环氧/粘土纳米复合材料的形成机理与性能

粘土／聚合物纳米复合材料由于具有优良的物理力学性能和特殊功能而倍受关注。实验证明,粘土也很容易被环氧树脂插层,并在固化过程中剥离,得到纳米复合材料。本文重点综述了粘土／环氧纳米复合材料的形成机理,结构形态和力学性能,并对该类材料的应用前景进行了展望。     

4,4'-二氨基二苯醚二苯酮固化环氧树脂/粘土纳米复合材料的研究

采用离子交换法, 用十六烷基三甲基溴化铵处理钙基蒙脱土(MMT), 使蒙脱土的层间距由1.49 nm扩大到2.21 nm, 制备了环氧树脂/ BADK/MMT纳米复合材料, 并用XRD等手段研究了有机蒙脱土在环氧树脂中的插层及剥离行为. 研究结果表明, 蒙脱土含量及环氧树脂与有机土的混合温度和时间均对固化后复合材料的剥离产生影响, 只有在特定条件下才能得到剥离型纳米复合材料.     

混合条件对环氧有机土纳米复合材料插层剥离行为及性能的影响

采用X 射线衍射仪、透射电镜 (TEM )研究了混合条件 ,即混合温度和时间 ,对环氧 /16 烷基胺有机蒙脱土体系在固化前的混合物以及加入固化剂、促进剂固化后有机土的插层与剥离行为的影响 .同时采用拉伸试验机、冲击试验机和热机械分析仪测定了插层与剥离型纳米复合材料的物理力学性能 .从X 射线衍射看出 ,有机土很容易在混合过程被环氧所插层 .混合物经固化后可以形成插层型或剥离型纳米复合材料 .存在一个混合温度 时间 插层剥离转变的 3 T图 .只有在一定的混合条件的区域内才能形成剥离型纳米复合材料 .剥离型比插层型纳米复合材料具有较高的力学性能     

聚合物/粘土纳米复合材料中的粘土有机化

回顾了聚合物/粘土纳米复合材料中所用粘土的有机化方法与有机粘土的热稳定性,及其对复合材料性能的影响,指出在聚合物/粘土复合材料中粘土片层间距的变化同样有可能受到层间插层剂构象变化的影响、聚合物/粘土纳米材料的长期热氧稳定性与热失重结果可能不一致。     

液晶环氧树脂/蒙脱土纳米复合材料的制备和固化反应动力学研究

用带有介晶基元的联苯二酚二缩水甘油醚 (BP)、4 氨基苯基磺酰胺 (SAA)和有机化蒙脱土 (93A)采用浇铸成模固化成型的方法制备出液晶环氧树脂 蒙脱土纳米复合材料 .WRXD结果表明 93A含量是 2 %时可形成剥离型纳米材料 ,而当 10 %时形成插层型纳米材料 ,5 %时则形成剥离和插层混合型的纳米材料 ;POM结果表明蒙脱土的存在能够破坏原有的扇形近晶相液晶织构 .DSC研究表明体系的固化反应动力学 ,可用变形的Kissinger Akahira Sunose法 (VKAS)表征 ,从求出的反应活化能和转化率关系 ,发现反应初期 ,蒙脱土使反应活化能降低 ,能够促进液晶环氧树脂的固化 .     

粘土层间距对粘土/环氧树脂插层复合材料热机械性能的影响

研究了混料温度对蒙脱土／环氧树脂复合材料相关性能的影响。用X射线衍射表征了复合材料的层间距，并且在动态热机械分析仪（DMTA）上用不同的模式表征了不同层间距的插层复合材料的性能。测试结果表明，混料温度对蒙脱土／环氧树脂插层复合材料的热机械性能有一定的影响。插层后蒙脱土／环氧树脂的软化温度提高了11℃，弹性模量也有相应的提高。     

几种高性能热塑性树脂与蒙脱土插层复合的研究

研究了PEK C ,PES ,PEI和PSU 4种刚性分子链高性能热塑性树脂与蒙脱土插层复合的行为 ,结果表明通过溶液混合PEK C和PES很容易插入到粘土层间并使粘土剥离 ,得到剥离型纳米复合材料 ,而PEI和PSU不能插入到粘土层间 ,分析认为插层能力的差异是由于它们与粘土间的作用力不同导致的 .PEK C和PES与粘土形成纳米复合材料后 ,玻璃化温度大幅度下降 ,但热分解温度有很大提高 ,认为是由于体积很大而且刚硬的聚合物分子与粘土片层混合后形成了较大的自由体积 ,使玻璃化温度下降 ,但聚合物端基与粘土间很强的作用力使它的热解温度提高 .PEI和PSU与粘土复合后热性能没有明显变化 ,说明如果粘土与聚合物间不能形成纳米复合 ,不会对聚合物性能产生显著影响     

聚合物基粘土纳米复合材料的流变行为研究

聚合物基粘土纳米复合材料具有与常规颗粒填充体系类似的流变特性 :在整个频率范围内 ,储能模量和损耗模量均随粘土含量的增加而变高 ,其频率依赖性会表现出非未端行为 :且当粘土含量超过临界值以后 ,储能模量会在低频区表现出似固体的平台发展。但与之不同的是前者在低粘土含量的条件下 (<10 % (wt) )就会表现出似固体行为或非末端行为。这些流变特性还会受到粘土的径厚比、化学特性、聚合物基体的分子结构参数和粘土与基体间的相互作用强度等因素的影响。聚合物基粘土纳米复合材料的流变行为是与其微观结构的形成和演化以及聚合物分子链在特定环境下的粘弹松弛过程紧密联系在一起的。本文综述了插层型、剥离型和聚合物分子链一端受限剥离型聚合物基粘土纳米复合材料在力场作用下的流变特性和粘弹松弛机理方面的研究进展。     

粘土/聚烯烃纳米复合材料研究进展

原位聚合;插层复合;粘土/聚烯烃纳米复合材料研究进展     

几种聚醚胺改性蒙脱土对环氧树脂固化过程的影响

首先制备了五种聚醚胺改性蒙脱土(MMT),并将这五种聚醚胺改性蒙脱土加入到双酚A型环氧树脂E51和聚醚胺D400体系中,采用差示扫描量热法(DSC)考察了五种聚醚胺改性MMT对环氧树脂升温固化进程的影响.随后,优选一种EP/MMT混合体系即EP/D400-T500-MMT混合体系,系统地研究了该体系与纯环氧树脂体系在130,140,150及160℃等几个温度下的等温固化过程,考察了等温固化时间对固化度和固化度变化速率的影响以及固化度与固化度变化速率之间的关系,并利用Kamal模型进行拟合计算了固化动力学参数.研究结果表明,与纯环氧树脂相比,几种聚醚胺改性MMT的固化放热峰均向高温迁移,同时聚醚胺D400协同插层MMT降低了高分子量聚醚胺插层MMT所导致的环氧树脂DSC曲线的畸变情况;EP/D400-T500-MMT混合体系和纯环氧体系的等温固化反应过程符合Kamal模型;在相同的固化温度下,EP/D400-T5000-MMT混合体系的反应速率常数k1和k2值以及反应级数m均比纯EP体系小,而反应级数n以及总反应级数m+n值比纯EP体系大,表明两种聚醚胺协同插层的改性蒙脱土D400-T5000-MMT的加入降低了环氧体系固化反应速率.另外,EP/D400-T5000-MMT混合体系的活化能Ea1和Ea2与纯EP体系的相比也略有升高.     

Exploitation of introducing of catalytic centers into layer galleries of layered silicates and related epoxy nanocomposites. I. Epoxy nanocomposites derived from montmorillonite modified with catalytic surfactant‐bearing carboxyl groups

Montmorillonite (MMT) was modified with the acidified cocamidopropyl betaine (CAB) and the resulting organo‐montmorillonite (O‐MMT) was dispersed in an epoxy/methyl tetrahydrophthalic anhydride system to form epoxy nanocomposites. The intercalation and exfoliation behavior of the epoxy nanocomposites were examined by X‐ray diffraction and transmission electron microscopy. The curing behavior and thermal property were investigated by in situ Fourier transform infrared spectroscopy and DSC, respectively. The results showed that MMT could be highly intercalated by acidified CAB, and O‐MMT could be easily dispersed in epoxy resin to form intercalated/exfoliated epoxy nanocomposites. When the O‐MMT loading was lower than 8 phr (relative to 100 phr resin), exfoliated nanocomposites were achieved. The glass‐transition temperatures (T_g's) of the exfoliated nanocomposite were 20 °C higher than that of the neat resin. At higher O‐MMT loading, partial exfoliation was achieved, and those samples possessed moderately higher T_g's as compared with the neat resin. O‐MMT showed an obviously catalytic nature toward the curing of epoxy resin. The curing rate of the epoxy compound increased with O‐MMT loading. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1192–1198, 2004     

Preparation of highly exfoliated epoxy/clay nanocomposites by "slurry compounding": process and mechanisms

Epoxy/clay nanocomposites with a high degree of exfoliation were achieved using a so-called "slurry-compounding" process with which the dispersed state of clay in water can be successfully transferred to an epoxy matrix. In this process sodium montmorillonite was first exfoliated and suspended in water. This suspension was further treated with acetone to form a clay-acetone slurry followed by chemical modification using silane. The modified slurry was then mixed extensively with epoxy to form epoxy/nanoclay composites. It has been shown that the morphologies of clay before and after curing are quite similar and the exfoliation process is termed "slurry compounding". Furthermore, the amount of organic modifier used is only 5 wt % of clay, in contrast to conventional organoclays which normally contain at least 25-45 wt % of organic surfactant. The resulting epoxy/nanoclay composites exhibit a high degree of clay exfoliation and a better thermal mechanical property.     

An observation of accelerated exfoliation in iPP/organoclay nanocomposite as induced by repeated shear during melt solidification

A well‐exfoliated morphology is usually observed for polar polymer/clay nanocomposites via dynamic melt processing techniques, whereas only an intercalated or a partially intercalated/partially exfoliated morphology is often obtained for nonpolar polymer/clay nanocomposites, even though some polar compatibilzer is used. In this study, an accelerated exfoliation effect was observed for the first time in iPP/organoclay nanocomposites prepared through so‐called dynamic packing injection molding, in which the specimen is forced to move repeatedly in a chamber by two pistons that move reversibly with the same frequency as the solidification progressively occurs from the mold wall to the molding core part. The disordered level and exfoliated degree of clay was found to dramatically increase from the skin to the core of the prepared samples and eventually the WAXD reflections of interlayer d‐spacing diminished in the core. The changed degree of exfoliation was also proved directly by TEM observation. The prolongation of processing time, the gradual growth of solidification front, the increased melts viscosity, and the shear amplification effect were considered to explain the higher degree of exfoliation in the center zone of mold chamber. Our result suggests that a critical shear force may be needed to break down clay into exfoliated structure. This can be also well used to explain at least partially the intercalated morphology, which is commonly observed for nonpolar polymer/clay nanocomposites via conventional processing. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2005–2012, 2005     

Preparation of highly exfoliated epoxy/clay nanocomposites by clay grafted with liquid crystalline epoxy

Epoxy/clay nanocomposites with a high degree of exfoliation were achieved by intercalating liquid crystalline epoxy into clay intragallery as well as using a so-called ‘solution compounding’ process. In this process, clay modified was first treated with trichloromethane to form organoclay-trichloromethane suspension followed by liquid crystalline epoxy modification. The liquid crystalline epoxy grafted clay was then mixed extensively with epoxy to form epoxy/nanoclay composites. The mechanism of exfoliation was explored by monitoring the change of morphology of organoclay during each stage of processing with X-ray diffraction (XRD). The liquid crystalline epoxy grafted clay synthesised was characterised by fourier transform infrared spectroscopy (FT-IR) and polarising optical microscopy (POM). The clay platelets uniformly dispersed and highly exfoliated in the whole epoxy matrix were observed using transmission electron microscopy (TEM) and FT-IR imaging system. The epoxy nanocomposites were fabricated by incorporating different liquid crystalline epoxy grafted clay loading. The results revealed that the incorporation of liquid crystalline epoxy grafted clay resulted in a significant improvement in glass transition temperature (Tg) derived from dynamic mechanical analysis (DMA) and thermal stability measured by thermogravimetric analysis (TGA).     

新环氧树脂纳米复合材料的合成和结构研究

以具有层状硅酸盐结构的累托石(REC)为主体,以烷基季铵盐为改性剂合成了有机累托石(OREC),以有机累托石和环氧树脂复合,制备出纳米复合材料。累托石含量在0.8wt.% 时,纳米复合材料具有最佳力学和热学性能,冲击强度增加到65.6 kJm-2,断裂伸长率从4.7 %增加到20.2 %,玻璃化转变温度提高到 197.9 ℃。用X-小角衍射法、透射电镜和红外吸收光谱研究了材料的微观结构,XRD 衍射图显示,未经处理REC 的层间距d001 = 2. 2 nm,经有机改性后,累托石片层间距扩大到2.8 nm,与环氧树脂复合后,其层间距扩大到4.2 nm 左右,FT-IR图显示,有机累托石中出现十六胺的特征吸收峰,TEM照片显示该复合材料是一种纳米复合材料。     

外力辅助分散作用下环氧树脂粘土纳米复合材料中粘土的微观结构与解离机理研究

采用不同分散方法(机械搅拌、高速均质搅拌和球磨分散)制备环氧树脂粘土纳米复合材料,研究了分散方法对不同有机粘土解离结构和纳米复合材料力学性能的影响,并在此基础上探讨了粘土的解离机理.结果表明,普通机械搅拌只能使小粒径粘土或大粒径粘土团聚体的外部片层解离;施加一定的外力(如高速均质搅拌)促进粘土团聚体分散,有利于粘土片层的解离;利用剪切摩擦作用较强的球磨法分散粘土,不同处理剂改性粘土的内外片层都可以充分解离,而有机改性剂中酸性质子的催化作用对粘土片层解离的影响不大,只要粒径足够小,片层解离的驱动力(基体弹性力、反应性等)能够克服其所受阻力(片层引力、层外基体粘性阻力、层内粘性引力等),粘土内外各片层将会同时向外迁移而解离.纳米复合材料的力学性能大大改善,冲击强度和弯曲强度分别提高近50%和8%;     

Organo-modified montmorillonite/poly(?-caprolactone) nanocomposites prepared by melt intercalation in a twin-screw extruder

Nanocomposites based on biodegradable poly(?-caprolactone) organo-modified clay have been prepared by melt intercalation using a twin-screw extruder. The screw configuration developed allowed us to obtain an intercalated/exfoliated nanocomposite structure using a modified montmorillonite containing no polar groups, in contrast to previous work using mainly alkyl ammonium containing hydroxyl polar groups in poly(?-caprolactone). Montmorillonite nanocomposites were prepared using a specific extrusion profile from a 30 wt% masterbatch of organo-modified clay, which was then diluted at 1, 3 and 5%. Intercalated and/or exfoliated nanocomposites structures were assessed using rheological procedures and confirmed by transmission electron microscopy analysis. Mechanical and thermal properties were found to be strongly dependent on morphology and clay percentage. Crystallinity was only slightly affected by the clay addition. Effect of exfoliation on Young's modulus and thermal stability was investigated. Young's modulus increased significantly and onset degradation temperature measured by TGA was significantly reduced for an exfoliated nanocomposite composition containing 5 wt% organoclay.