ゴム系接着剤による接着の耐水性に関する考察

概要

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The adhesive joint made with the crystalline CR adhesive often fails on exposure to water. In this paper, we discuss the results of some measurements on this phenomenon. We prepared four model adhesives, No. 1 is based on CR (crystalline), No. 2 on IIR/CR (=1/1, continous phase: CR), No. 3 on CR/IIR (=1/1, continous phase: IIR) and No. 4 is based on IIR.From the results of the water immersion test, these adhesives can be classified into two groups, one is a group of No. 1 and No. 2 showing a poor water resistance, and the other (No. 3 and No. 4) showing an excellent resistance. Samples of the poor group have a continous crystalline phase and the residual tention of them are about ten times or above that of the excellent group's. By the microscopic observation, we found out that the small crack cavities appear in the CR layer of the poor group as the solvent evaporates, and they grow slowly. When these samples are exposed to water, these cavities are displaced by water and are spread out by the capillary action of water and residual strain.We consider that the process of the cavities caused by the residual strain and the capillary action of water may be the main mechanism resulting in lowering of the adhesive strength by exposure to water.
日本ゴム協会の論文