부산대학교 도서관

Effect of wax on the ozone resistance of vulcanized natural rubber (NR) and vulcanized isoprene rubber (IR) was investigated by exposing to ozone at 40 °C and -30 °C. The vulcanized rubbers were prepared by sulfur vulcanization of NR and IR with sulfur, ZnO, stearic acid, accelerator and wax in the presence of carbon black and they were heated at 40 °C for 72 hours under 20% straining to form wax layer on their surfaces. The ozone exposure test of the vulcanized rubbers was carried out at -30 °C or 40 °C for 24 hours in the presence of 50 pphm ozone and crack propagation of vulcanized rubber was observed by optical microscopy. The crack propagation of the vulcanized rubbers took place at -30 °C, whereas it was suppressed at 40 °C, which were distinguished from the theory of reaction kinetics. It was found that the crack propagation of vulcanized rubbers was caused by the difference in thermal contraction coefficient between wax and the rubbers.