Research On The Morphology And Fracture Behavior Of Sandbag Toughened PA6/EPDM-M/NANO-CaCO₃Ternary Composite

In this paper, ethylene propylene diene terpolymer rubber (EPDM)/maleated ethylene propylene diene terpolymer rubber (EPDM-MAH), named as EPDM-M, and nano-calcium carbonate (nano-CaCO3) are employed to modify the toughness of Polymide6(PA6). Relationship among the compouding route, microstructure and mechanical properties are researched. And the fracture energy dissipating of "sandbag" toughened PA6/EPDM-M/nano-CaCO3composites under different temperatures is studied by instrument Charpy impact test and single-edge notched tensile test (SENT). With the investigating of the fracture surface after impact test, the toughening mechanism of "sandbag" toughened composites is further discussed. The main works and conclusions are listed as follows:1、 The effect of the compouding routes on the morphology of "sandbag" microstructure and the mechanical properties of PA6/EPDM-M/nano-CaCO3composites are studied. The result shows that, the effect of the compouding routes on the tensile and flexural property is little. However, it has obvious effect on the morphology and impact properties of the PA6/EPDM-M/nano-CaCO3composites. EPDM-M and nano-CaCO3agglomerates are dispersed in the PA6matrix respectively by the compounding route of "all of PA6, EPDM-M, nano-CaCO3are put into the extrusion from the main feed throat or the lateral feed throat to obtain the composites", and the impact strength is just about32kJ/m2."Sandbag" microstructure is formed by the compounding route of "nano-CaCO3and EPDM-M are firstly mixed in a two-roll mill to get the master batch, and then, the master batch are melt-mixed with PA6, which are put into the extrusion from the main feed throat to get the composite". For this composite,"sandbag" microstructure particles are small and the diameter distribution is uniform which leads to the high impact strength of90kJ/m2with lots of voids and striations observed in the fracture surface of impact test. The "sandbag" microstructure particles are much larger for the composite prepared by the compounding route of "nano-CaCO3and EPDM-M are firstly mixed in a two-roll mill to get the master batch, and then, the master batch was melt-mixed with PA6which are put into the extrusion from the lateral feed throat to get the composite", and the impact strength is much lower, just about45kJ/m2.2> The effect of temperature on the energy dissipating of PA6based composites under instrument Charpy impact test and SENT is studied. Compared to other PA6based composites, the crack propagation energy of the composites with "sandbag" microstructure is much higher, which indicates that "sandbag" microstructure can effectively improve the resistance of crack propagation.3、 The morphology evolution of "sandbag" microstructure under tensile process was observed via scanning electron microscope (SEM). The morphology evolution of "sandbag" microstructure exhibits following characteristics:(1) the nano-CaCO3agglomerates in the "sandbag" microstructure slips, and the "sandbag" microstructure stretches along the direction of the two poles of particles.(2) The debonding between nano-CaCO3agglomerates and EPDM-M in the "sandbag" microstructure is observed, accompanied with lots of voids and microfibrils connecting nano-CaCO3agglomerates and EPDM-M.(3) microfibrils connecting nano-CaCO3agglomerates and EPDM-M are disappeared, while lots of large voids appear.4、 The morphology of "sandbag" microstructure in the different zone of the fracture sample after impact test is investigated by SEM, and the force analysis of "sandbag" microstructure under impact test is also discussed. Result shows that, paralleling to the direction of crack propagation, the stretching direction of "sandbag" microstructure at different points is different. The morphology of the "sandbag" microstructure under the direction of perpendicular to the crack propagation shows, the nearer to the fracture surface, the more stretching of the "sandbag" microstructure is.