Poly(ethylene-cb-propylene) (P(E-cb-P)), prepared by copolymerization of vinyl terminated atactic polypropylene and ethylene was used to compatibilize immiscible blends of high density polyethylene (HDPE) and isotactic polypropylene (iPP). Addition of 5 wt% P(E-cb-P) resulted in microdomain size reductions and the concomitant increase in the elastic modulus, as typically observed in immiscible blends compatibilized with linear block copolymers. A more intriguing phenomena is the development of extensional strain hardening by the addition of P(E-cb-P) to the HDPE/iPP blends. This effect is stronger in blends with cocontinuous microstructure (50/50 HDPE/iPP) than in blends with matrix-droplet morphology (75/25 or 25/75 HDPE/iPP). We postulate that the enhancement in strain hardening observed in the compatibilized blends is due to strengthening of the interface via two mechanisms: (1) the increase in the blend interfacial area and (2) entanglement of the PE and PP blocks from P(E-cb-P) within the corresponding homopolymer phases.

Strain hardening in immiscible PE/PP blends via interfacial reinforcement with PE-cb-PP comb-block copolymers

253rd National Meeting (2017)

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