干法纺聚酰亚胺纤维氧化处理及其对结构性能的影响

以H2O2为湿化学处理液,利用扫描电镜、热重分析仪、纤维检测系统、单纤维电子强力仪、傅里叶变换红外光谱仪、X射线光电子能谱仪、X射线粉末衍射仪分别研究了H2O2氧化对干法纺聚酰亚胺纤维浸润性能、微观形貌、热失重性能、直径及力学性能、化学结构、表面元素含量和微观聚集态结构的影响。结果表明,H2O2氧化后,纤维表面凹凸不平,比表面积及粗糙度增加,局部发生刻蚀,引入了活性基团,表面能提高,O/C比值增加,浸润性能得到改善,且随着H2O2浓度或温度提高、处理时间延长,浸润性能改善趋势加快,热失重性能保持较好,直径及力学性能略微下降。表面氧化使纤维化学结构变化不大,微观聚集态结构发生改变,非结晶区比例上升,采用适当的H2O2处理工艺,有助于聚酰亚胺纤维表面进行功能化改性。     

酸处理对干法纺甲纶聚酰亚胺纤维增强体性能的影响

以HCl为湿化学处理液,研究了HCl处理对聚酰亚胺纤维增强体浸润性能、微观形貌、热性能、细度及力学性能、化学结构和微观聚集态结构的影响,在分析纤维浸润性能改善的同时也分析了其他性能及结构的变化。结果表明:HCl处理后纤维表面凹凸不平,粗糙度增加,局部发生了刻蚀,引入了活性基团,表面能提高,浸润性能改善。且随着HCl浓度或温度的提高、处理时间的延长浸润性能改善趋势加快,热性能保持较好,细度及力学性能略有降低。在H+的作用下纤维酰亚胺环少量开环水解为聚酰胺酸,化学结构变化不明显,微观聚集态结构发生改变,非结晶区比例上升。HCl处理能有效地对纤维表面进行功能化改性。     

表面改性离子交换化学镀制备表面覆镍聚酰亚胺纤维

以高强度的聚酰亚胺（PI）纤维为基纤,采用表面改性离子交换和化学镀相结合的方法,成功制备了高强度、高导电性和热稳定性好的聚酰亚胺-Ni （PI-Ni）复合导电纤维,采用SEM观察纤维的微观形貌,通过XRD和EDS表征了镀层组成及相态结构,测试了纤维的力学性能、导电性、界面黏结性能及热性能。结果表明,PI-Ni纤维表面平整光滑,完整致密,镀层为非晶态Ni-P合金。PI-Ni束丝拉伸强度约为1.2 GPa,电阻率为1.76×10^-4 Ω·cm,5%热失重温度为611℃,耐热性能优异,是一种高性能的有机导电纤维。     

酸碱处理对聚酰亚胺薄膜的表面改性

采用酸碱处理的方法对聚酰亚胺(PI)薄膜表面改性。利用万能试验机和热失重仪考察了处理前后PI薄膜力学性能和热性能的变化情况,并通过傅立叶红外光谱仪、原子力显微镜及视频接触角仪对PI薄膜改性前后表面性能进行了表征。结果表明,经酸碱处理后,PI薄膜表面化学组成和表面形貌均发生变化,表面亲水性增大;当处理时间为4min时,力学性能保持在97%以上,热稳定性略有下降;均方根粗糙度从1.057nm增大到3.002nm,接触角从77.32°下降到46.70°,粘接功提高了38.20%。     

聚酰亚胺纤维制备及应用

聚酰亚胺是指分子主链中含有酰亚胺环的一类聚合物材料,这种高度共轭的主链结构赋予了聚酰亚胺纤维优异的力学性能,较高的耐热氧化稳定性、耐溶剂腐蚀性能等,在航空航天、环境保护等领域具有广阔的应用前景.由于聚酰亚胺加工过程中的基础问题尚未攻克,影响了这类高性能纤维的发展和使用.高新材料发展的需要、聚酰亚胺化学结构的多设计性和合成技术的改进以及纺丝技术的进步促进了聚酰亚胺纤维的发展,通过大分子结构设计和聚集态结构的调控,可以得到不同化学结构的高强高模、耐高温、耐辐射特性的聚酰亚胺纤维.主要概述了聚酰亚胺纤维的性能、制备方法及应用领域,并对近年来国内外最新研究进展和产业化情况进行了介绍.     

碱处理对竹纤维/聚乳酸可降解复合材料性能影响研究

以NaOH溶液为改性剂对竹纤维进行碱处理,再与聚乳酸(PLA)熔融共混制备竹纤维/PLA可降解复合材料。探讨了NaOH溶液浓度、碱处理时间和碱处理温度对复合材料拉伸强度、抗弯强度和耐水性能的影响规律,并采用扫描电子显微镜(SEM)对碱处理竹纤维的表面形貌进行了观测。结果表明,碱处理使竹纤维表面粗糙度增大,单纤维的强度提高,有效提高了与PLA基体的机械黏接力。但碱浓度过大、处理时间过长或处理温度过高时,纤维素分子链排列致密程度降低,整体纤维的力学性能下降。NaOH溶液浓度为3%,处理时间为4h,处理温度为60℃时,所制得竹纤维/PLA复合材料拉伸性能、弯曲性能和耐水性能均最佳。     

酸/碱腐蚀对玄武岩纤维纱线特性的影响

采用2.0mol/L的HCl及NaOH溶液为腐蚀介质,在60℃条件下处理玄武岩纤维纱线,研究玄武岩纤维纱线的耐酸/碱腐蚀性能及其腐蚀机理。结果表明,经酸与碱处理后纤维纱线的断裂强度总体上均呈下降趋势,只是下降的规律有所不同。酸与碱处理的纱线表面腐蚀程度不同,且表面的各元素含量也有不同幅度的降低,促使表面处理剂的相对含量增大。另外,碱腐蚀后结构中还产生了羟基(-OH)官能团,因此玄武岩纤维纱线的耐酸性能强于耐碱性能。     

不同环境因素作用下玻纤/环氧乙烯基酯复合材料的冲蚀行为

为探究环境因素对玻璃纤维增强环氧乙烯基酯树脂基(GF/EVE)复合材料性能的影响,对其进行了湿热和碱腐蚀老化试验,通过对不同老化时间下GF/EVE复合材料吸湿率、微观形貌、表面元素含量、表面化学结构及冲蚀失重率变化的分析,探讨了GF/EVE复合材料在湿热环境和碱腐蚀介质中的老化机理以及不同老化时间下的抗冲蚀性能变化.结果表明:随着老化时间延长,吸湿率增大,且碱性介质中的吸湿率较湿热环境大;在水分子及腐蚀介质的扩散作用下,树脂基体发生塑化、水解,纤维/基体界面出现脱黏,纤维表面腐蚀降解;同时老化造成树脂分子链断裂,交联密度降低,导致树脂初始分解温度下降;湿热和碱腐蚀老化初期冲蚀失重率分别下降了3. 2%和1. 8% ,老化结束后分别增加了17. 6%和20. 8% .     

棉秆皮纤维的提取及其结构、性能研究

为更有效地利用废弃农作物秸秆资源,研究了常温常压碱处理提取天然棉秆皮纤维的技术,讨论了氢氧化钠溶液质量浓度、温度和时间等碱提取工艺参数对棉秆皮失重率的影响,并采用FT-IR、SEM、XRD等方法对优化工艺提取的棉秆皮纤维的化学成分、表面形态、结晶结构、力学性能等进行了表征。结果表明,NaOH质量浓度为15g/L、液固比为30mL/g、处理温度为100℃、处理时间为120min时,棉秆皮失重率较大,木质素、半纤维素、果胶等杂质去除较多。天然棉秆皮纤维结晶度为53.72%,断裂强度约1.6cN.dtex-1,断裂伸长率为5.91%,性能接近天然纤维素纤维黄麻。     

碳纤维高温退浆处理对聚酰亚胺复合材料热老化的影响

分别从复合材料热氧化失重、表面和微观形貌、力学性能和玻璃化转变温度等方面，对比研究了碳纤维退浆和未退浆两种状态的聚酰亚胺复合材料在330℃下热老化过程中的性能变化规律及机理。结果表明：碳纤维退浆可以降低聚酰亚胺复合材料的热氧化失重率。碳纤维未退浆的复合材料由于界面层含耐温性低的环氧上浆剂，在热老化过程中界面容易破坏，导致裂纹较多，边缘纤维较快发生脱离。未退浆的复合材料虽然在老化前具有较高的层间剪切强度，但在热老化前期降低较快，退浆的复合材料在200 h老化后层间剪切强度反而更高。两种复合材料老化前的弯曲强度基本相当，但未退浆的复合材料在老化前期弯曲强度下降较快；退浆对弯曲模量影响不大。退浆后的复合材料玻璃化转变温度提高了15℃左右；经热老化后，未退浆的复合材料玻璃化转变温度略有提高，而退浆的复合材料基本不变。因此，对碳纤维进行高温退浆处理有利于提高聚酰亚胺复合材料在高温下长期使用的稳定性。     

Investigation of physical,chemical and mechanical properties of raw and alkali treated Borassus fruit fiber

The natural fibers nowadays play a major role as reinforcement in composites due to their important properties like lightweight, biodegradability and non-toxicity. Borassus fruit fiber is one such type possessing high cellulose which is inexpensive and available in plenty. The Borassus fruit fibers were extracted and its physical, chemical and mechanical properties such as density, diameter, cellulose, hemicellulose, lignin, wax, denier, tenacity and tensile force were experimentally determined. In this study, the Borassus fruit fibers were treated with 5%, 10% and 15% NaOH and the effect of alkali treatments on the fiber properties were explored. It is interesting to note that 5% NaOH treatment yielded significant improvement in tensile properties of the fibers than the others. The Fourier Transform Infrared Spectrometry (FT-IR) analysis was made to identify the chemical compounds of the raw and alkali treated fibers. The morphological study on raw and alkali treated fibers by Scanning Electron Microscope (SEM) revealed the existence of the impurities on the raw fiber surface and the removal of the same on the treated fibers.     

Investigation of physical,chemical and mechanical properties of raw and alkali treated Borassus fruit fiber

The natural fibers nowadays play a major role as reinforcement in composites due to their important properties like lightweight, biodegradability and non-toxicity. Borassus fruit fiber is one such type possessing high cellulose which is inexpensive and available in plenty. The Borassus fruit fibers were extracted and its physical, chemical and mechanical properties such as density, diameter, cellulose, hemicellulose, lignin, wax, denier, tenacity and tensile force were experimentally determined. In this study, the Borassus fruit fibers were treated with 5%, 10% and 15% NaOH and the effect of alkali treatments on the fiber properties were explored. It is interesting to note that 5% NaOH treatment yielded significant improvement in tensile properties of the fibers than the others. The Fourier Transform Infrared Spectrometry (FT-IR) analysis was made to identify the chemical compounds of the raw and alkali treated fibers. The morphological study on raw and alkali treated fibers by Scanning Electron Microscope (SEM) revealed the existence of the impurities on the raw fiber surface and the removal of the same on the treated fibers.     

Fiber surface treatment and its effect on mechanical and visco-elastic behaviour of banana/epoxy composite

Natural fibers offer many advantages over synthetic fibers but the notable disadvantage of natural fibers is its hydrophilic nature. Due to this nature an incompatibility between the fiber and matrix exist which decreases the properties of the composite. This defect can be overcome by chemical modification of fiber surface so as to make it less hydrophilic. In this work, alkali (NaOH) of various concentrations (0.5%, 1%, 2%, 5%, 10%, 15% and 20%) was used to treat the fiber surface and the effect of these concentrations on the mechanical and visco-elastic behaviour of the composites were carried out. From the experimental investigation, it is found that 1% NaOH treated fiber reinforced composites behaves superiorly than other treated and untreated fiber composite. Further, SEM image analysis also shows the effect of alkali concentration over the fiber surfaces which leads to improving the mechanical properties of the composite.     

Chemical treatment of sisal fiber using alkali and clay method

In this study the chemical treatment of sisal fiber using the combined alkali (NaOH) and clay is discussed. The purpose of this fiber treatment is to improve the fiber–matrix compatibility, interface strength, mechanical, thermal and water barrier properties. The phase change due to chemical treatment of raw sisal fiber was examined by Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) methods. The result shows the presence of about 20 wt.% clays in NaOH–clay treated sisal fiber with 2.6× reduced water uptake and also with improved mechanical and thermal properties. Subsequently the treated and untreated fibers were reinforced in polypropylene (PP) matrix and the mechanical and thermal properties were examined. The result indicates that the fiber–matrix interface strength, adhesion, glass transition temperature and tensile properties of composites were improved in NaOH–clay treated fiber composites.     

The effect of alkaline treatment on mechanical properties of kenaf fibers and their epoxy composites

In this work, kenaf fibers were pre-treated in a NaOH solution (6% in weight) at room temperature for two different periods (48 and 144 h). The chemical treatment of kenaf fibers for 48 h allowed to clean their surface removing each impurity whereas 144 h of immersion time had detrimental effect on the fibers surface and, consequently, on their mechanical properties.Untreated and NaOH treated kenaf fibers (i.e. for 48 h) were also used as reinforcing agent of epoxy resin composites. The effect of the stacking sequence (i.e. using unidirectional long fibers or randomly oriented short fibers) and the chemical treatment on the static mechanical properties was evaluated showing that the composites exhibit higher moduli in comparison to the neat resin. As regards the strength properties, only the composites reinforced with unidirectional layers show higher strength than the neat resin. Moreover, the alkali treatment increased the mechanical properties of the composites, due to the improvement of fiber–matrix compatibility.The dynamic mechanical analysis showed that the storage and the loss moduli are mainly influenced by the alkali treatment above the glass transition temperature. Moreover, the alkali treatment led to a notable reduction of tan δ peaks in addition to significant shifts of tan δ peaks to higher temperatures whereas the stacking sequence did not influence the trends of storage modulus, loss modulus and damping of the composites.     

竹纤维/聚乳酸复合材料界面调控

分别采用碱(NaOH)处理、 异氰酸酯(MDI)处理以及NaOH+MDI处理的界面调控方法对竹纤维/聚乳酸复合材料界面进行调控。结果表明, NaOH处理可以进一步细化竹纤维, 增加比表面积, 实现对竹纤维/聚乳酸复合材料界面的物理调控; MDI处理能够实现对复合材料界面的化学调控; 三种界面调控方法均可以改善竹纤维/聚乳酸复合材料的力学性能, 而NaOH+MDI界面调控效果最佳, 调控处理后复合材料拉伸强度和冲击强度分别增加了36.9%和36.5%。     

Chemical modification of kenaf fibers

The interest in using natural fibers in composites has increased in recent years due their lightweight, non-abrasive, combustible, non-toxic, low cost and biodegradable properties. However, lack of good interfacial adhesion, low melting point and poor resistance to moisture absorption make the use of natural fiber reinforced composites less attractive. Chemical treatment of the fiber can clean the fiber surface, chemically modify the surface, stop the moisture absorption process and increase the surface roughness. In this study, kenaf bast fibers, supplied by MARDI, for use in fiber-reinforced composites, were modified using NaOH of different concentrations. Morphological and structural changes of the fibers were investigated using scanning electron microscopy (SEM). A series of fiber bundle tensile tests were also performed to evaluate the effect of the treatments on the fiber tensile strength. It has been found that the alkalization treatment has improved the mechanical properties of the kenaf fiber significantly as compared to untreated kenaf fiber. It is also interesting to note that 6% NaOH yields the optimum concentration of NaOH for the chemical treatment.     

Chemical composition and structural characterization of Napier grass fibers

Napier grass fibers were analyzed by chemical, FTIR and solid-state ¹³C NMR methods. These fibers were also treated with 2% and 5% aq. NaOH solutions and the effect of alkali treatment on the composition and structure of the fibers was studied. Alkali treatment eliminated the amorphous hemicellulose component of the fibers to a larger extent. The morphology of the fibers before and after alkali treatment was observed with a scanning electron microscope. The fibers became thin with a rough surface and the cell structure collapsed after alkali treatment and showed enhanced tensile properties.     

表面改性自金属化技术制备表面导电热固性聚酰亚胺复合材料

采用碱刻蚀/离子交换的方法对碳纤维增强热固性聚酰亚胺基复合材料进行了表面自金属化,制备了表面覆银导电聚酰亚胺复合材料。表征了聚酰亚胺复合材料表面酰亚胺五元环开环程度随碱液刻蚀条件的变化,研究了碱液刻蚀、酸洗、离子源和离子交换时间对复合材料表面导电性和力学性能的影响。当碱液刻蚀5 h、离子交换9 h时,热固性聚酰亚胺复合材料表面方块电阻可达0.26 Ω·sq?1,且基本力学性能得到保持。