Identification of volatile products and determination of thermal degradation mechanisms of polybenzoxazine model oligomers by GC-MS

The polybenzoxazine model trimer and tetramer were utilized to extend the use of model compounds for the decomposition study of polybenzoxazines. The use of polybenzoxazine model dimers was proven to be effective in our previous study. The study of the decomposition of the benzoxazine dimers makes the interpretation for the oligomers as well as that of the polymers simpler. The use of the benzoxazine oligomers shows a good agreement with those of the dimers, and at the same time confirms the mechanisms previously proposed. The fragments containing methyl-substituted at ortho position, such as those at both end groups, make no contribution to char formation. The fragments without methyl-substituted at the ortho position, such as those in the repeating unit in the main chain, contribute considerably to the formation of char residues.