【作者】 李艳伟；

【导师】 黄玉东；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2013， 博士

【摘要】 PBO纤维是一种低密度、高强度、高模量、耐高温且阻燃的高性能有机纤维，在众多尖端领域中有着广泛的应用。然而如此优异的PBO纤维仍存在一些缺陷，如实际模量与理论模量存在很大差距，与树脂的粘结性能不好等缺点。本文以提高PBO纤维的力学性能、耐热性能及复合材料界面性能为主要目标，设计合成了碳纳米管和石墨烯增强PBO基体的两种复合纤维，着重分析了这两种复合纤维的结构和性能，为制备综合性能更为优异的复合纤维进行有益的探索。采用两种酸处理方法，浓硫酸/浓硝酸体系和含有20%三氧化硫的发烟硫酸/浓硝酸体系分别对单壁碳纳米管(SWCNTs)进行纯化、切短和氧化处理。采用化学接枝法对SWCNTs进行功能化接枝修饰处理，分别接枝上三种氨基二元羧酸，柔性链小分子的L-天门冬氨酸(I)、L-谷氨酸(II)和刚性链小分子的5-氨基间苯二甲酸(III)，得到了三种功能化接枝修饰后的SWCNT I-III。接枝化修饰处理使SWCNTs酸化后的一元羧酸基团转变成二元羧酸基团，获得更多的羧酸活性基团参与到聚合反应中，在聚合体系中具有更好的分散性。采用化学改性Hummers法成功制备了氧化石墨烯，得到的氧化石墨烯没有进一步还原成石墨烯，而是保留了其表面的活性官能团，以便下一步功能化处理。采用独特的“复合内盐法”合成了DADHB-is-(GO/TPA)复合内盐。设计“复合内盐”的目的是为了实现GO在聚合体系中具有更好的分散性，并且参与到聚合反应中。研究发现，GO在复合内盐中能够均匀分散，同时GO在复合内盐中起到了结晶模板剂的作用，有效地阻止了GO的重新堆积，为GO在下一步聚合体系中均匀分散打下了基础。采用脱氯化氢原位聚合法制备了三种SWCNT I-III&PBO复合纤维，分析了SWCNT I-III&PBO复合纤维的化学组成、特性粘数及粘均分子量、复合纤维的表面和断面形貌、结晶行为及复合纤维中SWCNTs的分布情况，证明不同功能化处理SWCNTs的加入对PBO纤维的结构有很大影响，通过对复合纤维的拉伸强度、拉伸模量及断裂伸长率测试，研究三种不同功能化SWCNT I-III对PBO纤维力学性能的增强作用，发现复合纤维拉伸强度和模量都有相应的增加，其中添加SWCNT III增加最多。研究添加三种不同功能化SWCNT I-III对PBO纤维热稳定性的影响。这些研究结果表明接枝刚性链小分子的SWCNTs要比接枝柔性链小分子的SWCNTs在增强PBO纤维的力学性能和热稳定性的效果上要更好些。通过对复合纤维的浸润性和与树脂结合的界面剪切强度测试，研究添加功能化SWCNT I-III对PBO纤维复合材料界面性能的增强作用。采用一锅原位聚合复合内盐法制备了两种不同GO含量的GO-co-PBO复合纤维，对其结构和性能进行深入研究和系统分析，并且对GO增强PBO纤维的机理进行了初步的探讨。通过对GO-co-PBO(1%)和GO-co-PBO(3%)复合纤维的化学组成分析、特性粘数的测定及粘均分子量的计算、复合纤维的表面和断面形貌的观察、结晶行为研究及对复合纤维中GO的分布情况进行观察，研究添加不同的GO含量对PBO纤维结构的影响。通过对GO-co-PBO复合纤维的拉伸强度、拉伸模量及断裂伸长率测试，研究GO的不同含量对PBO纤维力学性能的增强作用，随着GO的添加量增加，GO-co-PBO复合纤维拉伸强度和模量增加，断裂伸长率降低。对GO-co-PBO复合纤维的耐热性能进行分析，GO的加入增强了PBO基体的热稳定性和阻燃性。通过对GO-co-PBO复合纤维的浸润性和与树脂的界面剪切强度测试，研究了添加GO对PBO纤维复合材料界面性能的增强作用。更多还原

【Abstract】 Poly(p-phenylene-2,6-benzobisoxazole)(PBO) fiber is one of high-performanceorganic polymer fibers, which is characterized by low density, superior mechanicalproperties, excellent thermal and thermo-oxidative stability and good flameretardance. It is widely applied in various frontier fields. However, there are someflaws in PBO fibers, such as a large gap between the actual tensile modulus and thetheoretical tensile modulus, weak interfacial property with resin, et al. In this paper,the main aims are to improve the mechanical, thermal properties and interfacialproperty of PBO fibers. So, PBO composite fibers reinforced by SWCNTs orgraphene were designed and synthesized, the microstructure and the properties ofcomposite fibers were studied. The researches are beneficial to develop morecomposite fibers with excellent comprehensive performance.SWCNTs were acid-treated by the two methods, concentrated H2SO4/HNO3system or20%SO3oleum/concentrated HNO3system. The process is in order toachieve the purifying, cutting short and carboxylation of SWCNTs. Threefunctionalized SWCNT I-III were obtained through chemical grafting of aminodicarboxylic acid including L-Aspartic acid (I), L-glutamic acid (II) and5-amino-isophthalic acid (III) onto SWCNTs surface, respectively. The functionalizedSWCNTs (SWCNT I-III) is to overcome the issues of limited dispersivity andprocessibility of SWCNTs in polymerization system.Graphene oxide (GO) sheets were successfully prepared through modifiedHummers method. The obtained GO sheets have not been further deoxidized andstill retained the active groups for the next functional treatment. The DADHB-is-(GO/TPA) inner salts were synthesized through the special composite inner saltsmethod. DADHB-is-(GO/TPA) inner salts were designed to improve the dispersionof GO in polymerization system and processibility of GO with PBO matrix. Theresults show that GO sheets disperse well in the inner salts. GO sheets work as thenucleating template agents in the composite inner salts, which effectively avoid theaccumulation of GO sheets and lay a solid foundation for the dispersion of GO inthe following polymerization procedure.The SWCNT I-III&PBO composite fibers were synthesized through in situpolymerication of dehydrochlorinated monomers. The chemical composition,intrinsic viscosity and viscosity average molecular weight, surface and crosssection morphology, crystallization behaviors of the SWCNT I-III&PBOcomposite fibers and the SWCNTs distribution in composite fibers were analyzed.The results show the additions of functionalized SWCNTs (SWCNT I-III) have the obvious effects on the structures of PBO fibers. The mechanical enhancements ofPBO fibers by functionalized SWCNTs (SWCNT I-III) were investigated by tensilestrength, tensile modulus and elongation at break. The results indicate that tensilestrength and modulus of all composite fibers have a certain extent increment, inwhich adding SWCNT III into PBO matrix has increased by the largest margin.The effect of SWCNT I-III in the thermal stabilities for PBO fibers were studied.All the results indicate that the enhancement effects of SWCNTs graftedrigid-chain molecules on mechanical and thermal properties are much better thanthat of SWCNTs grafted flexible-chain molecules. The effects of adding SWCNTI-III on the interfacial properties of PBO fibers composite materials were evaluatedby surface wettability, surface free energy and interfacial shear strength.The GO-co-PBO composite fibers with different GO contents were synthesizedby in situ polymerization of a novel composite inner salts. The structures andproperties of GO-co-PBO composite fibers were lucubrated and systematicalanalyzed. The intensification mechanism of GO in PBO fibers is proposed andsimply discussed. The effects of different GO contents on PBO fibers structureswere evaluated by chemical composition, the intrinsic viscosity and viscosityaverage molecular weight, surface and cross section morphology, the crystalliz-ation behavior of the compositite fiber and the GO distributions in composite fiber.The mechanical enhancement of PBO fibers with differen GO contents werestudied by tensile strength, tensile modulus and elongation at break. Comparedwith PBO fibers, tensile strength and modulus of composite fibers have asignificant increments with GO content. The thermal stabilities of GO-co-PBOcomposite fibers were studied and it was found that the incorporation of GOimproved the thermal stabilities and flame retardancy of PBO fibers. The effects ofGO on the interfacial properties of PBO fibers composite materials were evaluatedby surface wettability, surface free energy and interfacial shear strength.更多还原