Unsaturated polyester/bentonite nanocomposites: Influence of clay modification on final performance

In this work, unsaturated polyester/bentonite nanocomposites were obtained and characterized. The bentonite used was unmodified and with different chemical treatments. The effects of these different chemical modifications (cation exchange reactions with quaternary ammonium and phosphonium salts) of this clay as well as the effect of clay content on the thermal, barrier (water absorption), mechanical (flexural) and dynamic-mechanical properties of unsaturated polyester matrix were analyzed. The results clearly show that the chemical modifications of the clay cause a desired effect on its final properties improving the performance of the nanocomposites. The enhancements could be directly related to the dispersion of the clay inside the matrix, as shown by transmission electron microscopy.     

Nanocomposites of ABS and sepiolite: Study of different clay modification processes

Melt compounding of acrylonitrile–butadiene–styrene (ABS) matrix and nanocomposites have been studied in order to evaluate the optimal modification process for sepiolite. Different screw speeds were tested to elucidate possible degradations related to a high shear effect, and thermal stability of pristine and modified sepiolite was carried out. Both processes of modification, via quaternary ammonium salts and silane coupling agents, have been compared by means of morphological, thermal and mechanical experiments, working out that ammonium salt modified sepiolite provided the best results in the final properties.     

Mechanical and thermal behavior of non-crimp glass fiber reinforced layered clay/epoxy nanocomposites

Mechanical and thermal properties of non-crimp glass fiber reinforced clay/epoxy nanocomposites were investigated. Clay/epoxy nanocomposite systems were prepared to use as the matrix material for composite laminates. X-ray diffraction results obtained from natural and modified clays indicated that intergallery spacing of the layered clay increases with surface treatment. Tensile tests indicated that clay loading has minor effect on the tensile properties. Flexural properties of laminates were improved by clay addition due to the improved interface between glass fibers and epoxy. Differential scanning calorimetry (DSC) results showed that the modified clay particles affected the glass transition temperatures (T_g) of the nanocomposites. Incorporation of surface treated clay particles increased the dynamic mechanical properties of nanocomposite laminates. It was found that the flame resistance of composites was improved significantly by clay addition into the epoxy matrix.     

Hybrid nanocomposites based on polystyrene and a reactive organophilic clay

The preparation of new hybrid nanocomposites, by emulsion polymerization of styrene in the presence of a reactive organophilic clay, and their characterization are described. The reactive organophilic clay is synthesized by exchanging the inorganic cations in the interlayer structure of a natural clay with the quaternary salt of the aminomethylstyrene. This salt is prepared by a Gabriel reaction starting from the (chloromethyl)styrene. The polymeric matrix of the resulting materials was found to be constituted by polystyrene homopolymer and by a blocky copolymer of styrene and quaternary salt of the (aminomethyl)styrene units. The glass transition temperature of the nanocomposites increase as the percentage of organophilic clay increases, although the average molar masses of the polymeric matrix decrease, because of termination and/or chain-transfer reactions caused by the organophilic clay during the polymerization. Accordingly, the inherent reinforcing action due to the presence of the reactive organophilic clay is higher than the observed one.     

Crosslinked aqueous dispersion of silylated poly (urethane–urea)/clay nanocomposites

Stable water-borne crosslinked silylated poly (urethane–urea) (CSPU)/clay nanocomposites, reinforced with various amounts of the organically modified clay, were prepared by a polyaddition reaction of toluene diisocyanate (TDI) or isophorone diisocyanate (IPDI), polytetramethylene glycol and dimethylol propionic acid. This was followed by end-capping the free NCO groups of the PU prepolymer with phenylamino propyl trimethoxysilane and self-crosslinking. The particle size, viscosity and storage stability of these nanocomposites were measured. The particle size and viscosity of the IPDI-based nanocomposites were higher than the TDI-based ones. Intercalation of the silicate layer in the CSPU matrix were conformed by X-ray diffraction pattern and transmission electron microscopy studies. The mechanical properties of the SPU/clay nanocomposites were tested by tensile, dynamic mechanical, and nano-indentation measuring techniques and the respective properties were found to be enhanced by the reinforcing effect of organophilic clay. Modulus and hardness increased with an increase in the clay content in the CSPU matrix. Thermal stability, water and xylene resistance of the nanocomposites increased, as compared to pure CSPU and these properties increased with an increase in clay content. The mechanical properties, water and xylene resistance of the TDI-based nanocomposites were higher compared to the IPDI-based nanocomposites. A marginal reduction in transparency was observed with the addition of clay. Storage stability results confirmed that the prepared nanocomposite dispersions were stable.     

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).     

三元乙丙橡胶/蒙脱土纳米复合材料的制备、结构、性能与应用前景

利用熔融插层和三甲基十八烷基氯化铵插层剂改性钠基蒙脱土原土的方法,制备了EPDM/粘土纳米复合材料.X射线衍射(XRD)和透射电镜(TEM)的测试结果表明,所制备的复合材料为插层型.该纳米复合材料在有机蒙脱土的加入量为15份时,即具有优良的物理机械性能、较低的气透率和较高的动态屈挠以及优良的磨耗性能,在作为轮胎的内胎和子午线轮胎的气密层胶料的应用上具有广阔的前景.     

Effects of modified Clay on the morphology and thermal stability of PMMA/clay nanocomposites

The potential to improve the mechanical, thermal, and optical properties of poly(methyl methacrylate) (PMMA)/clay nanocomposites prepared with clay containing an organic modifier was investigated. Pristine sodium montmorillonite clay was modified using cocoamphodipropionate, which absorbs UVB in the 280–320 nm range, via ion exchange to enhance the compatibility between the clay platelets and the methyl methacrylate polymer matrix. PMMA/clay nanocomposites were synthesized via in situ free-radical polymerization. Three types of clay with various cation-exchange capacities (CEC) were used as inorganic layered materials in these organic–inorganic hybrid nanocomposites: CL42, CL120, and CL88 with CEC values of 116, 168, and 200 meq/100 g of clay, respectively. We characterized the effects of the organoclay dispersion on UV resistance, effectiveness as an O₂ gas barrier, thermal stability, and mechanical properties of PMMA/clay nanocomposites. Gas permeability analysis demonstrated the excellent gas barrier properties of the nanocomposites, consistent with the intercalated or exfoliated morphologies observed. The optical properties were assessed using UV–Visible spectroscopy, which revealed that these materials have good optical clarity, UV resistance, and scratch resistance. The effect of the dispersion capability of organoclay on the thermal properties of PMMA/clay nanocomposites was investigated by thermogravimetric analysis and differential scanning calorimetry; these analyses revealed excellent thermal stability of some of the modified clay nanocomposites.     

Preparation and characterization of poly (styrene-acrylonitrile) (SAN)/clay nanocomposites by melt intercalation

Poly (styrene-acrylonitrile) (SAN)/clay nanocomposites have been prepared by melt intercalation method from pristine montmorillonite (MMT), using hexadecyl trimethyl ammonium bromide (C16) and hexadecyl triphenyl phosphonium bromide (P16) as the reactive compatibilizers between polymer and clay. The influence of the reactive compatibilizers proportion relative to the clay on the structure and properties of the SAN/clay nanocomposites is investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM), high-resolution electron microscopy (HREM), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The effects of the two different clays (MMT and organic modified MMT) on the nanocomposites formation, morphology and property are also studied. The results indicate that the SAN cannot intercalate into the interlayers of the MMT and results in microcomposites. In the presence of the reactive compatibilizers, the dispersion of clay in SAN is rather facile and the SAN/clay nanocomposites reveal an intermediate morphology, an intercalated structure with some exfoliation and the presence of small tactoids. The appropriate proportion with 3 wt% reactive compatibilizers to 5 wt% MMT induces well-dispersed morphology and properties in the SAN matrix. The TGA analyses show that the thermal stability properties of the SAN/clay nanocomposites have been improved compared with those of the pristine SAN. The DMA results show that the storage modulus and glass transition temperature (Tg) of the SAN/clay nanocomposites have remarkably enhancements compared with the pristine SAN. At last the intercalation mechanism of the technology is discussed.     

Investigation on the competing effects of clay dispersion and matrix plasticisation for polypropylene/clay nanocomposites. Part I: morphology and mechanical properties

The key compatibiliser role of maleated polypropylene (MAPP) to improve the clay dispersability has been explicitly addressed in the fabrication process and material characterisation of polypropylene (PP)/clay nanocomposites. However, its matrix plasticiser role, which has been rarely mentioned, could adversely influence the excellent mechanical properties of such nanocomposites, resulting from the homogeneous clay dispersion. PP/clay nanocomposites in the presence of MAPP were prepared by twin screw extrusion and subsequently injection moulded with three typical material formulations in fixed parametric settings: (1) weight ratio (WR) of clay and MAPP, WR = 1:2; (2) MAPP content of 6 wt% and (3) clay content of 5 wt%. The morphological structures and mechanical properties of PP/clay nanocomposites were examined by using X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and universal mechanical testing. The further improvement of mechanical properties was evidently hindered with very inconsiderable alteration of morphological structures in terms of the clay dispersion level. This observation could be ascribed to the change of MAPP role from a compatibiliser to a plasticiser because of its excessive amount used above a certain saturation level, which was found in the range of 3–6 wt% in MAPP contents for the enhancements of tensile and flexural properties of PP/clay nanocomposites.     

Effect of processing parameters and clay volume fraction on the mechanical properties of epoxy-clay nanocomposites

The influence of processing parameters and particle volume fraction was experimentally studied for epoxy clay nanocomposites. Nanocomposites were prepared using onium ion surface modified montmorillonite (MMT) layered clay and epoxy resin (DEGBF). Two different techniques were used for dispersing the clay particles in the epoxy matrix, viz. high-speed shear dispersion and ultrasonic disruption. The volume fraction of clay particles was systematically varied from 0.5 to 6%, and mechanical properties, viz. flexural modulus and fracture toughness, were studied as a function of clay volume fraction and the processing technique. The flexural modulus was observed to increase monotonously with increase in volume fraction of clay particles, while, the fracture toughness showed an initial increase on addition of clay particles, but a subsequent decrease at higher clay volume fractions. In general, nanocomposites processed by shear mixing exhibited better mechanical properties as compared to those processed by ultrasonication. Investigation by X-ray diffraction (XRD) revealed exfoliated clay structure in most of the nanocomposites that were fabricated. Morphologies of the fracture surfaces of nanocomposites were studied using a scanning electron microscopy (SEM). Presence of river markings at low clay volume fractions provided evidence of extrinsic toughening taking place in an otherwise brittle epoxy.     

Porous nanocomposites prepared from layered clay and PMMA [poly(methyl methacrylate)]

The aim of the present work is the preparation of PMMA based porous nanocomposites that contain clay (montmorillonite, MMT) platelets as reinforcements within the cell walls of the porous structure. To render the clay layers organophilic, MMT was surface treated by an ion exchange reaction between interlayer cations of the clay and ammonium ions of a surfactant. Clay/PMMA based porous nanocomposites were prepared by polymerization of water-in-oil emulsions with and without clay addition. The microstructure and compressive mechanical behavior of the nanocomposites were investigated. The results of mechanical tests showed that the porous systems with the addition of 1 wt.% of organoclay (OMMT) exhibited a 90% and 50% increase of collapse stress and elastic modulus values, respectively, as compared to neat porous PMMA.     

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.     

Thermal properties of ethylene octene copolymer (Engage)/dimethyldioctadecyl quaternary ammonium chloride-modified montmorillonite clay nanocomposites

The nanocomposites of ethylene octene copolymer (Engage^®) with an organically modified (dimethyldioctadecyl quaternary ammonium chloride) montmorillonite (M-MMT) clay were synthesized by using a solution intercalation technique. The intercalation of M-MMT layers for M-MMT loading of 2.5–7.5% was verified by the shift of X-ray diffraction peak to a lower angle, showing change in basal d-spacing from 1.26 for M-MMT to 1.35 nm. Internal structure and the dispersion state of M-MMT in the nanocomposites were observed by transmission electron microscope, which confirmed the clay in the intercalated state. Thermomechanical analysis results showed improved dimensional stability under compression at 30 °C for nanocomposites with increasing M-MMT. By DMA, the storage moduli of nanocomposites below glass transition temperature were higher than the neat Engage and increased with increasing M-MMT content. The glass transition temperature was lowest for the nanocomposite containing 2.5% M-MMT (E-2.5M-MMT), suggesting the optimal concentration of M-MMT in nanocomposite being 2.5% or higher from the viewpoint of thermal properties. The oxidation induction time (OIT) of the nanocomposites was obtained by using pressure-differential scanning calorimeter. The Engage/M-MMT nanocomposites were superior in thermal oxidation resistance as compared to the neat Engage, with E-5.0M-MMT yielding highest OIT_time value.     

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.     

Effect of clay and PEO-PPO-PEO block copolymer on the microstructure and properties of cyanate ester/epoxy composite

In this study, processing, morphology and properties of poly (ethylene oxide)-block-poly (propylene oxide)-block-poly (ethylene oxide) (PEO-PPO-PEO) triblock copolymer and clay modified cyanate ester/epoxy hybrid nanocomposites were investigated. The PEO-PPO-PEO triblock copolymer preferentially reaction-induced microphase separate into spherical micelles in the cyanate ester/epoxy matrix. PEO-PPO-PEO was used as both nanostructuring agent for cyanate ester/epoxy blended resin and thus the predominantly intercalated and few exfoliated platelets of were also observed with clay, which successfully reduced the brittleness of the cyanate ester/epoxy blended resin increasing the toughness of designed materials. The stiffness and heat resistance of the neat BCE/EP resin could be retained in the BCE/EP/F68/clay hybrid nanocomposites. The optimum property enhancement was observed in the hybrid nanocomposites containing 5 wt% PEO-PPO-PEO and 3 wt% clay. The thermo/mechanical properties of the hybrid nanocomposites depend on microstructure, dispersion state and the ratio between organic and inorganic modifiers content.     

Investigation on the competing effects of clay dispersion and matrix plasticisation for polypropylene/clay nanocomposites. Part II: crystalline structure and thermo-mechanical behaviour

In view of the structure–property relationship, the mechanical property enhancement of polypropylene (PP)/clay nanocomposites can also be associated with the alterations of their crystalline structures and behaviour in addition to the general interpretation of intercalation/exfoliation level and uniform dispersion of more rigid clay platelets with higher aspect ratios in the PP matrix. Wide-angle X-ray diffraction (WAXD) was utilised to evaluate the effects of clay content, maleated PP (MAPP) content (MAPP as the compatibiliser) on PP crystalline structures of nanocomposites. Furthermore, the melting and crystallisation behaviour of PP/clay nanocomposites was also investigated by conducting differential scanning calorimetry (DSC). The thermo-mechanical properties were characterised via dynamic mechanical thermal analysis (DMTA). It is observed that enhancement of mechanical properties are mainly affected by the preferred orientation of PP crystals, the growth of α-PP phase and effective nucleating agent role of additional clay while the excessive amount of MAPP becomes detrimental to these crucial aspects, which is also evidently revealed in DMTA measurements.     

粘土/热塑性聚氨酯弹性体插层复合材料制备与性能

本文对不同种类的层状硅酸盐粘土膨润土（BEN）及累托石（REC）进行有机改性，利用X射线衍射（XRD）分析有机粘土的层间结构变化，研究不同有机粘土与聚氨脂弹性体熔融共混后复合材料的力学性能。结果表明：改性后的有机粘土层间距均有不同程度的增大，复合材料的力学性能均有不同程度的增加，其中有机累托石补强的效果较好；有机粘土在添加两份时均表现出较大的拉伸强度，累托石在两份添加量的拉伸强度由原来的37.2MPa提高到53.8MPa，提高了44.6%；撕裂强度在所研究范围是增加的，8份时从纯基体的92.8kN/m提高到138kN/m，提高了49%。     

Biodegradable nanocomposites from toughened polyhydroxybutyrate and titanate-modified montmorillonite clay

Montmorillonite clay treated with neopentyl (diallyl)oxy tri(dioctyl) pyrophosphato titanate was used as a reinforcement for toughened bacterial bioplastic, Polyhydroxybutyrate (PHB) in order to develop novel biodegradable nanocomposites. The modified clay, PHB, toughening partner and specific compatibilizer were processed by extrusion followed by injection molding. Different microscopy and goniometry techniques, rheology analysis, X-ray diffraction and thermo-mechanical testing were used to characterize the nanocomposites. Results showed that the nanocomposites with 5 wt% titanate-modified clay loading exhibited about 400% improvement in impact properties and 40% reduction in modulus in comparison with virgin PHB. The novel aspect of the titanate-based modification was that the nanocomposites still maintained nearly the same impact strength value as that of toughened PHB. The diffraction patterns suggest exfoliation of the organically modified clays and this was further supported by transmission electron microscopy and melt rheological analysis. The mechanical properties of the nanocomposites were correlated with a modified Halpin-Tsai theoretical model and the predictions matched significantly with the experimental results. Toughened and compatibilized PHB showed significantly lower biodegradation rate than virgin PHB and most significantly the addition of the titanate-modified clay in the same formulation enhanced the biodegradation several fold.     

Synthesis,characterization and dielectric properties of polynorbornadiene–clay nanocomposites by ROMP using intercalated Ruthenium catalyst

Polynorbornadiene clay nanocomposites were prepared for the first time by the ring opening metathesis polymerization (ROMP) using modified montmorillonite and polynorbornadiene the latter of which is used commonly in electric–electronic industry. The Na–MMT clay was modified by a quaternary ammonium salt containing Ruthenium complex as a suitable catalyst and intercalant as well. The norbornadiene monomers were polymerized within the modified montmorillonite layers by in-situ polymerization method in different clay loading degrees. Intercalation ability of the Ru catalyst and partially exfoliated nanocomposite structure were proved by powder X-ray Diffraction (XRD) Spectroscopy and Transmission Electron Microscopy (TEM) methods. The nanocomposite materials with high thermal degradation temperature and low dielectric constant compared to the pure polynorbornadiene were obtained. The dielectric constants decreased with the increase of the clay content.