Synthesis and properties of new fluoroelastomer nanocomposites from tailored anionic layered magnesium silicates (hectorite)

In the field of polymer clay nanocomposites, naturally occurring smectite group of clays are the most commonly used nanofillers. In the present work, smectite group clay, hectorite was synthesized in the laboratory with an intention to understand the structure–property relationship of polymer nanocomposites, with special reference to the characteristics of the nanoclays. The nanocomposites were prepared using these synthetic clays and fluoroelastomer by a solution mixing process. The clays and their nanocomposites were characterized by using X‐ray diffraction, X‐ray fluorescence, infra‐red spectroscopy, and transmission electron microscopy. It was observed that clay formation was a function of the concentration of the constituent materials. The gallery spacings and surface areas of synthetic clays are higher than those of the natural clay. Mechanical, dynamic mechanical, swelling, and thermal properties of these nanocomposites were also studied. The properties of these nanocomposites were compared with the nanocomposites obtained from natural clays, available commercially. Synthetic clay filled samples showed better properties than the natural clay filled samples, e.g., synthetic hectorite filled sample exhibited 75% increment in tensile strength and 24% improvement in 100% modulus compared with the natural hectorite based system. The results were explained with the help of thermodynamics and morphology. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A flammability performance comparison between synthetic and natural clays in polystyrene nanocomposites

Polymer‐clay nanocomposites are a newer class of flame retardant materials of interest due to their balance of mechanical, thermal and flammability properties. Much more work has been done with natural clays than with synthetic clays for nanocomposite flammability applications. There are advantages and disadvantages to both natural and synthetic clay use in a nanocomposite, and some of these, both fundamental and practical, will be discussed in this paper. To compare natural and synthetic clays in regards to polymer flammability, two clays were used. The natural clay was a US mined and refined montmorillonite, while the synthetic clay was a fluorinated synthetic mica. These two clays were used as inorganic clays for control experiments in polystyrene, and then converted into an organoclay by ion exchange with an alkyl ammonium salt. The organoclays were used to synthesize polystyrene nanocomposites by melt compounding. Each of the formulations was analysed by X‐ray diffraction (XRD), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). Flammability performance was measured by cone calorimeter. The data from the experiments show that the synthetic clay does slightly better at reducing the heat release rate (HRR) than the natural clay. However, all the samples, including the inorganic clay polystyrene microcomposites, showed a decreased time to ignition, with the actual nanocomposites showing the most marked decrease. The reason for this is postulated to be related to the thermal instability of the organoclay (via the quaternary alkyl ammonium). An additional experiment using a more thermally stable organoclay showed a time to ignition identical to that of the base polymer. Finally, it was shown that while polymer‐clay nanocomposites (either synthetic or natural clay based) greatly reduce the HRR of a material, making it more fire safe, they do not provide ignition resistance by themselves, at least, at practical loadings. Specifically, the cone calorimeter HRR curve data appear to support that these nanocomposites continue to burn once ignited, rather than self‐extinguish. Copyright © 2004 John Wiley & Sons, Ltd.     

Review on Nanocellulose Polymer Nanocomposites

Recently, nanocellulosic materials have been received significant research interest as potential nanofiller for the reinforcements in the polymer matrices due to its renewable in nature, readily availability, biocompatibility, inexpensive, excellent physical properties, tailorable surface properties, etc. In this review, author attempted to provide an overview of various methods for nanocellulose reinforced polymer nanocomposites fabrications, properties of nanocellulose-based nanocomposites, and their applications. The review has been emphasized for the reinforcement of nanocellulose in various polymer matrices viz. hydrophilic, hydrophobic matrices. Nanocellulose reinforced polymer nanocomposites have huge potential in diverse applications which ranges from biomedical, packaging, electronic to environmental, water treatment fields etc.     

Effect of clay with different cation exchange capacity on the morphology and properties of poly(methyl methacrylate)/clay nanocomposites

PMMA/clay nanocomposites were successfully prepared by in situ free‐radical polymerization with the organic modified MMT‐clay using methyl methacrylate monomer and benzoyl peroxide initiator. Two clays with different cation exchange capacity have been used to prepare and compare the several properties. The clays have been modified using Amphoterge K2 by ion exchange reaction to increase the compatibility between the clay and polymer matrices. The modified clays have been characterized by wide‐angle X‐ray diffraction pattern, Fourier transform infrared spectroscopy, and thermogravimetric analysis (TGA). The powdered X‐ray diffraction and transmission electron microscopy techniques were employed to study the morphology of the PMMA/clay nanocomposites which indicate that the modified clays are dispersed in PMMA matrix to form both exfoliated and intercalated PMMA/modified clay nanocomposites. The thermomechanical properties were examined by TGA, differential scanning calorimetry, and dynamic mechanical analysis. Gas permeability analyzer shows the excellent gas barrier property of the nanocomposites, which is in good agreement with the morphology. The optical property was measured by UV–vis spectroscopy which shows that these materials have good optical clarity and UV resistance. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Graphene-polymer nanocomposites for structural and functional applications

The introduction of graphene-based nanomaterials has prompted the development of flexible nanocomposites for emerging applications in need of superior mechanical, thermal, electrical, optical, and chemical performance. These nanocomposites exhibit outstanding structural performance and multifunctional properties by synergistically combining the characteristics of both components if proper structural and interfacial organization is achieved. Here, we briefly introduce the material designs and basic interfacial interactions in the graphene-polymer nanocomposites and the corresponding theoretical models for predicting the mechanical performances of such nanocomposites. Then, we discuss various assembly techniques available for effectively incorporating the strong and flexible graphene-based components into polymer matrices by utilization of weak and strong interfacial interactions available in functionalized graphene sheets. We discuss mechanical performance and briefly summarize other physical (thermal, electrical, barrier, and optical) properties, which are controlled by processing conditions and interfacial interactions. Finally, we present a brief outlook of the developments in graphene-based polymer nanocomposites by discussing the major progress, opportunities, and challenges.     

生物可降解聚乳酸/层状硅酸盐纳米复合材料的研究进展

生物可降解聚乳酸是一种具有广泛应用前景的环境友好型的生物高分子材料,但是其力学性能、热稳定性能不稳定.利用层状硅酸盐的特殊结构,以各种有机改性的层状硅酸盐为添加物,通过原位插层聚合、溶液插层、熔融插层和剥离.吸附等方法制备生物可降解聚乳酸/层状硅酸盐纳米复合材料,其力学性能、热稳定性、生物降解性等均有显著提高,其展现出极其广阔的应用前景.本文概述了近年来生物可降解聚乳酸/层状硅酸盐纳米复合材料的制备、结构、性能和应用等方面的研究进展,并且对各种制备方法进行了分析比较.     

Foams based on low density polyethylene/hectorite nanocomposites: Thermal stability and thermo‐mechanical properties

Novel polymer nanocomposite foams made by a two step compression molding method are analyzed in this article. Nanocomposites of low density polyethylene and an organo‐modified hectorite were first melt compounded and then foamed using a compression molding method. To study the influence of the presence and the amount of hectorite in both mechanical and thermal properties, samples with 3% and 7% content of hectorite were prepared. Polyethylene crystalline characteristics and thermal stability of the samples were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. Mechanical properties of foams and solid nanocomposites were analyzed by using dynamical mechanical analysis (DMA). Thermal expansion of the samples was analyzed by thermomechanical analysis. The results indicate that the exfoliation of hectorite platelets was achieved after the foaming process, but not during the melt mixing step. Foams with hectorite nanoparticles exhibit improved thermal stability and mechanical properties when compared with neat polymeric foams. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Supercritical CO2 as an efficient medium for layered silicate organomodification: Preparation of thermally stable organoclays and dispersion in polyamide 6

In this study, the preparation of organoclays via a new process using supercritical carbon dioxide is described. This method turns out to be very efficient with various surfactants, in particular nonwater-soluble alkylphosphonium salts. The influence of the surfactant as well as of the clay nature on the thermal stability of the organoclay is evaluated by thermogravimetric analysis. Phosphonium-based montmorillonites are up to 90 °C more stable than ammonium-based montmorillonites. Moreover, the use of hectorite adds another 40 °C of thermal stability to the phosphonium-modified clays. These organomodified clays have been melt-blended with polyamide 6 and morphology as well as fire properties of the nanocomposites are discussed, in terms of influence of the stability of organoclays. For the first time, comparison of nanocomposites based on clay organomodified by ammonium and phosphonium salts of the very same structure is reported.     

Short Review on Sepiolite-Filled Polymer Nanocomposites

Latest developments in mineral clay nanocomposites area are reviewed in this report, with a specific focus on sepiolite clay mineral. Rigorous research has been conducted on the sepiolite clay mineral by both academicians and industrial researchers. The properties of the nanocomposites are significantly dependent on the polymer matrices, their nature, modification, and preparation technique. Thus, preparation, structure, and characteristics of polymer sepiolite nanocomposites are thoroughly discussed, in addition to the scientific literature to support and find any gaps for future research.     

Acrylonitrile butadiene nanocomposites containing different clays by latex compounding method

Considering elastomers nanocomposites, most of the works are focused on natural rubber, styrene butadiene rubber and rubber blends, while few of them deal with nitrile butadiene rubber (NBR). This article presents the reinforcing effect of two raw sodic montmorillonites (Mts) and one organoclay on NBR matrix prepared by the latex compounding method. Raw Mts increase the mechanical properties of neat matrices. A pseudoplastic behavior is observed with the incorporation of clays into the NBR latex, indicating interactions between polymer chains and clay sheets, in agreement with the results of zeta potential analysis. X‐ray diffraction evaluates changes in the interlayer distance of the clay, indicating the NBR intercalation phenomenon in all cases. Matrices with different clay proportions present variations in the mechanical properties, depending if the aggregation phenomenon is promoted. Morphological analysis of clays and nanocomposites as well as thermal analysis were performed. The variation in mechanical properties after an aging process was studied, evaluating the effects on the tensile strength, ultimate strain and 300% modulus. POLYM. ENG. SCI., 59:736–744, 2019. © 2018 Society of Plastics Engineers     

Effect of clay exfoliation and organic modification on morphological,dynamic mechanical,and thermal behavior of melt‐compounded polyamide‐6 nanocomposites

Polyamide‐6/clay nanocomposites were prepared employing melt bending or compounding technique followed by injection molding using different organically modified clays. X‐ray diffraction and transmission electron microscopy were used to determine the molecular dispersion of the modified clays within the matrix polymer. Mechanical tests revealed an increase in tensile and flexural properties of the matrix polymer with the increase in clay loading from 0 to 5%. C30B/polyamide‐6 nanocomposites exhibited optimum mechanical performance at 5% clay loading. Storage modulus of polyamide‐6 also increased in the nanocomposites, indicating an increase in the stiffness of the matrix polymer with the addition of nanoclays. Furthermore, water absorption studies confirmed comparatively lesser tendency of water uptake in these nanocomposites. HDT of the virgin matrix increased substantially with the addition of organically modified clays. DSC measurements revealed both γ and α transitions in the matrix polymer as well as in the nanocomposites. The crystallization temperature (T_c) exhibited an increase in case of C30B/polyamide‐6 nanocomposites. Thermal stability of virgin polyamide‐6 and the nanocomposites has been investigated employing thermogravimetric analysis. POLYM. COMPOS., 28:153–162, 2007. © 2007 Society of Plastics Engineers     

高分子/无机纳米复合材料的研究进展

详细概述了采用纳米粒子直接填充分散法帛备高分子基无机钠米复合材料，对纳米粒子表面处理方法及纳米复合材料的性能及应用进行了介绍。     

改性粘土作为载体在农药控制释放中的应用

粘土可与多种阳离子发生离子交换,制备具有不同吸附性能的改性粘土。后者作为农药控制释放载体,可适用于各类性质和用途不同的农药,从而提高农药利用率,控制农药污染。通常,改性粘土对农药的吸附作用越强,农药释放越慢。将改性粘土与天然水溶性高分子一起制备复合农药载体,有利于提高载药能力,进一步拓展应用范围,强化对农药释放过程的调控作用。     

Newly emerging applications of halloysite nanotubes: a review

Halloysite nanotubes (HNTs) are types of naturally occurring 1:1 clays with nanotubular structures and similar chemical composition to kaolin. Due to various characteristics such as nanoscale lumens, high length‐to‐diameter ratio, relatively low hydroxyl group density on the surface, etc., numerous exciting applications have been discovered for this unique, cheap and abundantly deposited clay. After briefly summarizing applications in controlled release, nanotemplating and sorption, we emphasize the applications of HNTs in the fabrication of polymer nanocomposites. The unique structures and performance of HNT‐incorporated polymer nanocomposites processed by various routes are described. The results suggest that these nanocomposites exhibit remarkable performance such as reinforcing effects, enhanced flame retardancy and reduced thermal expansion. Accordingly, HNTs should be of interest in the area of polymer nanocomposites for structural and functional applications. Copyright © 2010 Society of Chemical Industry     

MWCNT/Hectorite hybrid filled acrylonitrile butadiene rubber/ ethylene-co-vinyl acetate blend nanocomposites: preparation and properties

Multiwalled carbon nanotube/hectorite hybrid filler (HMH) was prepared by simple dry grinding method. It was subsequently used for the reinforcement of technologically compatible acrylonitrile butadiene rubber (NBR)/ ethylene-co-vinyl acetate (EVA) blend through solution intercalation method. Analysis of the prepared blend nanocomposites confirms homogeneous dispersion of the constituent fillers in the polymer matrix and significant interaction between two types of constituent fillers. Mechanical properties of NBR/EVA blend are significantly improved with HMH content up to 4 wt.% followed by reversion. Maximum improvement observed in tensile strength, elongation at break and toughness are 106%, 37% and 171% respectively without significant rise in Young’s modulus. Results also show best dynamic mechanical and dielectric response at 4 wt.% and 3 wt.% HMH content respectively. Enhanced mechanical, dynamic mechanical and dielectric properties of the blend nanocomposites attained may be attributed to fair degree of compatibility between the two polymer matrices, homogeneous dispersion of fillers and improved polymer-filler interaction.     

Characterization of polyisoprene-clay nanocomposites prepared by solution blending

The effects of clay dispersion and the interactions between clays and polymer chains on the viscoelastic properties of polymer/clay nanocomposites are investigated using oscillatory shear rheology, X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). Four different montmorillonite silicates of natural clays, plasma-treated clays, and organically modified clays (OCs) have been used in this study. For the polyisoprene (PI)/clay nanocomposites, the exfoliation of the OC dispersed in the PI matrix is confirmed with XRD and SAXS although TEM images show both exfoliated and non-exfoliated nanoclay sheets. In contrast aggregation or intercalation is obtained for the other PI/clay composites studied here. Additionally, the effective maximum volume packing fraction of OC for the exfoliated nanocomposites is determined from the overlapping of dynamic viscosity at low frequency regime, in which the effective maximum volume packing fraction is larger than the percolation threshold determined from the storage modulus of the nanocomposites.     

Single-ion conducting polymer-silicate nanocomposite electrolytes for lithium battery applications

Solid-state polymer-silicate nanocomposite electrolytes based on an amorphous polymer poly[(oxyethylene)₈ methacrylate], POEM, and lithium montmorillonite clay were fabricated and characterized to investigate the feasibility of their use as ‘salt-free’ electrolytes in lithium polymer batteries. X-ray scattering and transmission electron microscopy studies indicate the formation of an intercalated morphology in the nanocomposites due to favorable interactions between the polymer matrix and the clay. The morphology of the nanocomposite is intricately linked to the amount of silicate in the system. At low clay contents, dynamic rheological testing verifies that silicate incorporation enhances the mechanical properties of POEM, while impedance spectroscopy shows an improvement in electrical properties. With clay content ≥15 wt.%, mechanical properties are further improved but the formation of an apparent superlattice structure correlates with a loss in the electrical properties of the nanocomposite. The use of suitably modified clays in nanocomposites with high clay contents eliminates this superstructure formation, yielding materials with enhanced performance.     

The structure‐property relationship of novolac cured epoxy resin/clay nanocomposites

Intercalated or exfoliated novolac cured epoxy resin nanocomposites were prepared with two different kinds of layered silicates – montmorillonite (PK‐802) and nontronite (PK‐805). The bifunctional modifiers (PI/BEN or MI/BEN) are used to modify the clays for improvement of the properties of polymer where benzalkonium chloride (BEN) acts as a compatibilizing agent and 2‐phenylimidazole (PI) or 2‐methylimidazole (MI) as the accelerators. Both the compatibilizer and accelerator are simultaneously intercalated into the gallery space of pure clays to form the modified clay. The novolac cured epoxy nanocomposites are prepared with these modified clays by crosslinking polymerization reaction. The properties of novolac cured epoxy/clay nanocomposites were characterized by wide‐angle X‐ray diffraction (WAXD), thermo‐gravimetric analysis (TGA), dynamic mechanical analysis (DMA), and transmission electron microscopy (TEM) methods. According to the measurement, these novolac cured epoxy‐clay nanocomposites have been shown the significant improvement in the thermal, mechanical, and barrier properties that may be applied to make printed circuit board. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

The influence of layered compounds on the properties of starch/layered compound composites

Glycerol‐plasticized starch films were modified by addition of various layered compounds as fillers, two being of natural origin (kaolinite, a neutral mineral clay, and hectorite, a cationic exchanger mineral clay) and two synthetic (layered double hydroxide, LDH, an anionic exchanger, and brucite, having a neutral structure). The effects of the filler type and the plasticizer were analyzed by X‐ray diffraction, dynamic mechanical analysis and thermogravimetry. The storage modulus was higher for kaolinite > brucite > hectorite than for LDH starch composites. However, only the hectorite filler presented a shift of the interplanar basal distance to higher values, which represents the intercalation of glycerol molecules between the clay layers. The glycerol intercalation is minimized in plasticized–oxidized starch films where the oxidized starch chains are preferentially intercalated. Copyright © 2003 Society of Chemical Industry     

Characterization,degradation and biocompatibility of PBAT based nanocomposites

The characterization, biocompatibility and hydrolytic degradation of poly(butylene adipate-co-terephthalate) (PBAT) and its nanocomposites based on 10 wt.% of an unmodified sepiolite and unmodified and modified montmorillonites and fluorohectorites were studied. All nanocomposites were prepared by melt blending using an internal mixer at 140 °C, showing a good level of clay distribution and dispersion into the PBAT matrix, especially those systems based on modified clays and sepiolite. The compression tests of all nanocomposites showed significant increases in the mechanical properties of PBAT matrix, associated to a reinforcement effect of nanoclays. An effective hydrolytic degradation of PBAT and nanocomposites in a phosphate buffered solution of pH 7.0 at 37 °C was also obtained. The addition of nanoparticles tended to delay slightly the hydrolysis of the polymer matrix in the early degradation stages; afterwards the presence of nanoparticles did not affect significantly the degradation trend of the polymer. Cytotoxicity tests, protein absorption analyses and complete blood count tests indicated that nanocomposites showed good biological safety: non-cytotoxicity, higher in vitro hemocompatibility than neat PBAT and non-negative hemostatic effects after contacting with blood. In general, these results showed that all the studied PBAT based nanocomposites could be very attractive for various tissue engineering applications, particularly to bone defects.