Long-chain branch-induced interfacial interaction and its effect on morphology development in polypropylene/ethylene octene copolymer blend

We studied the microstructure–rheology relationship of polypropylene (PP)/ethylene octene copolymer (EOC) blends by means of rheology in combination with scanning electron microscopy. The blends varying in blend ratio all prepared by melt mixing were considered. The results of the frequency sweep experiment performed on the blend sample with matrix-dispersed morphology showed a pronounced positive deviation of storage modulus values at a low frequency range from those predicted by Palierne’s viscoelastic model. This could be explained in terms of EOC droplets interconnectivity which was generated by in situ increased chain-branched entanglements. That is, the thermo-mechanically induced PP macro-radicals produced during the melt mixing could graft onto the more stable EOC macro-radicals in the interface leading to much longer-chain-branched EOC molecules, which had the capability of creating favorable entanglements for the EOC droplets conductivity.