聚合物／层状硅酸盐纳米复合材料的研究进展

聚合物／层状硅酸盐（PLS）纳米复合材料是近十多年迅速发展起来的新交叉科学。由于聚合物纳米复合材料具有常规聚合物复合材料所没有的结构、形态以及较常规聚合物复合材料更优异的物理力学性能、耐热性和气体液体阻隔性能等，因而显示出重要的科学意义和应用前景。综述了聚合物／层状硅酸盐纳米复合材料的制备、结构、性能和应用情况，最后展望了其应用前景。     

聚合物／层状硅酸盐纳米复合材料制备原理

围绕着分散相尺寸和两相界面粘接这两个关键问题,简单回顾了复合材料从熔融共混,聚合复合到纳米复合的发展历程。通过对具有重要理论意义和应用价值的聚合物／层状硅酸盐（PLS）纳米复合材料制备过程热力学驱动力的考察以及制备原理的分析,我们首次从理想状态下推导出了能在一定范围内预测聚合物相对分子质量与层状硅酸盐含量,层状硅酸盐片层间距与层状硅酸盐含量以及层状硅酸盐片层间距与聚合物相对分子质量关系的理论公式,并用文献中的实验数据进行了验证。结果表明这些理论关系与文献中的实验数据精确吻合。     

聚合物/层状硅酸盐纳米复合材料的研究进展 --层状硅酸盐粘土的有机改性

综述了近年来国内外聚合物/层状硅酸盐纳米复合材料领域中层状硅酸盐有机改性的最新研究进展情况.主要对有机改性剂的结构、作用机理、改性后有机粘土的特性,及其在聚合物基纳米复合材料中的应用进行了详细的阐述.在此基础上,提出了一条新的研究思路.     

聚合物/层状硅酸盐纳米复合材料制备研究进展

近年来,聚合物基有机/无机纳米复合材料作为材料科学领域中的一枝新秀,已引起人们的广泛关注,这类材料具有有机和无机材料的特点,并通过两者之间的耦合产生出许多优异的性质,有着广阔的应用前景.聚合物与蒙脱土插层是制备高性能聚合物/层状硅酸盐纳米复合材料的一种新方法,也是当前材料科学领域的研究热点.本文从材料结构及性能、制备方...     

聚合物/层状硅酸盐纳米复合材料的制备研究

本文以聚丙烯和有机蒙脱土为原料，采用插层复合法制备聚合物／层状硅酸盐纳米复合材料，用透射电镜对复合材料的结构进行表征，测定了复合材料的力学性能，结果表明，用马来酸酐化聚丙烯作界面相容剂，聚丙烯大分子链分子插层进入到有机改性蒙脱土的硅酸盐片层中间，并且聚丙烯／蒙脱土纳米复合材料的力学性能有一定的提高。     

聚合物/层状硅酸盐纳米复合材料

目前,聚合物／层状硅酸盐纳米复合材料是重要的工程材料之一。由于层状硅酸盐的特殊结构,聚合物层状硅酸盐纳米复合材料的各项性能得到较大改善。聚合物／层状硅酸盐纳米材料的制备、表征、结构与性能的研究取得了重要进展。本文简要概述了聚合物／层状硅酸盐的结构及其有机改性机理,研究表明,插层剂和离子交换容量是插层的重要因素。最后,讨论了聚合物／层状硅酸盐纳米复合材料的制备方法和性能。     

聚合物/蒙脱土纳米复合材料的研究进展

介绍了蒙脱土的结构特点，聚合物／蒙脱土复合材料的帛备方法和分类，讨论了各种聚合物／蒙脱土纳米复合材料的性能特点和应用。聚合物／层状硅酸盐蒙脱土纳米复合材料具有优异的性能，是目前材料学科研究的热点之一。     

聚合物—层状硅酸盐纳米复合材料制备及应用

聚合物－层状硅酸盐（ＰＬＳ）纳米复合材料因其优异的性能是目前材料科学研究的热点,简要回顾ＰＬＳ纳米复合材料研究发展的概况,概述ＰＬＳ纳米复合材料的特点,种类,微观结构与物理力学性能,着重介绍ＰＬＳ纳米复合材料的各种制备方法和原理,并从热力学角度对插层复合过程进行了分析,讨论了层状硅酸盐的表面修饰,提出了插层剂的选择原则,展望了ＰＬＳ纳米复合材料的应用前景。     

熔融插层制备聚烯烃/层状硅酸盐纳米复合材料研究进展

简述聚烯烃/层状硅酸盐纳米复合材料的结构、表征及优点,并对采用熔融插层法制备的此种复合材料的力学性能、结晶性能及相关工艺、表征方法、分散机理等进行较为详细的综述。     

层状硅酸盐 /聚合物纳米复合材料的研究现状与前景

基于1996年以后的40余篇文献和作者的研究成果，综述了层状硅酸盐／聚合物纳米复合材料在制备技术、新品种、新性能、相关理论及应用等方面的最新研究进展，并总结出了以下观点：（1）粘土的有机化是制备纳米复合材料的第一关键要素，单体、预聚体、聚合物熔体与有机土的相容性是制备纳米复合材料的必要条件，外界剪切力可提供帮助；（2）剥离型结构最能体现层状硅酸盐／聚合物纳米复合材料的性能优势，是层状硅酸盐／聚合物纳米复合材料的制备方向；（3）聚合物熔体插层法为简单，是重要的发展方向，要形成剥离型结构，需要同时考虑热力学和动力学因素，基体或相容剂与层间环境的相容性要适中；（4）聚合物乳液共混共凝法有利于传统的制备方法，适合于具有乳液形成的聚合物；（5）在聚合物中原位生成硅酸盐片层的方法具有新意；（6）层状硅酸盐／聚合物纳米复合材料的主要特点是高刚性、高强度、高耐热性、高阻隔性、较好的阻燃性、质轻，目前，该的制备研究正向所有的聚合物品种扩展。汽车部件、包装材料将是层状硅酸盐／聚合物纳米复合材料先应用的两大领域；（7）层状硅酸盐／聚合物纳米复合材料的理论研究进展延慢。界面区状态以及结构－性能间的关系是理论研究的两个主题。     

层状硅酸钠的制备及插层性能的研究进展

从晶体结构、制备工艺、插层改性和应用的角度,对层状硅酸钠的研究进行较全面阐述。介绍了层状硅酸钠存在的多种晶相及结构特点;指出了喷雾干燥结晶法或水热合成工艺在制备结晶层状硅酸钠中存在的技术问题;从反应类型的角度详细介绍了层状硅酸钠的插层改性技术和赋予改性层状硅酸钠丰富的功能性;分析了层状硅酸钠的不同晶相或改性技术在实际应用中的研究思路和存在问题,为层状硅酸钠的深度研究与开发指出方向。     

硅酸盐无机胶粘剂的研究进展

硅酸盐胶粘剂以其优异的粘接性能和耐高温性能,在金属、玻璃、陶瓷等材料的生产和粘接等方面起着重要的作用。本文系统地综述了3类新型硅酸盐无机胶粘剂,及其在模具铸造、陶瓷及陶瓷复合材料、涂料等方面的应用,并对粘接机理做了简要的介绍,指出了硅酸盐胶粘剂的发展方向。     

The role of preconditioning on morphology development in layered silicate thermoset nanocomposites

The impact of preconditioning constituent materials on the morphology development of organically modified montmorillonite–epoxy nanocomposites is examined to determine the sensitivity of exfoliation to material conditions. In situ synchrotron small‐angle X‐ray scattering studies were performed to relate the initiation and levels of exfoliated morphologies with various silicate preconditioning processes. Significantly, exfoliation could be achieved in systems initially considered intercalated by preconditioning through epoxy–silicate mixture aging. The resulting morphologies lead to slightly improved toughness. Implications for nanocomposite morphology development models include the necessity of further investigation of the complexities of both local and global morphologies. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 89–100, 2004     

片层硅酸盐纳米复合聚氨酯橡胶的结构及性能

将聚四氢呋喃二醇和富羟基活性蒙脱土(HMMT)进行预混插层处理,然后与甲苯二异氰酸酯(TDI)进行反应,得到层状硅酸盐复合预聚体。随后预聚体与扩链剂(DMTDA)反应制备出聚氨酯橡胶/片层硅酸盐纳米复合材料。采用材料拉伸机、X射线衍射(XRD)、透射电镜 (TEM)、差示扫描量热仪 (DSC)和热失重分析仪 (TGA) 等检测设备对聚醚型聚氨酯脲的结构与性能进行分析。结果表明：当PMMT的质量百分含量在2％时,片层硅酸盐粒子在聚氨酯基体内分散较均匀,形成了以剥离型为主、插层型为辅的复合型结构,聚醚型聚氨酯脲复合材料的拉伸强度比纯PUU提高了21%,断裂伸长率提高了12%,PUU复合材料的玻璃化转变温度(Tg)提高了5.8℃,第一失重区分解温度和最高分解温度高出纯聚氨酯17.33 ℃和13.94 ℃。无机纳米片层硅酸盐粒子的存在,聚氨酯橡胶的强度、韧性和热稳定性均得到改善。     

Possible mechanism of interaction among the components in MAPP modified layered silicate PP nanocomposites

Model reactions were carried out with components frequently used for the preparation of intercalated or exfoliated polypropylene (PP) nanocomposites. The results prove that maleinated polypropylene (MAPP) can react chemically with the surfactant applied for the organophilization of the filler, if this latter contains active hydrogen groups. The reaction of hexadecylamine (HDA) and MAPP was detected by MALDI-TOF spectroscopy, DSC measurements and FTIR spectroscopy. Anhydride groups are consumed and mainly amide groups form in the reaction. The formation of cyclic imides could not be proved by the techniques used. MAPP reacts also with the surfactant adsorbed on the surface of the silicate in ionic form. On the other hand, N-cetylpyridinium chloride (CPCl) not containing active hydrogen atoms does not react with maleinated PP. Intercalated or exfoliated composites could be prepared from the silicate organophilized with HDA, while microcomposites formed from the filler treated with CPCl. Chemical reactions remove the surfactant from the surface of MMT and hydrogenated silicate sites are left behind. The high energy surface interacts either with the anhydride or the amide groups by dipole-dipole interactions. Even the unmodified polypropylene chains may be attached much stronger to the surface by London dispersion forces than to the silicate covered with aliphatic chains. Although the effect of competitive adsorption (MAPP, HDA) and mutual solubility of the components (PP, MAPP, surfactant, reaction products) cannot be neglected, chemical reactions play a crucial role in structure formation in PP nanocomposites containing a functionalized polymer. Direct interaction of the silicate surface and the functionalized polymer as well as the formation of hydrogen bridges seem to play a lesser role, but the relative influence of processes may change with the type of surfactant, functionalized polymer, surface coverage and processing conditions.     

Role of organically modified layered silicate as an active interfacial modifier in immiscible polystyrene/polypropylene blends

The role of organically modified layered silicate as a compatibilizer for immiscible polystyrene (PS) with polypropylene (PP) or polypropylene grafted with maleic anhydride (PP-g-MA) blends was investigated. Scanning electron micrographs (SEM) revealed efficient mixing of the polymers in the presence of organically modified layered silicate. X-ray diffraction (XRD) patterns and transmission electron microscopic (TEM) observations showed that silicate layers were either intercalated or exfoliated, depending on their interactions with the polymer pair, and were located at the interface between the two polymers. The compatibilizing action of the organically modified layered silicate resulted in a decrease in interfacial tension and particle size and in a remarkable increase in mechanical properties of the modified immiscible blends.     

Analysis of the cure of epoxy based layered silicate nanocomposites: Reaction kinetics and nanostructure development

The cure reaction kinetics of epoxy resin, with organically modified montmorillonite loadings of up to 20 wt % and with stoichiometric conditions, has been studied by differential scanning calorimetry with a view to understanding further the fabrication of epoxy‐based polymer layered silicate nanocomposites. The kinetic analysis of isothermal and nonisothermal cure shows that the autocatalytic model is the more appropriate to describe the kinetics of these reactions, and it is observed that a dominant effect of the montmorillonite is to catalyze the curing reaction. However, it was not possible to model the reactions over the whole range of degrees of conversion, in particular for nonisothermal cure. This attributed to the complexity of the reactions, and especially to the occurrence of etherification by cationic homopolymerization catalyzed by the onium ion of the organically modified montmorillonite. The homopolymerization reaction results in an excess of diamine in the system, and hence in practice the reaction is off stoichiometric, which leads to a reduction in both the heat of cure and the glass transition temperature as the montmorillonite content increases. Small angle X‐ray scattering of the cured nanocomposites shows that an exfoliated nanostructure is obtained in nonisothermal cure at slow heating rates, whereas for nonisothermal cure at faster heating rates, as well as for isothermal cure at 70°C and 100°C, a certain amount of exfoliation is accompanied by the growth of d‐spacings of 1.4 nm and 1.8 nm for dynamic and isothermal cure, respectively, smaller than the d‐spacings of the modified clay before intercalation of the resin. A similar nanostructure, consisting of extensive exfoliation accompanied by a strong scattering at distances less than the d‐spacing of the modified clay, is also found for resin/clay mixtures, before the addition of any crosslinking agent, which have been preconditioned by storage for long times at room temperature. The development of these nanostructures is attributed to the presence of clay agglomerations in the original resin/clay mixtures and highlights the importance of the quality of the dispersion of the clay in the resin in respect of achieving a homogeneous exfoliated nanostructure in the cured nanocomposite. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Determination of the glass transition temperature of polymer/layered silicate nanocomposites from positron annihilation lifetime measurements

The glass transitions of acrylonitrile-butadiene rubber (NBR)/organoclay nanocomposites with various silicate contents were investigated using positron annihilation lifetime spectroscopy (PALS). The nanocomposites were prepared through melt intercalation of NBR with various concentrations of organoclay (OC30B) modified with the organic modifier, methyl tallow bis(2-hydroxyethyl) quaternary ammonium (MT2EtOH), i.e., Cloisite^® 30B. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) measurements of the NBR/OC30B nanocomposites showed that the NBR chains were intercalated between the silicate layers, thereby increasing the gallery heights of the organosilicates. The glass transition temperature of NBR was determined using differential scanning calorimetry (DSC). However, it seemed to be very difficult to clearly resolve the very small differences in T_gs caused from various loading of nanosized silicate in NBR/OC30B nanocomposites. Hence, we performed positron annihilation lifetime spectroscopy (PALS) on NBR/OC30B nanocomposites containing various amounts of OC30B (1-10 wt%). Significant changes in the temperature dependencies of free volume parameters (i.e., lifetimes and intensities) were observed at the transition temperature, T_g,PALS, and the T_g,PALS values were found to increase with increasing organoclay content in the samples. These observations are consistent with PALS having a higher sensitivity in the detection of very small changes in free volume properties. The present findings thus highlight the usefulness of PALS for studying phase transition phenomena in polymeric materials with nanoscale structural variations.     

One-dimensional structure of exfoliated polymer-layered silicate nanocomposites: A polyvinylpyrrolidone (PVP) case study

Classical modeling of powdered lamellar structures by X-ray diffraction (XRD) only applies to periodic or quasi-periodic structures and another approach is needed for non-periodic structures. XRD patterns of the non-periodic structures contain a relatively small amount of information and therefore certain initial assumptions are necessary. In case of exfoliated polymer–clay mineral nanocomposites it is possible to assume the chemical composition and the structure of the clay mineral layer while the actual structure of the polymer remains unknown. This paper offers an approach which can be used to provide an approximate solution for the structure of the polymer. This new approach is based on modeling of the LpG² factors, recorded from oriented samples in order to obtain the one-dimensional structure of the polymer.Although LpG² factors for various smectites are quite different, in the case of polyvinylpyrrolidone (PVP) adsorbed on smectite it was found that the structure of the polymer was insignificantly affected by charge in the tetrahedral or octahedral positions of the smectite. The electron density distribution models of PVP directly adsorbed on the smectite layer suggest that PVP chains directly bound to the surface are more rigid and organized than the molecules occurring farther away. The approximate thickness and distribution of PVP layer adsorbed on the surface was calculated to be equal ca. 5–6 Å.