| In this paper, two polyester liquid crystal (butanediol ester liquid crystal and diethylene glycol ester liquid crystal) were synthesized with methyl p-hydroxybenzoate,1,4-butanediol, diethylene glycol, terephthalic acid and thionyl chloride as materials through three steps. First, bis(P-hydroxybenzoic acid) butanediol ester was synthesized from methyl p-hydroxybenzoate and1,4-butanediol by melting transesterification method. Bis(P-hydroxybenzoic acid) diethylene glycol ester was synthesized from methyl p-hydroxybenzoate and diethylene glycol by melting transesterification method and solution method respectively. Second, terephthaloyl chloride was synthesized from terephthalic acid and thionyl chloride. Last, two polyester liquid crystal (butanediol ester liquid crystal and diethylene glycol ester liquid crystal) were synthesized from bis(P-hydroxybenzoic acid) butanediol ester, bis(P-hydroxybenzoic acid) diethylene glycol ester and terephthaloyl chloride. The products were characterized by FTIR spectra, elementary analysis, DSC, TGA and so on. The effects of the synthetic methods, temperature, catalytic and ratio of reactants on the product structures, yield and melting point were discussed in detail. The results showed that the better temperature of synthesis on bis(P-hydroxybenzoic acid) butanediol ester by melting transesterification method is180℃. The better temperature of synthesis on bis(P-hydroxybenzoic acid) diethylene glycol ester by melting transesterification method is135℃. To the reaction between terephthalic acid and thionyl chloride, catalytic efficiency of N, N-dimethyl formamide is better than pyridine. The yield is up to91.4%for an8h reaction. The melting point of the liquid crystal changed with the changing of the ratio of reactants. When the ratio of reactants is4:3, the melting point of butanediol ester liquid crystal is240℃, and the decomposition temperature is starting from329℃. The melting point of diethylene glycol ester liquid crystal is243.5℃, and the decomposition temperature is starting from270℃. When the ratio of reactants is7:6, melting point of butanediol ester liquid crystal is up to274℃.In this paper, epoxy resin is modified by home-made polyester liquid crystal. Different polyester liquid crystal/EP composites were prepared by changing content of polyester liquid crystal. The effects of polyester liquid crystal content on properties of composites were discussed. The fracture surface feature of impact specimens were observed by scanning electron microscope. The results showed that with the content of butanediol ester liquid crystal increased, the tensile strength of composites increased. While the content of butanediol ester liquid crystal is4%, impact resistance and bonding shear strength of composites achieve to the maximum (the impact strength is up to25.9kJ/m2, and bonding shear strength is up to15.7MPa). While the content of butanediol ester liquid crystal is4%, the Tg of the products is166.5℃. The fracture surface feature of the modified specimens have flexible character. With the content of diethylene glycol ester liquid crystal increased, the tensile strength of composites increased. While the content of diethylene glycol ester liquid crystal is4%, the impact resistance and bonding shear strength of composites achieve to the maximum (the impact resistance is up to25.7kJ/m2, the bonding shear strength is up to16.0MPa). While the content of diethylene glycol ester liquid crystal is4%, the Tg of the composites is165.1℃.Finally, epoxy resin is modified by diethylene glycol ester liquid crystal and nano-TiO2. Nano-TiO2was treated with silane coupling agent KH570. The effects of nano-TiO2content on the properties of composites were studied. The properties of the products were tested by DSC, tensile strength, impact resistance and bonding shear strength. The fracture surface feature of specimens and distribution status of nano-TiO2were observed by scanning electron microscope. The results showed that while the content of nano-TiO2is2%, the tensile strength, impact resistance and bonding shear strength of composites achieve to the maximum (tensile strength74.5MPa, impact resistance31.6kJ/m2, and bonding shear strength20.2MPa). While the content of nano-TiO2is2%, the Tg of composite is up to174.3℃,7.8℃higher than composites without nano-TiO2. The results showed that the modified epoxy resin composites with polyester liquid crystal and nano-TiO2performed good properties. |
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