Structure effect of benzofuranone on the antioxidant activity in polypropylene

This work deals with the antioxidant activity of benzofuranone compounds in polypropylene (PP). The antioxidant activities of ten benzofuranone compounds in PP were compared using melt flow index (MFI) values of PP stabilized by benzofuranone compounds primarily. The results show: firstly, that the increase of electron donating ability of substituent in 3-substituted benzene ring is beneficial to the improvement of antioxidant activity. Secondly, it has been verified that the steric hindrance of 2′-position substituent can weaken the antioxidant activity of benzofuranone. But when 2′-position substituent forms a hydrogen bond with 3-position reactive hydrogen, the steric hindrance is offset efficiently. Finally, the methyl and tert-butyl groups in the 5 and 7-position of parent benzene ring do not affect the antioxidant activity of benzofuranone compounds in PP obviously.