Kevlar纤维表面接枝改性及其稳定化

文章试图通过化学处理方法在Kevlar纤维表面引入活性基团,从而达到对Kevlar纤维进行表面接枝改性的目的。采用红外光谱分析甲苯-2,4-二异氰酸酯(TDI)接枝kevlar纤维的表面组成,用己内酰胺及聚乙二醇PEG(400)对接枝物进行封端稳定化处理;分析了不同n_TDI∶n_PEG值对其产物表面组成的影响。实验结果表明,当n_TDI∶n_PEG=1∶3时, 接枝后红外谱图在3 300 cm-1处的吸收峰强度有所减弱,而在1 700～1 720 cm-1处得到加强;当n_TDI∶n_PEG=1∶1和1∶2时,接枝后红外谱图在3 300及1 700～1 720 cm-1处的吸收峰强度基本相同。n_TDI∶n_PEG=1∶3时稳定化效果最佳。     

Kevlar纤维的聚丙二醇及丁烯二醇改性研究

探讨了聚丙二醇(PPG)及2-丁烯-1,4-二醇对Kevlar纤维的改性机理,并采用红外光谱分析法考察了Kevlar纤维表面用甲苯-2,4-二异氰酸酯(TDI)酯化的情况。同时分别分析了用聚丙二醇和丁烯二醇对Kevlar纤维封端后产物的红外光谱图,结果表明：封端后样品在1 700～1 720 cm-1处的吸收峰得到了加强,即—NCO转化成—CONH—,封端效果明显;在相同用量的条件下,丁烯二醇的封端效果明显优于PPG。文中还比较了不同的n_TDI∶n_丁烯二醇值对稳定化产物封端效果的影响,表明过量的丁烯二醇不利于纤维的进一步反应,n_TDI∶n_丁烯二醇应控制在1∶1左右。     

光谱法研究MC尼龙6/芳纶复合材料的结构

将经甲苯二异氰酸酯(TDI)和己内酰胺改性的Kevlar纤维作为MC尼龙6的增强体,X射线光电子能谱观察到改性后纤维表面C,N和O元素的含量发生了改变,谱峰也相应发生变化。从红外光谱分析发现,Kevlar纤维和MC尼龙6相混所得谱图只是二者红外谱图的简单叠加,而改性Kevlar纤维可作为己内酰胺阴离子开环聚合的活性中心,且接枝链上的酰胺基可以与基体尼龙形成较强的氢键,有利于提高界面结合。XRD测试表明Kevlar纤维的引入并没有明显改变MC尼龙6的晶型,但其晶粒将具有更严格的三维周期性结构。在相同纤维用量时,改性Kevlar纤维增强的MC尼龙6的晶粒较未改性纤维的完善。当纤维含量小于2%时,纤维的加入有利于生成完善的α球晶,纤维含量大于2%时,α球晶结构含量随着纤维用量的增多反而下降。     

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本研究用氮气等离子体固相表面修饰改性对丙纶纤维进行表面处理。用傅立叶变换红外光谱分析改性前后样品表面官能团变化,用扫描电镜分析改性前后样品表面的形貌变化,用紫外可见分光光度计测试样品的上染率。结果表明:等离子体表面处理及丙烯酸接枝后的丙纶纤维表面引入了羰基、胺(氨)基或酰胺等活性基,使丙纶纤维从不可上染到能染上鲜艳的阳离子艳兰,显著改善了丙纶纤维的染色品质。     

多胺型纤维素基螯合纤维的合成和光谱学研究

将漂白化学桉木浆(BCEP)与甲基丙烯酸缩水甘油酯(GMA)的接枝共聚产物(CPGMA)与乙二胺(EDA)反应,合成了多胺型纤维素基螯合纤维CPGMA-EDA。利用傅里叶变换红外光谱(FTIR)、固体核磁共振碳谱(13C CP/MAS NMR)和X射线衍射(XRD)对产物进行了分析。FTIR和13C CP/MAS NMR的研究结果表明,与EDA反应后,CPGMA在904 cm-1波数处的环氧基特征吸收峰基本消失,3 200～3 500 cm-1处的吸收峰因新增N—H伸缩振动而明显增宽,说明大量氨基通过开环反应被接枝到了CPGMA表面;XRD结果表明所得纤维素基螯合纤维的结晶度为48.1%,相对于原漂白化学桉木浆的结晶度下降了31.0%,说明反应不仅发生在纤维素的非结晶区,同时也发生在结晶区。     

电子能谱法研究改性的聚丙烯纤维性能与结构关系

本文讨论了聚丙烯纤维(PPF)在Ar、N_2、O_2和空气等离子体作用时,改变时间和功率对PPF表面进行等离子体处理,发现处理后纤维的吸湿性变化很大,回潮率是未处理样品的120-400%,染色性能从5级提高到1级标准。这一变化的光电子能谱法研究结果表明:PPF表面的结构发生较大变化。表面大量引入含O、N极性基团。经谱图拟合可知,这些基团是亲水性的极性结构,应归属于C-OH、C=O、COOH、C-NH_2和CONH_2基团。     

基于银纳米粒子的局域表面等离子体共振效应提高草甘膦基于茚三酮间接检测的灵敏度（英文）

常规的农药残留检测一般存在前处理操作复杂,耗时较长,方法不够灵敏等问题。根据氨基与茚三酮显色原理和局域表面等离子体共振(LSPR)增强光吸收原理,利用紫外-可见吸收光谱对水样品中草甘膦含量进行定量分析,并利用密度泛函理论进一步分析了显色的类似罗曼紫产物的光吸收增强机理。草甘膦与茚三酮在钼酸钠催化下反应生成类似罗曼紫产物;该物质在紫外–可见吸收光谱570nm处有最大吸收峰,当其吸附在银纳米粒子(Ag NPs)表面上时,最大吸收峰蓝移至568nm处,同时吸收强度显著提高;本研究中检出限为2.017 4×10^-11 mol·L^-1,显著低于文献中约6.5×10^-7 mol·L^-1的检出限。Gaussian 09软件计算得出,类似罗曼紫产物经由茚三酮的C=O基团垂直吸附在Ag NPs表面,静电势表明茚三酮的C=O基团优先与Ag稳定相互作用并形成Ag—O键,C=O基团和C—N基团构成了π键共轭系统;连接草甘膦和茚三酮之间的C—N键是类似罗曼紫产物的生色团。因此,茚三酮衍生法可用于间接检测水样品中草甘膦,银纳米...     

异丁烷部分氧化V-P-O/SiO2催化剂的研究

采用溶胶 凝胶法制备了V2 O5 /SiO2 和V2 O5 P2 O5 /SiO2 催化剂 ,用XRD、TPR、IR、TPD和微反应等技术研究了催化剂的表面结构、晶格氧活泼性、化学吸附和异丁烷部分氧化反应性能 .结果表明 ,催化剂的活性组份在无定型的SiO2 表面上呈超细粒子均匀分布 ,表面活性位主要由Lewis碱位 (V =O键的端氧、V -O -V键的桥氧 )和Lewis酸位 (Vn + )构成 ,PO43 - 的引入可以降低表面Lewis碱位V =O键端氧的活泼性 ;异丁烷分子主要通过两个甲基中H双位吸附在催化剂表面Lewis碱位V =O的端氧上 ,PO43 - 的引入使异丁烷的吸附强度略有下降 ;异丁烷在V2 O5 P2 O5 /SiO2 催化剂上反应产物主要是i C4H8、MAL、MAA和COx,PO43 - 的引入可以明显的提高部分氧化产物的选择性     

基于XRD和FITR的Ce-V-Ti催化剂减排烧结烟气二噁英的活性分析（英文）

二噁英是一类含氯挥发性有机污染物,具有环境持久性、生物蓄积性和长期残留性等特性,可造成致畸、致癌和致突变等危害。铁矿烧结过程中含氯前驱物在碱性环境下通过Ullman反应或经飞灰中某些催化性成分催化生成二噁英;碳、氢、氧和氯等元素可通过基元反应"从头合成"(de novo)二噁英,是二噁英最主要的排放源之一。物理吸附技术仅能实现污染物由气相向固相转移,加重了飞灰处理负担,并存在特定温度条件下(250～350℃)二噁英再生风险。催化降解技术能彻底矿化有机污染物,生成CO_2, H_2O和HCl/Cl_2,是一种避免二次污染高效节能、成本较低的方法。但由于传统催化剂活性温度区间较高,无法达到烧结烟气末端温度。选择合适的催化剂,提高催化剂低温降解活性,能实现低温、高效催化降解烧结烟气中有机污染物的目标。过渡金属Ce具有稀土金属的4f轨道配位效应和路易斯酸活性位点,对有机污染物C—H和C—Cl键活化起到至关重要的作用,掺杂过渡金属、调整活性组分比例可进一步提高铈基催化剂的抗中毒性能和降解活性。因此,本文采用溶胶凝胶法制备Ce-V-Ti复合催化剂,以氯苯为二噁英模型分子,研究了不同活性组分比例对铈基催化剂降解烧结烟气中二噁英活性影响。利用X射线衍射仪、比表面积及孔径测定仪和拉曼光谱仪对催化剂进行表征,研究Ce-V-Ti催化剂的相组成、比表面积和分子结构,并推测铈基催化剂的降解机理。结果表明,在实验室模拟烧结烟气气氛下,反应条件为GHSV=30 000 h~(-1)、 20%O_2和100 ppm CB,当Ce质量分数为15%、 V质量分数为2.5%时, Ce-V-Ti催化降解氯苯活性最高, 150℃能达到约60%转换率, 300℃能实现95%降解率。催化剂载体与活性组分之间化学交互作用,影响催化剂的降解活性。通过光谱学分析发现, Ce-V-Ti催化剂XRD图谱主要为锐钛矿相的TiO_2,比表面积为95.53 m~2·g~(-1),孔容0.29 cm~3·g~(-1),孔径6.5 nm。表面官能团主要为C—H基团和H—O官能团。引入V作为Ce-Ti催化剂助剂,促进了Ce元素固溶,增加了催化剂表面氧空位,有利于提升催化剂降解活性。通过对催化剂机理分析,认为反应物首先通过发生亲核取代而垂直吸附于催化剂表面,再被活性组分Ce活化,活化后氯苯分子被表面活性氧分解矿化。同时,过渡金属V的低价态氧化物发生氧化反应,促进Ce的还原反应。     

大鼠体内青石棉纤维表面变化的红外光谱研究

肌体蛋白质在与青石棉的相互作用过程中,组织结构对称性降低,结构疏松;青石棉的硅已与蛋白质中的烷基、胺基交联成键,存在明显的Si—O—C(N),Si—R新的吸收谱带;青石棉残留的粉尘仅为以硅为主的物质。石棉小体(斑)内的纤维表面基团和组织内的某些蛋白反应形成新的表面介体。染尘肌体组织在加热过程中,蛋白质类结构对称性降低并逐渐氧化,末端基团如—CH_3,—CH_2振动减弱。C—C长链骨架的分解,并可分成200,400和600℃三个相变温区。Si—O,Si—O-Si吸收加强,新生成的表面介体的稳定性(Si—O—C,Si—C,Si—CH_3)基团介于二者之间。在500℃以上,肌体组织、表面介体和体内残留纤维已全部破坏。体内青石棉被生物作用溶解和生化反应结合后,其热稳定温度大为降低。     

Modification of glass fiber surface by nylon-6,6 grafting

Polycondensation of nylon-6,6 onto Kevlar and glass fibers has been previously proposed by our group as a surface treatment for composite fabrication. The present article reports the optimisation of this procedure for glass fibers via a study of the first two steps of the polymerisation, the esterification of pendant OH groups at the glass fiber surface by adipoyl chloride, and the amidation reaction occurring between the grafted acid chloride moiety and diamino-1,6-hexane. X-ray photoelectron spectroscopy (XPS) and potentiometric results show that esterification proceeds within the first 30 min of the reaction. The amidation reaction was characterised by Kjeldahl and XPS procedures and was found to be complete after less than one minute. Results also underline the importance of pH control during the reaction to limit hydrolysis of the ester bond at the fiber surface. Thermogravimetric analysis of samples obtained by a manual procedure as well as by an automated lab-scale reactor show that the amount of grafted material increases linearly with number of passes, indicating the occurrence of a negligible amount of termination reactions up to 60 passes.     

Radical grafting from carbon fiber surface: graft polymerization of vinyl monomers initiated by azo groups introduced onto the surface

This paper describes the radical graft polymerizations of vinyl monomers from carbon fiber surface initiated by azo groups introduced onto the fiber surface. The carbon fiber used in this experiment was the polyacrylonitrile type. The introduction of azo groups onto the carbon fiber surface was achieved by the reaction of 4,4'-azobis (4-cyanopentanoic acid) with isocyanate groups which were previously attached onto the surface by the treatment of the fiber with tolylene 2,4-diisocyanate. The amount of surface azo groups introduced onto nitric acid-treated carbon fiber was determined to be 0.60 x 10^-5 mol 9^-1 by nitrogen analysis. The radical graft polymerization of methyl methacrylate (MMA) was tried. Though the thermal polymerization of MMA proceeded slightly in the absence or in the presence of untreated carbon fiber, the rate of the polymerization was considerably low. In contrast, the graft polymerization of MMA was initiated in the presence of the carbon fiber having surface azo groups, and part of resultant poly(MMA) grafted onto the surface. The percentage of grafting increased with an increase in polymerization time and reached 42.8% after 24 h. The graft polymerizations of other monomers, such as styrene, vinyl acetate, and acrylic acid, were also initiated by the surface azo groups attached onto the carbon fiber, and the corresponding polymer effectively grafted onto the surface.     

The influence of surface treatment of stitch threads and stitching on interlaminar properties of unidirectional laminates

An experimental investigation was carried out to study the influence of graft treatment for Kevlar stitch threads on the interlaminar properties of stitched unidirectional laminates. The surfaces of Kevlar stitch threads were immersed in a solution of Dimethyl sulfoxide mixed with NaH for some time, and then alkoxysilane was grafted onto the surface of modified Kevlar threads. The corresponding physical and chemical changes in the surface of Kevlar threads were carefully evaluated using XPS, SEM, water absorption, and tensile measurement. Results show that the treated Kevlar threads have much rougher surface morphologies, its tensile strength is slightly improved, and their wettability are greatly improved. The stitched carbon /epoxy composite using surface-treated Kevlar threads has excellent hydrothermal property. The resins can better wet the surface treatment of Kevlar stitch threads, and the sizes of rich resin can be reduced. The moisture uptake of stitched composites decreases by 53.3% and its residue ratio of interlaminar shear strength in a wet state improves by 13.1%.     

Radical graft polymerization initiated by azo groups introduced onto the surface of carbon whisker

The radical graft polymerization of vinyl monomers onto carbon whisker, i.e. vapor grown carbon fiber, initiated by azo groups introduced onto the surface has been investigated. The introduction of azo groups onto the surface is achieved by (1) the reaction of 4,4'-azobis(4-cyanopentanoic acid) with isocyanate groups on the surface, which are introduced by the treatment of surface carboxyl and phenolic hydroxyl groups with tolylene-2,4-diisocyanate and (2) the reaction of 2,2'-azobis(2-cyano-n-propanol) with acyl chloride groups on the surface, which are introduced by the treatment of surface phenolic hydroxyl groups with terephthaloyl dichloride. The carbon whiskers having azo groups prepared from the above two methods are abbreviated as CW-Azo 1 and 2, respectively. The azo group content of CW-Azo 1 and 2 is determined to be 0.04 and 0.07 mmol/g, respectively. It is found that the radical polymerization of methyl methacrylate and styrene is initiated by the surface azo groups to give the corresponding polymer-grafted carbon whisker. The polymer-grafted carbon whisker gives a stable colloidal dispersion in good solvents for grafted polymer.     

The effect of oxygen-plasma treatment on Kevlar fibers and the properties of Kevlar fibers/bismaleimide composites

The effect of oxygen-plasma treatment for Kevlar fibers on the interfacial adhesion and typical macro-properties of Kevlar fiber/bismaleimide composites was intensively studied. It is found that oxygen-plasma treatment significantly affects the interfacial adhesion by changing the chemistry and morphology of the surfaces of the fibers, and thus leading to improved interlaminar shear strength, water resistance and dielectric properties of the composites. However, the improvement is closely related to the treatment power and time. The best condition for treating Kevlar fiber is 70 W for 5 min. Oxygen-plasma treatment provides an effective technique for overcoming the poor interfacial adhesion of Kevlar fiber based composites, and thus showing great potential in fabricating high performance copper clad laminates.     

Radical graft polymerization from carbon whisker initiated by peroxyester groups introduced onto the surface

The radical graft polymerization of vinyl monomers onto carbon whiskers, i.e. vapor grown carbon fibers, initiated by tert-butyl peroxyester groups that are introduced onto the surface was investigated. The introduction of tert-butyl peroxyester groups onto the carbon whisker surface was achieved by the reaction of acyl chloride groups on the surface with tert-butyl hydroperoxide. The carbon whisker having acyl chloride groups was prepared by the following three methods: (1) reaction of surface carboxyl groups with thionyl chloride, (2) reaction of surface phenolic hydroxyl groups with succinyl dichloride, and (3) reaction of surface phenolic hydroxyl groups with phthaloyl dichloride. The carbon whiskers having tert-butyl peroxyester groups prepared from these three methods were abbreviated as CW-POE 1, 2, and 3, respectively. The peroxyester group content of CW-POE 1, 2, and 3 was determined to be 0.06, 0.05, and 0.17 mmol/g, respectively. It was found that the radical polymerization of vinyl monomers such as methyl methacrylate, styrene, and N-vinylcarbazole was successfully initiated in the presence of CW-POE 2 and 3, and the corresponding polymers were grafted onto the surface. However, CW-POE 1 failed to initiate the radical graft polymerization, because surface phenyl radicals formed by the thermal decomposition of the tert-butyl peroxyester groups are stabilized by the aromatic rings of the carbon whisker surface.     

Studies on surface modification of UHMWPE fibers via UV initiated grafting

In this research, the surface of ultra high molecular weight polyethylene (UHMWPE) fiber was modified by high energy ultraviolet (UV) initiated grafting reactions and acrylamide groups were grafted onto UHMWPE chains. The initiating and grafting mechanism of the reactions was studied. Some important factors influencing the grafting effect, e.g. crystallinity of UHMWPE fiber, concentration of the initiating reagent, grafting time and the concentration of grafting monomer (acrylamide) were discussed. Fourier transform infrared (FTIR) was used to manifest the mechanism of the grafting reaction. Scanning electron microscopy (SEM) was used to show the morphology changing of the fiber surface. Single fiber pull-out strength and ILSS tests of the composite showed that acrylamide grafted onto the surface of the fiber could improve the interfacial adhesion between treated fibers and matrices.