| In this thesis, the morphology, microstructure and properties of poly(ethylene terephthalate)/polyamide-6 blend were studied.A kind of ethylene-acrylate-maleic anhydride terpolymer (E-AE-MA) was added to PET/PA-6 blends as toughening agent. Melt-mixed blends were prepared at various component ratios and different E-AE-MA levels. Izod impact tests indicated excellent toughening effect of E-AE-MA. Morphological, thermal measurements and Fourier transform infrared spectroscopy were carried out to investigate the phase morphology and toughening mechanism of PET/PA-6/E-AE-MA blends. It was observed that E-AE-MA particles were selectively dispersed at the interface between PET and PA-6 phases and in the domain of PA-6 phase. The formation of E-AE-MA layers around PA-6 particles could cut off the interaction between PET and PA-6, resulting in an enlarged PA-6 phase domain. Based on the experimental results, core-shell microstructure, with PA-6 as a hard core and E-AE-MA as a soft shell, could be suggested. It was proposed that the main toughening mechanism of E-AE-MA on PET/PA-6 blends could be due to the increased PA-6 phase domain size and the existence of the observed core-shell microstructure, which could resist against crack propagation and absorb more impact energy.Then the effect of SiO2 on phase morphology and mechanical properties of PET/PA-6 blends was investigated. After adding SiO2 particles into the blends, the impact strength, tensile strength and modulus were obviously enhanced in the whole composition range investigated. However, the impact values were still lower than the theoretical ones that could be predicted from "mixing rule" of polymer blending. The SiO2 particles were found to be preferentially dispersed in PA-6, and this led to the increased size of PA-6 phase. Observation of tensile fractured surface revealed that the addition of SiO2 enhanced the interfacial adhesion between PET and PA-6. DMA results showed that the addition of SiO2 made the Tg of PA-6 shift to higher temperature, and the increment became bigger with the increase of SiO2 content. Meanwhile, the addition of SiO2 had no obvious effect on the Tg of PET. Onlyα-relaxation of PA-6 was confined by SiO2 revealed that SiO2 particles dispersed only in PA-6 phase, which was consisted well with the morphological observation. DSC data showed that PA-6 and SiO2 particles could facilitate the crystallization of PET separately, but when the ternary system contained both PA-6 and SiO2, the crystallization of PET was restrained. It demonstrated the selective dispersion of SiO2 in PA-6. FT-IR investigated the shifting of absorption bands of PET/PA-6 composite after the addition of SiO2 and attributed the selective dispersion of SiO2 to the formation of hydrogen bonds. So it was concluded that the phase morphology of PET/PA-6 could be prominently changed through adding SiO2 and thus resultd in increased mechanical properties, restricted molecular relaxations and restrained crystallization.The morphology development of PET/PA-6 system was investigated by SEM. The crystallization and melting behavior were investigated by DSC, and Avrami equation was used to analyze the crystallization data. It was revealed from the SEM photos that the phase transition of PET/PA-6 system occurred at the composition ratio between 60/40 and 50/50. The results of nonisothermal crystallization showed that the crystallization temperature and the starting point of crystallization of PET were increased by the addition of PA-6, while those of PA-6 were decreased by PET. The results of isothermal crystallization showed that low content PA-6 could promote the crystallization of PET and decrease the crystallization time, while too much PA-6 would restrain the growth of PET crystallite. And PET would always restrain the crystallization of PET. Using Avrami equation to analyze the isothermal crystallization data, it was found that when the content of PA-6 was lower than 30wt%, the Avrami exponent was increased with the increase of PA-6 content. But when the content of PA-6 further increased, the Avrami exponent of PET decreased. This indicated that the morphology of PET/PA-6 system had great influence on the pattern of PET crystallization. And despite of the morphology, PET could always confine the crystallizing space of PA-6, thus decrease the crystallizing speed of PA-6. Comparing the melting curves of PET/PA-6 blends with different composition ratio, it was found that the PA-6 made the PET crystallite less perfect, while PET had the same effect on PA-6 and decreased its melting temperature.
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