【作者】 杨拯；

【导师】 潘婉莲；

【作者基本信息】 东华大学 ， 材料学， 2006， 硕士

【摘要】 聚对苯二甲酰对苯二胺（poly（p-phenyleneterephthalamide）PPTA）纤维，在我国被称为芳纶1414，由于其具有高强、高模、耐高温的性能而广泛应用于特种服装，航空航天，电缆以及复合材料中。低温溶液聚合法是生产PPTA最为成熟且早已工业化的方法，而PPTA纤维则是由PPTA的液晶溶液采用干喷湿纺法制备而成。但由于PPTA树脂难溶难熔，必须在浓硫酸中进行液晶纺丝，工艺复杂，设备要求耐强酸腐蚀，加工比较困难，而加入第三或第四单体进行共缩聚，是改进其难溶性最有效最彻底的方法，改性后的共缩聚PPTA可溶解于极性有机溶剂中，能够直接进行纺丝。本文在聚合物的合成部分，首先采用亚磷酸三苯酯（TPP）为催化剂，对以对苯二甲酸为初始单体的聚合工艺进行了初步研究，系统探讨了反应时间、反应温度、单体摩尔浓度以及吡啶添加量对PPTA直接缩聚工艺的影响，但由于该工艺要求非常低的单体浓度（＜0.1mol／L），并且需要耗大量的吡啶（吡啶用量占溶剂体积分数为20％），因此不具有工业化应用前途。其次，以3，4’-二氨基二苯醚（3，4’-ODA）为第三单体，分别在N，N-二甲基乙酰胺（DMAc）／CaCl₂和N-甲基-2-吡咯烷酮（NMP）／CaCl₂溶剂体系中对PPTA的共缩聚工艺进行了研究，系统探讨了在两种溶剂体系中反应时间、反应温度、单体摩尔浓度、3，4’-ODA的含量以及不同的加料方式对体系状态和共聚物比浓对数粘度的影响，并对两种溶剂体系的聚合工艺进行了对比。结果表明，在DMAc／CaCl₂和NMP／CaCl₂溶剂体系中能够通过低温溶液缩聚法制备出分子量比较高（ηinh＞2.0dl/g）的PPTA共聚物。通过FTIR表征，可发现样品中苯撑的含量随参与反应的3，4’-ODA含量的增加而上升，说明ODA参与了共聚反应。热分析结果表明，添加第三单体3，4’-ODA，共聚物的耐热性降低，最大热失重速率时的温度为528℃（25mol％，混合投料），低于PPTA的最大热失重速率温度（582℃），并且随着ODA含量的增加，最大热失重速率温度呈下降趋势。两种二胺单体分别加料方式下的共聚物的最大热失重速率温度要大于混合投料时的最大热失重速率温度，主要在于混合投料时大分子链的无规程度增加，而分别加料方式下的大分子链中存在一定长度的PPD链，增加了共聚物的热稳定性。共聚物溶解性测试表明，随着ODA含量的增加共聚物的溶解性增加，可以溶于NMP／CaCl₂体系中，而两种二胺单体分别加料方式下制备的共聚物溶解性要差于混合投料下的共聚物。通过对PPTA共聚物的NMP和DMAc溶液体系的流变性研究，可以看出以3，4’-ODA为第三单体的PPTA共聚物溶液为典型的切力变稀流体，浆液的表观粘度随着温度的升高而降低，随着浓度的升高而增大，非牛顿指数n随着温度升高而增大，即溶液的牛顿性增大，随着浓度的升高非牛顿指数n下降，即溶液的切力变稀现象显著。凝固值测定表明，对于两种溶剂体系而言，水均是一种非常强的凝固剂，随着凝固液中溶剂（NMP或DMAc）比例的提高，凝固值增大。凝固液中添加CaCl₂凝固值增大，并且随着CaCl₂含量的增大凝固值逐渐增大。温度对凝固液的凝固值影响不是太大，变化趋势比较缓和。浆液稳定性测试表明，NMP和DMAc两种溶剂体系中的浆液在室温和60℃下都具有非常好的稳定性。以H₂O／DMAC／CaCl₂为凝固浴，以PPTA共聚物的DMAc浆液采用干湿法纺丝可以得到较好力学性能的初生丝。初生纤维的强度随着喷头拉伸倍数的提高而增大，随着沸水拉伸倍数的提高也增大，断裂伸长率随着喷头拉伸的提高而减小，而沸水拉伸倍数对断裂伸长率的影响趋势不明显。通过干湿法纺丝得到的共聚PPTA纤维的截面几乎观察不到空穴，只存在少量的裂纹，可见我们采用的H₂O／DMAC／CaCl₂凝固浴和凝固条件纺制出的纤维具有较佳的形态结构。本论文研究的主要创新点为：1．以3，4’-二氨基二苯醚（3，4’-ODA）为第三单体，分别在N，N-二甲基乙酰胺（DMAc）／CaCl₂和N-甲基-2-吡咯烷酮（NMP）／CaCl₂溶剂体系中对PPTA的共缩聚工艺进行了研究，获得了较高分子量的PPTA共聚体：2．系统的研究了添加第三单体3，4’-ODA对PPTA的耐热性的影响，并分析了共聚PPTA的热分解动力学；3．系统的研究了以3，4’-ODA为第三单体的PPTA共聚物的NMP和DMAc溶液的凝固性和流变性，为后续的纺丝奠定了基础；4．以共聚物的DMAc溶液采用干湿法纺丝制备了共聚体纤维，对纺丝工艺进行了初步探索并对纤维的形态结构进行了研究。更多还原

【Abstract】 Poly（P-phenyleneterephthalamide） fiber as we call aramid fiber 1414 is a kind of high performance fiber with high modulus and high strength, and can be used in many high technology fields, such as aviation, cable, and composites.Poly（P-phenyleneterephthalamide） （PPTA） is polymerized in polar organic solvents such as N-Methyl-Pyrrolidone.Adding CaCl₂ in the solvent can significantly improve the solubility of PPTA,and high molecular weight PPTA is polymerized. PPTA is dissolved in Concentrated sulfonic acid and the dope is lyotropic liquid crystal, the dope is spinned from the spinneret and the fiber is prepared. For the use of concentrated sulfonic aicd, it is so difficult to produce this kind of fiber. Adding the third or the forth monomer in the main chain can significantly improve the solubility and the resultant polymer can be dissolved in the solution, and can be spinned directly, so the process and productivity is improved.In this paper, firstly, high molecular weight (η_inh＞3.8dl/g)PPTA is synthesized by direct polycondensation using triphenyl phosphate （TPP） as condensing agent. In this process, the reaction time, reaction tempreture, monomer concentration, concentration of pyridine, the molar ratio of TPP to TPA are discussed. Secondly, the copolymerization process using 3,4’-diaminodiphenyl ether（3,4’-ODA） as third monomer is discussed. As we can see from the result, the optimized process is as follows: the reaction time is between 20-30min, the initial reaction tempreture is below -10℃,and the late tempreture is as high as 80℃,the molar ratio of 3,4’-ODA is 25%, and the best concentration of CaCl₂ is 3%wt, and also the sequence of adding monomers is discussed, when the two diamines are mixed and the terephthaloyl dichloride is added subsequently, the resultant polymer has the highest molecular weight.As we can see from the result of FTIR figure, the adsorption intensity of-O- increases with the increase of the molar ratio of third monomer. The thermal analysis（TG） indicates that the thermal resistant property of the polymer decreases with the increase of the molar ratio of third monomer.When the molar ratio of 3,4-ODA and the monomers are polymerized randomly, the highest decomposition tempreture is 528℃, and the highest dccomposition tempreture decreases with the increase of the molar ratio of third monomer. The solubility is also significantly affected by the molar ratio of 3,4 -ODA. In the N,N-dimethylacetamide（DMAc）/CaCl₂ system, the copolyamide cannot be dissolved in the solvent system when the molar ratio of 3,4 -ODA is less than 25%, in the N-Methyl-Pyrrolidone（NMP）/CaCl₂ system, the copolyamide cannot be dissolved in the solvent system when the molar ratio of 3,4 -ODA is less than 15%.So we can get the conclusion that the NMP has better solubility and is more suitable to the process.The result of the study on the rheology indicates that both of the copolymer dopes are shear sensitive liquid, the viscosity of copolymer dope decreases when the shear rate is increased. The apparent viscosity of copolymer dope decreases with the increase of tempreture, increases with the decrease of concentration. The non-Newton Index increases with the increase of tempreture, decreases with the increase of polymer concentration. The coagulation value indicates water is a kind of strongest coagulation matter as to the two solvent systems. Using H₂O/DMAC/CaCl₂ system as coagulation bath, the DMAc dope of PPTA copolymer is spinned from the spinneret by dry-jet wet-spin mothod and the corresponding fiber with good mechanical property is prepeared.The tensile strength of initial fiber increases with the increase of spinneret draw ratio and boil water draw ratio, and the elongation rate at break decreases correspondingly.As we can see from the SEM picture of the cross section of copolymer fiber, there is little holes in the cross section, only a few crack are obserbed. So it can be conclusioned that copolymer has good morphology structure under the process used.The new ideas mainly brought forward in this paper are as follows: first, chosing 3,4-ODA as third monomer, the copolymerizaton process in DMAc/CaCl₂ and NMP/CaCl₂ solvent system are discussed. Second, The thermal property of copolymer, and the thermal decomposition kinetics are discussed systemly.Third, the rheology and coagulation property are studyed systemly. Forth, the copolymer fiber is prepared by dry-jet wet-spin method, and the morphology structure is observed.更多还原