| Firstly, mesomorphic monomer p-acetoxy-benzoic (p-AHB), phosphorous flame retardant monomer10-(2,5-dihydroxyphenyl)-10-hydrogen-9-oxa-10-phosphorin-10-oxide (DOPO-AHQ), nitrogenous flame retardant monomers and four different kinds of flexible monomers were prepared. And five kinds of flame retardant thermotropic liquid crystal copolyesters (TLCP) with low melting temperature were synthesized by melt condensation polymerization. The molecular structure, texture of liquid crystal, intrinsic viscosity and molecular weight of TLCP were investigated by Fourier transform infrared spectra (FT-IR), wide angel x-ray diffraction (WAXD), hot-stage polarizing optical microscope (POM) and Ubbelohde viscosity meter. The results showed that the texture of all the five kinds of TLCP was the type of nematic liquid crystalline, and their molecular weights were at about20000. In addition, the effect of flame retardant elements on the flame retardant property of TLCP was researched. Based on the analysis, it could be learned that the vertical combustibilities of five kinds of TLCP have all reached V-0, but the Limiting Oxygen Index (LOI) of phosphorous-nitrogenous synergily flame retardant TLCP was higher than that of simplex phosphorous flame retardant TLCP, and the LOI of TLCP-5was the highest (77). Besides, the influence of flexible spacer units on Tm, Tg and the thermal stability of TLCP were investigated, the result showed that Tm and Ta of TLCP were both reduced with the increasing of methylene, and the decrease of Tm and Tg of TLCP-5was biggest, which reduced by122℃and118℃, respectively. However, their thermal stability and char yield were still better, the maximum rate of thermal degradation (Vdmax) of this five kinds of TLCP all appeared at450℃, and the yields of charred residue at700℃were all higher than33.00%, the maximum was40.93%.Secondly, ABS/TLCP-5and PP/TLCP-5in-situ composites were prepared through blending ABS and PP with TLCP-5whose synthetic performance was optimal. The influences of TLCP-5on microstructures, crystalline morphology, mechanical properties, processing properties and thermal properties of in-situ self-enhancement composite were investigated. The results of POM and scanning electron microscope (SEM) demonstrated that TLCP-5 formed microfibrillars in ABS and PP matrix. POM and WAXD results showed that TLCP-5induced PP to form sectional β crystalline morphology. It was found that ABS and PP were both reinforced by adding TLCP-5(tensile strength and elastic modulus of ABS respectively increased by24%and50%, and those of PP both increased by29%), furthermore, the toughness properties of PP raised by adding TLCP-5(its impact strength increased by81%). It was also found that the processing fluidity of ABS/TLCP-5and PP/TLCP-5in-situ composites were improved significantly compared to pure ABS and pure PP from the results of melt flow rate (MFR) and the rheology measurement. Meanwhile, it was proved by TG and DTG testing that the thermal properties of ABS/TLCP-5and PP/TLCP-5were both enhanced because of the prominent heat resistance of TLCP-5.Finally, PP/TLCP-5/PP-g-MAH in-situ composite was prepared for researching the effect of compatibilizer PP-g-MAH on the properties of PP/TLCP-5. The results of POM and SEM demonstrated that the compatibility between PP and TLCP-5was improved, and the dispersivity of β crystalline nucleating agent (TLCP-5) which possessing a smaller particle size was more evenly. Besides, fiberizability of TLCP-5was increased by adding PP-g-MAH, and the length-diameter ratio of TLCP-5microfibrillar increased about1time. Therefore, impact properties and tensile properties of in-situ composite were further raised by adding PP-g-MAH (its impact strength and tensile strength were increased by4.7KJ/m2and5.5MPa, respectively). In addition, the results of MFR, rheology measurement, TG and DTG testing showed that the processing fluidity and the thermal stability of in-situ composite were further improved. |
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