Effect of Added Poly (vinyl pyrrolidone) during Condensation on Properties of Poly(p-phenylene terephthalamide)Pulp

Poly(p-phenylene terephthalamide)(PPTA)pulp was prepared by polycondensation of the p-phenylene diamine(PPDA)with terephthaloyl chloride(TPC)in the completely anhydrous solvent system of N-methyl pyrrolidone(NMP)having calcium chloride,in the presence of poly(vinyl pyrrolidone)(PVP)having a viscosity average molecular weight lower than 40 000.It was confirmed that the polycondensation could be accelerated,the inherent viscosity of the polymer could be increased,and the polymers could be fibrillated more easily by the addition of the PVP.FTIR and X-ray spectra proved that PVP had not combined into molecular chains of the resultant PPTA pulps.The morphology of the resultant pulps,the effect of viscosity average molecular weight,amount and adding mode of PVP on inherent viscosity,specific surface area,and mean length of the resultant pulps were discussed in detail.And the friction and wear properties of the compound reinforced by the resultant pulps were simply investigated.

Mechanical Property and Crystal Structure of Poly(p-phenylene terephthalamide)(PPTA) Fibers during Heat Treatment under Tension

The relationship between property and structure of poly( p-phenylene terephthalamide)( PPTA) was investigated for the purpose of obtaining products with better performance. PPTA fiber subjected to heat treatment under different conditions was intensively studied. Simultaneous wide-angle X-ray diffraction( WAXD) technique was introduced to study the changes of crystal structure. It was found that the tensile modulus was strongly sensitive to the levels of temperature and tension. The structure parameters including crystal size and crystal orientation after heat treatment evolve similarly to the tensile modulus,indicating a direct structure-property relationship. The lattic c-dimension increases after heat treatment and is greatly affected by the tension. An optimal temperature can be found around 400 ℃,where big change can happen in the crystal structure due to α-relaxation in the crystal region as supported in dynamic mechanical analysis( DMA).

ELECTRICALLY CONDUCTIVE COMPOSITE PREPARED BY ELECTROCHEMICAL POLYMERIZATION OF PYRROLE IN POLY-(p- PHENYLENE TEREPHTHALAMIDE) MATRIX

The preparation of PPy/PPTA conductive composite films by electrochemical method is presented.The first step is to cast a thin layer of poly (p-phenylene-terephthalamide) (PPTA) on a slice of Pt working electrode. The second step is to electrochemically polymerize pyrrole on the PPTA/Pt working electrode. Both of the electrical conductivity and the mechanical properties of the PPy/PPTA composite film are better than those of the pure PPy film, and the film has excellent flexibility at low temperature, even in liquid nitrogen.The SEM picture of the cross-section of PPy,/PPTA composite film showed that the two components were well mixed.Cyclic voltammograms of PPy,/PPTA film in aqueous solution showed that the conductive films could be reduced and reoxidized.

STUDIES ON THE POLYPYRROLE/POLYELECTROLYTE MOLECULAR COMPOSITES

The potyelectrolyte of propane sulfonate(PS) grafted PPTA copolymers——PPTA-PS, PPTA[O]-PS, PPTA[C]-PS were prepared and used as electrolyte in the process of electrochemical polymerization of pyrrole to form the molecular composite polypyrrole (PPY)/Polyelectrolyte.The preparation and liquid crystalline property of three kinds of polyelectrolyte, the electrical conductivity, mechanical properties, SEM and thermoproperties of PPY/polyelectrolyte are presented in detail.

KINETICS OF MESOPHASE FORMATION OF A LYOTROPIC AROMATIC POLYAMIDE

The kinetics of mesophase formation of a lyotropic aromatic polyamide from isotropic state has been studied by means of depolarized light intensity. Avrami type analysis of the data gives an exponent close to 1, which suggests the nucleation followed by one-dimensional growth. No influence of blending flexible chain from nylon 6 to the aromatic polyamide on the kinetics of mesophase formation was observed.

对位芳纶的结构与缺陷对其力学性能的影响

聚对苯二甲酰对苯二胺(PPTA)纤维具有优异的力学性能、耐化学腐蚀性能以及阻燃性能,在航空航天、国防、民用等领域得到了广泛应用,是一种新型战略性材料。对4种不同规格的对位芳纶的力学性能、相对分子质量、聚集态结构以及纤维表面及内部缺陷进行研究,建立纤维结构、缺陷与性能之间的关系。结果表明:在具有相同化学分子结构的前提下,聚合物相对分子质量是影响纤维力学性能的重要因素之一,随着相对分子质量的增加,纤维的强度和模量增加。对位芳纶的拉伸强度主要与其结晶度、取向度、表面缺陷以及内部微孔缺陷有关,其中结晶度和微孔缺陷最为重要。纤维的模量主要与纤维的取向度有关,结晶度及纤维内外部缺陷对纤维模量的影响较小。

聚对苯二甲酰对苯二胺气凝胶纤维的制备与性能

气凝胶纤维具有良好的柔韧性,其织物在可穿戴保温隔热领域受到了人们高度的关注。聚对苯二甲酰对苯二胺(PPTA)具有优异的耐热性、耐化学品腐蚀等性能,是制备气凝胶纤维的理想材料。然而,目前利用PPTA纤维(对位芳纶)的纳米纤维分散液制备气凝胶纤维的过程复杂、耗时且成本高,因此本工作通过合成具有良好可加工性的PPTA溶液,利用湿法纺丝和冷冻干燥工艺制备PPTA气凝胶纤维,极大地简化了工艺流程。实验分析表明,通过改变PPTA溶液的浓度可以有效地控制气凝胶纤维的孔结构及机械强度。当PPTA溶液的质量分数为2%时,制得的气凝胶纤维的孔隙率高达94.5%,断裂强度可达7.8 MPa;除此之外,该气凝胶纤维还具有高的比表面积(291 m2/g)和低的热导率,其织物的热导率为29.65 mW/(m·K)。当PPTA溶液的质量分数为5%时,气凝胶纤维的断裂强度高达20.5 MPa。本工作中所制备的气凝胶纤维具有极高的孔隙率、超低的密度和热导率以及良好的力学性能,为新一代保温隔热纺织品的设计和制造开辟了新的途径。

小分子羧酸对耐高温PA10T结晶性能的影响

聚对苯二甲酰癸二胺(PA10T)是一款生物基耐高温聚酰胺材料,具有低吸水率、高耐热性、良好加工性等性能,广泛应用于LED照明、电子电气、新能源汽车等领域。相关研究发现,聚合过程中未加入添加剂(通常为小分子羧酸类)的PA10T树脂存在结晶温度低、结晶速率慢的问题,影响其在LED多模穴快速成型中的应用,而小分子羧酸添加剂的含量对PA10T树脂结晶性能的影响的相关研究甚少。以癸二胺和对苯二甲酸(PTA)为单体,去离子水环境中,合成了PA10T并研究了挤出造粒过程中四类常见的小分子羧酸如苯甲酸(BA)、硬脂酸(SA)、乙酸、环己甲酸作为添加剂及其含量对PA10T结晶温度的影响。差示扫描量热仪测试结果显示,当BA用量(PTA物质的量的百分数)从1%增加到5%时,PA10T的结晶温度从274℃增加到283℃,结晶峰宽从14.6℃下降到9.2℃,说明结晶速率增大。在3%的小分子羧酸添加量的条件下,SA对PA10T结晶速率的提升效果最大,结晶峰宽为11.4℃。同时,基质辅助激光解吸飞行时间质谱仪测试结果显示含5%BA添加剂的PA10T样品中,游离的PTA对PA10T的结晶有促进作用。

Non-aqueous Suspension Polycondensation in NMP-Ca Cl_2/Paraffin System―A New Approach for the Preparation of Poly(p-phenylene terephthalamide)

A non-aqueous suspension polycondensation method was proposed to proceed the reaction ofp-phenylenediamine and terephthaloyl chloride for the preparation of poly（p-phenylene terephthalamide） （PPTA）. The system was operated with NMP-CaCI2 solution as the dispersed phase and inert liquid paraffin as the continuous phase. Each of NMP-CaCl2 solution microdroplet suspended in paraffin served as a microreactor where the polycondensation took place. According to the results of TGA, XRD, IR, SEM and EA, PPTA with good quality was obtained through this novel method, and a number of main factors influencing this process were investigated to determine the optimum condition for the preparation of PPTA. Besides, this two-phase polycondensation system brings many unique advantages compared to the conventional solution polycondensation method, including a sealed reaction environment keeping the reactants away from oxygen and water, easy removal of HCI to promote the reaction, well-controlled temperature and low viscosity which means less energy cost.

苯乙烯共聚物增容玻纤增强PA10T/PPE复合材料

以熔融己内酰胺为溶剂,通过自由基共聚制得一系列苯乙烯-甲基丙烯酸缩水甘油酯(GMA)共聚物(PSG),然后通过熔融共混法制备了PSG增容玻璃纤维(GF)增强聚对苯二甲酰癸二胺(PA10T)/聚苯醚(PPE)复合材料。考察了PSG增容剂的物化特性以及PSG增容剂中GMA的含量对GF/PA10T/PPE复合材料热学性能、力学性能、微观结构和形貌的影响。结果表明,制备的PSG增容剂5%热失重温度不低于374℃,满足GF/PA10T/PPE复合材料增容剂的使用要求。加入PSG显著改善了PA10T相与PPE相的相容性,有效细化了PPE分散相,增强了GF与树脂间的界面结合。当PSG中的GMA物质的量分数为4%时,复合材料展现出最佳的力学性能,拉伸强度为130.4 MPa,弯曲强度为164.4 MPa,缺口冲击强度为7.5 kJ/m^(2),同时该复合材料的饱和吸水率降低至1.32%。该复合材料表现出良好的综合性能,有望在汽车、电器和通信等领域得到应用。

Kinetics Analysis on the Polycondensation Process of Poly(p-phenylene terephthalamide):Experimental Verification and Molecular Simulation

The conventional low-temperature method of solution polycondensation was developed to realize the reaction of p-phenylenediamin and terephthaloyl chloride for the preparation of poly（p-phenylene terephthalamide）（PPTA）. Some main factors influencing this process were investigated to determine the optimum condition for high molecular weight. Experiment showed significant slowing of the reaction and gradual deviation of second-order reaction kinetics due to diffusion control. These phenomena were studied theoretically via dynamic Monte Carlo simulation. A concise expression,n～c0^-0.88·t^0.37, was proposed to describe the diffusioncontrolled polycondensation process as a function of the monomer concentration and reaction time. The theoretical results provided a good description of diffusion-effected kinetics for the polycondensation process of PPTA, and demonstrated good agreement with the experimental data. Some differences of scaling relations between model and experiment results were also discussed.

半芳香族尼龙的结构性能及其应用

综述了近年来几种已商品化的半芳香族尼龙(PPA),特别是聚对苯二甲酰己二胺、聚对苯二甲酰壬二胺、聚对苯二甲酰癸二胺、聚己二酰间苯二甲胺的结构、性能、改性及加工应用等;介绍了一种改善PPA加工性能的方法,即添加少量热致液晶高分子可改善PPA的加工性能,同时可保持其良好的力学性能;总结了PPA的应用领域,综述了国内PPA的研究水平,并指出了PPA的主要研究方向。

芳纶浆粕取代石棉摩擦材料的摩擦学性能

对本实验室直接缩聚法制备的芳纶浆粕以及传统的纺丝切割法制备的Kevlar浆粕和Twaron浆粕取代石棉在酚醛树脂基摩擦材料中的摩擦性能进行了研究.结果表明,3种芳纶浆粕增强的摩擦材料都具有优良的摩擦磨损性能,特别是随着温度升高,摩擦系数有较大提高的同时,磨损率明显下降,克服了石棉增强的摩擦材料在较高温度下磨损率较大的缺点.直接缩聚法制备的PPTA浆粕增强的摩擦材料摩擦性能与Kevlar浆粕和Twaron浆粕增强的相近,为芳纶浆粕增强摩擦材料的国产化奠定了基础.

电纺丝形成纤维的过程分析

采用静电喷雾等方法研究了聚丙烯腈 (PAN) ,聚间苯二甲酰间苯二胺 (MPIA) ,聚对苯二甲酰对苯二胺 (PPTA)的电纺丝成纤过程。结果表明 ,高聚物溶液受电场力及表面张力的影响形成喷射细流 ,两种作用力的扰动及作用引起射流的不稳定 ,从而发生射流分裂 ;在相同电纺丝条件下 ,PAN纤维细度远大于PPTA及MPIA纤维细度。

合成方法对共缩聚PPTA比浓对数粘度的影响

以4,4’-二氨基二苯醚(ODA)为第三单体对聚对苯二甲酰对苯二胺(PPTA)进行共缩聚改性,研究了共缩聚反应工艺条件对PPTA比浓对数粘度(ηinh)的影响。结果发现,当CaCl2用量为4%-6%时,单体摩尔浓度为0.35-0.45mol/L,爬杆后升温至80-85℃,总的反应时间30—40min,加入Ca(OH)2中和20min,制得的共缩聚PPTA的比浓对数粘度可达到2.50-3.37dL/g。不同的第三单体含量和不同的初始投料比对PPTA溶解性和ηinh有很大的影响。

Kevlar 49纤维与芳纶Ⅲ的结构与性能研究

借助傅立叶变换红外光谱仪、扫描电子显微镜、X射线光电子能谱仪和强力拉伸仪分析研究了Kevlar 49和芳纶Ⅲ的化学结构、表面特征及力学性能。结果表明:芳纶Ⅲ的红外谱图上多出了苯并咪唑环的吸收峰;芳纶Ⅲ的表面较粗糙,Kevlar 49表面较光滑,芳纶Ⅲ和Kevlar 49纤维表面的碳、氧元素均比化学式计算值有所增加,但氮元素含量下降;芳纶Ⅲ表面的极性基团种类比Kevlar 49多。芳纶Ⅲ的单纤维拉伸强度是Kevlar 49的1.5倍,断裂伸长率比Kevlar49提高了45%～65%;2种纤维的断裂方式均为劈裂断裂,具有皮芯结构,但芳纶Ⅲ分子间的作用力比Kevlar49纤维强。

聚对苯二甲酰对苯二胺共缩聚工艺研究

通过添加第三单体3,4'-二氨基二苯醚(3,4'-ODA)对聚对苯二甲酰对苯二胺(PPTA)进行改性,能够使其溶于一般的极性有机溶剂中,得到的聚合物溶液可以直接纺丝。研究了PPTA共聚合工艺,探讨了反应时间、反应温度、单体摩尔浓度、CaCl2含量以及第三单体含量和初始投料比对共聚物比浓对数黏度的影响。

高性能碳纤维增强尼龙10T复合材料制备与性能

以半芳香族尼龙聚对苯二甲酰葵二胺(PA10T)为基体树脂,采用碳纤维(CF)增强改性的方式制备高性能CF增强PA10T复合材料,研究不同质量分数的CF对PA10T/CF复合材料力学性能的影响。通过扫描电子显微镜对PA10T/CF复合材料的断面形貌进行分析,结合X射线衍射分析和差式扫描量热分析对复合材料的熔融、结晶过程和晶体结构进行分析,采用热重分析测试了复合材料的热稳定性。结果表明,CF的加入显著提高了PA10T/CF复合材料力学性能,当CF质量分数为30%,PA10T/CF复合材料的拉伸强度、弯曲强度和弯曲弹性模量分别达到253,360 MPa和20.1 GPa,比纯PA10T的性能分别提高216%,323%和675%。CF在复合材料结晶过程中起到异相成核作用,为结晶过程提供大量晶核,CF诱导α晶型PA10T晶态结构发生变化;同时也对分子链的运动折叠产生阻碍,导致晶粒生长不完善出现晶粒细化现象。加入CF后,复合材料结晶温度提高,结晶度随CF含量提高呈先下降后上升的变化趋势,同时热稳定性提高,当CF质量分数为10%时,复合材料热分解起始温度及失重50%的温度分别比纯PA10T提高10.7℃和12.4℃。

对位芳纶的合成及纺丝工艺研究进展

介绍了合成对位芳纶的界面缩聚法、直接缩聚法、低温溶液缩聚法、酯交换法、气相合成法等主要方法。详细论述了已工业化的对位芳纶成纤方法如：一步法工艺、两步法工艺及其芳纶浆粕纤维的制备方法,指出生产对位芳纶采用低温溶液缩聚法的合成、原液纺丝法纺丝的工艺,是我国对位芳纶实现工业化的合适路线。

基于PA10T的生物基耐高温聚酰胺的合成

采用生物基单体2,5–呋喃二甲酸(FDCA)作为第三单体,与癸二胺、对苯二甲酸(PTA)进行共聚合,合成了相对于聚对苯二甲酰癸二胺(PA10T)(55.6%)具有更高生物基含量的聚对苯二甲酰癸二胺/聚呋喃二甲酰癸二胺(PA10T/10F)共聚物(61.6%)。采用核磁共振波谱(NMR)技术表征了共聚物的结构,明确了共聚合过程中FDCA发生了脱羧反应,导致预聚物端基失衡、增黏产物黏度较低。研究了预聚合温度、排水量、固相增黏温度和氮气流速等反应条件对共聚物结构的影响,确定较优的聚合反应条件为:预聚合温度225℃、排水量70 g、增黏温度235℃以及氮气流速≥0.2 L/min。同时研究了聚合条件对共聚物颜色的影响。