Molecular Design of Reactive Compatibilizers for Polypropylene — Nitrile Butadiene Rubber Blends
Polypropylene melt grafted with glycidyl methacrylate (and styrene as a comonomer) was synthesized in a batch reactor and used as a reactive compatibilizer in polypropylene-nitrile butadiene rubber blends (NBR contained 7 wt% acrylic acid). The effects of the degree of grafting (DG), molecular weight, and concentration of the PP-g-GMA copolymer on the extent of interpolymer reaction in and impact performance of the blends were examined. The morphology of the PP-NBR blends was unaffected by the molecular weight of the compatibilizer. The impact performance, however, increased rapidly with number average molecular weight up to about 25 000 g/mol, above which the impact strength changed relatively little. The effect of using a larger amount of a low DG copolymer versus a smaller amount of a higher DG copolymer was to increase the impact performance of the blends. The copolymers containing both grafted GMA and styrene were less efficient as blend compatibilizers, possibly due to steric hindrance from the bulky benzene ring. It is also highly probable that these copolymers were lightly crosslinked.
KeywordsBlock Copolymer Interfacial Tension Impact Strength Graft Copolymer Diblock Copolymer
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