The role of β-hydrogen in the degradation of polyesters

Linear polyesters based on phthalic anhydride and any one of the following C 4 diols, 1,4-butanediol, 2-butene-1,4-diol or 2-butyne-1,4-diol were synthesised by the melt condensation technique and characterised by infrared spectroscopy. The thermal degradation of the polyesters was carried out under high vacuum and the products separated and identified using gas chromatography—mass spectrometry. The results revealed that a decrease in the β-hydrogen content of the diol component leads to a decrease in the amount of phthalic anhydride formed during degradation. It was also observed that the amount of diol released during the degradation of the polyesters increases with the decrease in the β-hydrogen content of the diol component. The results emphasise the fact that β-scission is one of the primary degradation processes in polyesters when β-hydrogen atoms are available in the diol component.