Poly(oxypropylene)-amide grafted polypropylene as novel compatibilizer for PP and PA6 blends

Abstract

Poly(oxypropylene)-amide grafted polypropylene (PP) was prepared in an extruder by the reaction of poly(oxypropylene) (POP)diamines and maleated PP (PP-g-MA). The resulting POP-grafted PP copolymers are confirmed by the FTIR analysis, and used as compatibilizers for polyamide 6 (PA6) and polypropylene blends. These compatibilizers, POP-functionalized PPs (PP-g-MA-co-POPs), have different amphiphilic properties depending on the content of MA in the starting PP-g-MA and the molar ratio of MA/amine. The compatibilization effect is examined in terms of morphologies, thermal and mechanical properties. The morphologies, affected by the molecular weight of POP diamine in PP-g-MA-co-POP copolymer, show a decreasing size of the dispersed PA6 particles as the molecular weight of POP diamine increasing from 230 to 400 to 2000. Using these PP-g-MA-co-POP copolymers, the compatibilized blends show improvements in mechanical properties, including Izod impact strength and tensile toughness, over a conventional compatibilizer. The POP and amide functionalities in the compatibilizers can facilitate the formation of hydrogen bonding with PA6 and, therefore, the compatibilizing effect. During the compounding process, the compatibilizers further react with PA6 in situ to afford the mixture of PP-g-MA-co-POP-PA6, PP-g-MA-co-POP-co-PA6 and PP-g-MA-co-PA6 copolymers, which further improves the compatibilizing effect.