MECHANISMS OF ANTIOXIDANT ACTION - EFFECTS OF SULFUR COMPOUNDS ON MELT STABILITY OF POLYPROPYLENE

The effects of a number of sulfur compounds on the melt stability of polypropylene milled at 165°C have been studied. Dilaurylthiodipropionate (DLTP), Mercaptobenzimidazole (MBI), and Mercaptobenzthiazole (MBT) are all antioxidiants in a polymer lightly stabilized with a phenolic antioxidant although the last two are initially pro‐oxidants. 2,2′‐Dibenzoylaminodiphenyldisulfide (22BDD) is a pro‐oxidant under the Conditions studied. In the absence of a phenolic antioxidant the effectiveness of DLTP is reduced in the early stages of oxidation, with increasing concentration although its over all antioxidant activity increases. The results are consistent with the view that both radical and non‐radical processes occur concomitantly. Copyright © 1969 John Wiley & Sons, Inc.