摘要 : Polyisoprene (IR), poly(styrene-cobutadiene) (SBR), and IR-SBR blends were vulcanized with 2-bisbenzothiazole-2,2'-disulfide (MBTS) and sulfur in a differential scanning calorimeter (DSC) at a programmed heating rate and isotermal... 展开 Polyisoprene (IR), poly(styrene-cobutadiene) (SBR), and IR-SBR blends were vulcanized with 2-bisbenzothiazole-2,2'-disulfide (MBTS) and sulfur in a differential scanning calorimeter (DSC) at a programmed heating rate and isotermally in a press at 150 deg C. The reaction was stopped at various stages, crosslink densities were measrued, and residual curativies and extractable reaction intermediates were analyzed by high-pressure liquid chromatography (HPLC). The reactivities of IR and SBR towards MBTS was found to be more similar than that of the rubbers towards tetramethylthiuram disulfide. In blends, the slightly greater reactivity of IR led to its earlier crosslinking, as shown by thermogravimetric analysis (TGA) of the insoluble material present at various cure times. The depletion of curatives in the IR phas led to their diffusing from SBR to IR; consequently, a zone of highly crosslinked material developed in IR close to the interface. The freezing point of a solvent, imbibed into a gel, is decreased as crosslinking proceeds; and dissimilarities in the crosslink densities of the phases in blends were demonstrated by comparing the crosslink density, calcullated from swelling experiments, with the depression of the freezing point of the imbibed solvent. 收起