高性能纤维表面改性及其双马树脂基复合材料界面

采用电感耦合射频等离子体(ICP)和介质阻挡放电(DBD)低温等离子体对高性能连续纤维表面进行改性,分别采用X光电子能谱(XPS)、原子力显微镜(AFM)和动态接触角测定仪(DCA)等分析测试手段系统地研究了等离子体处理时间、放电功率、放电气压等对连续碳纤维、聚苯并二噁唑(PBO)纤维改性处理前后,纤维表面状态、表面组成、表面形貌、浸润性能的变化规律以及经等离子体处理前后纤维增强双马树脂基复合材料界面结构与性能的影响关系及变化规律、复合材料界面粘结和破坏机理.研究结果表明,经过等离子体处理后,纤维表面接枝上了大量的含羧基、羟基等极性官能团,表面粗糙度增加,表面自由能增加,纤维浸润性能得到明显改善,导致纤维与双马树脂基体界面层间剪切强度(ILSS)明显提高,复合材料的破坏模式由未处理的界面脱粘破坏转变为等离子体处理后的树脂基体破坏.最后,对纤维表面时效性及其对纤维增强双马树脂基复合材料界面性能的影响关系也进行了论述.     

石墨烯改性树脂基复合材料力学性能研究进展

树脂基复合材料具有比强度高、比模量大、耐高温、耐腐蚀、质轻等诸多优点,在航天军工、生物医疗、电子封装、体育器材等众多领域得到广泛应用。石墨烯作为一种典型的二维纳米材料,凭借其独特结构以及优异的物理化学性能而备受关注。近年来的研究表明石墨烯可以通过对增强纤维改性和对基体树脂改性的方法来提高树脂基复合材料的力学性能。本文介绍了石墨烯改性树脂基复合材料的增强增韧机理,对石墨烯改性纤维(碳纤维、玻璃纤维、芳纶纤维)增强复合材料以及树脂的改性方法进行了综述;着重阐述了石墨烯改性树脂基复合材料力学性能的研究进展,分析了石墨烯改性树脂基复合材料研究中依旧存在的两大问题,即石墨烯的分散性和界面结合问题,并对石墨烯改性树脂基复合材料的未来发展前景进行了展望。     

纤维增强树脂基复合材料中的横穿结晶研究

在以结晶性聚合物为基体树脂的纤维或织物增强复合材料中,经常出现横穿结晶(横晶)界面相。本文综述了近年来对纤维增强树脂基复合材料中横穿结晶的研究,内容包括横晶的概念,纤维表面诱导成核的机理,纤维诱导成核的能力和条件,横晶的生长和终止以及横晶的力学效应等。在不同的树脂/纤维复合材料体系中,由于其横穿结晶本身和本体球晶在尺寸和数目比例等方面呈现各不相同的复杂局面,横晶对复合材料性能的影响显得复杂。通过各种手段调控横晶的形态、尺寸及数量,使横晶的存在有利于复合材料整体性能的提高,是进行纤维增强结晶性聚合物基复合材料设计时应该遵循的一个基本原则。     

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。     

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。     

热塑性碳纤维复合材料界面研究

综述了热塑性碳纤维复合材料界面研究的新进展。指出由于热塑性复合材料基体树脂是高聚物,熔体牯度很大,很难均匀地分布在增强纤维之中并与纤维形成良好浸溃,存在界面结合不良的问题,因此对其界面优化设计要有一个新的认识。界面上没有化学键结合,界面结合不良,但只靠短化学键的连接,界面结合也不良,必须有一个强韧结合的界面,既有强结合又具有界面松弛能力,同时又能与高聚物基体融合的界面缓冲层的优化设计。对于Plueddemann偶联剂的概念中偶联剂“必须成为树脂的一部分”,作者认为最好的方法是就是树脂本身,即它既与纤维化学键键合,又与树脂良好相容,界面匹配。这将是热塑性复合材料界面层设计的一种新方法。     

碳纤维表面改性研究进展

碳纤维因其优异的综合性能常被用作树脂基体的增强材料.然而由于碳纤维与树脂基体之间的界面结合性能较差,其增强的复合材料的力学性能往往与理论值相差甚远,因此必须对碳纤维进行表面改性,以提高其与聚合物基体的界面粘结性能.本文作者综述了国内外关于碳纤维表面改性技术的研究进展,概述了涂层法、氧化法、高能辐射法等改性方法对碳纤维增强复合材料界面强度的改性效果.     

环氧树脂体系固化反应及其复合材料介电性能

环氧树脂是一类综合性能优异的热固性高分子材料，作为胶粘剂、复合材料用树脂基体、涂料等形式广泛应用于电子电气、机械制造、化工防腐、航空航天等众多领域中，成为各工业领域中不可缺少的基础材料。本文综述了本研究室在咪唑／环氧树脂体系，稀土有机化合物、叔胺羧酸复盐／酸酐／环氧树脂体系，氰酸酯／环氧树脂体系，硼胺络合物／环氧树脂体系的固化反应机理、固化反应动力学及其固化物结构与性能关系，纤维含量、排列方向、偶联剂种类等对玻璃纤维增强环氧树脂基复合材料及其界面介电性能的影响等6个方面的研究进展。     

含二氮杂萘酮联苯结构热塑性聚芳醚树脂基复合材料研究进展

含二氮杂萘酮联苯结构聚芳醚是一类综合性能优异的耐高温热塑性树脂,可采用多种方式加工成型。与传统聚芳醚相比,具有低成本、优异的高温力学性能和良好的溶解性等优势,可作为基体树脂应用于制备复合材料。本文主要介绍了近几年在含二氮杂萘酮联苯结构热塑性聚芳醚树脂基复合材料方面的研究进展,包括玻璃纤维增强复合材料、碳纤维增强复合材料...     

kevlar纤维增强尼龙6复合材料的力学性能

对Kevlar纤维进行了改性,使其成为己内酰胺阴离子开环聚合的活性中心,采用阴离子接枝法在Kevlar纤维(KF)表面接枝尼龙6低聚物,并与基体尼龙6混合,用挤出和注塑方式制备了尼龙6/改性Kevlar纤维(PA6/KF1)复合材料。ESEM和XPS分析表明,Kevlar纤维表面接枝上了尼龙6低聚物。比较了尼龙6/未改性Kevlar纤维(PA6/KF0)和PA6/KF1复合材料的力学性能及破坏形态,同时探讨了其破坏机理。结果表明,接枝尼龙6的KF1增强了KF与尼龙6复合材料界面的相互作用,拉伸强度、弯曲强度和弯曲模量分别提高了20.69%、12.26%和14.23%,但冲击强度降低了8.2%;当复合材料被破坏时,未改性纤维表面只粘附有少量的树脂尼龙6,而改性纤维的表面有较多的树脂包覆层,呈部分非界面脱粘破坏,具有良好的界面结合能力。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.