| In this paper, sulfur-cured butyl rubber (ⅡR) was devulcanized by using supercritical CO2. In order to obtain the maximum sol content of reclaimed butyl rubber (RIIR), the optimum devulcanizing conditions were studied and the optimum conditions for devulcanization were as follows:the reaction temperature was 180℃, the reaction temperature was 14.1 MPa, and the reaction time was 120 min when 4 g of diphenyl disulfide (DD) was put into the reactor. The sol content of the reclaimed natural rubber was up to 98.5%.Then, RIIR was characterized by GPC,DSC,TGA and 1HNMR. The results showed that the molar mass and Mooney viscosity of RIIR was decreased, while the Tg and the thermal property of RIIR keep constant. Some phenyl groups derived from the devulcanizing reagent were attached onto the main chain. Due to that some sulfurated functional groups were grafted onto the main chain during vulcanization and devulcanization, the chemical shift of olefinic proton changed. Combined with the optimum devulcanizing conditions, we speculated the possible mechanism for butyl rubber devulcanization and the progress of sol component formed. During devulcanization, scission occured at not only S-S and S-C bonds, but also main chains. It was the main chain scission and the thermol degradation that resulted to decrease in the molar mass of RIIR.RIIR was revulcanized by using sulfur and resin, respectively. It was found that RIIR could not be cured by using sulfur as curing agent, but by resin, due to the decrease in the active cross-linking sites and the effect of DD left in RIIR on vulcanization. Then, the compounds containing of different content of RIIR and virgin butyl rubber were revulcanized by sulfur and resin, respectively. The mechanical properties,DMA,thermal properties,ageing resistance and gas permeabitity of the revulcanizates were investigated.Then, we studied the feasibility of reclaiming waste rubber by using "two-steps" method. We studied the optimum impregnating conditions for the devulcanizing reagent (DD) impreganating and dispersing into the crosslinked network. At the same time, we tried to devulcanize the waste rubber containing DD by using different methods. The results showed that "two-steps" including impregnation of DD into the crosslinked network at first and then devulcanization saved the devulcanization time greatly. Besides, it proved that the decrease of the molar mass of reclaimed rubber was related to the devulcanization time and the amount of DD. |
