| Semi-aromatic polyamides could be prepared by aliphatic diamine and aromatic diacid or arom-atic diamines with aliphatic diacids, result in improvement of heat resistance and mechanical prope-rties, while decrease of water absorption, since the introduce of aromatic rings into the main chain (or backbone). Semi-aromatic polyamides are mainly used in automobile, electronic and national defence industries because of their excellent thermal, mechanical properties. With the rapid develop-ments of science and technology, demands of semi-aromatic polyamide are growing in market. The semi-aromatic polyamide fibers are also attracted great interests in garment, automobile, telecommu-nications and other industries.In this work, MXD6and MXD6fibers are studied. Glass-transition temperature, melting point and decomposition temperature are tested. The non-isothermal crystallization kinetics and the therm-al degradation processes, mechanisms of MXD6are also analyzed to provide a reference for the heat treatment of MXD6as-spun fiber. After these works, MXD6fibers are prepared by melt-spinning, then suitable process parameters of heat treatment such as single drawing, two-steps drawing process, heat setting at constant length and under tension are set, finally the treated fibers’ mechanical properties, orientation and crystallization were analyzed. The result indicated:1. TGA, DSC, and DMA were used to test semi-aromatic polyamide MXD6row material. It was found that the decomposing temperature, melting, and glass-transition temperature were431℃,294℃and124℃respectively.2. Non-isothermal crystallization process and its dynamics of semi-aromatic polyamide MXD6were studied using DSC. In addition, the non-isothermal crystallization kinetic of MXD6was studi-ed by Jeziorny method, Ozawa method, and Mo method. Mo method can be found as the appropr-iate approach to deal with the non-isothermal crystallization kinetics of MXD6. The crystal growth of MXD6might transfer from two dimensional dislike into one dimensional growth way under the non-isothermal condition. The non-isothermal crystallization of MXD6was calculated by Kissinger method, and the value was-190.22kJ.mol-1. 3. The thermal degradation of semi-aromatic polyamide MXD6fiber was one-step reaction by the analysis of TGA, then calculated the thermal degradation temperature Ti0were T00=405.51℃, Tp0=466.03℃, Tf0=480.07℃, respectively. The thermal degradation kinetics of MXD6was studied using Kissinger method, Flynn-Wall-Ozawa method, and Coats-Redfern method. Corresponding thermal degradation activation energies of the first two-methods were192.11kJ.mol-1and202.47kJ.mol-1, respectively. Possible mechanism of degradation was random nucleation with one nucleus on the individual particle of deceleration curves, showed that the introduce of rigid structures play a role of nucleation.4. The value of strength and modulus of MXD6fiber increased as the drawing temperature and drawing ratio increased in the first drawing in air. The results show that the optimum drawing temperature was130℃, drawing ratio was6. Drawing temperature in first drawing was found as the biggest factor in orthogonal experiment of two-step drawing, next was drawing ratio in second drawing, drawing ratio in first drawing and drawing temperature in second drawing were the minim-um factors. T1=130℃,λ1=3.6, T2=160℃, λ2=1.35were determined as a appropriate processing parameters.5. The value of strength decreased, and modulus decreased and then increased as temperature reached140℃, while the variation of strength and modulus over time were opposite as temperature rose in the heat-setting at constant length of semi-aromatic polyamide MXD6fiber, and the appropri-ate temperature was140℃, appropriate heating time was20min. However, Strength increased and then decreased, and modulus increased as temperature reached160℃, while the variation of strength and modulus were complex in the heat setting under1.31cN/dtex in739.5dtex of MXD6fibers, and the appropriate temperature was160℃, appropriate heating time was60min. |
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