氧化聚丙烯腈纤维

<正> 氧化聚丙烯腈纤维——国内亦称"预氧丝"是生产碳纤维的中间产品,也可以作为独立产品出售。近十年来英国、联邦德国、日本、以色列、美国、南朝鲜等均有工业化产品销售。将带有羧基的乙烯类单体为共聚组分的腈纶大丝束在210—280℃的空气中控制张力     

大丝束聚丙烯腈氧化纤维的开发

本研究以含依康酸的或含丙烯磺酸钠的大丝束聚丙烯腈纤维为原料,采用多段氧化工艺及气流分布工艺,控制反应热量的分布与散发,提高反应温度,加快反应速度,缩短反应停留时间,制造耐燃,耐焰,耐腐蚀,耐磨损的新型材料——民用氧化纤维。     

硫酸处理聚丙烯腈预氧化纤维的研究

采用不同浓度的硫酸对聚丙烯腈(PAN)预氧化纤维进行处理。介绍了硫酸对PAN预氧化纤维的作用机理,探讨了硫酸浓度和处理时间对PAN预氧化纤维结构和质量的影响。通过扫描电镜(SEM)观察并定量评价纤维皮芯结构。借助傅里叶变换红外光谱(FTIR)和X射线衍射(XRD)手段对硫酸处理的PAN预氧化纤维的化学组成和晶体结构进行表征。结果表明:PAN预氧化纤维经过不同浓度硫酸处理后,通过SEM能够观察到预氧化纤维的皮芯结构,经98%硫酸处理2 min后出现孔洞,在10 min后芯部比例为10.9%,趋于稳定;在硫酸处理过程中,纤维中氰基发生水解,环化结构(C=C/C=N)特征吸收峰因化学环境的改变而红移;PAN微晶结构受到硫酸破坏,预氧化纤维环化结构仍然保存。     

聚丙烯腈纤维预氧化工艺条件对孔隙结构的影响

借助场发射扫描电镜和小角X-射线散射对聚丙烯腈纤维的孔隙结构进行了研究。结果表明,聚丙烯腈纤维中的孔洞多为长条形且具有取向性的微孔。在预氧化温度区域,孔隙结构参数(平均孔径和孔隙率)变化不明显;但随着拉伸比的增大,其均呈下降趋势。因此,对聚丙烯腈纤维孔隙结构在预氧化过程中演变情况的研究,为进一步探讨孔隙结构对预氧化过程的影响奠定了基础。     

聚丙烯腈纤维及其预氧化前处理的研究进展

综述了聚丙烯腈纤维的预氧化前处理研究,并介绍了近年来我国聚丙烯腈纤维的最新研究进展,最后指出了今后聚丙烯腈纤维的发展方向。     

聚丙烯腈纤维在预氧化过程中的分子运动

本文主要叙述用动态力学试验方法研究碳纤维原丝(PAN纤维)在不同温度的连续预氧化处理中的动态力学性能、结构及热变形行为的相关性,为制备优质的碳纤维提供依据。     

聚丙烯腈纤维孔隙结构对预氧化的影响

采用湿法纺丝,通过不同的牵伸条件,制备具有相同的化学组分和不同孔隙率(体密度)的聚丙烯腈纤维,然后在相同的条件下预氧化。借助红外吸收光谱(FT-IR)、场发射扫描电子显微镜(FESEM)、差示扫描量热(DSC)等表征手段对原丝和预氧丝的环化度、皮芯结构及预氧丝横截面的氧径向分布进行分析对比。实验结果表明,随着孔隙率降低(体密度增加),纤维径向的氧含量梯度变大,皮芯结构趋于严重。     

聚丙烯腈纤维的氧化碳化工艺

主要研究了氧化温度、氧化牵伸、碳化牵伸对最终碳纤维性能的影响,结果表明:氧化一区温度适中,可以避免纤维形成皮芯结构,从而制备强度较高的碳纤维;氧化一区施加适当的牵伸,可保持纤维取向,从而制备较高强度的碳纤维;碳化过程中,对低温碳化阶段施加适当的正牵伸,高温碳化阶段施加一定的负牵伸,能够提高碳纤维的力学性能。     

聚丙烯腈纤维连续预氧化过程的研究—纤维的物化行为

采用密度、元素分析、广角X射线衍射等多种测试分析方法对制备碳纤维的聚丙烯腈原丝纤维在连续预氧化过程中的物化行为进行了表征研究。实验结果表明,聚丙烯腈纤维的物化行为大致可分为三个区域。Ⅰ区,纤维主要表现为物理行为,即产生熵收缩;Ⅱ区,纤维内的预氧化反应迅速进行,逐渐形成梯形环化结构及鞘芯结构;Ⅲ区,纤维中的预氧化反应趋于缓和,逐渐达到稳定化。     

Mechanism and kinetics of oxidation during the thermal stabilization of polyacrylonitrile fibers

The thermal behavior and structural evolution during the thermal stabilization of polyacrylonitrile (PAN) fibers in N₂ and air were investigated using differential scanning calorimetry and solid‐state ¹³C nuclear magnetic resonance. It was found that an oxidation reaction, that generated carbonyl (C?O) groups could occur at 160°C which has not been reported in the literature. It is proposed that the cyclized structures in the PAN macromolecule chains are a prerequisite for the oxidation. Further investigations indicate that with more cyclized structures in the PAN macromolecule chains, the oxidation proceeds more readily, which is consistent with the proposed mechanism. The kinetic parameters for the oxidation and cyclization reactions were estimated using the Kissinger method. The activation energies for the reactions of oxidation and cyclization for PAN fibers are about 96.4 kJ/mol and 190.0 kJ/mol, respectively, which implies that the cyclization is the rate determining step during the thermal stabilization of PAN fibers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

干湿法制备异形PAN原丝及其力学性能的研究

对二甲基亚砜(DMSO)干湿法制备三角形截面聚丙烯腈(PAN)基碳纤维原丝的截面形成因素进行了研究,并比较了不同条件下纤维的性能。结果表明:在干湿法纺制三角形截面PAN基碳纤维原丝过程中,凝固浴条件对PAN纤维的截面影响非常明显,同时凝固浴条件和拉伸条件对纤维的力学性能也有非常显著的影响。     

聚丙烯腈原丝预氧化过程中的结构与性能变化

综述了聚丙烯腈原丝在预氧化过程中的结构与性能变化规律,总结了预氧丝的表征方法。指出预 氧化过程中影响纤维结构与性能变化的主要因素有预氧化温度、预氧化时间和对纤维的拉伸倍数等。     

The formation of polyacrylonitrile nascent fibers in wet‐spinning process

The formation of polyacrylonitrile (PAN) nascent fibers in wet‐spinning process was studied by KMnO₄ back titration method and scanning electron microscopy (SEM). It has been found that the rate of DMSO diffusion was rapid at the beginning of coagulation then decreased and reached balance at 24 s. With coagulation time increase, the nascent fibers became denser and had fewer inner defects gradually, but transverse stripes appeared on the surface at 24 s, and got deeper. The main defects of nascent fibers included transverse stripes, impurity, fish tail, inner microvoids etc. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Dynamic oxidation and protection of the PAN pre-oxidized fiber C/C composites

Pre-oxidized fibers as reinforcement are candidates for reducing the overall cost of C/C composites with superior properties. This study investigated the dynamic oxidation and protection of the pre-oxidized fiber C/C composites (Pr-Ox-C-C). According to the Arrhenius equation, the oxidation kinetics of the Pr-Ox-C-C consisted of two different oxidation mechanism with the transition point was at about 700 °C. Scanning electron microscopy investigation showed that oxidation initiated from the fiber/matrix interface of composites, whereas the matrix carbon was easily oxidized. To improve the anti-oxidant properties of Pr-Ox-C-C, a ceramic powder-modified organic silicone resin/ZrB₂-SiC coating was prepared by the slurry method. The coated samples were subjected to isothermal oxidation for 320 h at 700 °C, 800 °C, 900 °C, 1000 °C and 1100 °C with incurred weight losses of ? 1.6%, 0.77%, ? 1.28%, 0.68% and 1.19%, respectively. After 110 cycles of thermal shock between 1100 °C and room temperature, a weight loss of 1.30% was obtained. The Arrhenius curve presented four different phases and mechanisms for coating oxidation kinetics. The excellent oxidation resistance properties of the prepared coating could be attributed to the inner layer which was able to form B₂O₃-Cr₂O₃-SiO₂ glass to cure cracks, and the ZrB₂-SiC outer layer that could provide protective oxides to reduce oxygen infiltration and to seal bubbles.     

Effect of DMSO/H2O coagulation bath on the structure and property of polyacrylonitrile fibers during wet‐spinning

The effect of coagulation bath condition on the structure and property of the nascent fibers and polyacrylonitrile fibers during wet‐spinning is studied. The best coagulation condition to produce polyacrylonitrile fibers has been found by examination of EA, XRD, SEM, and so on. The results indicated that when the coagulation bath was DMSO/H₂O system, the temperature was 60°C, the concentration was 65%, the minus stretch ratio was ?10%, fine crystallites and high degree of crystallization in the nascent fibers and polyacrylonitrile fibers could be achieved, and less solvents remained in the nascent fibers with circular cross section morphology. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

植物纤维工艺性能及其复合材料应用研究进展

概述了近年来在植物纤维的渗透率、可压缩性等工艺性能方面的研究进展,揭示了植物纤维织物渗透性能及可压缩性能影响因素,并总结了多种植物纤维复合材料的研究进展,包括植物纤维/热塑性复合材料、植物纤维/可降解复合材料、植物纤维/热固性复合材料等。随着研究的不断深入,植物纤维复合材料会有更广泛的应用。     

碳纤维热氧化行为及其机理

对聚丙烯腈(PAN)基碳纤维进行热氧化处理,借助扫描电子显微镜、X射线光电子能谱,拉曼光谱等手段表征了PAN基碳纤维的热氧化行为,研究了其热氧化机理。结果表明:热氧化使PAN基碳纤维表面氧元素含量大幅升高,碳含量下降,氧以C—OH或C—O—C基团的形式吸附到表面、在550℃左右以C=O基团大量分解的形式腐蚀纤维,破坏纤维形貌;同时热氧化腐蚀纤维中的非石墨碳,使得有序的石墨结构向非石墨无序结构转变,破坏碳纤维的晶体结构。     

Diffusion coefficient of DMSO in polyacrylonitrile fiber formation

A H₂O/dimethyl sulfoxide(DMSO) mixture was used as the coagulation bath for the wet‐spun process of acrylonitrile/ammonium itaconate copolymers fibers. Diffusion coefficient of DMSO in the protofibers prepared by acrylonitrile/ammonium itaconate copolymers was determined. It has been found that diffusion coefficient of DMSO outflow of the protofibers prepared by acrylonitrile/ammonium itaconate copolymers synthesized by the solution polymerization is highest compared with those of acrylonitrile/ammonium itaconate copolymers synthesized by H₂O/DMSO mixture suspension polymerization and the aqueous suspension polymerization. With an increase of copolymer concentration in the dope, diffusion coefficient of DMSO decreases continuously. Diffusion coefficient of DMSO increases along with the bath temperature, but the changes of diffusion coefficient values are less prominent as temperature goes beyond 60°C. When DMSO concentration in the coagulation bath was 55 wt %, the value of the diffusion coefficient of DMSO was minimal. Diffusion coefficient of H₂O increases with the jet stretch minus ratio increasing. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4447–4451, 2006     

吸湿发热聚丙烯腈纤维的性能研究

采用傅立叶变换红外光谱、扫描电子显微镜、X射线衍射仪和热重分析仪对交联改性制备的吸湿发热聚丙烯腈(PAN)纤维的吸放湿性能进行表征,与普通PAN纤维及进口吸湿发热PAN纤维进行对比。结果表明:交联改性制备的吸湿发热PAN纤维红外光谱出现了较强的羟基峰和羧酸盐的伸缩振动峰,相比普通PAN纤维,表面沟槽加深、粗糙度增加,在100℃内失重率达17.17%,热分解温度提高近70℃,结晶度大幅下降,力学性能降低;交联改性PAN纤维的吸放湿性能较普通PAN纤维大幅度提高,并高于进口吸湿发热PAN纤维,其平衡回潮率约30%,吸湿积分热达155 J/g。