Toughening of PA6/EPDM-g-MAH/HDPE ternary blends via controlling EPDM-g-MAH grafting degree: the role of core-shell particle size and shell thickness

The formation of core-shell morphology for composite droplet polymer-blend systems containing a polyamide-6 (PA6) matrix, MAH grafted ethylene-propylene-diene rubber (EPDM-g-MAH) shell and high-density polyethylene (HDPE) core was studied. Core-shell morphology with various shell thickness of blends was controlled via adding EPDM-g-MAH with varying grafting degree. Smaller size of core-shell composite droplets and thicker EPDM-g-MAH shell are formed in PA6/EPDM-g-MAH/HDPE ternary blends with lower grafting degree of EPDM-g-MAH and the corresponding Izod impact strength reaches a optimal value of 35.7 kJ/m(2), which is almost 9-10 times higher than pure PA6 (3.6 kJ/m(2)). Further, the toughening mechanism was proposed and the results showed that the thicker EPDM-g-MAH shell can better transfer the stress between polymer matrix and dispersed phase particles, resulting in easier fibrillation progress of dispersed phase particles, which absorbs a significant amount of impact energy. However, for the blends with higher grafting degree of EPDM-g-MAH, during impact processing the easier deformation of the thinner EPDM-g-MAH shell caused overlarge cavitations and naked/debonding fiber or spherical dispersed particles, which reduces the Izod impact strength of blends.