Effects of EVA-g-MAH on the properties of CaSO4 whiskers/nylon 6 composites
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摘要: 采用马来酸酐接枝乙烯-醋酸乙烯酯共聚物（EVA-g-MAH）对CaSO4晶须/尼龙6（CaSO4W/PA6）增韧改性。通过双螺杆挤出机制备了CaSO4W/PA6二元、CaSO4W-（EVA-g-MAH）/PA6三元复合材料，用SEM、DSC、XRD等观察和表征了形貌、结构和结晶参数，并测试了力学性能。研究表明：添加少量CaSO4W可提高PA6的结晶速率，而高含量CaSO4W导致PA6结晶速率降低，促进γ晶型形成。添加10%（质量分数） CaSO4W可同时提高PA6的刚性和韧性；添加30% CaSO4W可进一步提高PA6的刚性，但PA6的韧性明显降低。添加2.5%和5%（质量分数） EVA-g-MAH，能使30% CaSO4W-（EVA-g-MAH）/PA6的抗冲击强度分别提高25.0%和76.7%，并使其具有较高韧性。冲击强度的提高主要源于EVA-g-MAH所产生的能量耗散、改善应力的有效传递、增强CaSO4W与PA6的界面以及EVA-g-MAH/PA6共混体系较好的相容性。Abstract: Maleic anhydride grafted ethylene-vinyl acetate copolymer (EVA-g-MAH) was used to toughen the calcium sulfate whiskers (CaSO4W)/nylon6 (PA6) composites. The CaSO4W/PA6 and CaSO4W-(EVA-g-MAH)/PA6 composites were prepared using by a twin screw extruder, and analyzed by means of SEM, DSC, XRD and mechanical testing. The results indicate that addition of small amounts of CaSO4W can increase the rate of crystallization, however, higher CaSO4W contents lead to a decreased rate of crystalization and promotion of forming γ-crystals of PA6. Adding 10% (mass fraction) CaSO4W increases both the stiffness and toughness of PA6. Adding 30% CaSO4W can further improve the stiffness but significantly decreases the fracture toughness of PA6. With 2.5% and 5% mass fraction of EVA-g-MAH, the impact strength of 30%CaSO4W-(EVA-g-MAH)/PA6 increases by 25.0% and 76.7%, respectively, thus imparting the higher toughness to the 30%CaSO4W/PA6. The improvement of impact strength of the composites mainly results from energy-absorption process, effective stress transfering, the increasing in interfacial adhesion between CaSO4W and PA6 in the presence of EVA-g-MAH as well as good miscibility of EVA-g-MAH/PA6 blend system.
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Keywords:
- grafted copolymer /
- CaSO4 whiskers /
- nylon 6 /
- composites /
- mechanical properties
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