甲基磺酸对PBO纤维的表面改性

采用甲基磺酸(MSA)溶液对PBO纤维表面进行化学改性,用单丝拔出试验测定了改性前后PBO纤维与环氧树脂基体的界面剪切强度,并通过扫描电镜(SEM)、X-射线光电子能谱(XPS)、接触角分别对处理前后纤维的表面形貌、表面组成以及表面自由能进行了表征.研究结果表明:在甲基磺酸质量分数为60%的溶液中,60℃下处理6 h的PBO纤维与环氧树脂基体的界面剪切强度比未处理的提高了81%,并且纤维表面O元素的质量分数增加了13.3%,表面自由能增加了17.3%.当溶液中甲基磺酸的质量分数、处理时间和处理温度进一步提高时,PBO纤维的皮层将遭受破坏,导致界面剪切强度下降.     

提高PBO纤维/环氧树脂复合材料界面结合的研究

本文采用表面化学蚀刻与溶胀法结合、化学偶联法与氩气低温等离子体表面处理技术结合的方法对聚苯撑苯并二。唑（PBO）纤维进行表面改性。探讨了不同改性方法对纤维表面性能的影响。同时，采用FTIR和SEM等方法对处理前后纤维表面化学结构及形态进行了表征。     

多聚磷酸吡哆醛血红蛋白的制备及性质研究

血红蛋白是利用不等渗裂解法从人的全血中提取得到的．在不同的温度和无氧条件下，用磷酸吡哆醛修饰血红蛋白，它们的摩尔比为４：１．随后用戊二醛在４℃，ｐＨ７．４条件下交联磷酸吡哆醛化血红蛋白，获得多聚磷酸吡哆醛血红蛋白．ＳＤＳ－ＰＡＧＥ显示了交联前后血红蛋白的分子量的变化。凝胶层析得到修饰交联后的血红蛋白的分子量分布是一个连续的整体，约从６万到６０万道尔顿之间．多聚磷酸吡哆醛血红蛋白溶液是一个可溶的有载氧能力的溶液，它的Ｐ５０在２０～２６ｍｍＨｇ之间．     

超高分子量聚乙烯纤维表面改性的研究进展

超高分子量聚乙烯(UHMWPE)纤维具有诸多优异性能,因此被广泛应用于纤维增强复合材料(FRP)。但是由于UHMWPE纤维表面光滑且无极性基团,与树脂基体粘接性差,可通过纤维表面改性有效提高FRP的界面强度,进而提升材料性能。本文总结了近几年基于化学处理、等离子体处理、电晕放电和辐射引发表面接枝等方法对UHMWPE纤维表面改性的研究进展,并对改性方法的发展进行了展望。     

芳纶纤维/SMPU-SiO2复合材料的界面性能研究

选用形状记忆聚氨酯(SMPU)和正硅酸乙酯(TEOS)为前驱体,固体酸对甲基苯磺酸(PTSA)为催化剂,利用空气中的水分为水解水源,通过溶胶-凝胶法原位制备了形状记忆聚氨酯与二氧化硅( SMPU-SiO2)杂化材料,并将杂化材料应用于芳纶纤维增强的柔性复合材料中,以期改善芳纶纤维与基体的界面性能.同时,针对芳纶纤维表面...     

高性能PBO纤维的成型、性能改善及其应用研究北大核心CSCD

聚苯撑苯并二噁唑(PBO)纤维具有超高强度和模量、优异的耐热性和阻燃性,是一种在国防军工、航空航天等领域有重要应用价值的有机高性能纤维。本文综述了国内外PBO纤维的发展历程、纤维的性能,重点介绍了制备高分子量PBO聚合物和纺制高性能PBO纤维的关键技术和先进工艺,提供了改善PBO纤维界面粘结性能、压缩性能和光老化稳定性能的不同技术途径。结果表明:PBO聚合只有多种因素包括单体、工艺、设备等同时优化才能获得高分子量的PBO聚合物,利用双螺杆挤出机同时完成聚合和液晶纺丝成型是工业化连续生产高性能PBO纤维的先进技术路线;通过在PBO大分子链上引入离子基团或双羟基能显著提高PBO纤维与环氧树脂的界面粘结强度,双羟基的存在能使PBO大分子链间建立氢建相互作用从而也提高了PBO纤维的压缩性能,双羟基单体特有的紫外吸收性能更是有效地改善了PBO纤维的光稳定性;在PBO聚合时添加光吸收剂,或在PBO纤维表面涂覆聚酰亚胺都是改善PBO纤维光稳定性的有效方法。     

纤维增强复合材料界面剪切强度及界面微观结构的表征

界面在纤维增强复合材料中具有特别重要的作用,它不但是纤维增强复合材料中增强相和基体相连接的纽带,也是应力及其他信息传递的桥梁。良好的界面粘结才能使纤维的性能得到充分发挥,进而纤维增强复合材料的力学性能得到提高,因此对纤维增强复合材料的界面粘结性能、界面微观结构的研究非常重要。本文总结了纤维增强复合材料界面剪切强度、界面微观结构的表征方法,包括单纤维拔出试验、纤维断裂试验、纤维压出试验等,并侧重介绍了拉曼光谱对纤维增强复合材料界面粘结性能、界面微观结构的研究。     

抗紫外老化聚对苯撑苯并二噁唑(PBO)纤维的制备与表征

通过化学添加2,5-二羟基对苯二甲酸(DHTA)共聚,以及添加金红石型纳米TiO2物理共混的方法,制备了聚对苯撑苯并二噁唑(PBO)的抗紫外改性纤维.考察了纤维的力学性能、特性粘度及表面形貌在紫外老化过程中的变化,并结合PBO纤维紫外加速老化后的红外分析,对PBO纤维的光老化机理进行了初步研究.结果表明,本实验所制备的DHPBO纤维以及DHPBO/n-TiO2纤维的抗紫外老化能力明显高于PBO纤维,并且金红石型纳米TiO2对PBO的抗紫外改性效果要优于有机紫外吸收剂(2,2'-(1,2-乙烷二基)双(4,1-亚苯基)双苯并噁唑).     

镧改性Cu/SiO2催化剂的乙酸甲酯高效加氢催化性能研究

采用蒸氨法制备了镧(La)改性的负载型铜硅(Cu/SiO₂)催化剂,并对其乙酸甲酯(MeOAc)气相加氢制乙醇(EtOH)的催化性能进行了研究。采用N₂吸附-脱附(N₂ adsorption-desorption)、X射线粉末衍射(XRD)、电感耦合等离子体发射光谱(ICP-OES)、氢气程序升温还原(H₂-TPR)、傅里叶红外光谱(FT-IR)、高分辨透射电镜(HRTEM)、光电子能谱(XPS)和原子发射光谱仪(AES)等手段对催化剂进行了的表征,发现La物种的加入产生了较多的层状硅酸铜,增强了Cu和La物种之间的相互作用。La物种的加入在结构方面提高了催化剂的比表面积,降低了铜物种的粒径,提高了铜物种的分散度;在电子还原调控方面提高了Cu⁺的含量,增强了催化剂吸附酰基和甲氧基的能力。与未改性的Cu/SiO₂催化剂相比,镧改性后Cu/SiO₂催化剂的乙酸甲酯加氢性能得到大幅提升;其中La掺杂量0.5%的Cu/SiO₂     

Improvement of surface wettability and interfacial adhesion ability of poly(p-phenylene benzobisoxazole) (PBO) fiber by incorporation of 2,5-dihydroxyterephthalic acid (DHTA)

By introducing 2,5-dihydroxyterephthalic acid (DHTA) into poly(p-phenylene benzoxazole) (PBO) macromolecular chains, dihydroxy poly(p-phenylene benzobisoxazole) (DHPBO) was synthesized and then DHPBO fibers were prepared by dry-jet wet-spinning method. Effects of hydroxyl polar groups on surface wettability and interfacial adhesion ability of PBO fiber were investigated. With the incorporation of double hydroxyl polar groups, contact angle on PBO fiber for water can decrease from 71.4° to 50.70°, and contact angle for ethanol can decrease from 37.2° to 27.40°. The wetting time on DHPBO fibers for water can be as short as 650 ms, which is half of that of PBO fibers. The interfacial shearing strength (IFSS) between DHPBO (10% mol content DHTA) fibers and epoxy resin is 18.87 MPa, 92.55% higher than that of PBO fibers. SEM images indicate that the PBO/epoxy composite failure mode may change from fiber/matrix adhesive failure to partially cohesive failure.     

Surface modification of PBO fibers with 2,2-Bis (3-amino-4-hydroxyphenyl) hexafluoropropane in supercritical carbon dioxide for enhancing interfacial strength

PBO fiber is one of the most promising reinforcements in resin matrix composite because of its excellent mechanical properties. However, the inert and smooth surfaces make it the poor interface adhesion with resin matrix, which seriously limits the application in composites. In this article, we report a method to modify the surface of PBO fibers with 2,2-Bis (3-amino-4-hydroxyphenyl) hexafluoropropane（BisAPAF）in supercritical CO₂ to enhance interfacial properties. Chemical structures, surface elemental composition and functional groups, and surface morphology were characterized by FT-IR spectrometer, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), respectively. The mechanical properties of the samples were tested by a tensile tester. Static contact angle and microdebonding tests were used to characterize the wetting ability and interfacial shear strength (IFSS) of the fiber and epoxy resin. The results showed that the BisAPAF could be solved in scCO₂ and introduced more groups, –NH₂, –OH, and –CF₃ on the fiber surface, resulting in the mechanical properties and the wettability of PBO fiber slightly improved. Moreover, the fiber surface roughness was also increased obviously. The IFSS between the modified PBO fiber and epoxy resin increased from 8.18 MPa to 31.4 MPa when the treating pressure was 14 MPa. In general, the method to modify PBO fibers surface using BisAPAF in scCO₂ can effectively improve their interfacial properties.     

Improvement of PBO fiber surface and PBO/PPESK composite interface properties with air DBD plasma treatment

The interface of fibrous composites is a key factor to the whole properties of the composites. In this study, the effects of air dielectric barrier discharge (DBD) plasma discharge power density on surface properties of poly(p‐phenylene benzobisoxazole) (PBO) fiber and the interfacial adhesion of PBO fiber reinforced poly(phthalazinone ether sulfone ketone) (PPESK) composite were investigated by several characterization methods, including XPS, SEM, signal fiber tensile strength, interlaminar shear strength, and water absorption. After the air DBD plasma treatment at a power density of 41.4 W/cm³, XPS analysis showed that some polar functional groups were introduced on the PBO fiber surface, especially the emergence of a new oxygen‐containing group (?O–C = O group). SEM observations revealed that the air DBD plasma treatment had a great influence on surface morphologies of the PBO fiber, while the signal fiber tensile strength results showed only a small decline of 5.9% for the plasma‐treated fiber. Meanwhile, interlaminar shear strength value of PBO/PPESK composite was increased to 44.71 MPa by 34.5% and water absorption of the composite decreased from 0.46% for the untreated specimen to 0.27%. The results showed that the air DBD plasma treatment can effectively improve the properties of the PBO fiber surface and the PBO/PPESK composite interface. Results obtained from the above analyses also showed that both the fiber surface and the composite interface performance would be reduced when an undue plasma discharge power density was applied. Copyright © 2011 John Wiley & Sons, Ltd.     

Novel mild synthesis of high-added-value p-hydroxyphenyl acetic acid and 3,4-dihydroxyphenyl acetic acid using the acidic clay/hydrogen peroxide catalytic system

Acid-activated clays KSF and KSF/0 were successfully used in the hydrogen peroxide conversion of phenyl acetic acid to high-added phenolic compounds: p-hydroxyphenyl acetic acid and 3,4-dihydroxyphenyl acetic acid, endowed with a powerful antioxidant capacity. The catalytic conversion enhancement could be correlated to the total surface acidity and the high iron content of the catalysts KSF/0 and KSF, respectively. The synthetic route described here was conducted under mild conditions with very low degree of mineralization and without significant Fe ion leaching observations. The synthesis reaction is operationally simple and could find application for industrial purposes.     

Surface modification of ultra‐high molecular weight polyethylene fibers by chromic acid

Ultra‐high molecular weight polyethylene (UHMWPE) fibers were modified by chromic acid. The effects of surface modification were evaluated with Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), contact angle measurement, and scanning electron microscope (SEM). The results showed that both the content of O‐containing functional groups and surface roughness of modified fibers increased. The polar groups on the modified fiber surface decreased the contact angles with water and ethylene glycol, as evidenced by contact angle measurement. The tensile test results showed the strength and the elongation at break of UHMWPE fibers decreased but the modulus increased after chromic acid modification. Copyright © 2016 John Wiley & Sons, Ltd.     

Surface modification of magnesium hydroxide particles using silane coupling agent by dry process

In order to improve the dispersion and compatibility of magnesium hydroxide (MH) when added in the polymer matrix as fillers, the surface of MH was modified by dry process using vinyltrimethoxysilane (VTMS), and the interfacial interaction between MH and VTMS was also studied. Scanning electronic microscopy, transmission electron microscopy, and X‐ray powder diffraction analyses showed that the agglomerations of MH particles were effectively relieved, and a thin layer was formed on the surface of modified MH. Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy analyses showed that the VTMS molecules bound strongly to the surface of MH particles and chemical bond (Si―O―Mg) was formed after modification. The effect of surface modification was evaluated by contact angle, the settlement curve, and thermogravimetric analysis. The results showed that the surface of MH particles was transformed from hydrophilic to hydrophobic, with the dispersibility and the compatibility of MH particles significantly improved in the organic phase. Additionally, the thermal stability of the VTMS modified MH particles had improved significantly.     

An acetic acid/water based sol-gel PZT process I: Modification of Zr and Ti alkoxides with acetic acid

The chemical reactions underlying the formation of a water based alkoxide sol gel solution for lead zirconate titanate thin films have been evaluated using infra-red spectroscopy and viscosity measurements. Titanium isopropoxide and zirconium propoxide are modified by acetic acid in order to use water as a solvent. Substitution reactions initially take place with the formation of titanium or zirconium alkoxide acetate and alcohol. The titanium or zirconium alkoxide acetate gradually associate through the formation of M-O-M linkages to increase the viscosity of the solution.     

Improving the interfacial property of carbon fibre/epoxy resin composites by grafting amine-capped cross-linked poly-itaconic acid

To improve the interfacial properties of carbon fibre-reinforced polymer composites, a surface treatment was used to cap cross-linked poly-itaconic acid onto carbon fibres via in-situ polymerization after itaconic acid grafting. The chemical composition of the modified carbon fiber (CF) surface was characterized by X-ray photoelectron spectral and Fourier-transform infrared spectroscopy. Scanning electron microscopy and atomic force microscopy images showed that the poly-itaconic acid protective sheath was uniformly capped onto the CF surface and that the surface roughness was obviously enhanced. Chemical bonds also played a key role in the interfacial enhancement. The results showed that the interfacial shear strength of the composites with poly-itaconic acid on the carbon fibres (72.2 MPa) was significantly increased by 89.5% compared with that of the composites with pristine CF (38.1 MPa). Moreover, the poly-itaconic acid sheath promoted a slight increase in mono-fibre tensile strength. In addition, the interfacial mechanisms were also discussed. Meanwhile, the mechanical property of the functionalized CF/epoxy resin composites was also significantly improved.     

Surface properties of aqueous solutions of trifluoroacetic and acetic acid mixture

The coadsorption of trifluoroacetic and acetic acid at the free surface of water was investigated. Knowing the composition of mixed monolayer and the effective dipole moments of individual molecules, the surface potential was calculated. The synergetic effect of the surface properties of mixed adsorbed films was observed.     

Surface oxidation of cellulose fibers by vacuum ultraviolet irradiation

The efficacy of vacuum ultraviolet irradiation for oxidizing the surface of cellulose fibers was compared to that of the conventional wet and dry processes. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 357–361, 1999