晶态结构对聚丙烯腈(PAN)原丝预氧化反应的影响

对不同晶态结构特点的聚丙烯腈(PAN)原丝进行预氧化处理,采用X射线衍射(XRD)、红外光谱法表征PAN纤维的晶态结构(物理)和化学结构变化。结果表明,PAN原丝的晶态结构影响预氧化反应及反应程度,结晶度小的PAN原丝由于其有序性差,易于向预氧纤维芳构化结构转化,而结构疏松,有利于氧的扩散,促进环化反应和初期氧化反应,PAN纤维芳构化指数和相对环化率都较高,预氧化反应程度较高;原丝结晶度的差异对纤维晶粒尺寸的变化起决定性作用,结晶度大的PAN原丝到预氧化后期仍保持较大的晶粒尺寸。     

碳纳米管/聚丙烯腈复合纤维热处理过程中结构演变规律研究

将聚丙烯腈(PAN)纤维与碳纳米管/聚丙烯腈(CNT/PAN)复合纤维分别置于空气中,在230℃进行不同时间的热处理,采用FT-IR,DSC分析手段考察了CNT对CNT/PAN复合纤维热处理过程结构和热焓的影响.结果表明,CNT促进了CNT/PAN复合纤维热处理过程中-C≡N的分解环化;而且对热处理过程中的其它反应也有促进作用.     

晶态结构对聚丙烯腈(PAN)原丝预氧化反应的影响EI北大核心CSCD

对不同晶态结构特点的聚丙烯腈(PAN)原丝进行预氧化处理,采用X射线衍射(XRD)、红外光谱法表征PAN纤维的晶态结构(物理)和化学结构变化。结果表明,PAN原丝的晶态结构影响预氧化反应及反应程度,结晶度小的PAN原丝由于其有序性差,易于向预氧纤维芳构化结构转化,而结构疏松,有利于氧的扩散,促进环化反应和初期氧化反应,PAN纤维芳构化指数和相对环化率都较高,预氧化反应程度较高;原丝结晶度的差异对纤维晶粒尺寸的变化起决定性作用,结晶度大的PAN原丝到预氧化后期仍保持较大的晶粒尺寸。     

不同溶剂配比对单轴共纺PVDF/PEI纤维薄膜性能影响的研究

聚偏氟乙烯(PVDF)/聚醚酰亚胺(PEI)为8/2(质量比)的混合聚合物溶解在N,N-二甲基甲酰胺(DMF)、四氢呋喃(THF)不同比例的混合溶剂中。利用静电纺丝技术制备PVDF/PEI复合纤维薄膜。通过扫描电镜(SEM)、X射线衍射(XRD)、差示扫描量热法(DSC)和拉伸实验考察THF含量对其微观结构、结晶度和力学性能的影响。结果显示:在电场力作用下,PVDF晶型由α晶型向β晶型和δ晶型转化,且随着THF含量的增加,PVDF/PEI复合纤维薄膜结晶度、拉伸强度、断裂伸长率呈现出先增大后减小。当DMF/THF质量比为7/3时,复合薄膜结晶度、断裂伸长率最大分别为31.27%、23.5327%。     

碳纳米管改性聚丙烯腈纳米纤维膜制备工艺及性能

聚丙烯腈(PAN)纳米纤维纸具有高孔隙率、三维连通等特点，其炭化后形成的碳纤维纸可应用于燃料电池质子交换膜中。提升PAN纳米纤维性能，有利于获得高质量碳纤维纸。文中采用碳纳米管(CNT)增强改性聚丙烯腈，通过静电纺丝制备CNT/PAN纳米纤维膜，研究了CNT的加入对纤维膜微观结构、热稳定性、导电性的影响。对纤维膜的扫描电镜照片、热稳定性等进行分析，结果表明CNT质量分数为2%时，纤维膜的孔隙率为86%、比表面积为21.1 m²/g；相较未加CNT的纤维膜的电阻下降40%，最大热分解温度提升了6℃。为后期制备电池用高性能碳纤维纸前驱体提供了支撑。     

湿法纺聚丙烯腈原丝的微观结构分析

利用扫描电镜和透射电镜研究了聚丙烯腈(PAN)纤维在湿法纺丝工艺中的微观形貌与结构演变.测试分析证实,初生纤维的结构会遗传至PAN原丝,PAN原丝为皮芯多层结构,最外面是一层极薄的表皮,向内依次为表层、内层、芯部.表皮的片层结构薄且致密,其分子链结晶度高且晶粒沿轴向取向度好.柱状表层的层状结构中晶粒分布均匀、沿轴向定向较好.由表皮至内层,层状结构的厚度逐渐增加,芯部组织较疏松.建立了PAN原丝的结构模型.     

多壁碳纳米管/聚丙烯腈复合纤维的动静态力学性能研究

采用干湿法纺丝工艺制备了多壁碳纳米管(MWNTs)增强的聚丙烯腈(PAN)复合纤维,表征了复合纤维的动静态力学性能。结果表明,采用空气拉伸新工艺并添加少量MWNTs后显著提高了PAN纤维的力学性能;由于MWNTs容易在拉伸作用下取向,且与PAN间存在较强的相互作用,使得与MWNTs作用的PAN分子更易取向并结晶,从而提高了复合纤维的结晶度和取向度,达到了增强的效果。     

成纤过程对PAN纤维晶态结构的影响

聚丙烯腈(PAN)原丝的晶态结构形成与其在制备过程所经历的传热、传质及力场作用有关,采用X射线衍射、紫外光谱和万能材料试验机等研究了不同外场环境下PAN原丝的晶态结构特征。研究结果表明,低温凝固成纤以传热为主,形成的初级凝胶网络结构物理交联点多,PAN纤维结晶度较大,晶粒尺寸较小;高温凝固成纤以传质为主,凝固剂水的扩散力使得PAN纤维结晶度较小,晶粒尺寸较大。较低温度下随着牵伸倍数的增加,PAN纤维结晶度增大,但晶粒尺寸变化较小。总牵伸一定时,结晶度变化不大,但随着较高温度牵伸倍数的增大,晶粒尺寸增长明显。     

PAN纤维的结构对纤维强度的影响

分别采用纤维强伸度仪、乌氏粘度计、X射线衍射仪等测定了4种不同PAN纤维的抗拉强度、分子量、结晶度以及沸水收缩率.结果表明,拉伸速率对4种纤维的强度测试方法的准确性都有影响.在低速拉伸时,由于拉伸速率的增加使分子链段的松弛时间缩短,测试强度随拉伸速率的增加而升高;而在高速拉伸情况下,缺陷成为导致纤维断裂的主要因素,测试强度又随拉伸速率的增加而逐渐降低.在一定范围内,分子量越大、结晶度越高,PAN纤维的强度就越高;作为表征纤维中非晶含量的一项指标,沸水收缩率越大,说明非晶区的比例越大.因此应控制PAN纤维的分子量,提高纤维结晶度,降低纤维的沸水收缩率,从而为制备高性能的碳纤维提供优质原丝.     

PAN基碳化纤维制备过程中纤维的晶态结构研究

采用X射线二维衍射图像和面扫描法对PAN碳化纤维制备过程中各阶段纤维进行了结构表征,揭示了干喷湿纺原丝在预氧化和碳化阶段各纤维晶区取向和晶态结构的差异。结果表明,利用赤道方向二维衍射图,可直观地观察到各纤维在不同阶段取向度以及结晶度的演变规律。与原丝相比,205℃预氧化纤维的取向度、晶粒尺寸以及结晶度都增大,晶面间距无明显变化。235℃预氧化纤维的取向度、晶粒尺寸以及结晶度都减小,晶面间距增大。与原丝以及预氧化纤维相比,碳化阶段纤维的取向度、晶粒尺寸、结晶度以及晶面间距都明显减小。     

湿法纺丝Amid-CNT/PAN复合纤维的结构与性能

通过溶液聚合得到胺化碳纳米管（Ami-CNT）/聚丙烯腈（PAN）复合溶液, 采用湿法纺丝技术制备了Amid-CNT/PAN复合纤维。利用红外光谱、 拉曼光谱、 差示扫描量热仪、 热失重仪和扫描电镜等方法分析Amid-CNT对PAN纤维结构的影响。结果表明: Amid-CNT与PAN大分子之间有很强的化学作用力; Amid-CNT在复合纤维中具有很高程度的取向, 使PAN纤维中氰基的取向从1.61提高到了2.30; 复合纤维在空气中的起始放热温度相对PAN纤维从212.30℃提前到206.01℃, 反应放热量从3054J/g降低到2346J/g; 复合纤维比PAN纤维的起始失重温度提前了3.7℃, 在700℃时的剩余质量提高了13.5%; 复合纤维的断面比PAN纤维具有更多的絮状结构。      

水相悬浮聚合制备MWCNTs/PAN复合微球及其电纺纤维

先用Fenton试剂（过氧化氢/硫酸亚铁）对多壁碳纳米管进行改性处理（-fMWCNTs）,再通过水相悬浮聚合法制备了多壁碳纳米管/聚丙烯腈（-fMWCNTs/PAN）复合微球,用静电纺丝技术制备了-fMWCNTs/PAN复合纤维膜。通过扫描电镜（SEM）、热重分析仪（TGA）和万能试验机研究了-fMWCNTs对电纺纤维...     

Hierarchical composites of carbon nanotubes on carbon fiber: Influence of growth condition on fiber tensile properties

Growing carbon nanotubes (CNT) on the surface of high performance carbon fibers (CF) provides a means to tailor the thermal, electrical and mechanical properties of the fiber–resin interface of a composite. However, many CNT growth processes require pretreatment of the fiber, deposition of an intermediate layer, or harsh growth conditions which can degrade tensile properties and limit the conduction between the fiber and the nanotubes. In this study, high density multi-wall carbon nanotubes were grown directly on two different polyacrylonitrile (PAN)-based carbon fibers (T650 and IM-7) using thermal Chemical Vapor Deposition (CVD). The influence of CVD growth conditions on the single-fiber tensile properties and CNT morphology was investigated. The mechanical properties of the resultant hybrid fibers were shown to depend on the carbon fiber used, the presence of a sizing (coating), the CNT growth temperature, growth time, and atmospheric conditions within the CVD chamber. The CNT density and alignment morphology was varied with growth temperature and precursor flow rate. Overall, it was concluded that a hybrid fiber with a well-adhered array of dense MWCNTs could be grown on the unsized T650 fiber with no significant degradation in tensile properties.     

The effect of surface modification with carbon nanotubes upon the tensile strength and Weibull modulus of carbon fibers

Carbon fibers are widely used as reinforcements in composite materials because of their high specific strength and modulus. Today, a number of ultrahigh strength polyacrylonitrile (PAN)-based (more than 6?GPa), and ultrahigh modulus pitch-based (more than 900?GPa) carbon fibers have been commercially available. In contrast, carbon nanotube (CNT) with the extremely high tensile strength have attracted attention as reinforcements. An interesting technique to modify the carbon fiber is CNT grafting on the carbon fiber surface. CNT-grafted carbon fibers offer the opportunity to add the potential benefits of nanoscale reinforcement to well-established fibrous composites to create micro-nano multiscale hybrid composites. In the present study, the tensile properties of CNT grown on T1000GB PAN- and K13D pitch-based carbon fibers have been investigated. Single filament tensile test at gauge lengths of 1, 5, and 25?mm were conducted. The effect of gauge length on tensile strength and Weibull modulus of CNT-grafted PAN- and pitch-based carbon fibers were evaluated. It was found that grafting of CNT improves the tensile strength and Weibull modulus of PAN- and pitch-based carbon fibers with longer gauge length (≥5?mm). The results also clearly show that for CNT-grafted and as-received PAN- and pitch-based carbon fibers, there is a linear relation between the Weibull modulus and the average tensile strength on log–log scale.     

Carbon nanotube reinforced small diameter polyacrylonitrile based carbon fiber

Polyacrylonitrile (PAN) and PAN/carbon nanotube (CNT) composite (99/1) based carbon fibers with an effective diameter of about 1 μm have been processed using island-in-a-sea bi-component cross-sectional geometry and gel spinning. PAN/CNT (99/1) based carbon fibers processed using this approach exhibited a tensile strength of 4.5 GPa (2.5 N/tex) and tensile modulus of 463 GPa (257 N/tex), while these values for the control PAN-based carbon fiber processed under the similar conditions were 3.2 GPa (1.8 N/tex) and 337 GPa (187 N/tex), respectively. Properties of these 1 μm diameter carbon fibers have been compared to the properties of the larger diameter (>6 μm) PAN and PAN/CNT based carbon fibers.     

PAN/插层高岭石复合材料制备及静电纺丝性能

以二甲基亚砜为前驱体制备插层高岭石(K-DMSO),通过原位聚合制备聚丙烯腈(PAN)与K-DMSO的复合物,利用静电纺丝技术制备PAN/K-DMSO复合纤维膜。采用XRD,FTIR,TEM和TGA研究PAN/K-DMSO复合物的微观形态和热性能,并采用SEM,POM和拉伸试验机对其纤维膜的形貌和拉伸强度进行测试表征。结果表明:PAN/KDMSO中含有高岭石的内外羟基峰,表征层间距的d001值随PAN进入高岭石的层间而增大,部分高岭石被剥离形成厚度为2~5nm的片层结构分散在PAN基体中。K-DMSO的加入使PAN的耐热性提高,PAN纤维膜的直径减小,拉伸强度增加。PAN与K-DMSO的质量比为8∶1时,PAN/K-DMSO纤维膜的拉伸强度与PAN相比,在未处理,冷压和热处理的情况下分别提高了0.92,1.73MPa和1.96MPa。     

Preparation of continuous carbon nanotube networks in carbon fiber/epoxy composite

In order to optimize carbon nanotube (CNT) dispersion state in fiber/epoxy composite, a novel kind of CNT organization form of continuous networks was designed. The present work mainly discussed the feasibility of preparing continuous CNT networks in composite: Fiber fabric was immersed into CNT aqueous solution (containing dispersant) followed by freeze drying and pyrolysis process, prior to epoxy infusion. The morphologies of fabric with CNTs were observed by Scanning Electron Microscope. The relationship between CNT networks and flowing epoxy resin was studied. Properties of composite, including out-of-plane electrical conductivity and interlaminar shear strength (ILSS), were measured. The results demonstrated that continuous and porous CNT networks formed by entangled CNTs could be assembled in fiber fabric. Most part of them were preserved in composite due to the robustness of network structures. The preserved CNT networks significantly improved out-of-plane electrical conductivity, and also have an effect on ILSS value.     

空气过滤用微纳米聚丙烯腈/皮芯型聚乙烯-聚丙烯双组分纤维多层复合材料的制备与性能

采用静电纺丝技术将聚丙烯腈(PAN)纳米纤维收集在皮芯型聚乙烯-聚丙烯(PE-PP)双组分微米纤维网上,制备PAN/PE-PP单层复合纤维网,再将多个单层复合纤维网层层堆叠,经热黏合加固,制备PAN/PE-PP多层复合空气过滤材料,研究了PAN/PE-PP复合纤维网的层数和纺丝时间对其孔径及过滤性能的影响。结果表明:多层复合的方式可得到与单层复合材料相似的孔径参数,但两种材料的孔道结构不同。在总面密度和总纺丝时间一定时,当PAN/PE-PP复合纤维网的层数大于10层时,PAN/PE-PP多层复合过滤材料的过滤效率和品质因子Q_F均明显大于PAN/PE-PP单层复合过滤材料,阻力略微增大;其中,相较PAN/PE-PP单层复合过滤材料,20层PAN/PE-PP复合过滤材料对≥0.3 μm颗粒的过滤效率提高了33%,阻力增加了5 Pa,Q_F值提高了30%。当总面密度和层数一定时,延长静电纺丝时间≥210 min,20层PAN/PE-PP复合过滤材料对颗粒的过滤效率可提高至90%以上,但阻力也急剧增大,因此静电纺丝时间为210 min的PAN/PE-PP多层复合材料的过滤性能最佳。因此,与相同面密度的PAN/PE-PP单层复合过滤材料相比,PAN/PE-PP多层复合过滤材料的过滤性能明显提高;微纳米纤维多层复合法是制备高效低阻复合空气过滤材料的有效方法。      

Damage detection of glass fiber reinforced composites using embedded PVA–carbon nanotube (CNT) fibers

Polyvinyl alcohol–carbon nanotube (PVA–CNT) fibers were embedded in glass fiber reinforced plastic composites and used as strain sensors for damage monitoring of the composite. Sensing of the structural integrity of the composite was made by the in situ measurement of the electrical resistance of the embedded PVA–CNT fiber during the mechanical tests. The multi-functional materials were tested in tensile progressive damage accumulation (PDA) tests. These tests aimed to seek the electrical response of untreated and pre-stretched PVA–CNT fibers with known level of progressively induced damage to the composite. The advantages and disadvantages of each PVA–CNT fiber used as a sensor are analyzed; the electrical resistance readings of the PVA–CNT fibers were correlated with known parameters that express the induced damage of the composite.     

Pore size control and electrochemical capacitor behavior of chemically activated polyacrylonitrile – Carbon nanotube composite films

Activated polyacrylonitrile (PAN)/carbon nanotube (CNT) composite film based electrodes have been prepared by chemical activation with potassium hydroxide for electrochemical capacitors. This paper analyses the following aspects of specific capacitance, pore size distribution and surface area: influence of activation temperature, molarity of activating agent, composition of PAN/carbon nanotube precursor films and electrolytes. A maximum value of specific capacitance of ∼302 Fg⁻¹ was achieved for the samples activated at 800 °C. Energy density for PAN/CNT 80/20 sample when tested with ionic liquid/organic electrolyte system was as high as ∼22 W h kg⁻¹. Pore size control predominantly below 5 nm was observed in these activated PAN samples. Data analysis showed that micropores make a significant contribution to the capacitance performance of these materials in both 6 M KOH as well as in BMIMBF₄/acetonitrile electrolytes.