NIPPON GOMU KYOKAISHI

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In this study, the coefficients of friction on the rubber surfaces having abrasion patterns which were abraded by abrasive cloth were examined. When a mating glass specimen was perpendicularly rubbed against parallel ridges of abrasion patterns, the effects of sliding direction and the spacing of the abrasion patterns on the coefficients of friction were investigated. From the experiments, the variations of the coefficients of friction were explained by the variation of contact area.
The coefficients of friction on the abrasion patterns were examined with same direction of abrasion by abrasive cloth and the counter direction of abrasion. The coefficients of friction on the abrasion patterns in a direction of abrasion were from twenty-five to fifty percents larger than those rubbed in a counter direction of abrasion. When the abrasion patterns were rubbed in a direction of abrasion, the coefficients of friction increased because of the increment of apparent applied load by friction force. While the abrasion patterns were rubbed in the counter direction of abrasion, the coefficients of friction decreased by the decrement of apparent applied load by friction force. The coefficients of friction decreased when the spacing of abrasion patterns and applied load increased. The load dependence was dominant as the spacing of patterns was large.

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In order to elucidate the degradation mechanism of EPDM rubber caused by a amount of chlorine in city water, EPDM rubbers containing 2 kinds of carbon black (ie. HAF and FT) were employed and corroded in chlorine water, Their morphology changes before and after degradation were observed by SEM. The effect of the amount of moisture Was examined by EPMA. The degradation mechanism was studied by XPS and ¹³C-NMR. The EPDM rubber loaded HAF was easier to absorb chlorine and to be deteriorated than the one loaded FT. As a result of XPS measurement, Cl (2p) peak was detected from the sample after degradation treatment. ¹³C-NMR measurement revealed that the methyl group of diene side chain of EPDM rubber was changed into the chlorinated methyl group. It was thought that as the chlorinated methyl group reacted with the other molecular chains of EPDM rubber, the crosslinking density increased. Therefore, the degraded EPDM rubber was brittle, collapsed and fell off.

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