【作者】 赵明良；

【导师】 俞建勇；

【作者基本信息】 东华大学 ， 纺织材料与纺织品设计， 2013， 博士

【摘要】 棉花具有良好的吸湿性、柔软的手感、易染色和不易产生静电等性能,因此棉织物既舒适又环保。棉纤维是纺织和服装工业的重要原料。但是我国棉花供需矛盾相当突出,求远大于供,每年都要从国外进口大量的棉花。聚对苯二甲酸乙二醇酯(PET)具有强度高、热性能好等优点,但其手感硬,吸湿性低,可染性差。现在我国的聚酯行业存在产品结构单一,聚酯产能过剩等问题。在此背景下,基于PET的新型仿棉共聚酯和纤维的研发,可以有效利用我国聚酯过剩的产能,提高PET产品的附加值。若能形成对棉花的一定规模的替代,可一定程度上缓解国内棉花的供需矛盾,因此,本课题的研究具有一定的实用价值和重要意义。本文通过大量的实验筛选出合成仿棉共聚酯的第三、第四和第五单体。第三单体为间苯二甲酸乙二醇酯-5-磺酸钠(SIPE);第四单体用聚乙二醇(PEG),且PEG的数均分子量Mn分别选用2000、4000和6000；第五单体是1,2-丙二醇(1,2-PDO)。确定了合成共聚酯的催化剂、投料顺序、醇酸比、反应温度、反应时间和真空度等关键工艺条件。在1L和10L的聚合装置中,采用直接酯化法,成功合成了所有系列的样品。通过核磁共振氢谱(1H-NMR),对共聚酯的化学结构进行了表征。实验结果表明,绝大部分的SIPE、PEG和1,2-PDO,都成功地嵌入聚合物的大分子链中；而且各自的投料比与其在共聚物中的实际含量基本一致。还对所有样品的特性粘度[n]进行了测试,结果显示,所有样品的特性粘度值大小适中。利用一维广角X射线衍射(1D-WAXD),分析了共聚酯的晶体结构。嵌入了第四单体PEG和第五单体1,2-PDO后,共聚酯的晶体结构和PET的晶体结构几乎完全相同,说明引入PEG和1,2-PDO,没有引起晶体结构的变化。随着PEG质量比和1,2-PDO摩尔比的增加,共聚酯的结晶度在总体上不断降低。当PEG的质量比相同(以10%为例),而数均分子量降低时,结晶度在不断减小。还通过部分样品加热拉伸后的二维广角X射线衍射(2D-WAXD)和二维小角X射线散射(2D-SAXS),研究取向度的变化规律。结果表明,刚开始沿轴向的应变适度变大时,2D-WAXD的衍射条纹和2D-SAXS的散射条纹都会逐渐增强,分子链的取向度提高；当应变增加到一定程度,再继续增加时,二维WAXD的衍射条纹和二维SAXS的散射条纹,总体上反而都变弱,说明分子链的取向度降低了。从一维WAXD和SAXS曲线的推算出的晶粒尺寸、结晶度和长周期等晶体参数的变化规律与上面类似。利用差示扫描量热法(DSC),研究了共聚酯的热性能。随着PEG和1,2-PDO含量的增加,样品的玻璃化转变温度(Tg)、冷结晶温度(Tcc)和熔点(Tm)总体上呈下降态势。当PEG的质量百分比相同(以10%为例),PEG的数均分子量降低时,Tg、Tcc和Tm不断下降。采用Jeziorny法,分析部分样品的非等温结晶动力学,发现共聚酯的结晶过程比Avrami模型要复杂；当数均分子量相同时,随着第四单体PEG6000含量的增加,半结晶周期t1/2的值减小,冷结晶速率增快。还利用Mo法,对部分样品在不同升温速率下的非等温结晶动力学进行研究。发现升温速率提高时,冷结晶温度(Tcc)升高；随着相对结晶度的增加,F(T)值变大,而α值却近似于一个常数。通过热重分析仪(TGA),详细研究了共聚酯的热稳定性。氮气中,TGA曲线出现一个热失重平台；空气里,TGA曲线都有两个热失重平台。在氮气和空气里,随着PEG和1,2-PDO含量的增加,热降解温度均下降。空气中的热降解比氮气中的热降解更容易发生。当PEG的质量百分比相同时(如10%),在氮气和空气里,随着PEG的数均分子量的降低,共聚酯热稳定性变差。随着升温速率提高,在氮气和空气中,TGA和dTGA曲线均向高温方向移动。利用Friedman法研究了热降解动力学。在氮气中,当升温速率相同(以10k/min为例),而改性组份PEG6000的质量百分数变化时,Ln(da/dt)对1/T曲线和Ln(1-a)对1/T曲线的线性关系较好。而且PEG6000含量增加时,热降解活化能(E)变低,表明共聚酯的热稳定性变差；热降解反应级数(n)下降,说明热降解速率加快。还发现,在氮气中对同一个样品,当升温速率变化时,Ln(da/dt)和Ln(1-a)对1/T曲线的线性关系较好。E、n、频率因子(Z)等热降解参数随升温速率等测试条件的变化而变化。此外,通过特性粘度的变化,对热稳定性能进行了分析。研究发现,PEG和1,2-PDO的含量越高,烘燥温度越高,烘燥时间越长,则特性粘度下降越快,说明热降解越容易发生。通过静态接触角(contact angle)的测试,详细研究了共聚酯的亲水性能。随着第四单体PEG和第五单体1,2-PDO含量的增大,接触角逐渐地减小,共聚酯的亲水性增强。PEG的质量比相同时(如10%),当PEG分子量降低,样品的接触角变小,亲水性增强。选择部分共聚酯切片进行熔融纺丝,制备成仿棉纤维。确定了干燥温度、纺丝温度和速度、牵伸倍数等主要工艺参数。利用缕纱测长仪,结合称重法,推算出纤维的纤度。通过WAXD法测试纤维结晶度,结果显示,当第五单体1,2-PDO含量增加时,结晶度变小。采用WAXD法和声波传播法测定了纤维取向度,随着1,2-PDO含量增加,纤维取向因子(fs)和取向度下降。利用电子单纱强力测试仪,测试了纤维力学性能,发现当1,2-PDO摩尔百分数增加,断裂强度和初始模量总体上呈减小趋势,但断裂伸长率却增大。回潮率的测试结果表明,1,2-PDO的含量增大,纤维的回潮率变大,吸湿性能提高。沸水收缩率的测试结果显示,1,2-PDO的含量越大,纤维的沸水收缩率越大。利用接触冷暖感测定仪,分析了仿棉织物的接触舒适性,发现所有仿棉织物的Qmax值比普通PET织物的Qmax值小。而且随着1,2-PDO的摩尔百分数的不断增加,仿棉织物的Qmax值总体上呈下降趋势,这表明1,2-PDO的引入使得仿棉织物的接触舒适性变好。更多还原

【Abstract】 Cotton possesses many superior properties such as good hygroscopicity, soft handling, easy dyeability and antistatic ability. Therefore, cotton fabrics are comfortable and environmental. Cotton fiber is a kind of crucial material in textile and fashion industries. However, the contradiction between supply and demand of cotton are very serious in China, the demand is much greater than the supply. In order to solve the above contradiction of cotton, China has to import a large number of cotton from other countries every year. Poly(ethylene terephthalate)(PET) has a lot of advantages such as high strength and excellent thermal property. However, disadvantages of PET are also obvious such as rigid handle, low moisture regain and poor dyeability. Nowadays, there are many problems in Chinese polyester industry. For example, the structure of products is too simple, and the supply of polyester is surplus. On this background, studies on the new cotton-like copolyester and its fiber can effectively consume surplus polyester products, and enhance the added value of PET. When modified PET fibers can replace some parts of cotton, it can partly relieve the contradiction between supply and demand of domestic cotton. Therefore, the studies have some practical value and significance in this thesis.On the basis of abundant experiments, the third, fourth and fifth comonomers are eventually chosen. The third comonomer is sodium-5-sulfo-bis-(hydroxyethyl)-isophthalate (SIPE). The fourth is poly(ethylene glycol)(PEG), and the number average molecular weight(Mn) is2000,4000and6000, respectively. The fifth unit is1,2-propanediol (1,2-PDO). The key technological conditions were ascertained in the esterification and polycondensation process such as the catalyst, feed order, feed ratio, temperature, time and vacuum. All samples were successfully synthesized with direct esterification method in the11and101reactor. Their chemical structures were characterized by nuclear magnetic resonance (1H-NMR). Experimental results showed that overwhelming units have been incorporated into molecular chains. The actual molar ratio of all comonomers was basically consistent with the correlative feed ratio. The intrinsic viscosity of all specimens was measured in detail. The results showed that the intrinsic viscosity value of all samples was moderate.Taking advantage of1D wide angle X-ray diffraction (1D WAXD), the crystal structure of copolyesters was explored. After incorporation with PEG and1,2-PDO units, the crystalline structure of copolyesters was nearly identical to the PET homopolymer. It indicated that PEG and1,2-PDO comonomers did not changed the crystal structure. The crystallinity of samples lessened gradually with the increase of PEG and1,2-PDO content. The crystallinity of copolyesters gradually lowered with the decrease of the molecular weight of PEG when the weight percent of PEG was identical (such as10%). Through2D Wide angle X-ray diffraction (2D WAXD) and2D small angle X-ray scattering (2D SAXS), we studied the variation tendency of orientation degree of copolyesters. Before measurements, all specimens were first heated and stretched into different strains along axial direction. At the beginning, the intensity of diffraction and scattering streaks both became stronger when the strain increased. It indicated that the degree of orientation enlarged. Interestingly, after the strain reached a certain value, diffraction and scattering streaks both became weaker when the strain continued to increase. It showed the degree of orientation reduced. The crystal size, crystallinity and long period calculated from ID WAXD and ID SAXS curves owned the similar variation tendency.From differential scanning calorimetry (DSC) measurement, thermal properties were systematically investigated. With the increase of PEG and1,2-PDO percentage, the glass-transition temperature (Tg), the cold-crystallization temperature (Tcc) and the melting temperature (Tm) all decreased gradually. When the weight ratio of PEG was same (such as10%), Tg, Tcc and Tm gradually reduced with the fall of the molecular weight of PEG The non-isothermal kinetics of part of samples was analyzed by Jeziorny method. Results showed that the crystallization process of copolyesters were more complicated than the Avrami model. When the number average molecular weight was identical, as the ratio of PEG6000unit increased, the semicrystalline time (t1/n) decreased, and the cold-crystallization rate improved. The non-isothermal kinetics under different heating rate was studied by Mo method. Tcc of samples enhanced as the heating rate increased. With the increase of crystallinity, the value of F(T) became bigger, but value of a was almost a constant.Thermal stability was investigated in detail by thermogravimetric analysis (TGA) measurement. TGA curves under nitrogen atmosphere were all found to have only one weight-loss stage. While TGA curves under oxygen atmosphere had two weight-loss stages. Under nitrogen and oxygen atmosphere, the degradation temperature all gradually reduced with the increase of PEG and1,2-PDO ratio. The thermal degradation under oxygen atmosphere was easier to occur than that under nitrogen atmosphere. Thermal stability both became worse with decreasing the molecular weight of feed PEG units under nitrogen and oxygen atmosphere. The TGA and dTG curves all seemed to shift towards higher temperature side as the heating rate increased under nitrogen and oxygen atmosphere. Thermal degradation kinetics was studied by Friedman method. Under nitrogen atmosphere, when heating rate is identical (such as10k/min), as the weight ratio of PEG6000unit changed, the curves of Ln(da/dt) vs.1/T and Ln(1-α) vs.1/T both presented linear relationship. Moreover, with the increase of PEG6000content, thermal degradation activation energy (E) became lower, the order of thermal degradation reaction (n) decreased, the thermal degradation rate increased. Under nitrogen atmosphere, for the same sample, as the heating rate changed, the curves of Ln(dα/dt) vs.1/T and Ln(1-α) vs.1/T all exhibited good linear relationship. Thermal degradation kinetics parameters such as E, n and frequency factor (Z) were greatly affected by heating rate. Thermal stability was also analyzed by the intrinsic viscosity variation. When the content of PEG and1,2-PDO were more, the drying temperature was higher and the drying time was longer, then the intrinsic viscosity decreased quickly. It indicated the thermal degradation was easier to happen.By means of contact angle measurements, the hydrophilicity of copolyesters was studied in detail. With the increase of weight ratio of PEG and molar ratio of1,2-PDO, all contact angle values gradually became smaller, and the hydrophilicity of samples were better. When the weight percent of PEG was identical (such as10%), the values of contact angle were detected to gradually reduce as the number average molecular weight of feed PEG units lowered, indicating that the hydrophilicity of samples was enhanced.Some copolyester chips were spun into cotton-like fibers by melt spinning method. Spinning technological parameters were determined such as drying temperature, spinning temperature and rate, draw ratio. By measuring reel and weight method, linear density of fibers was calculated. The crystallinity of fibers was studied by wide angle X-ray diffraction (WAXD). Results showed that the crystallinity decreased with the increase of content of1,2-PDO. By means of WAXD and acoustic wave propagation method, the degree of orientation of fibers was explored. It was found that the orientation factor (fs) and degree of orientation both lowered as the1,2-PDO content increased. The mechanical properties of fibers were measured by electronic single yarn strength tester. Experiments indicated that when molar ratio of1,2-PDO unit increased, The breaking tenacity and initial modulus were gradually reduced, yet elongation at break enhanced. The moisture regain of cotton-like fibers was tested. Results exhibited the increase of1,2-PDO content improved their moisture regain and hygroscopicity. The boiling water shrinkage of fibers was measured. The results indicated that the shrinkage increased with the increase of content of1,2-PDO. Making use of contact cool and warm feeling tester, the contact comfort of cotton-like fabrics was analyzed. It was found the Qmax value of cotton-like fabrics was smaller than that of PET fabrics. Moreover, the Qmax value of cotton-like fabrics gradually decreased when the molar ratio of1,2-PDO unit enhanced. The Results indicated the contact comfort of cotton-like fabrics became better with the incorporation of1,2-PDO comonomer.更多还原