外力辅助分散作用下环氧树脂粘土纳米复合材料中粘土的微观结构与解离机理研究

采用不同分散方法(机械搅拌、高速均质搅拌和球磨分散)制备环氧树脂粘土纳米复合材料,研究了分散方法对不同有机粘土解离结构和纳米复合材料力学性能的影响,并在此基础上探讨了粘土的解离机理.结果表明,普通机械搅拌只能使小粒径粘土或大粒径粘土团聚体的外部片层解离;施加一定的外力(如高速均质搅拌)促进粘土团聚体分散,有利于粘土片层的解离;利用剪切摩擦作用较强的球磨法分散粘土,不同处理剂改性粘土的内外片层都可以充分解离,而有机改性剂中酸性质子的催化作用对粘土片层解离的影响不大,只要粒径足够小,片层解离的驱动力(基体弹性力、反应性等)能够克服其所受阻力(片层引力、层外基体粘性阻力、层内粘性引力等),粘土内外各片层将会同时向外迁移而解离.纳米复合材料的力学性能大大改善,冲击强度和弯曲强度分别提高近50%和8%;

MICROSTRUCTURE AND EXFOLIATION MECHANISM OF CLAY PARTICLES OF EPOXY/CLAY NANOCOMPOSITES UNDER EXTERNAL SHEARING FORCE

Different processing methods such as magnetical stirring,high-speed emulsifying and homogenizing and ball milling,were used to homogenously disperse the clay agglomerates and facilitate their exfoliation in epoxy/clay nanocomposites.The mechanical properties and effect of external shearing force on the exfoliation of organic clay modified with organic amine,quaternary ammonium salts and the combination of quaternary ammonium salts and meta-xylylenediamine (MXDA) were investigated.It was found that,for the general stirring,only partially exfoliated structure for the small clay particles or the external layers of large clay agglomerates were obtained.While the fine exfoliation for the external and central layers can be easily achieved by exerting vigorous shearing force,and the catalytic role of acid primary alkylammonium is not the key influencing the exfoliation of clay in epoxy matrix.The impact strength and flexural strength of epoxy/clay nanocomposites can be dramatically improved,which was about 50% and 8% higher than those of the pristine epoxy,respectively.The degree of exfoliation of clay particles will be substantially determined by the pulverization of the clay agglomerates.The smaller the size of clay particles,the better the dispersion and exfoliation of clay layers are, and a simultaneous outward shift of the external and central layers occurs.