Reactions of sulfur dioxide with oxidized polyolefins

Abstract

The reactions of gaseous sulfur dioxide with partially oxidized polypropylene and polyethylene have been investigated by iodometry and by Fourier Transform Infra-red (FTIR) spectroscopy. Comparison was also made with chemical changes observed in model liquid hydroperoxides which were analysed by FTIR, nmr and ultraviolet-visible spectroscopies. Reaction of macro- and model hydroperoxide groups with SO 2 proceeds by two consecutive reactions which occur in varying proportions depending upon the SO 2/hydroperoxide ratio. Because of this, the use of the SO 2 reaction products detected by infra-red (believed to be hydrosulfates) to quantify hydroperoxide is unreliable and gives little improvement in detection level over direct measurement of hydroperoxide by infra-red. Exposure to SO 2 and then gaseous ammonia produces some ammonium sulfate from hydroperoxide groups. The ammonium sulfate can be detected with high sensitivity by infra-red, but the stoichiometry of its generation is again variable.