Characterization of pyrolysis products formed from styrene-1,2-unit heterosequence of styrene–butadiene copolymer

Styrene–butadiene rubbers (SBRs) were pyrolyzed and the pyrolysis products were analyzed using gas chromatography/mass spectrometry (GC/MS). 3-Phenylcyclopentene (3-PCP) and 4-phenylcyclohexene (4-PCH) were found to be characteristic pyrolysis products formed from the styrene-1,2-unit heterosequence. 4-PCH can be also generated from the styrene-1,4-unit heterosequence. Relative abundance of 4-PCH was larger than that of 3-PCP. Relative intensities of 3-PCP and 4-PCH decreased with increasing the pyrolysis temperature. By comparing the (3-PCP + 4-PCH)/butadiene ratios of bound and unbound rubbers of an SBR compound, relative abundance of the styrene-1,2-unit heterosequence in the bound rubber was found to be smaller than that in the unbound one. Degree of the styrene-1,2-unit heterosequence of raw SBR or bound rubber can be estimated by analyzing the 3-PCP and 4-PCH using pyrolysis-GC/MS.