静电纺丝法制备聚丙烯腈基纳米碳纤维的研究
发布时间：2018-09-17 13:52
【摘要】： 纤维增强复合材料在航空航天、军工和能源等领域已得到广泛应用,随着各种先进技术的发展,对于复合材料性能的要求越来越高,需要开发新一代高性能增强纤维。聚丙烯腈(PAN)基碳纤维已经商业化几十年了,在所有商用的先进纤维增强体中,它拥有最高的比强度和比模量。但目前传统碳纤维在结构方面存在各种缺陷,如纤维表面裂纹,孔洞,皮芯结构等,限制了碳纤维性能的提高。因此,要制备更高性能的PAN基碳纤维,最有效的办法就是减少各种结构缺陷。本文通过静电纺丝法制备了平行排列的PAN纳米纤维膜,引入多步热牵伸工艺,经过预氧化和碳化,最终制得连续的高度有序排列且低缺陷的纳米碳纤维,为制备高性能碳纤维探索出了一条新的途径。 论文的主要研究如下： 1.研究了纺丝液浓度对于对纤维形貌的影响,并根据实验结果优化了静电纺丝工艺条件。只有当PAN纺丝液浓度不低于14 wt%时,才能制得形貌均一的PAN纳米纤维。 2.制备PAN纳米纤维膜,研究了PAN原丝、牵伸前后PAN纳米纤维热力学性能。PAN纳米纤维在空气中的环化反应可以分为分子内环化和分子间环化,分子内环化与氧气无关,但分子间环化必须有氧气的参与才能发生,且纳米纤维的牵伸程度越大,越有利于分子间环化反应的进行。 3.引入多步热牵伸的方法,对制备的PAN纳米纤维膜进行热牵伸,研究了牵伸前后纤维的结构与性能的变化。多步热牵伸提高了纤维分子链取向,使纤维平行排列更加有序,纤维直径分布趋于均一化。且有效减少断丝现象,牵伸后纤维直径从537 nm降低到412 nm。 4.优化预氧化工艺,在张力作用下对PAN纳米纤维预氧化,研究不同预氧化温度和时间对纳米纤维结构的影响。随预氧化温度的升高和预氧化时间的延长,PAN分子链逐渐由链式结构转化成梯形环状结构,纤维的耐热性不断增强。280℃下预氧化120 min后,氧元素含量趋于稳定值,表明环化反应已基本完成,纤维被充分预氧化。 5.氮气保护下,在1200℃对预氧化的纳米纤维进行恒应变碳化,制得纳米碳纤维,对制得的纳米碳纤维表面、内部形貌和微观结晶进行了表征。纳米碳纤维高度有序排列、表面光滑,粗糙度为0.249nm,纤维内部结构均一,无皮芯结构缺陷。纤维大部分呈现乱层石墨结构,但部分晶区石墨片层平行排列,晶面间距为0.347 nm,晶层厚度为7-15层不等。 6.在聚醚酰亚胺中加入实验制得的纳米碳纤维,对材料介电损耗没有太大影响,但可以显著提高材料的介电常数,降低材料的电阻率。加入1.0 wt%纳米碳纤维,聚醚酰亚胺的电性能改善效果要优于同样含量的碳纳米管。
[Abstract]:Fiber reinforced composites have been widely used in aerospace, military and energy fields. With the development of various advanced technologies, the requirements for the properties of composite materials become more and more high, so it is necessary to develop a new generation of high performance reinforced fibers. Polyacrylonitrile (PAN) based carbon fibers have been commercialized for decades and have the highest specific strength and modulus of all commercial advanced fiber reinforcements. However, there are various defects in the structure of traditional carbon fiber, such as surface cracks, holes, skin core structure and so on, which limit the improvement of carbon fiber performance. Therefore, the most effective way to prepare higher performance PAN based carbon fiber is to reduce various structural defects. In this paper, PAN nanofiber films with parallel arrangement were prepared by electrospinning method. After preoxidation and carbonization, continuous, highly ordered and low defect carbon nanofibers were prepared by introducing multi-step thermal drafting process. A new way for the preparation of high performance carbon fiber was explored. The main research contents are as follows: 1. The influence of spinning solution concentration on fiber morphology was studied, and the process conditions of electrostatic spinning were optimized according to the experimental results. Only when the concentration of PAN spinning solution is not less than 14 wt%, the homogeneous PAN nanofibers can be obtained. PAN nanofiber membranes were prepared. The thermodynamic properties of PAN nanofibers before and after drafting. The cyclization of pan nanofibers in air could be divided into intramolecular cyclization and intermolecular cyclization, and the intramolecular cyclization was independent of oxygen. However, intermolecular cyclization can only take place with the participation of oxygen, and the greater the drafting degree of nanofibers is, the more favorable the intermolecular cyclization is. The structure and properties of PAN nanofibers were studied before and after drafting by the method of multi-step thermal drafting. The multi-step thermal drafting improves the orientation of the fiber molecular chain, makes the fiber parallel arrangement more orderly, and the fiber diameter distribution tends to homogenize. The fiber diameter decreased from 537 nm to 412 nm. 4 after drawing. The effects of different preoxidation temperature and time on the structure of PAN nanofibers were studied by optimizing the preoxidation process and preoxidation under tension. With the increase of preoxidation temperature and the prolongation of preoxidation time, the chain structure of pan was transformed into a trapezoidal ring structure, and the heat resistance of the fiber was enhanced continuously at .280 鈩，
本文编号：2246131
[Abstract]:Fiber reinforced composites have been widely used in aerospace, military and energy fields. With the development of various advanced technologies, the requirements for the properties of composite materials become more and more high, so it is necessary to develop a new generation of high performance reinforced fibers. Polyacrylonitrile (PAN) based carbon fibers have been commercialized for decades and have the highest specific strength and modulus of all commercial advanced fiber reinforcements. However, there are various defects in the structure of traditional carbon fiber, such as surface cracks, holes, skin core structure and so on, which limit the improvement of carbon fiber performance. Therefore, the most effective way to prepare higher performance PAN based carbon fiber is to reduce various structural defects. In this paper, PAN nanofiber films with parallel arrangement were prepared by electrospinning method. After preoxidation and carbonization, continuous, highly ordered and low defect carbon nanofibers were prepared by introducing multi-step thermal drafting process. A new way for the preparation of high performance carbon fiber was explored. The main research contents are as follows: 1. The influence of spinning solution concentration on fiber morphology was studied, and the process conditions of electrostatic spinning were optimized according to the experimental results. Only when the concentration of PAN spinning solution is not less than 14 wt%, the homogeneous PAN nanofibers can be obtained. PAN nanofiber membranes were prepared. The thermodynamic properties of PAN nanofibers before and after drafting. The cyclization of pan nanofibers in air could be divided into intramolecular cyclization and intermolecular cyclization, and the intramolecular cyclization was independent of oxygen. However, intermolecular cyclization can only take place with the participation of oxygen, and the greater the drafting degree of nanofibers is, the more favorable the intermolecular cyclization is. The structure and properties of PAN nanofibers were studied before and after drafting by the method of multi-step thermal drafting. The multi-step thermal drafting improves the orientation of the fiber molecular chain, makes the fiber parallel arrangement more orderly, and the fiber diameter distribution tends to homogenize. The fiber diameter decreased from 537 nm to 412 nm. 4 after drawing. The effects of different preoxidation temperature and time on the structure of PAN nanofibers were studied by optimizing the preoxidation process and preoxidation under tension. With the increase of preoxidation temperature and the prolongation of preoxidation time, the chain structure of pan was transformed into a trapezoidal ring structure, and the heat resistance of the fiber was enhanced continuously at .280 鈩，
本文编号：2246131
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