Improving the mechanical properties of thermoplastic starch/poly(vinyl alcohol)/clay nanocomposites

Thermoplastic starch/poly(vinyl alcohol) (PVOH)/clay nanocomposites, exhibiting the intercalated and exfoliated structures, were prepared via melt extrusion method. The effects of clay cation, water, PVOH and clay contents on clay intercalation and mechanical properties of nanocomposites were investigated. The experiments were carried out according to the Taguchi experimental design method. Montmorillonite (MMT) with three types of cation or modifier (Na⁺, alkyl ammonium ion, and citric acid) was examined. The prepared nanocomposites with modified montmorillonite indicated a mechanical improvement in the properties in comparison with pristine MMT. It was also observed that increases in tensile strength and modulus would be attained for nanocomposite samples with 10%, 5% and 4% (by weight) of water, PVOH and clay loading, respectively. The clay intercalation was examined by X-ray diffraction (XRD) patterns. The chemical structure and morphology of the optimum sample was also probed by FTIR spectroscopy and transmission electron microscopy (TEM).     

Preparation and properties of poly HTBN-based urethane--urea/organo reactive montmorillonite nanocomposites

With ultrasonic assistant mixing way, an intercalated mixture of polyol/organo reactive montmorillonite (ORMMT) was pretreated. The prepolymer composed MMT clay was prepared by reaction of polyol/ORMMT mixture with toluene diisocyanate (TDI). The resultant prepolymer reacted with extender (DMTDA) and then the polyurethane--urea/organo reactive montmorillonite (PUU/ORMMT) nanocomposites were obtained. The structure, morphology and properties of PUU/ORMMT nanocomposites were characterized by FT-IR, TEM, AFM, strain-stress machine, TGA, and dynamic mechanical analysis (DMA). The results showed that when the OMMT content is 3%, the PUU/ORMMT nanocomposities performed super mechanical properties. Because of the presence of ORMMT, both T_g of the soft segment and tanδ of the PUU increased, and the decomposition temperature for the first step and the second step increased respectively. TEM images showed that the organophilic MMT particles in the PUU composite exhibit a high degree of intercalation and exfoliation.     

Investigation of physical and chemical properties of polypropylene hybrid nanocomposites

Hybrid nanocomposites fabricated based on an optimized physical and chemical properties modified polypropylene (PP)/polypropylene grafted maleic anhydride (PP-g-MA) with varied concentrations (1–7 wt% at a step of 2 wt%) of organoclay, montmorillonite (MMT). The morphology of the nanocomposites was studied by scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). It was found that partly intercalated and partly exfoliated structure (intercalated–exfoliated structures) existed in the system. The degree of exfoliation is a key factor to determine the reinforcement efficiency. The ratio of exfoliation to intercalation plays an important role in determining the properties of PP nanocomposites and only completely exfoliated silicate layers can significantly improve the properties. PP hybrid nanocomposites showed good thermal stability in the thermogravimetric analysis (TGA). Introduction of ∼3% MMT in the nanocomposites increased the onset temperature of degradation by 27.5 °C compared to that of pure PP, while the 5 wt% MMT resulted the maximum hardness in these nanocomposites. The solvent resistance of PP hybrid nanocomposites slightly increased with increasing the clay content.     

Preparation,microstructure and thermal mechanical properties of epoxy/crude clay nanocomposites

To improve the performance/cost ratio of epoxy/clay nanocomposites, epoxy resin was reinforced with crude clay with the help of a silane modifier. The epoxy/crude clay nanocomposites were produced through a recently developed “slurry compounding” approach. The microstructure of the nanocomposites was characterized with X-ray diffraction (XRD), optical microscopy and transmission electron microscopy (TEM). The thermal mechanical properties were studied with dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). It has been shown that only 5 wt% of silane modifier is required to facilitate the dispersion and exfoliation of crude clay in epoxy matrix. The storage moduli and thermal stability were improved with the addition of crude clay.     

Environmentally friendly polymer hybrids Part I Mechanical, thermal, and barrier properties of thermoplastic starch/clay nanocomposites

As an attempt to develop environmentally friendly polymer hybrids, biodegradable thermoplastic starch (TPS)/clay nanocomposites were prepared through melt intercalation method. Natural montrorillonite (Na⁺ MMT; Cloisite Na⁺) and one organically modified MMT with methyl tallow bis-2-hydroxyethyl ammonium cations located in the silicate gallery (Cloisite 30B) were chosen in the nanocomposite preparation. TPS was prepared from natural potato starch by gelatinizing and plasticizing it with water and glycerol. The dispersion of the silicate layers in the TPS hybrids was characterized by using wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). It was observed that the TPS/Cloisite Na⁺ nanocomposites showed higher tensile strength and thermal stability, better barrier properties to water vapor than the TPS/Cloisite 30B nanocomposites as well as the pristine TPS, due to the formation of the intercalated nanostructure. The effect of clay contents on the tensile, dynamic mechanical, and thermal properties as well as the barrier properties of the nanocomposites were investigated.     

Synthesis and characterization of thermoplastic polyurethane/montmorillonite nanocomposites produced by reactive extrusion

The novel polyurethane/montmorillonite (PU/MMT) nanocomposites based on poly (propylene oxide) glycol (POP), 4,4′-diphenymethylate diisocyanate (MDI), 1,4-butanediol (1,4-BD) and MMT has been synthesized using a one-step direct polymerization-intercalation technique by twin-screw extruder. Its structure and thermal properties are characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and High-resolution electron microscopy (HREM), Fourier-transform infrared spectroscopy (FTIR) and Thermogravimetry analysis (TGA), respectively. The results of XRD and HREM analyses show that the silicate layer is well dispersed in PU matrix and this mesostructure can be considered as a delaminated nanocomposites. The TGA analysis indicates that the thermal stability properties of the PU/MMT nanocomposites are increased slightly compared with the pristine PU, due to the increase of the char residue. The mechanical and flammability performances are examined by electronic Universal Tester and Cone calorimetry, respectively. The layered silicate, which acts as a high aspect ratio reinforcement, enhances tensile strength of the PU. Specifically, there is a 25% increase in the tensile strength of PU nanocomposites containing 4 wt.% MMT compared with that of pristine PU. However, the elongation at break of PU/MMT nanocomposites is lower than that of pristine PU. The loading of MMT leads to the remarkably decrease of heat release rate (HRR), contributing to the improvement of flammability performance.     

Chlorinated polyethylene nanocomposites: thermal and mechanical behavior

Chlorinated polyethylene (CPE) nanocomposites prepared with natural and organically treated montmorillonite (MMT) clays by solution intercalation method were investigated. X-ray diffraction and transmission electron microscopy techniques showed separation of organically modified clay MMT layers and indicated formation of exfoliated nanocomposites. Fourier transform infrared spectroscopy results showed interaction between the CPE matrix and the clay intercalants of Cloisite^® 30B and Cloisite^® 15A (natural MMT modified with quaternary ammonium salts). Organically treated MMT clays were found to be better dispersed in CPE in comparison to natural MMT clay. Mechanical testing showed enhanced tensile strength, Young’s modulus, and storage modulus of chlorinated-polymers/organically treated MMT clay nanocomposites. Significant improvements in the above properties were obtained with Cloisite^® 15A nanoclay. The temperature, at which maximum degradation occurred, was higher for the nanocomposite having 5 wt% Cloisite 15A than that of neat CPE. Differential scanning calorimetric results revealed that the same composition also absorbed more heat during the heating, indicating better thermal stability. CPE rubber nanocomposite could be a promising heat resistant polymeric material.     

Modification of montmorillonite by novel geminal benzimidazolium surfactant and its use for the preparation of polymer organoclay nanocomposites

A new benzimidazolium derivative, the benzimidazolium-N,N′-hexadecane-2-hydroxy-ethyl bromide (Bz) featuring two geminal hexadecyl hydrophobic buttress has been synthesized and used for the functionalization of sodium montmorillonite (MMT-Na) via cationic exchange process. The resulting benzimidazolium-modified MMT (MMT-Bz) exhibits a large d-spacing of 3 nm between silicate layers and shows a high thermal stability compared to the commonly used clay modified alkyl ammonium salts (cloisite 20A and cloisite 20B). MMT-Bz was incorporated in high density polyethylene (HDPE) matrix via melt mixing method to produce HDPE/MMT-Bz nanocomposites. The microstructure and the morphology of these nanocomposites were studied by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The dispersion state of the organoclay within HDPE was monitored by UV–Vis spectroscopy and melt rheology. A more homogeneous dispersion or a greater content of the MMT-Bz in the matrix produced stronger solid-like and non-terminal behavior in the nanocomposites. Tensile properties and thermal stability were evaluated and discussed on the basis of the amount of clay incorporated within the nanocomposites. The intercalated structure in the nanocomposites, resulting from both the better dispersion/distribution of clay nano-platelets and their strong interaction with the polymer chains, provides the driving force to significantly enhance the HDPE properties.     

Morphology development and stability of polypropylene/organoclay nanocomposites

A series of polypropylene (PP)/organoclay nanocomposites with varied concentrations of clay, from 1 to 7 wt%, was successfully prepared via melt intercalation using a PP functionalized with maleic anhydride as compatibilizer. The morphology/property relationships of the nanocomposites were investigated by XRD, TGA and DSC analyses. Two distinct groups of composites, from a quasi-exfoliated to an intercalated/flocculated morphology, were identified. In particular, intercalated/flocculated morphologies were obtained for those composites with an organoclay concentration beyond the threshold (3 wt%), as evidenced by XRD analysis and confirmed by the increase of the glass transition temperature. This last effect was related to the confinement of polymer chains between the silicate layers, generating a reduction of the chain mobility. The variable increase of the thermal stability of the nanocomposites was also likely related to the different degree of exfoliation/intercalation of the samples. The toluene extraction of composites was used as a powerful methodology to distinguish between polymer phases differently interacting with the inorganic surface: composites having a semi-exfoliated structure were split into two fractions having a similar morphology. For those samples having the higher organoclay concentration and intercalated morphology, a toluene-residue fraction was obtained containing almost all the clay present in the pristine composite. Furthermore, in this case the morphological analysis of the residue fraction evidenced a collapse of the inorganic structure compared to that of the unextracted composite. A careful characterization of both soluble and residue fractions is reported and the results are discussed considering the interactions at the interface between the functionalized PP chains and silicate layers and their effects on the organoclay dispersion degree and stability.     

溶液插层法制备PPC/OMMT纳米复合材料及性能表征

通过溶液插层法制备了聚甲基乙撑碳酸酯/有机蒙脱土(PPC/OMMT)纳米复合材料,采用X射线衍射仪、热失重分析仪、透射电子显微镜(TEM)、动态力学性能测试仪(DMA)等对PPC/OMMT的性能进行了表征.XRD和TEM测试表明,OMMT均匀分散于PPC基体中并形成了插层型的纳米复合结构;DMA分析结果表明,复合材料的...     

Biopolymer/montmorillonite nanocomposite: preparation, drug-controlled release property and cytotoxicity

In order to combine the advantages of a biopolymer with clay in a drug delivery system, the hot intercalation technique was used to prepare quaternized chitosan/montmorillonite (HTCC/MMT) nanocomposites. Transmission electron microscopy (TEM), x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) results revealed that HTCC chains entered into the interlayer of MMT, and the interaction between them has taken place. This is the basis of the advantage combination. Then the HTCC/MMT nanocomposites were modified to prepare the nanoparticles, whose drug-controlled release behaviours were evaluated. The results suggested that, compared to pure HTCC nanoparticles, certain montmorillonite loadings on quaternized chitosan enhanced the drug encapsulation efficiency of the nanoparticles and slowed the drug release from the nanocomposites. Finally, a study of 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) indicated that the nanocomposites are not cytotoxic. Therefore, the HTCC/MMT nanocomposites are of great potential in the biomedical field.     

In situ polymerization preparation of blends of poly(methyl methacrylate) and poly(styrene-co-acrylonitrile)

The in situ polymerization of methyl methacrylate (MMA) with poly(styrene-co-acrylonitrile) (SAN) was studied. The PMMA/SAN in situ polymerization blends obtained were examined by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), tensile tests and scanning electron microscopy (SEM). The blends with compositions of 95/5, 80/20, 70/30, and 60/40 in weight ratios were miscible and had a single phase structure. However, the 90/10 PMMA/SAN in situ polymerization blend obtained was inhomogeneous and had a two-phase structure; polymerization-induced phase separation occurred during the preparation process of the blend. Both tensile strength and elongation at break increase with increasing SAN content up to 30 wt%. The degradation temperature and thermal stability of PMMA increased remarkably on incorporation of SAN up to 30 wt%.     

Reinforcement of polyurethane composites with an organically modified montmorillonite

A clay with reactive activity prepared by treatment of natural montmorillonite with Methylene-bis-ortho-chloroaniline (MOCA) was incorporated into polyurethane matrix and a series of PU/clay nanocomposites were obtained by in situ polymerization. The microstructure of the nanocomposites with different content of the clay was examined by atomic force microscopy (AFM). The thermal and mechanical properties of the nanocomposites with different organic clay content were characterized by dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). It was found that the moduli and thermal stability of the nanocomposites were improved with augment of clay, especially, for the PU/9 wt% MO-MMT nanocomposite, compared to pure PU, the storage modulus and the loss modulus were increased by about 300% and 667% at −45 °C, respectively.     

聚苯乙烯/粘土纳米复合材料研究进展

介绍了采用各种插层荆插层处理蒙脱土并用插层聚合、熔融插层法制备聚苯乙烯／粘土纳米复合材料及其结构特性、性能的研究进展．并对乳液聚合法制备聚苯乙烯／粘土纳米复合材料及其性能进行了简单介绍。     

Long-term and controlled release of chlorhexidine–copper(II) from organically modified montmorillonite (OMMT) nanocomposites

Drug/metal ion complexes exhibit improved antimicrobial activity and intercalating the above complexes into the interlayer of clay endows a long-term and controlled-release behavior. In this study, chlorhexidine was first complexed with copper (II) ion and then intercalated into the interlayer of MMT to form chlorhexidine–copper (II)/montmorillonite (CHX–Cu/MMT) nanocomposites. The nanocomposites were characterized with Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). A nearly lateral-monolayer arrangement of CHX–Cu was supposed for the intercalation. Release kinetics indicated that the release process satisfied a pseudo-second-order mode. The antibacterial results showed that the CHX–Cu/MMT composites had long-term and controlled-release behavior.     

Itaconic acid and amino alcohol functionalized polyethylene as compatibilizers for polyethylene nanocomposites

The compatibilization provided by itaconic acid (IA) and 2-[2-(dimethylamino)-ethoxy] ethanol (DMAE) functionalized polyethylene for forming polyethylene-based nanocomposites was studied and compared. IA was grafted into PE by melt mixing to obtain PEgIA (compatibilizer 1), thereafter, PEgIA was reacted with DMAE also by melt mixing to obtain PAgDMAE (compatibilizer 2). PE-clay nanocomposites were prepared by melt mixing polyethylene with each of the two quaternary ammonium modified montmorillonite clays (Cloisite 30B and Nanomer I28E) plus each of the two previously prepared compatibilizers (PEgIA and PEgDMAE). FTIR characterization confirmed the formation of these two compatibilizers. All the compatibilized nanocomposites had better clay exfoliation–intercalated compared to the uncompatibilized PE nanocomposites. X-ray diffraction and transmission electron microscopy results, as well as the mechanical properties attained showed that the PEgDMAE with the I28E clay produced the better exfoliated–intercalated nanocomposites. Samples with C30B clay did not show any intercalation improvement, as compared to the uncompatibilized samples, which was attributed mainly to the smaller initial intergallery spacing of this clay. Finally, it is concluded that the PEgDMAE offers an outstanding capability for preparing highly exfoliated PE clay nanocomposites.     

Magnesium hydroxide sulfate hydrate whisker flame retardant polyethylene/montmorillonite nanocomposites

Flame retardant maleated polyethylene/magnesium hydroxide sulfate hydrate whisker (MAPE/MHSH) composites containing organo-modified montmorillonite (OMT) were prepared by direct melt intercalation. Their morphology, combustion behaviour and thermal stability were carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM), cone calorimetry and thermogravimetric analyses (TGA). The exfoliation of silicate layers within MAPE has been verified by XRD and TEM images. Cone calorimetry results indicated that a synergistic flame retardant effect on reducing heat release rate (HRR) occurred when MHSH and OMT were both present in nanocomposite. The reduction in HRR improved as the mass fraction of OMT was increased from 2 to 10 wt%, but there was little improvement above 5 wt% OMT loading level. TGA profiles of the nanocomposites revealed that the thermodegradation stability of the nanocomposites decreased as the OMT fraction increased from 2 to 10 wt%.     

球磨分散法制备新型改性粘土/环氧纳米复合材料的结构与性能

采用十二烷基二甲基卞基氯化铵(DBDA) 和间苯二甲胺(MXDA) 设计并制备了一种新型有机化改性蒙脱土(MMT Ⅱ), 通过球磨法来促进其在环氧树脂中的细化与分散, 制备出具有良好解离结构的MMT Ⅱ/ 环氧纳米复合材料。利用红外光谱(FTIR) 、X-射线衍射(XRD) 和透射电镜( TEM) 表征了新型MMT Ⅱ及其纳米复合材料的结构, 测试了力学性能。结构表征与分析表明, 大颗粒粘土聚集体并不能在搅拌混合过程中分散开, 在固化过程中很难充分解离, 而通过球磨过程中产生的剪切力可促进其分散与细化, 从而获得良好解离结构。MMTⅡ中MXDA 的引入, 减少了季铵盐分子链所产生的悬键, 增加了MMT Ⅱ片层的界面反应性, 大大提高了纳米复合材料的力学性能, 冲击强度由3211kJ / m2 提高到4811 kJ / m2, 提高近50 %, 弯曲强度提高近8 %。     

Morphological and thermomechanical characterization of thermoplastic starch/montmorillonite nanocomposites

A combination of starch and clay for the preparation of nanocomposite materials is proposed. In this work, starch was plasticized by pequi (Caryocar brasiliense) oil, and thermoplastic starch (TPS)/montmorillonite (MMT) nanocomposites were analyzed by X-ray diffraction (XRD), thermogravimetry (TG), thermomechanical analyses (TMA) and scanning electron microscopy (SEM). Exfoliated and intercalated nanocomposites were found to be dependent on MMT content. Exfoliation is the predominant mechanism of clay dispersion for low filler loading. Increase of the clay loading (>5 wt.%) causes intercalation. The introduction of low content (?5 wt.%) of MMT improves the thermal stability and the stiffness of the materials. There is a limit content of clay that can be added to improve the thermal and thermomechanical properties of the composites. Beyond that value the composite presents properties below the original polymer.     

聚氨酯/蒙脱土纳米复合弹性体材料--(Ⅱ)结构及性能的表征

借助锥体磨的研磨剪切外力，将聚醚多元醇插层进入蒙脱土片层中，使其片层间距扩大并发生部分剥离，从而利用本体插层聚合法制备了综合性能优异的聚氨酯／蒙脱土纳米复合弹性体材料。当有机蒙脱土添加量仅为1％时，其拉伸强度比纯聚氨酯弹性体高30％．达到30．2MPa，断裂伸长率也略有增加。TGA及吸水实验分析表明聚氨酯／蒙脱土纳米复合材料有更高的热失重温度和更低的吸水率．研究了蒙脱土含量对聚氨酯／蒙脱土纳米复合材料各项性能的影响。