PU/MOMMT纳米复合材料的制备与研究

纳米复合材料由于其纳米尺寸效应，表面效应以及纳米粒子与基体界面间强的相互作用，具有优于相同组分常规复合材料的力学、热学等性能，引起了人们的广泛关注。用纳米材料改性聚合物，制备纳米复合材料是获得高性能高分子复合材料的重要方法。1998年以来，Pinnavaia等首先制备了聚氨酯，蒙脱土（PU／MMT）纳米复合材料，研究了有机蒙脱土在聚醚中的分散性。其后Chen等将聚羟基己内酯/蒙脱土（PCL／MMT）纳米复合材料加入到PCL和二苯基甲烷-4，4＇-二异氰酸酯（MDI）合成的预聚体与1，4-丁二醇扩链反应后的溶液中，制备了PU／MMT纳米复合材料。少量PCL／MMT的引入可使复合材料的综合性能大幅提高。     

Poly(styrene‐b‐tetrahydrofuran)/clay nanocomposites by mechanistic transformation

Synthesis of poly(styrene‐block‐tetrahydrofuran) (PSt‐b‐PTHF) block copolymer on the surfaces of intercalated and exfoliated silicate (clay) layers by mechanistic transformation was described. First, the polystyrene/montmorillonite (PSt/MMT) nanocomposite was synthesized by in situ atom transfer radical polymerization (ATRP) from initiator moieties immobilized within the silicate galleries of the clay particles. Transmission electron microscopy (TEM) analysis showed the existence of both intercalated and exfoliated structures in the nanocomposite. Then, the PSt‐b‐PTHF/MMT nanocomposite was prepared by mechanistic transformation from ATRP to cationic ring opening polymerization (CROP). The TGA thermogram of the PSt‐b‐PTHF/MMT nanocomposite has two decomposition stages corresponding to PTHF and PSt segments. All nanocomposites exhibit enhanced thermal stabilities compared with the virgin polymer segments. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2190–2197, 2009     

Synthesis and characterization of organosoluble,thermoplastic elastomer/clay nanocomposites

We synthesized organosoluble, thermoplastic elastomer/clay nanocomposites by making a jelly like solution of ethylene vinyl acetate containing 28% vinyl acetate (EVA‐28) and blending it with organomodified montmorillonite. Sodium montmorillonite (Na⁺‐MMT) was made organophilic by the intercalation of dodecyl ammonium ions. X‐ray diffraction patterns of Na⁺‐MMT and its corresponding organomodified dodecyl ammonium ion intercalated montmorillonite (12Me‐MMT) showed an increase in the interlayer spacing from 11.94 to 15.78 Å. However, X‐ray diffraction patterns of the thermoplastic elastomer and its hybrids with organomodified clay contents up to 6 wt % exhibited the disappearance of basal reflection peaks within an angle range of 3–10°, supporting the formation of a delaminated configuration. A hybrid containing 8 wt % 12Me‐MMT revealed a small hump within an angle range of 5–6° because of the aggregation of silicate layers in the EVA‐28 matrix. A transmission electron microscopy image of the same hybrid showed 3–5‐nm 12Me‐MMT particles dispersed in the thermoplastic elastomer matrix; that is, it led to the formation of nanocomposites or molecular‐level composites with a delaminated configuration. The formation of nanocomposites was reflected through the unexpected improvement of thermal and mechanical properties; for example, the tensile strength of a nanocomposite containing only 4 wt % organophilic clay was doubled in comparison with that of pure EVA‐28, and the thermal stability of the same nanocomposite was higher by about 34 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2065–2072, 2002     

Characterization and thermal degradation studies on polyaniline‐intercalated montmorillonite nanocomposites prepared by a solvent‐free mechanochemical route

Polyaniline (PANI)‐montmorillonite (MMT) nanocomposites were prepared by direct intercalation of aniline molecules into MMT galleries, followed by in situ polymerization within the nano‐interlamellar spaces under solvent‐free conditions. The basal spacing of aniline‐intercalated MMT increased gradually up to 1.5 nm with increasing amounts of aniline loaded. This result suggests that aniline molecules were adsorbed by MMT clay and that intercalated aniline likely located perpendicular to the silicate sheets. After polymerization, X‐ray diffraction and Fourier transform infrared analyses confirmed the successful synthesis of PANI chains between the MMT nano‐interlayers. The scanning electron microscopy images indicated that the surface morphologies of PANI–MMTs were strongly different depending on the PANI content. The electrical conductivities of PANI nanocomposite particles in pressed pellets ranged in the order of between 10^?3 and 10^?2 S/cm. UV–vis spectroscopy and doping level measurement were further used to discuss the conductivities of nanocomposites. The thermal stabilities of PANI–MMT nanocomposites were examined by using thermogravimetric‐differential thermal analysis and derivative thermogravimetric analysis, and both analyses consequently demonstrated the improved thermal stabilities of the PANI chains in the nanocomposites as compared to pure PANI. The thermal stabilities of resulting nanocomposites were strongly related to the PANI content, which increased as the PANI content decreased in the nanocomposites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2705–2714, 2005     

氨基硅烷偶联剂对蒙脱石的修饰改性研究

研究了氨基硅烷偶联剂对蒙脱石的修饰改性,并和长链烷基硅烷偶联剂作对比.通过改性前后蒙脱石的傅立叶红外光谱(FT-IR),广角X射线衍射(WAXD),热失重分析(TGA)研究发现,在冰醋酸的处理下,氨基硅烷偶联剂不但能够对蒙脱石进行表面偶联修饰而且能够以插层剂的形式进入蒙脱石的层间.初步的浸润/分散性实验结果表明:氨基硅烷插层/表面修饰改性的蒙脱石在弱极性乙醇溶剂中的分散性能明显提高.     

Synergistic flammability and thermal stability of polypropylene/aluminum trihydroxide/Fe‐montmorillonite nanocomposites

In the present study, polypropylene/aluminium trihydroxide/Fe‐montmorillonite (PP/ATH/Fe‐MMT) nanocomposites were prepared by melt‐intercalation method. This was been designed to determine whether the presence of structural iron in the matrix could enhance the thermal stability and flammability of nanocomposites. In order to prove the effect of Fe³⁺ in the structural silicate layers, samples of PP/ATH and PP/ATH/Na‐MMT (no Fe³⁺ in structural silicate layers) were prepared under the same conditions. Fe‐MMT and Na‐MMT were modified by cetyltrimethyl ammonium bromide (CTAB). The nanocomposite structures were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) was applied to test the thermal properties of nanocomposites. In addition, the limiting oxygen index (LOI) of PP/ATH/Fe‐MMT nanocomposites was increased, and no dripping phenomenon was found through the UL‐94 vertical burning test. Copyright © 2009 John Wiley & Sons, Ltd.     

原位聚合制备聚乙烯/蒙脱土(MMT)纳米复合材料的研究

利用MgCl₂在醇中溶解和蒙脱土(MMT)在醇中层间膨胀的特性,制备了MgCl₂/TiC_l4负载于MMT层间的MMT/MgCl₂/TiC_l4催化剂,并通过原位聚合合成了聚乙烯/蒙脱土纳米复合材料.经广角X射线衍射(WAXD)和透射电子显微镜(TEM)分析表明,蒙脱土片层在乙烯聚合过程中发生了层间剥离,以单片层或几片层共存的形式无规地分散于聚乙烯基质中.与分子量相近的纯聚乙烯相比,极低的蒙脱土含量(质量分数<1%)能使复合材料的屈服强度、拉伸强度和拉伸模量有很大提高.复合材料中蒙脱土片层以纳米尺寸在聚乙烯基质中的良好分布和对聚乙烯分子链运动的限制作用是力学性能提高的主要因素.     

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     

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.     

Synthesis and characterization of polycyanurate/montmorillonite nanocomposites

The advantages of cyanate esters (CEs) versus competitor systems such as epoxies and polyimides, as well as the great reinforcing potential of organoclays properly dispersed into a polymeric matrix, have been examined in a series of polycyanurate (PCN)/montmorillonite (MMT) nanocomposites prepared under appropriate polymerization conditions. The curing schedule applied resulted in gradual propagation of polymerization. Through this procedure, the intragallery curing rate becomes comparable to the extragallery one, allowing intercalation before gelation. Systems with clay loadings from 1 to 3% per weight were synthesized, and their morphology and mechanical properties were studied by means of scanning electron microscopy (SEM), atomic force microscopy (AFM), wide angle X‐ray scattering (WAXS), dynamic mechanical analysis (DMA), and tensile tests. Microscopy investigations revealed better dispersion for the 3 wt % system compared to smaller concentrations, in which aggregation and, in some cases, agglomeration were the conspicuous features. Roughness and area analyses revealed more homogeneous dispersion for this nanocomposite. Topology and 3D‐phase images further suggested considerable reduction of the average particle diameters. WAXS analysis showed that the interlayer spacing of nanocomposites was increased compared to pristine MMT, indicating the formation of intercalated structures. On the other hand, tensile strength and elongation at break values displayed abrupt diminution with MMT addition, while Young's modulus exhibited a slight but systematic increment with MMT content. The decreasing glass transition tendency observed for small clay loadings was reversed in the case of 3 wt %, while secondary transitions were practically unaffected by the presence of MMT. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1036–1049, 2008     

Shear‐induced change of exfoliation and orientation in polypropylene/montmorillonite nanocomposites

For the improved dispersion of montmorillonite (MMT) in a polypropylene (PP) matrix, PP/MMT nanocomposites prepared via direct melt intercalation were further subjected to oscillating stress achieved by dynamic packing injection molding. The shear‐induced morphological changes were investigated with an Instron machine, wide‐angle X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy. The original nanocomposites possessed a partly intercalated and partly exfoliated morphology. A transformation of the intercalated structure into an exfoliated structure occurred after shearing, and a more homogeneous dispersion of MMT in the PP matrix was obtained. However, the increase of the exfoliated structure was accompanied by the scarifying of the orientation of MMT layers along the shear direction. Some bended or curved MMT layers were found for the first time by TEM after shearing. However, the orientation of PP chains in the PP/MMT nanocomposites became very difficult under an external shear force; this indicated that the molecular motion of PP chains intercalated between MMT layers was highly confined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1–10, 2003     

Preparation and characterization of poly(propylene carbonate)/montmorillonite nanocomposites by solution intercalation

Poly(propylene carbonate) (PPC) is a new biodegradable aliphatic polycarbonate. However, the poor thermal stability and low glass transition temperatures (T_g) have limited its applications. To improve the thermal properties of PPC, organophilic montmorillonite (OMMT) was mixed with PPC by a solution intercalation method to produce nanocomposites. An intercalated-and-flocculated structure of PPC/OMMT nanocomposites was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The thermal and mechanical properties of PPC/OMMT nanocomposites were investigated by thermal gravimetric analysis (TGA), differential scanning calorimetric (DSC), and electronic tensile tester. Due to the nanometer-sized dispersion of layered silicate in polymer matrix, PPC/OMMT nanocomposites exhibit improved thermal and mechanical properties than pure PPC. When the OMMT content is 4 wt%, the PPC/OMMT nanocomposite shows the best thermal and mechanical properties. These results indicate that nanocomposition is an efficient and convenient method to improve the properties of PPC.     

Saturation ratio of poly(ethylene oxide) to silicate in melt intercalated nanocomposites

Melt intercalation has been found to be a very successful approach for preparation of polymer-clay nanocomposites. An aspect of this area that has been little investigated is the amount of polymer required to fill the interlayer galleries of the clay. This paper reports experiments which determine the amount of poly(ethylene oxide) (PEO) required to saturate the spacing between montmorillonite (MMT) or organically-modified bentonite (B34) layers. Differential scanning calorimetry (DSC), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were used to determine the saturation ratios of PEO to silicates, which are then compared to theoretical calculations. The deduced saturation ratio of PEO to MMT is 28:72, and PEO to B34 15:85 by XRD and DSC, whilst ratios of PEO to MMT of 21:79 and PEO to B34 10:90 were obtained via TGA. The density of intercalated PEO in the silicate galleries is estimated to be 0.82 g/cm³, which suggests that PEO in the silicate galleries is far less efficiently packed than in the amorphous region of the bulk polymer.     

In situ intercalative polymerization of conducting polypyrrole/montmorillonite nanocomposites

Conducting polypyrrole (PPy)‐montmorillonite (MMT) clay nanocomposites have been synthesized by the in situ intercalative polymerization method. The PPy‐MMT nanocomposites are characterized by field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), ultraviolet–visible (UV–vis) spectroscopy, thermogravimetric analysis (TGA), and Fourier‐transform infrared (FTIR) spectroscopy. XRD patterns show that after polymerization by the in situ intercalative method with ammonium persulfate and 1 M HCl, an increase in the basal spacing from 1.2 to 1.9 nm was observed, signifying that PPy is synthesized between the interlayer spaces of MMT. TEM and SEM micrographs suggest that the coexistence of intercalated MMT layers with the PPy macromolecules. FTIR reveals that there might be possible interfacial interactions present between the MMT clay and PPy matrix. The study also shows that the introduction of MMT clay results in thermal stability improvement of the PPy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2279–2285, 2008     

Gas barrier of polystyrene montmorillonite clay nanocomposites: Effect of mineral layer aggregation

Three polystyrene (PS)/clay hybrid systems have been prepared via in situ polymerization of styrene in the presence of unmodified sodium montmorillonite (Na‐MMT) clay, MMT modified with zwitterionic cationic surfactant octadecyldimethyl betaine (C18DMB) and MMT modified with polymerizable cationic surfactant vinylbenzyldimethyldodecylammonium chloride (VDAC). X‐ray diffraction and TEM were used to probe mineral layer organization and to expose the morphology of these systems. The PS/Na‐MMT composite was found to exhibit a conventional composite structure consisting of unintercalated micro and nanoclay particles homogeneously dispersed in the PS matrix. The PS/C18DMB‐MMT system exhibited an intercalated layered silicate nanocomposite structure consisting of intercalated tactoids dispersed in the PS matrix. Finally, the PS/VDAC‐MMT system exhibited features of both intercalated and exfoliated nanocomposites. Systematic statistical analysis of aggregate orientation, characteristic width, length, aspect ratio, and number of layers using multiple TEM micrographs enabled the development of representative morphological models for each of the nanocomposite structures. Oxygen barrier properties of all three PS/clay hybrid systems were measured as a function of mineral composition and analyzed in terms of traditional Nielsen and Cussler approaches. A modification of the Nielsen model has been proposed, which considers the effect of layer aggregation (layer stacking) on gas barrier. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1733–1753, 2007     

Nanocomposites of NLO chromophore‐modified layered silicates and polypropylene

Intercalation of guest species into layered inorganic solids is a method of producing ordered inorganic–organic assemblies with unique microstructures controlled by host–guest and guest–guest interactions. Smectite clay minerals, such as montmorillonite, having appropriate functional molecules in between the silicate layers are supposed to exhibit a wide range of novel characteristics. Nanocomposite material based on maleic anhydride‐grafted polypropylene and dye‐modified layered silicate was developed. Characteristics of organo‐modified montmorillonite particles and polymer/clay hybrids have been investigated through FTIR, SAXS, DSC, UV measurements, and transmission electron microscopy. The results of the intercalation process, structural characterization, and thermal properties will be discussed in comparison with the intercalation and nanocomposite preparation results. The intercalation was successfully conducted by the ion‐exchange method. It was shown that intercalated dibenzilidene acetone type chromophores exist in the clay galleries in an aggregated form, probably as J‐aggregates. This feature strongly effects on optical and nonlinear optical properties of nanocomposites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2493–2502, 2005     

三元乙丙橡胶/蒙脱土纳米复合材料制备中硫化体系的比较

采用了熔融插层和两种硫化体系硫磺 促进剂和过氧化物体系制备了三元乙丙橡胶 蒙脱土纳米复合材料 ,并将这两种体系形成的纳米复合材料进行了形态、力学性能和光学性能的比较 ,同时采用Flory Rehner方程对它们的硫化行为进行了评价 .X射线衍射 (XRD)、透射电镜 (TEM)、力学性能和光学性能的测试结果表明 ,由硫磺硫化体系制备的纳米复合材料为不透明和剥离型 .其原有的d0 0 1 衍射峰消失 ,有序层被剥离成 10 0～ 2 0 0nm的片层均匀分散在EPDM基体中 ,其力学性能有了极大的提高 ;而过氧化物体系制备的纳米复合材料为半透明和插层型 .对两种体系的硫化行为的评价结果表明 ,随着有机蒙脱土加入量的增加 ,硫磺 促进剂硫化体系的t90 延长 ,交联密度减小 ,最大 最小转矩也变小 ;而过氧化物硫化体系的相应值却变化不大     

辐照法制备PVAc/蒙脱土纳米复合材料及其表征

蒙脱土有机化后 ,片层结构间距离增大 ,对有机物的亲和性有所增强 .采用VAc单体渗入有机化蒙脱土层间 .经γ 射线辐照引发原位插层聚合 ,使蒙脱土片层结构发生剥离 ,形成无机 有机纳米复合材料 .并用X衍射、红外光谱、扫描电镜以及透射电镜等现代测试手段对复合材料进行了表征     

Synthesis of polybenzoxazine/clay nanocomposites by in situ thermal ring‐opening polymerization using intercalated monomer

A new class of polybenzoxazine/montmorillonite (PBz/MMT) nanocomposites has been prepared by the in situ polymerization of the typical fluid benzoxazine monomer, 3‐pentyl‐5‐ol‐3,4‐dihydro‐1,3‐benzoxazine, with intercalated benzoxazine MMT clay. A pyridine‐substituted benzoxazine was first synthesized and quaternized by 11‐bromo‐1‐undecanol and then used for ion exchange reaction with sodium ions in MMT to obtain intercalated benzoxazine clay. Finally, this organomodified clay was dispersed in the fluid benzoxazine monomers at different loading degrees to conduct the in situ thermal ring‐opening polymerization. Polymerization through the interlayer galleries of the clay led to the PBz/MMT nanocomposite formation. The morphologies of the nanocomposites were investigated by both X‐ray diffraction and transmission electron microscopic techniques, which suggested the partially exfoliated/intercalated structures in the PBz matrix. Results of thermogravimetric analysis confirmed that the thermal stability and char yield of PBz nanocomposites increased with the increase of clay content. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Crystallization behavior and thermal stability of poly(trimethylene terephthalate)/clay nanocomposites

Poly(trimethylene terephthalate) (PTT)/montmorillonite (MMT) nanocomposites were prepared by the solution intercalation method. Two different kinds of clay were organomodified with an intercalation agent of cetyltrimetylammonium chloride (CMC). X‐ray diffraction (XRD) indicated that the layers of MMT were intercalated by CMC, and interlayer spacing was a function of the cationic exchange capacity of clay. The XRD studies demonstrated that the interlayer spacing of organoclay in the nanocomposites depends on the amount of organoclay. From the results of differential scanning calorimetric analysis, it was found that clay behaves as a nucleating agent and enhances the crystallization rate of PTT. The maximum enhancement of the crystallization rate for the nanocomposites was observed in nanocomposites containing about 1 wt % organoclay with a range of 1–15 wt %. From thermogravimetric analysis, we found that the thermal stability of the nanocomposites was enhanced by the addition of 1–10 wt % organoclay. According to transmission electron microscopy, the organoclay particle was highly dispersed in the PTT matrix without a large agglomeration of particles for a low organoclay content (5 wt %). However, an agglomerated structure did form in the PTT matrix at a 15 wt % organoclay content. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2902–2910, 2003