螯合纤维的制备——聚丙烯腈纤维改性

聚丙烯腈纤维与羟胺试剂通过化学反应,腈基转变为偕胺肟基团,使聚丙烯腈纤维改性成为对金属离子具有螯合能力的螯合纤维。系统地探讨和研究了聚丙烯腈纤维改性的实验参数:反应温度、时间、反应物浓度、酸度等。并用红外光谱对螯合纤维进行表征。     

辐射交联聚丙烯腈偕胺肟纤维的制备及其对钒(Ⅲ)的吸附研究

采用60Coγ射线对聚丙烯腈纤维进行预辐射交联,并经偕胺肟化反应,制备了含有偕胺肟基的聚丙烯腈螯合纤维,用于钒(Ⅲ)离子的吸附行为研究。结果表明,辐射交联可以有效提高聚丙烯腈纤维的肟胺化反应速率;经肟胺化和吸附之后的纤维力学性能良好;较高的肟胺化程度导致聚丙烯腈纤维对三氯化钒具有很高的吸附容量。     

偕胺肟基螯合纤维的制备

以聚丙烯腈纤维为原料,加入羟胺试剂,将腈基转变为偕胺肟基团,使聚丙烯腈纤维改性成含有偕胺肟基团的螫合纤维。探讨了聚丙烯腈纤维改性的工艺参数,结果表明:聚丙烯腈在温度为65~75℃,pH值6~7的羟胺溶液中反应3 h,螫合纤维产率最高达到41％。用傅里叶变换红外光谱(FT-IR)对螯合纤维进行了表征,部分腈基转化成了偕胺肟基团。     

聚丙烯腈基中空炭膜的研究发展

概述了聚丙烯腈基活性炭纤维的制备和结构,制备条件对聚丙烯腈基中空纤维炭膜的影响,以及聚丙烯腈基中空纤维炭膜作为医用吸附剂的可行性。     

偕胺肟基螯合纤维制备的反应动力学研究

通过研究聚丙烯腈纤维与盐酸羟胺的反应制备偕胺肟基螯合纤维,考察了反应时间、盐酸羟胺浓度、反应温度对反应的影响规律。较适宜的反应条件为:反应温度70℃,反应时间180 min,纤维、盐酸羟胺和无水碳酸钠摩尔比为1:1:0．5,浴比1:50。根据反应速率定律和Arrhenius方程,对实验数据进行处理,得出螯合纤维中偕胺肟基的生成速率与盐酸羟胺浓度为0．9级的关系,反应的活化能为62．4 kJ/mol,指前因子为1．6×106 mmol·L0.9/(mol0.9·g·s),70℃时螯合纤维中偕胺肟基的生成速率常数为8．3×10-4 mm01．L0.9/(mol0.9·g·s)。     

阴离子交换纤维的制备及其对氟离子交换性能的影响的研究

通过以聚丙烯腈纤维进行NH2 OH化学改性制得的含有偕胺肟基的螯合纤维为原料 ,经FeCl3 化学处理 ,制得阴离子交换纤维 ,并以氟离子为研究对象 ,系统地探讨和研究制备阴离子交换纤维的实验条件对氟离子交换性能的影响。实验表明 ,该交换纤维对氟离子交换具有速度快、交换量大、再生处理便利和重现性好等优点 ,最高交换量 30mg g ,交换率 90 %以上。     

偕胺肟基螯合纤维的研究进展

介绍了偕胺肟基螯合纤维的制备方法及其与金属离子作用的螯合机理、吸附等温线、吸附反应影响因素等;概述了偕胺肟基螯合纤维在提取金属、废水处理净化等方面的应用;综述了对偕胺肟纤维—金属离子配合物应用于离子交换与吸附材料、抗菌纤维、催化剂等方面的研究;展望了偕胺肟基螯合纤维的发展趋势;指出制备力学性能较好的偕胺肟基螯合纤维的关...     

高性能纤维热牵伸研究进展

热牵伸贯穿聚丙烯腈基纤维制备全过程,能够使纤维内部类石墨微晶尺寸增大、沿纤维轴向取向度提高,明显改善纤维的微观结构,从而提高其物理性能.本文概述了牵伸处理在纤维制备过程中的关键作用,主要介绍了牵伸在聚丙烯腈基炭纤维、中间相沥青基炭纤维、黏胶基炭纤维、纳米炭纤维以及生物可降解纤维生产过程中的应用研究进展,重点分析了聚丙烯...     

阴离了交换纤维的制备及其对氟离子交换性能的影响的研究

通过以聚丙烯腈纤维进行NH2OH化学改性制得的含有偕胺肟基的螯合纤维为原料，经FeCl3化学处理，制得阴离子交换纤维，并以氯离子为研究对象，系统地探讨和研究制备阴离子交换纤维的实验条件对氟离子交换性能的影响，实验表明，该交换纤维对氟离子交换具有速度快、交换量大、再生处理便利和重现性好等优点，最高交换是30mg/g，交换率90%以上。     

聚丙烯腈基离子交换纤维制备研究进展

因聚丙烯腈具有易改性的功能基团及优良的力学性能,故对聚丙烯腈纤维进行化学改性制备离子交换纤维已成为当前研究的热点。对以聚丙烯腈为基体通过化学改性来合成螯合、弱酸、弱碱、两性离子交换纤维的制备方法进行了综述,分析了制备方法的优缺点,并展望其发展前景。     

Characterization of surfaces of carbon fibres by scanning tunneling microscopy

Summary The experimental results obtained by scanning tunneling microscopy (STM) studies of different carbon fibres are presented and discussed. The comparative analysis of the STM images at scales from hundreds of nanometers down to atomic scale reveals the differences of surface features for carbon fibres processed from different precursors, polyacrylonitrile fibres and pitch. The high temperature treatment of carbon fibres — the so-called graphitization process — as used to improve the stress modulus induces drastically increased ordering phenomena at the atomic level. Structural information obtained by STM on the surface of the fibres as well as in their cross sectional areas is discussed in comparison with known results of diffraction studies. STM appears to be the new powerfull technique for the detailed structural studies of surfaces of carbon fibres. The perspectives of these studies are under discussion.     

Morphology of the noncoloured and coloured polypropylene fibres

The scanning electron microscopy investigations of the morphology of the polypropylene fibes were carried out. The studies were performed for gravity spun fibres as well for fibres taken at different take-up velocities in the range from 100 to 1350 m/min. The noncoloured fibres and fibres coloured with quinacridone and phthalocyanine pigments were investigated.The studies revealed that the morphology of fibres is strongly influenced by take-up velocity and the presence of pigments.At low take-up velocity the spherulitic structure is observed. While in noncoloured fibres the big spherulites are formed in coloured fibres fine spherulites occur. In fibres coloured with quinacridone pigment spherulites possess a sheaf-like structure. The wide angle X-ray scattering measurements showed that spherulites occurred in noncoloured fibres consist of the α modification, whereas the sheaf-like spherulites in fibres coloured with quinacridone pigment of the β modification.At higher velocities the spherulitic structure transforms into a fibrillar one. The fibrils possess a hierarchical structure and consist of microfibrils formed from a bundle of nanofibrils.The change of the fibres morphology was interpreted by a change of the nucleation mechanism.     

Structural and thermal characteristics of polyacrylonitrile fibres as raw material for production of carbon fibres

Three samples of polyacrylonitrile fibres used for production of carbon fibres were investigated by x-ray diffraction, differential scanning calorimetry, and thermogravimetry. It was found that spinning of polyacrylonitrile fibre with the thiocyanate method ensures a smaller crystallite size, while the composition of the copolymer affects the thermogravimetric parameters.     

Catalytic initiation of polyacrylonitrile stabilization

A catalytic surface treatment of polyacrylonitrile fibres by dibutyltin dimethoxide is investigated as to its capacity to facilitate the stabilization of the fibres to produce a satisfactory carbon fibre precursor. The stabilization is based on a combination of the catalytic treatment step and of the usual thermal oxidation step which follows. The effectiveness of the surface treatment is determined through comparing physical, thermal and mechanical properties of stabilized fibres with and without catalytic pre-treatment. The results show that a 1 minute catalytic treatment shortens the usual 220°C thermal oxidation process by at least 2 hours, and that the process is applicable in particular to polyacrylonitrile fibres which are ‘slow oxidizers’ in general due to their chemical composition.     

Properties of polycaproamide fibres which have been modified by grafting polyacrylonitrile

Conclusions The properties of modified polycaproamide fibres containing various amounts of grafted polyacrylonitrile have been investigated.It has been shown that the attachment of polyacrylonitrile to polycaproamide fibres leads to an improvement in a number of properties (light resistance, heat resistance, wool-like appearance) which determine the customer acceptance of fibres and articles made from them.Translated from Khimicheskie Volokna, No. 3, pp. 32–33, May–June, 1984.     

Dependence of the combustibility of fibres on their degree of pyrolysis and carbonization

Conclusions The combustibility characteristics of pyrolyzed and carbonized viscose and polyacrylonitrile fibres have been investigated: oxygen index, limiting oxygen concentration, autoignition temperature, and glow point.It has been shown that the combustibility of pyrolyzed and carbonized fibres prepared from polyacrylonitrile is somewhat lower than the combustibility of those made from viscose fibres: this is connected with a more perfect aromatic structure and with the presence of nitrogen atoms in the first and of oxygen atoms in the second.Translated from Khimicheskie Volokna, No. 2, pp. 47–49, March–April, 1984.     

Fibre mortar composites in fire conditions

A small-scale test series was carried out using the heating system (radiant exposure) of a cone calorimeter to detect any differences in the way different fibres affect the thermal properties of a standard mortar. The fibres were different polypropylene, polyacrylonitrile, aramide, carbon or steel. Fibres affect the release of moisture from the fibre mortar material. Local pressures caused by water vaporization due to rapid heating can be decreased by incorporating fibres. Fibres have a weak insulating effect. However, use of polyacrylonitrile fibres in mortar may increase the risk to spalling under rapid thermal exposure such as fire. The moisture level in specimens is highly significant for their thermal properties and hence their fire behavior.     

Effect of silane treatment on the Curaua fibre/polyester interface

ABSTRACT

Good adhesion at fibre/matrix interface of lignocellulosic fibres is crucial when substituting synthetic fibres in polymer composites. The great variability presented by those fibres requires diverse characterisation studies for better insights on fibre surface treatments and resin systems interactions. In this work, Curaua fibres were treated using silane coupling agents to improve their interfacial properties with polyester. The fibres were pre-treated using 4?wt% solution of NaOH and then treated with 5?wt% solution of (3-aminopropyl) trimethoxysilane (AMPTS) or triethoxymethylsilane (TEMS). Characterisation of the treated fibres was carried out using infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. Fibre wettability and adhesion towards polyester was investigated using contact angle measurements and pull-out tests, respectively. The AMPTS treatment yielded a significant result of 20.2?MPa in interfacial shear strength (≈2.5 times that of the untreated fibre), attributed to the increase in availability of binding sites with polyester.     

Defect content and nonuniformity in mechanical properties of polyacrylonitrile fibres

Conclusions Defect content and nonuniformity in mechanical properties of polyacrylonitrile fibres have been investigated in the cross section of tow and over the length of individual elementary fibres.For a generalized evaluation of defectiveness and nonuniformity in mechanical properties we have used the scale dependence of strength and histograms for strength distribution. Scale coefficients for the strength of polyacrylonitrile fibres have been determined.For rapid characterization of defectivity and nonuniformity of mechanical properties of fibres one can use the ratio of the mean strengths at two clamped lengths which differ significantly (by an order of magnitude or so).Translated from Khimicheskie Volokna, No. 1, pp. 33–34, January–February, 1989.     

Effect of a constant electrical field on the shrinkage of polyacrylonitrile fibres

Conclusions The possibility of physically modifying polyacrylonitrile fibres by stretching them in a constant electrical field, with the objective of attaining a high degree of shrinkage, has been demonstrated.The mechanism of the effect of an electrical field on polyacrylonitrile fibres consists in breaking up part of the dipole-dipole bonds between nitrile groups and partial polarization of the polymer.Translated from Khimicheskie Volokna, No. 2, pp. 34–36, March–April, 1985.