Thermal and photodegradation of MnO 2-, NaBO 3- and organic hydroperoxide-cured polysulfides: products and pathways

Abstract

The thermal and photodegradation of a number of linear polysulfides (LP) H(SC 2H 4OCH 2OC 2H 4S) n H, cured using inorganic (MnO 2, NaBO 3) and organic (t-butyl hydroperoxide or TBHP) curatives, have been studied by 1H and 13C NMR spectroscopy, IR spectroscopy and electrospray ionisation mass spectrometry (ESI). We have found that cured-LPs degrade thermally and photochemically by two main parallel pathways namely (i) a free radical autoxidation mechanism and (ii) a hydrolysis mechanism. The nature of the curative used determines the principal pathway, thus LP blocks cured using TBHP degrade predominantly by the hydrolysis mechanism, while LPs cured using MnO 2 and NaBO 3 degrade almost exclusively via the free radical autoxidation route.