Abstract: Four different benzofuranone/1010/168 ternary complex antioxidants for polypropylene (PP) had been studied via comparing their melt flow rate after multiple extrusions and oxidation induction time (OIT).Aftcr 5 times of extrusions at 250℃，the PP sample containing 1%of 5一tcrt-butyl-7-methyl-(3-methoxyphenyl)-3H- benzofuran-2-one(ANBF2)/1010/168 system exhibited the smallest flow rate and the longest OIT, and thus the highest thermal stability.At the same loading of 1010 and 168，the stabilizing effect of八}BF2 was compared with Irganox HP-2225.Even when the loading of ANBF2 was one third that of HP-2225，the stabilizing effect of the former was still better than the latter.

Key words: benzofuranone, polypropylene, complex antioxidant, melt flow rate, oxidation induction time