木材接着に関する研究(第5報) : 微視的観察によるフェノールおよびメラミン樹脂接着層の耐久性について

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Beech and lauan plywood glued with phenol-resin adhesive or melamine-resin adhesive were exposed to boil and dry repeating cycle and to continuous boiling. Glue-joint durability of these plywoods was studied by means of the microscopic observation of glue-line and tension shear test.
The following conclusion may be drawn from the experiments.
1 ) Surface check and end check of plywoods occured from the boundary of compound ray. These caused the delamination of glue-line of plywood.
2 ) Delamination of glue-line occured from the end of compound ray and the latewood adjacent to the glue-line, and also from the lathe check of veneer.
3 ) The glue-joint strength of plywood glued with phenol-resin adhesive gradually decreased as the exposure to boil and bry repeating cyele proceeded. This phenomenon was caused mainly due to the deterioration of adherend.
4 ) The glue-joint strength of plywood glued with melamine-resin adhesive decreased rapidly toward twelve cycles, and then it was no longer observed. The deterioration of adhesive was chiefly responsible to this phenomenon.