Thermal degradation studies of alternating copolymers—V. Degradation of the alternating copolymer of isopropenyl acetate and maleic anhydride

Abstract

The thermal degradation of the alternating copolymer of isopropenyl acetate and maleic anhydride has been investigated using thermal volatilisation analysis (TVA), thermogravimetry (TG) and differential scanning calorimetry (DSC) under vacuum and nitrogen conditions using programmed heating up to 500 °C. The decomposition products, i.e. gas, liquid and tar fractions, have been separated and then analysed by GC-MS and FTIR spectroscopy. The structural changes in the copolymer during degradation at various temperatures up to 440 °C and also for isothermal heating for various periods at 170 °C have been investigated by FTIR spectroscopy.The alternating copolymer of IPA-MAn degrades in two main stages as the temperature is progressively raised. In the first stage up to about 260 °C, the acetate groups are completely eliminated from the isopropenyl units through side group reactions whilst leaving the backbone intact. Above 260 °C, the anhydride groups break down producing large quantities of CO 2 and CO along with gradual breakdown of the backbone to give a variety of other products. Unlike the homopolymer of isopropenyl acetate, the IPA-MAn copolymer leaves a significant amount of residue after 500 °C.By controlled degradation at 170 °C, acetate groups can be removed without decomposition of the MAn units, to produce what is in effect a new copolymer of regular structure with backbone double bonds conjugated to the anhydride carbonyls.