MECHANISMS OF ANTIOXIDANT ACTION - THE EFFECT OF SPIN TRAPS DURING THE PROCESSING AND PHOTOOXIDATION OF PVC

It is demonstrated by the use of spin traps that during the early stages of thermal processing of PVC considerable concentrations ( greater than 3 multiplied by 10** minus **6 mol g** minus **1) of free radicals are produced which are primarily responsible for the initial products (hydroperoxides, unsaturation, and hydrogen chloride) previously shown to be formed in the polymer. From a semiquantitative analysis of these products, it is estimated that more than 50% of the radicals are formed from hydroperoxides and the rest by mechanoscission of the polymer chain. The spin traps are effective processing stabilizers in combination with a tin maleate HCl scavenger. One of them (2-methyl-2-nitroso propane, MNP) has also been shown to be a photoantioxidant.