Behavior of Products Having High Molecular Weight Formed during Thermal Degradation of Polystyrene

Abstract

Behavior of products having high molecular weight formed upon thermal degradation of polystyrene have been investigated.
As a result of the qualitative analysis of the above products, three kinds of dimer ([2] cis1, 3-dipheny1-2-butene (isomer), [3] 2, 4-diphenyl-1-butene, and [ 5 ] trans-1, 3-dipheny1-2- butene (isomer)) and three kinds of trimer ([6] isomer (M+=312), [ 7 ] 2, 4, 6-tripheny1-1- hexene, and [ 8 ] isomer (M+=312)) were identified.
It was considered that the initial products, having high molecular weight, formed during degradation of polystyrene (see Table 1), resulted from the intramolecular transfer reaction (back-biting) of secondary radical, which formed upon random scission of main chain of polystyrene.
In the presence of steam, results of pyrolyses of [3] and [7] are represented as follows:
Dimer and trimer having terminal methylene groups isomerized (a, c) rather than degraded (b, d, e). As the back-biting and intermolecular transfer reaction of polymer radicals as well as the above isomerization were predominant at a low temperature, various kinds of isomer formed in the degraded polymer fraction (see Scheme 2).
Under the same conditions, the ratio of isomer to dimer or trimer, was much greater in steam dilution than that in nitrogen dilution (see Fig.5). Water participated in isomerization and a mechanism of isomerization, via cyclic-transition state under which HO molecules were adsorbed to double bonds, was estimated (see Scheme 3).