| Poly (butylene terephthalate) (PBT) are widely used in electronic appliances, automobiles, mechanical industries and fiber optic cable due to its excellent mechanical properties, chemical resistance, excellent resistance to heat aging properties and dielectric properties. While some properties remain poorly, such as notched impact strength, warping and so on. Especially the domestic PBT still have low molecular weight, low intrinsic viscosity, poor mechanical properties which cannot meet the requirements for fiber-grade material. In this paper, PBT was modified by chemical chain-extension, toughening and reinforcing.Firstly, the epoxy chain extender (ADR4370S) was used to modify PBT. The effects of different amounts of chain extender for PBT chain structure and properties of the product were studied. The results showed that the molecular structure of PBT was changed with the addition of ADR4370S which indicated that comb-branched structure generate internally. The chain-extender could effectively improve the melt viscosity and melt strength of PBT. The mechanical properties of the system were significantly improved while the thermal stability and Tg changed little. When excessive ADR4370S was added, sol-gel transition occurs in PBT molecular chains.Secondly, the effect of the chain extender was investigated by comparison of the intrinsic viscosities between pure PBT and chain extended PBTs. The non-isothermal crystallization behavior of PBT and chain extended PBTs was also studied by Differential Scanning Calorimetry (DSC). The result showed that when the introduction of ADR4370S was 1.5 wt%, the intrinsic viscosity of PBT was increased from 1.061 dL/g to 1.486 dL/g and viscosity-average molecular weight was improved from 35117 to 51681 which went near to the PA1.25. It was also clear that the addition of ADR4370S improved the crystallization temperature of PBT without changing its nucleation mechanism and crystal growth. Compared with the Jeziorny method, Mo method gave a better description for the non-isothermal crystallization of PBT and chain extended PBTs. The activation energies of PA1.25 calculated by Flynn-Wall-Ozawa method was lower than that of pure PBT, revealing that the present of ADR4370S lead to decrement of the activation energy of PBT crystallization.Thirdly, the ADR4370S filled POE was used to melt blend with PBT, then the effect on the structure and properties of PPAs was investigated. The results indicated that the epoxy chain extender didn’t react with the POE. The storage modulus, loss modulus and complex viscosity of the composites were improved because of the chain extending reaction between PBT and epoxy groups. Furthermore, the tensile strength, notched impact strength and flexural modulus of the PPAs were increased, but the branched structure was generated in the composites due to the chain extension.Finally, PBT which was modified by 1.25 wt% chain extender ADR4370S was synthesized with OMMT by melt-blending intercalation. The phase morphology and properties based on different amount of OMMT was investigated. The result showed that a small amount of OMMT caused the decreasing on the modulus and melt viscosity of the systems. On the contrary, the tensile strength and flexural modulus of the PA1.25/OMMT was improved. When the OMMT content was 0.5 wt%, it has the highest crystallization temperature and the maximum notched impact strength, but the crystallization half time reached the minimum. |
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