MECHANISMS OF ANTIOXIDANT ACTION - PHOTO-ANTIOXIDANT ACTIVITY OF POLYMER-BOUND HINDERED AMINES .1. BISMALEATE ESTERS

Bis(2,2,6,6-tetramethylpiperidin-4-yl) maleate (BPM) has been reacted with polypropylene in the melt to a high level (90 percent) in the presence of dicumyl peroxide (DCP). Concentrates of polymer bound BPM (BPM-B) were used as masterbatch additives to unstabilized polypropylene and maximal photo-oxidant activity was observed at 70 percent binding. The photoantioxidant effectiveness of BPM-B (from the exhaustively extracted masterbatch) was found to be linearly related to its concentration in the polymer up to 70 percent binding and on a molar basis it is as effective as conventional low molar mass additives. The implication of these results for the theories of antioxidant behavior in polymers is discussed.