PREPARATION AND PROPERTIES OF NEW ANTIOXIDANTS WITH HIGHER MW

Five new antioxidants containing hindered phenol groups with higher mo lecular weight(MW) have been synthesized by direct addition reaction o f 2,6-di-tert-butyl-4-hydroxy methyl phenol (DBHMP) and isocyanates. T hey are 3,5-di-tert-butyl 4-hydroxyl benzyl n-octadecyl carbamate (MW = 531), 3, 5-di-tert-butyl-4-hydroxyl benzyl toluene-2,4-dicarbamate ( MW = 646) 3,5-di-tert-butyl-4-hydroxyl benzyl hexamethylene dicarbamat e (MW = 640), 3,5-di-tert-butyl-4-hydroxyl benzyl isophorone dicarbama te (MW = 694), and 3,5-di-tert-butyl-4-hydroxyl benzyl methylene diphe nylene dicarbamate (MW = 722). Structures of these new antioxidants ha ve been characterized by IR, NMR and Elemental Analysis. The stabilizi ng action of these antioxidants for protecting polypropylene against t hermal oxidation was examined. Results show that an increase in the MW of the antioxidant by isocyanation enhanced its thermal stability, he nce its stabilizing effectiveness for protecting PP against thermal ox idation is enhanced. Introduction of very long alkyl chains into the a ntioxidant can effectively improve compatibility of the antioxidant wi th the polymer substrate. (C) 1998 Elsevier Science Limited. All right s reserved.