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The formation of core‐shell morphology within the dispersed phase was studied for composite droplet polymer‐blend systems comprising a polyamide‐6 matrix, ethylene‐propylene‐diene terpolymer (EPDM) shell and high density polyethylene (HDPE) core. In this article, the effect of EPDM with different molecular weights on the morphology and properties of the blends were studied. To improve the compatibility of the ternary blends, EPDM was modified by grafting with maleic anhydride (EPDM‐g‐MAH). It was found that core‐shell morphology with EPDM‐g‐MAH as shell and HDPE as core and separated dispersion morphology of EPDM‐g‐MAH and HDPE phase were obtained separately in PA6 matrix with different molecular weights of EPDM‐g‐MAH in the blends. DSC measurement indicated that there may be some co‐crystals in the blends due to the formation of core‐shell structure. Mechanical tests showed that PA6/EPDM‐g‐MAH/HDPE ternary blends with the core‐shell morphology exhibited a remarkable rise in the elongation at break. With more perfect core‐shell composite droplets and co‐crystals, the impact strength of the ternary blends could be greatly increased to 51.38 kJ m−2, almost 10 times higher than that of pure PA6 (5.50 kJ m−2). POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

In this article, polyamide 6 (PA6), maleic anhydride grafted ethylene-propylene-diene monomer (EPDM-g-MA), high-density polyethylene (HDPE) were simultaneously added into an internal mixer to melt-mixing for different periods. The relationship between morphology and rheological behaviors, crystallization, mechanical properties of PA6/EPDM-g-MA/HDPE blends were studied. The phase morphology observation revealed that PA6/EPDM-g-MA/HDPE (70/15/15 wt %) blend is constituted from PA6 matrix in which is dispersed core-shell droplets of HDPE core encapsulated by EPDM-g-MA phase and indicated that the mixing time played a crucial role on the evolution of the core-shell morphology. Rheological measurement manifested that the complex viscosity and storage modulus of ternary blends were notable higher than the pure polymer blends and binary blends which ascribed different phase morphology. Moreover, the maximum notched impact strength of PA6/EPDM-g-MA/HDPE blend was 80.7 KJ/m 2 and this value was 10-11 times higher than that of pure PA6. Particularly, differential scanning calorimetry results indicated that the bulk crystallization temperature of HDPE (114.6 C) was partly weakened and a new crystallization peak appeared at a lower temperature of around 102.2 C as a result of co-crystal of HDPE and EPDM-g-MA.

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