. Otherwise, five-ply laminations of Makamba wood species did not satisfy the criterion of JAS. The measurement of the relative amount of residual NCO groups showed that within 2 months observation time the NCO groups seemed to remain in adhesive film. It indicated that the adhesive film did not yet cure completely.

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