【作者】 王二轲；

【导师】 陈惠芳；

【作者基本信息】 东华大学 ， 材料科学与工程， 2009， 硕士

【摘要】 碳纤维（Carbon Fiber简称CF）是指含碳量大于90%的纤维材料,它是一种具有高强度,高模量,耐高温,耐腐蚀等一系列优异性能的新型材料。作为先进复合材料的增强纤维,其已被广泛地应用在各个领域。碳纤维可以用粘胶、PAN以及沥青等有机纤维在高温下碳化而成,随着科技的快速发展,PAN基碳纤维已成为了当前碳纤维工业中的主流。目前,国内外学者一致认为PAN原丝的质量是高性能PAN基碳纤维的关键所在。要获取高性能的PAN基碳纤维,其原丝必须具备高强、高纯、高致密性和均匀的纤维结构等性能。首先,本文主要研究了新型的喷丝头用材料及其在PAN纺丝工艺中的应用。以尽力避免孔口胀大现象为目的,我们综合考虑了喷丝头用材质的基本要求及各种材料的生产加工工艺,并通过接触角实验分析了不同材质与PAN/DMSO纺丝溶液间的表面张力,开发新型的喷丝头用材料。实验确定了一种新型的喷丝头用材料—Si₃N₄陶瓷材料,其与PAN/DMSO溶液间的表面张力相对较大,且具有“先切割后烧结”的制造工艺,可加工成具有令人满意的长径比（L/D）的喷丝头,能有效地减小纺丝过程中出现的出口膨胀效应,避免纺丝溶液沿喷丝头表面漫流的现象。同时,在固定的工艺条件下,我们分别使用具有相同几何条件的新型的Si₃N₄陶瓷喷丝头和传统的1Cr18Ni9Ti不锈钢喷丝头来纺制PAN原丝。通过对比纺制出的PAN初生纤维的截面形状及直径大小、PAN原丝的可纺性、结晶度、晶区取向度以及强度等结构性能,得出了可以采用新型的陶瓷喷丝头来代替传统的金属喷丝头应用于纤维生产工业中的结论。其次,本文又着重研究了不同长径比（L/D）的新型喷丝头对PAN原丝性能的影响。实验分别采用湿法、干湿法以及凝胶法进行纺丝,从多方面地分析了长径比（L/D）对PAN纺丝过程中产生的挤出胀大现象的影响,以及其对PAN原丝的膨润度、可纺性、结晶度、晶区取向度及强度等性能的影响。结果表明,随着L/D的增大,可有效地减小出口膨胀效应,避免PAN/DMSO纺丝溶液沿喷丝板漫流的现象,提高纺丝的稳定性;同时,PAN原丝的性能也随之提高,且当L/D达到某一值时,影响将逐渐消失。最后,本文又研究了纺制PAN基碳纤维原丝常用的PAN/DMSO体系湿法及干喷湿法的可纺性,其用直观函数V_1m—出凝固浴的第一辊最大卷绕速度来表征。在影响聚合物可纺性的因素中,我们研究了凝固浴条件、空气层高度、非溶剂（NSA）含量、纺丝温度和纺丝原液浓度等几种重要的因素对于干喷湿法纺丝可纺性的影响,并与湿法纺丝作了比较。研究结果表明,对于干湿法纺丝来说,凝固浴条件对可纺性(V_1m)几乎没有什么明显的影响,影响其可纺性的因素主要是:纺丝原液的温度和浓度、喷丝口孔径的大小及空气层的高度等。更多还原

【Abstract】 Carbon fibers,the fibrous materials with more than 90%of carbon content,are new-style materials which have high tenacity,high modulus, heat-resistance,corrosion resistance,and a series of excellent performances.As a kind of reinforcing fiber of advanced materials,it is used widely in all kinds of fields.Carbon fibers can be made by carbonization in high temperature from organic fibers of rayon,PAN and pitch.With the rapid development of technology,PAN-based carbon fibers play the main role in the carbon fiber industry.Currently, researchers home and aboard show no differences that the quality of PAN precursor fiber is critical for high-quality PAN-based carbon fiber.To yield the high-quality PAN-based carbon fiber,the PAN precursor fiber must have some performances of high tenacity,high purity,high compactness and the uniform structure,etc.Firstly,the new type of spinneret materials and the application of this new-style spinneret in the spinning process of PAN-based carbon fiber precursor were mainly investigated in this paper.For the purpose of avoiding die swell as well meeting the basic requirements of spinneret materials and the manufacture techniques of these materials,we made the contact angle experiments to test the surface tension between different materials and PAN/DMSO spinning solution and finally developed the new type of materials for the spinneret in the experiments.It was found that the surface tension between the Si₃N₄ ceramic material and PAN/DMSO spinning solution was relatively larger.In addition,the Si₃N₄ ceramic materials have an advanced“incising comes before sintering”manufacture technique,so it can be made for the spinneret with satisfied ratio of length to diameter（L/D）,which can decrease the die swell effect in the spinning process effectively and avoid the spreading phenomenon of spinning solution on the spinneret surface.Therefore,the Si₃N₄ ceramic materials are chosen for the new-style spinneret material.Then in the fixed conditions,we used the Si₃N₄ ceramic spinneret and the traditional 1Cr18Ni9Ti stainless steel spinneret for spinning.Through comparing the cross-section shape and diameter of PAN as-spun fiber,the swellability,the crystallinity,the preferred orientation,and the tenacity of PAN precursor fiber,we get the conclusion that the new-style ceramic spinneret can replace the traditional metal spinneret in the industry of fibers.Secondly,the effects of ratio of length to diameter（L/D） of new-style spinneret on properties of PAN precursor fiber were investigated in this article.Using wet spinning、dry-jet wet spinning and gel spinning in experiments,we analyzed the effects of ratio of length to diameter（L/D） on die swell phenomenon in the spinning process,and on the swellability,the crystallinity,the preferred orientation and the mechanics performance of PAN precursor fiber comprehensively.The results show that with the increase of ratio of length to diameter（L/D）, die swell effect in the spinning process decreases and the spreading phenomenon of spinning solution on the spinneret surface can be avoided effectively.So the stability of spinning and the performance of PAN precursor fiber can be improved.But when the L/D value reaches a certain one,the effects will diminish gradually.Lastly,the spinnability(V_1m) of PAN spinning solution using DMSO as the solvent was investigated for wet spinning and dry-jet wet spinning of PAN precursor fiber in this paper.It is expressed by the intuitionistic parameter V_1m-the maximal rotational speed of the first winding roller after the coagulating bath.Among many variables responsible for spinnability,the coagulating conditions,the air gap length,the nonsolvent（NSA） content in spinning solution,the spinning temperature and the spinning solution concentration have been viewed as the key factors.We investigated these factors in the dry-jet wet spinning of PAN precursor fiber,and compared them to the wet spinning.For the dry-jet wet spinning,the results show that the coagulation bath conditions exert little influence on spinnability(V_1m).It depends on many spinning variables,including the spinning temperature and the spinning solution concentration,the spinneret hole size and shape,the air gap length,etc.更多还原