Preparation and properties of new antioxidants with higher MW

Abstract

Five new antioxidants containing hindered phenol groups with higher molecular weight(MW) have been synthesized by direct addition reaction of 2,6-di-tert-butyl-4-hydroxy methyl phenol (DBHMP) and isocyanates. They 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 dicarbamate (MW = 640), 3,5-di-tert-butyl-4-hydroxyl benzyl isophorone dicarbamate (MW = 694), and 3,5-di-tert-butyl-4-hydroxyl benzyl methylene diphenylene dicarbamate (MW = 722). Structures of these new antioxidants have been characterized by IR, NMR and Elemental Analysis. The stabilizing action of these antioxidants for protecting polypropylene against thermal oxidation was examined. Results show that an increase in the MW of the antioxidant by isocyanation enhanced its thermal stability, hence its stabilizing effectiveness for protecting PP against thermal oxidation is enhanced. Introduction of very long alkyl chains into the antioxidant can effectively improve compatibility of the antioxidant with the polymer substrate. © 1998 Elsevier Science Limited. All rights reserved.