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Title: Effect of Blending Methods on the Properties of Nylon 6/ EVA/Organoclay Nanocomposites Writer: Chuan Chen Supervisor: Wei Wu Abstract:Through changing the feeding order of blending and use the organic montmorillonite, nylon 6/ EVA-g-MAH/montmorillonite composites was prepared. The effects of the types of the montmorillonite, EVA grafted conditions and the blend feeding order on the mechanical property and thermal properties of nylon 6/ EVA/MMT composites were studied. The results showed that the notched Izod impact strength of the nanocomposite exhibited a great reinforcement by adding the hydrophilic organoclay and EVA-g-MAH. The composites was prepared by masterbatch process, the MMT could be dispersed into nylon 6 phase or EVA phase better, and got the best toughness effect, also reduced the loss of the tensile and flexure strength to the minimum.
Title: Preparation and Properties Research of the Nylon/Polycarbonate/Elastomer Nanocomposites Writer: Jun Chen Supervisor: Wei Wu Abstract：The research mainly focused on the combine toughening system of polycarbonate and elastomer in nylon nanocomposites. Three different kinds of combine toughening systems were developing step by step from phase, micro-structure, to molecular angle according to the dispersion state of PC in the nylon matrix. The relationship of nano-montmorillonite and the combine toughening systems was also investigated. The first part mainly focused on the combine toughening mechanism of polycarbonate and the (polystyrene-polyacrylamide)/organic montmorillonite core–shell structures for nylon 6 composites. In this experimentation the P(St-AM)/OMMT core–shell structures were synthesized through emulsion polymerization. Core–shell structure particles and PC were used to combine toughen Nylon 6 and their influence on mechanical properties, processability, crystallization behavior and thermal stability of the PA6 composites was also investigated. The results showed that the inducing of core–shell structures and PC has improved the flexile properties of PA6. The core–shell structures acted as nucleating agent can improve the crystallinity of the PA6 composites(the melting temperature increased by 8.5oC and the crystallinity increased by 3.3%) and the PA6 composites also show a good thermal stability and processability(the MFR valve increased by 118%). In the second part the combine toughening system of polycarbonate and silicone rubber was studied through the introduction of the morphology and properties of the PA66/PC/silicone rubber composites. By adding silicone rubber as a toughener, the composites were prepared via dynamic vulcanization. The crosslinking of silicone rubber in the PA66/PC matrix formed the netlike structure like semi-IPN which is propitious to enhance the interaction between PA66 matrix and PC and in further makes the PC particles embed in PA66 matrix closely. Novel composites are gained with outstanding mechanical properties and high-temperature-resistance, so the combine toughening by silicone rubber and PC is an ideal toughening system because of the synergistic effect. In addition, The PA66/PC/silicone rubber/OMMT composite exhibits better flexile strength and flexile modulus without the weakening of other mechanical properties. The thermal properties of PA66/PC/silicone rubber composites prepared by dynamic vulcanization were also investigated systematically. The PA66/PC/silicone rubber composites show very good retention of impact strength and higher hardness even after heat aging. The average degradation and softening temperatures of the composites are higher than that of other common engineering plastics which we mainly attribute to the introduction of the dynamically vulcanized silicone rubber and the forming of a netlike structure in the PA66/PC matrix. Of the fillers studied, the introduction of montmorillonite even improved the hardness and the degradation temperature of the composites. In the third part the compatiblizing effect of chain extender on the combine toughening system of polycarbonate and elastomer was studied. This part focused on a new kind of super-tough PA6 engineering plastic. Based on the combine toughening by polycarbonate (PC) and polyolefin elastomer(POE), the PA6/PC/POE/HDI composites were prepared via reactive extrusion by adding of chain extender (HDI). Novel toughening alloy is gained with outstanding mechanical properties. Toughening mechanism was studied and the relationship between properties and the multi-network structure was analyzed. The influence of different loading of HDI on mechanical properties of the composites was also studied. The results showed that the compatibility between PA6 and PC can be improved by adding the chain extender (HDI), the viscosity of the composites increased sharply and the crystallization degree decreased in some degree with the adding of HDI. In addition, the adding of montmorillonite (OMMT) improve the flexile property of the composite remarkably. In the fourth part the synergistic effect of elastomer and nano-filler were studied. The elastomer toughening of PA66/PA6 nanocomposites prepared from the organic modified montmorillonite (OMMT) was examined as a means of balancing stiffness/strength versus toughness/ductility. Several different formulations varying in OMMT content were made by mixing of PA6 and OMMT as a master-batch and then blending it with PA66 and different elastomers in a twin screw extruder. In this sequence, the OMMT layers were well exfoliated in the nylon alloy matrix. The introduction of silicate layers with PA6 induced the appearance of the γ crystal phase in the nanocomposites which is unstable and seldom appears in PA66 at room temperature and in further affected the morphology and dispersion of rubber phase resulting in much smaller rubber particles. The incorporation of POE-g-MA particles toughened the nanocomposites markedly, but the tensile modulus and strength were both reduced. Conversely, the use of OMMT increased the modulus but decreased the fracture toughness. The nanocomposites exhibited balanced stiffness and toughness.
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