Study Of The Construction Of Sandbag Microstructure In PA6/EPDM/nano-CaCO₃ Ternary Composite And Its Toughening Mechanism

PA6/EPDM/nano-CaCO₃ ternary composites have been rapidly developed recently because of their excellent comprehensive properties. In this paper,EPDM and EPDM-g-MAH blend was employed as elastomer respectively.The relationship beween the morphology and the properties of the PA6 ternary composites toughened by EPDM and nano-CaCO₃ together was studied.The key works and conclusions were listed as following:1.The effect of compounding route on properties and morphology of PA6/EPDM/nano-CaCO₃ ternary composite was investigated.One called one-step compounding route,in which EPDM and nano-CaCO₃ was directly melt blended with PA6 matrix.Another called two-step compounding route,in which EPDM and nano-CaCO₃ was mixed by the twin-roll mill to get masterbatch first,and then the masterbatch was melt blended with PA6 matrix.The results showed the ternary composite prepared via two compounding route could form a "sandbag structure". Toughness and stiffness of the ternary composite with sandbag structure particle would be improved with the increase of nano-CaCO₃ content.2.The interfacial compability between PA6 and elastomer,elastomer and nano-CaCO₃ were controlled by adjusted the ratio of EPDM to EPDM-g-MAH in the composite and the coupling agent for nano-CaCO₃. It was found that only when interfacial properties of the EPDM and nano-CaCO₃ phase is given,the sandbag structure dispersed phase morphology will be formed.3.Influence of injection rate for sample on the morphology and properties of PA6/EPDM/nano-CaCO₃ ternary composites was studied. The distribution of nano-CaCO₃ in different phase can affect the properties of the ternary composites and the morphology of dispersed phase.It is interesting that the sandbag structure of elastomer/ nano-CaCO₃ can eliminate the deterioration effect of nano-CaCO₃ agglomerates on toughness of the ternary composites and dissipate impact energy through the deformation of nano-CaCO₃ agglomerates embedded in elastomer.4,The synergetic toughening mechanism of PA6/EPDM/nano-CaCO₃ ternary composites was proposed when embedded by EPDM elastomer to form "sandbag structure".We s??sted EPDM and the nano-CaCO₃ aggregates happen synergy deformation and sandbags particles will cause corresponding deformation at the horizontal impact stress.Owing to the reaction-between the matrix PA6 and the EPDM-g-MAH,the interaction force between PA6 and EPDM is stronger than between nano-CaCO₃ and EPDM.Hence,nano-CaCO₃ particles will be subject to a compressive stress along the equatorial direction and a tensile stress along two poles and the cavitation will happen between nano-CaCO₃ and EPDM at two poles.When integration with the hole-hole was happen with the impact of the process,the sandbag structure of particles will be damaged,impact fracture surface of the composite exhibited fiber-forming.