Structure And Properties Of Polyester Alloy-Based Nanocomposites

The study on the structure and properties of Polymer nanocomposites is the focal point and hotspot in the modern polymer materials; it is of great significance in science and practice. This thesis starts from the surface treatment of inorganic particles and the preparation of PBT/SiO2 nanocomposites. The relationship between the structure and properties of the PBT/PET/SiO2 ternary nanocomposites was studied systematically. Deep investigation and analysis on the control and design of structure and performance optimization of the nanocomposites were carried out and applied to other systems. A lot of valuable information was obtained that can act as theoretical basis for development of PBT nanocomposites with high mechanical and thermal properties. The main works and conclusions were listed as following:1. SiO2 nanoparticles were treated with siliane coupling agent by simple two phase blending method. Surfaces of SiO2 nanoparticle were successfully coated by silane coupling agent with analysis of FTIR and the surface oxhydryl degree. The results indicated that the dispersion of SiO2 was strongly affected by the kinds and the concentration of siliane coupling agent. SiO2 nanoparticles could be well dispersed in PBT matrix when the concentration of KH560 is 3-8%wt.2. The mechanical properties of the PBT/SiO2 nanocomposites were obviously enhanced. Compared with the pure PBT, the tensile and flexible strength of nanocomposite with 0.3wt% SiO2 were enhanced 9.5% and 15.1% respectively without losing the impact strength. The thermal deformation temperature increased 25.7℃when 3wt% SiO2 nanoparticles were added. The DSC results showed that crystallization peak temperature for the nanocomposites increased distinctly in comparison to that of pure PBT, which indicated that addition of SiO2 nanoparticles had heterogeneous nucleating effect on PBT. The Ozawa model failed to describe the non-isothermal crystallization of PBT nanocomposites, while Mo model is suitable. The crystallization active energies of pure PBT and nanocomposites with 0.3wt% and 3.0wt% SiO2 determined by Kissinger model were -235.35kJ/mol,-356.14kJ/mol and-351.18kJ/mol respectively.3. The effect of SiO2 nanoparticles on the phase morphology, transesterification between PBT and PET and mechanical properties of the PBT/PET/SiO2 nanocomposites prepared by two methods were studied, which made a theoretical basis for the control and design of structure and performance optimization of the nanocomposites. SiO2 nanoparticles dispersed well in the PBT/PET matrix. DSC and HNMR results showed that the addition of SiO2 nanoparticles restrained the transesterification between PBT and PET to some degree., which is because that SiO2 nanoparticles can react with the end groups of polyesters especially when they exist at the interface of PBE and PET phases. PBT/PET/SiO2 nanocomposites exhibited higher properties than those of PBT/PET blend. For PBT/PET/SiO2 nanocomposite prepared by one-step method, the tensile strength, flexural modulus and HDT were enhanced by 3%, 23% and 18℃respectively.4. PBT/EPOXY/SiO2 and PBT/PET/clay ternary nanocomposites were prepared by melt blending in a twin-screw extruder. The effect of epoxy on phase morphology and mechanical properties of PBT/SiO2 nanocomposites was investigated. FTIR rusult showed that the epoxy groups of the epoxy resin react with the hydroxyl groups of the SiO2 surfaces and PBT chains. Addition of epoxy improved the dispersion SiO2 nanoparticles and interfacial adhesion between the SiO2 nanoparticles and PBT matrix, which resulted in not only the enhancement of the tensile and flexural properties, but also improvement of impact strength and elongation, with a good balance of stiffness and toughness. For PBT/PET/clay nanocomposites, an inserted and exfoliated structure was observed by TEM. When the PBT/PET composition is 80/20wt and the MMT content is 2wt%, overall mechanical properties is optimum, and the thermal deformation temperature reached 184.8℃.