Melt-Grafting of Maleimides Having Hindered Phenol Group onto Polypropylene

Abstract

Monomeric antioxidant 1 was prepared by the reaction of 3,5-di-tert-butyl-4-hydroxybenzyl alcohol with N-[4-(chlorocarbonyl)phenyl]maleimide in the presence of imidazole. Monomeric antioxidant 2, bearing carbamate group, was synthesized from the reaction of 3,5-di-tert-butyl-4-hydroxybenzyl alcohol and azidomaleimide. Antioxidant 3 was prepared by the reaction of N-(4-hydroxyphenyl)maleimide and 3- (3,5-ditert-butyl-4-hydroxyphenyl) propionic chloride in the presence of triethylamine. These reactive antioxidants were grafted onto polypropylene (PP) by melt-processing with free radical initiators in a mini-max moulder. From the infrared spectra of the grafted PP, it was found that the monomeric antioxidants were grafted onto PP. IR spectroscopic methods were used for the quantitative determination of the extent of grafting of monomeric antioxidant. To optimize the reaction conditions, the influences of the concentration of DCP, monomeric antioxidant, reaction time and temperature on the extent of grafting were studied.

Grafting of Hindered Phenol Groups onto Ethylene/α-Olefin Copolymer by Nitroxide Radical Coupling

“…Alternatively, the literature reports examples of AO immobilization onto polymer matrices by formation of a covalent bond. The grafting of AOs was obtained by modification of a pre-formed polymer by a radical functionalization procedure [10,11,12,13] or by copolymerization between functionalized and un-functionalized monomers [14,15,16,17,18].…”

“…Acryloyl or methacryloyl monomers as well as bis-maleate and maleimide, all substituted with AO groups, were grafted to different polymer matrices [10,11,13]. For example maleate derivatives bearing hindered amine groups were covalently bonded to PP by radical grafting [19], whereas maleimides substituted with a hindered phenol group were grafted to PE and PP [13].…”

“…Acryloyl or methacryloyl monomers as well as bis-maleate and maleimide, all substituted with AO groups, were grafted to different polymer matrices [10,11,13]. For example maleate derivatives bearing hindered amine groups were covalently bonded to PP by radical grafting [19], whereas maleimides substituted with a hindered phenol group were grafted to PE and PP [13]. An alternative to post-polymerization modification is the polymerization or co-polymerization of ad hoc chosen monomers, like for example the polymerization of monomers bearing hindered phenol groups [17] or the copolymerization of ethylene with AO functionalized norbornene [14,15,16,17,18].…”