Considering factors on determination of microstructures of SBR vulcanizates using pyrolytic analysis

Abstract Properties of styrene-butadiene rubbers (SBRs) are depending on their microstructures (contents of 1,4-unit, 1,2-unit, and styrene), but it is hard to determine the microstructures of SBR vulcanizates. Pyrolytic method such as pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) has been used for microstructures of cured rubbers without pretreatment. Microstructure of SBRs can be estimated using the major pyrolysis products (butadiene, 4-vinylcyclohexene (VCH), and styrene). In this study, considering factors for determination of microstructures of SBR vulcanizates using Py-GC/MS were investigated. The principal considering factors were found to be change of the major pyrolysis products due to radicals formed in carbon backbone and sulfur by dissociation of sulfide crosslinks in SBR vulcanizates. Relative abundances of the major pyrolysis products of raw and cured SBRs were different due to rearrangements of the radicals. Influencing factors on pyrolysis behaviors of SBR vulcanizates were found to be 1,2-unit block, alternating sequence of 1,4- and 1,2-units, styrene-1,4-unit and styrene-1,2-unit sequences, and location of the radicals. Especially, the 1,2-unit block influenced on change of the VCH/butadiene ratio, while the styrene-1,2-unit sequence affected change of the styrene/(butadiene + VCH) one.