Natural Sodium Montmorillonite Research Articles

Nacre-Inspired Nanocomposites from Natural Polypeptide ε-Poly-l-Lysine and Natural Clay Montmorillonite: Remarkable Reinforcing Effect at Low Polymer Content and Its Mechanism.

Nanocomposites composed of the cationic polypeptide ε-poly-l-lysine (ε-PL) and natural sodium montmorillonite (MMT) were prepared and evaluated. These MMT/ε-PL composites formed highly ordered nanostructures resembling natural nacreous layers by a simple process. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses confirmed that a small amount of ε-PL remarkably enhanced the MMT orientation in the composites. This MMT orientation-enhancing effect of ε-PL was more pronounced than that of poly(vinyl alcohol) (PVA), which is one of the most popular ingredients of MMT-based composites. The orientation enhancement provided by ε-PL was primarily driven by ionic interactions and responsible for high mechanical properties at low polymer content. This remarkable reinforcing effect of ε-PL on MMT at a low polymer content will help to develop high-performance and sustainable nacreous composites. In addition, it improves our understanding of the reinforcing mechanism of natural nacre, which exhibits excellent mechanical properties even with relatively small amounts of organic component.

Development of natural sodium montmorillonite as a cathode material

Montmorillonite (MMT) is naturally occurring clay mineral in Sri Lanka. It is an aluminosilicate crystalline compound with layered structure. In this structure an octahedral sheet of aluminum-oxygen (Al-O) is sandwiched between two tetrahedral sheets of silicon-oxygen (Si-O). The MMT structure can accommodate various monovalent and divalent cations such as H⁺, Li⁺, Na⁺, Mg²⁺ within the interlayer spacing. Natural Li-MMT and Na-MMT are found in various parts of the world. The MMT structure has an ability to exchange interlayer cations with various other divalent cations. MMT with interlayer alkali cations show appreciable ionic conductivity. Natural Na-MMT found in Sri Lanka was used for the present study. To improve the ionic conductivity of natural Na-MMT, the structure was further saturated with Na⁺ ions. The Na⁺ ion concentration of saturated Na-MMT was measured by Inductive Couple Plasma Mass Spectroscopy. The structural and electrical properties of Na saturated MMT were characterized by SEM and Complex Impedance Spectroscopy. As a result of Na⁺ ion saturation the bulk conductivity of Na-MMT was increased to 3.41×10^–4 S cm^–1 at 30⁰C . Saturated Na-MMT has negligible electronic conductivity which is less than 0.001%. For using Na-MMT as intercalation cathode materials in rechargeable batteries, an appreciable electronic conductivity must also be present. To enhance the electronic conductivity of saturated Na-MMT, carbon black was mixed. The electronic transference number of saturated Na-MMT pellets was measured by the DC polarization technique. The electronic transference number of saturated Na-MMT with 25% and 30% carbon black were 0.81 and 0.87 respectively.

Effect of interfacial interactions on static and dynamic behavior of hyperbranched polymers: Comparison between different layered nanoadditives

The structure and dynamics of a hyperbranched poly (ester amide) and its nanocomposites with natural sodium montmorillonite (Na+-MMT) and graphite oxide (GO) are investigated to provide an understanding of the influence of different polymer-inorganic interfacial interactions on the polymer behavior. In both systems, the favorable interactions lead to intercalated structures; however, the different interaction strengths create polymer nanofilms of different thicknesses between the inorganic layers. The composition of the nanohybrids is such that all chains are expected to reside within the galleries of the nanoadditives. Thermal reduction of GO in the presence of the polymer forces the system to lose its periodic structure; nevertheless, the deoxygenation temperature decreases in the presence of the polymer when compared to the respective one for the bare GO. At the same time, the thermal stability of the polymer decreases in the presence of GO. In both cases, the glass transition of the intercalated chains is fully suppressed. The different surface interactions affect polymer dynamics by modifying the number of relaxation processes, their relaxation times which become faster or slower than the bulk, as well as the temperature dependencies of the processes.

PERFORMANCE CHARACTERISTICS OF COATINGS ON BASIS OF POLYVINYL ACETATE MODIFIED WITH MONTMORILLONITE

Water-dispersion materials based on poly (vinyl acetate) are widely used in industry as adhesive compositions and binders for polymer coatings due to their low cost, ecological safety and good performance characteristis. Drawbacks of such materials are insufficient water resistance and relatively low physical-mechanical properties. For improvement of performance characteristics of poly (vinyl acetate) based coatings it is proposed to modify the water-dispersion materials by incorporation of small amounts of sodium montmorillonite. In the article characteristics of model pigmented paint materials and coatings based on poly (vinyl acetate) dispersion modified with sodium montmorillonite are presented. Commercial water dispersion of PVA plasticized with dibutyl phatalate, natural sodium montmorillonite and titanium dioxide (pigment) were used for preparation of model paint materials. The obtained specimens of model paint materials are pseudoplastic fluids, incorporation of monmtorillonite leads to significant increase in yield stress. Materials modified with montmorillonite exhibit thixotropic properties. Addition of 1-2 % wt. montmorillonite to the material leads to increase in the Young modulus of dried films up to 8 times without decrease in tensile strength. The obtained effect is attributed to adhesion strengthening of the composite material. Incorporation of montmorillonite does not hinder the covering power of the paint material. Montmorillonite-modified coatings show increased hardness and reduced water absorption capacity (up to 2.5 times with addition of 2 % wt. montmorillonite). Reduction of water uptake of polymer material modified with montmorillonite can be attributed to reduction of free volume in the composite, formation of interface layers of polymer with different physico-phemical properties, and also to the decrease in the diffusion coefficient of water in the composite. The suggested approach to inprovement of the coating characteristics can be implemented without major expenditure due to low cost of natural sodium montmorillonite and simplicity of its incorporation in water-dispersion materials.

Vinyl intumescent coatings modified with platelet-type nanofillers

A solvent-borne poly(vinyl acetate)-based intumescent paint was modified with two types of platelet-type nanofillers, i.e. a natural sodium montmorillonite (MMT) and a 3-layer graphene (Gn). MMT was incorporated into the coating formulation after its pre-swelling in cyclohexanol while Gn was applied in a powder form. Thermal insulation features of dry coatings were investigated by means of a gas flame-heated programmable furnace (according to a cellulosic fire curve). Additionally, thermogravimetrical, structural (FTIR, XRD) and mechanical properties of the coatings and obtained chars were analyzed. It was revealed that Gn positively affected the thermal insulation and intumescence effectiveness as well as compressive strength of charred coatings. The highest values of that parameters (+13%, +74% and +92%, respectively) were noted for samples containing the lowest dose of Gn (1 wt. part/100 wt. parts of the paint solids). MMT-based system exhibited a far higher mechanical resistance, however, its thermal protection was limited in relation to the other samples. Moreover, the addition of MMT (or Gn) affected chemical composition as well as size and distribution of cells in a foamed char.

Synthesis and Properties of Plasticized Sulfur-Montmorillonite Nanocomposites by Melt-Blending

Plasticized sulfur/montmorillonite nanocomposites were prepared by the melt-blending method and the dispersion of montmorillonite (MMT) and the mechanical properties of the nanocomposites were studied. Natural sodium montmorillonite (NaMMT) and organically modified montmorillonite (OMMT) were used as filler. Scanning electron microscope (SEM), X-Ray powder Diffraction (XRD) and Transmission Electron Microscopy (TEM) indicated that OMMT is dispersed effectively in the plasticized sulfur matrix.The effect of varying amounts of natural sodium montmorillonite (NaMMT) and organically modified montmorillonite (OMMT) on the mechanical properties of the prepared nanocomposites were studied. The compressive, tensile, and flexural strengths of the plasticized sulfur nanocomposites containing OMMT compared to that containing NaMMT were, in general, greatly improved. Best MMT dispersion observed at 1.6 wt. %.

Incorporation of amoxicillin-loaded organic montmorillonite into poly(ester-urethane) urea nanofibers as a functional tissue engineering scaffold

A dual drug-loaded system is a promising alternative for the sustained drug release system and skin tissue engineering. In this study, a natural sodium montmorillonite (Na-MMT) modified by cetyl trimethyl ammonium bromide (CTAB) was prepared as a carrier to load a model drug – amoxicillin (AMX), the modified organic montmorillonite (CTAB-OMMT) loaded with AMX was marked as AMX@CTAB-OMMT and was subsequently incorporated into poly(ester-urethane) urea (PEUU) and gelatin hybrid nanofibers via electrospinning, resulting in a new drug-loaded nanofibrous scaffold (AMX@CTAB-OMMT-PU75). The scanning electron microscopy (SEM) result showed that the fiber morphology did not change after the embedding of AMX@CTAB-OMMT. Meanwhile, there was a significant increase of mechanical properties for PEUU/Gelatin hybrid nanofibers (PU75) after the incorporation of AMX@CTAB-OMMT and CTAB-OMMT. Importantly, AMX@CTAB-OMMT-PU75 nanofibers showed a kind of sustained drug release property which could be justified reasonably for the controlled release of AMX depending on the various application. The sustained release property could be identified roughly by the result of antibacterial test. The anaphylactic reaction test proved that there was no any anaphylactic reaction or inflammation on the back of rat for AMX@CTAB-OMMT-PU75 nanofibers. Consequently, the prepared drug-loaded AMX@CTAB-OMMT-PU75 nanofibrous scaffold is a promising candidate for application in the skin tissue engineering field and controlled drug release system.

Influence of a novel organo-silylated clay on the morphology, thermal and burning behavior of low density polyethylene composites

Abstract The functionalization of a natural sodium montmorillonite (MMT) with (3-glycidyloxypropyl)trimethoxysilane by a silylation procedure is presented, and its use as nanofiller in the melt compounding of low density polyethylene (LDPE) nanocomposites. In particular, the effects on the thermal stability and flame retardant properties of melt compounded LDPE nanocomposites are analyzed, with and without magnesium hydroxide (MH) as an additional conventional flame retardant. The purpose was to investigate possible synergistic effects between the two inorganic fillers on fire behavior. The obtained organosilylated clay showed higher interlayer spacing than the original MMT and good thermal stability, higher than that of many commercial organoclays modified with alkylammonium salts. Its addition to LDPE allowed the production of hybrids with nanoscale dispersion of the filler, as demonstrated by X-ray diffraction. The simultaneous presence of MH, which strongly interacts with the nanoclay, hindered intercalation of the polymer chains between the clay galleries and clay layer exfoliation within the LDPE resin. The investigation of the thermal and burning behavior of the LDPE nanocomposites indicated that the organosilylated clay alone shows only a limited residual protection layer effect. In combination with MH the nanocomposites have a small adverse effect on the reaction to small flame as measured by the oxygen index and UL 94 testing, and, surprisingly, no effect on the peak heat release rate in the cone calorimeter. The quality of the fire residue was lacking on the microscopic scale. The ternary LDPE/MH/organoclay systems investigated did not open the door to reducing MH content in halogen-free flame retardant LDPE yet, but demand further research.

The Effect of Mycotoxins Adsorbents Beta Glucans or Montmorillonite on Bovine Ruminal Fermentation In Vitro

Background: The addition of adsorbents in foods has been the strategy used by nutritionists to reduce the toxic effects of mycotoxins in animals. Mycotoxins are found in a range of foods and commonly they present variations in the chemical structure therefore, it has been appropriate to include adsorbents from different sources in the diet of ruminants. However, few researches were conducted in order to better understand the interaction of adsorbents on ruminal fermentation. Our objective in this study was to investigate the possible effects of two adsorbent products on bovine ruminal fermentation. One consists of 65% of β-glucan (β-glu), originating cell wall of Saccharomyces cerevisiae and used at a concentration of 1% and natural sodium montmorillonite (MMT) at a concentration of 5%.Materials, Methods & Results: The effects of β-glu adsorbents (1%) and MMC (5%) in culture medium that simulated ruminal fermentation were evaluated. Bottles, with a capacity of 120 mL, were used to be filled with substrate such as maize and ryegrass hay ground, nutrient solution (medium of Menke), liquid extracted rumen fistulated bovine and the two adsorbents evaluated, totaling 50 mL. The experiment was conducted with three treatments, named after: control (Cont), β-glu and MMT. In the control treatment adsorbents were not added. Six replicates were used for each treatment and two trials were conducted. One of the tests aimed to determine the fermentation kinetics by means of the gas production after 72 h’ incubation and quantifying the production of methane (CH4) at 48h. While another test aimed to quantify the production of short chain fatty acids (SCFA) - acetic, propionic and butyric acid - and the production of ammonia (NH3) in 24 h incubation. All assays were measured by gas chromatography. The highest total SCFA concentration was observed in β-glu treatment (67.71 mM) significantly superior to CONT (57.7 mM) treatment and MMT (53.28 mM), which was significantly lower than the β-glu treatment, but similar to CONT. The average representation (%) of acetic acid for the treatment MMT (62.9%) was significantly higher than the β-glu treatment (61.0%). The average proportions of propionic acid were similar between treatments, while the average representation (%) of butyric acid production was significantly higher for the β-glu treatment (13.1%) compared to CONT treatments (11.3%) and MMT (11.4%). The amount of NH3 was significantly reduced in MMT (9.6 mM) treatment compared to β-glu treatments (12.2 mM) and CONT (11.3 mM). In another test, the greater volume of gas (mL) was produced by β-glu treatment (103.4 mL), which was significantly greater than the treatments CONT (89.0 mL) and MMT (91.6 mL). The lag time, i.e. the time taken by the bacteria inoculum to develop lead-through in the substrate, in the MMT treatment took 6.2 h, slowing significantly compared to CONT treatments (4.8 h) and β Glu (4.33 h). The concentration of CH4 was significantly lower in MMT treatment (33.0%) compared to the CONT treatments (36.3%) and β-glu (35.68%).Discussion: The glucans which constitute the main cell wall S. cerevisae are the β-glucans with β-1-3 and β-1,6 glycosidic bonds. The largest and most significant concentration of SCFA and gas volume in the β-glu treatment can be explained by the degradation of β-glucans by rumen bacteria. The possible reason of reduced concentration of methane (CH4) in samples collected during 48 h of incubation in MMT treatment stands on the reduction in symbiotic activity of methanogenic bacteria and protozoa. Also, the possible reason of reduction in the concentration of ammonia (NH3) in MMT treatment could be associated to damage on protozoa with proteolytic activity. Our results showed that the amount of montmorillonite in rumen fluid influenced negatively the fermentative activity, therefore, delaying the colonization of bacteria in rumen substrate composed of maize and ryegrass hay. Moreover, the use of β-glu (1%) significantly increased the amount of short chain fatty acids such as, acetic acid and butyric acid, with the exception of propionic acid.

Nano Determination of Kinase Inhibitor Sorafenib Drug in Pharmaceutical Formulation and Human Blood at a Modified Carbon Paste Electrode

Sorafenib (SORA) has clinical activity against several tumor types. Carbon paste electrode modified with natural sodium montmorillonite clay (Na-MMT/CPE) was used as a sensor for sensitive and selective determination of SORA drug using square-wave adsorptive anodic stripping voltammetry (SW-AdASV). Unmodified CPE as well as the modified one were characterized using scan electron microscopy (SEM), N2 sorption isotherms (BET) and electrochemical impedance spectra (EIS). In spite of the very low conductivity of Na-MMT, a shift in the peak potential to less positive and about two times enhancement in the peak current were observed at 5% (w/w) Na-MMT/CPE compared to that at bare CPE, reflecting electrocatalytic activity of Na-MMT toward oxidation of SORA. This may be attributed to strong adsorptive property of Na-MMT due to its high surface area or specific bonding reactions of SORA with the functional groups at the edges of clay sheets. The method was employed successfully to determine SORA in its pharmaceutical formulation (Nexavar tablets). Detection limit of 1.5 × 10−10 M was also achieved in human serum. The described method is reliable, simple and sensitive enough for assay of SORA in real plasma samples, pharmacokinetic studies, quality control and assurance of the drug in industry and in clinical laboratories.

ChemInform Abstract: Chlorination of Benzylic and Allylic Alcohols with Trimethylsilyl Chloride Enhanced by Natural Sodium Montmorillonite.

AbstractThe practical method allows the chlorination of primary, secondary, and tertiary benzylic and allylic alcohols and can be scaled up.

Chlorination of Benzylic and Allylic Alcohols with Trimethylsilyl Chloride Enhanced by Natural Sodium Montmorillonite

A new and practical method for the efficient chlorination of tertiary, secondary, and primary benzylic and allylic alcohols is described. The method is characterized by the formation of hydrogen chloride from trimethylsilyl chloride and trace water, the formation of a carbenium ion through the protonation of an alcohol and subsequent dehydration, and the chlorination of the carbenium ion. During the process, sodium ion-exchanged montmorillonite plays a crucial role in capturing the generated hydrogen chloride, stabilizing the carbenium intermediate as well as promoting the chlorination.

Facile Access to Large-Scale, Self-Assembled, Nacre-Inspired, High-Performance Materials with Tunable Nanoscale Periodicities

Although advances have been reported to mimic the mechanically excellent structure of natural nacre, larger-scale applications are still limited due to time and energy-intensive preparation pathways. Herein, we demonstrate that simple high-shear homogenization of dispersions containing biobased high molecular weight sodium carboxymethyl cellulose (700 kg/mol, CMC) and natural sodium montmorillonite (MTM), serving as the soft energy-dissipating phase and reinforcing platelets, respectively, can be used to prepare large-area and thick films with well-aligned hard/soft nacre-mimetic mesostructure. During this process, core-shell nanoplatelets with intrinsic hard/soft structure form, which then self-assemble into a layered nanocomposite during water removal. The nanoscale periodicities of the alternating hard/soft layers can be precisely tuned by changing the ratio of CMC to MTM, which allows studying the evolution of mechanical properties as a function of the lamellar nanoscale periodicity and fractions of hard to soft material. Remarkable mechanical stiffness (25 GPa) and strength (320 MPa) can be obtained placing these materials among the top end of nacre-inspired materials reported so far. Mechanical homogenization also allows direct preparation of concentrated, yet homogeneous, gel-like dispersions of high nanoclay content, suited to doctor-blade large-area and thick films with essentially the same properties as films cast from dilute dispersions. In terms of functional properties, we report high-transparency, shape-persistent fire-blocking and the ability to surface-pattern via inkjet printing. Considering the simple, fully scalable, waterborne preparation pathway, and the use of nature-based components, we foresee applications as ecofriendly, bioinspired materials to promote sustainable engineering materials and novel types of functional barrier coatings and substrates.

Surface modification of natural Na-montmorillonite in alkane solvents using a quaternary ammonium surfactant

The surface properties of a natural sodium montmorillonite (Na-MMT) was dramatically altered by a cationic surfactant dioctadecyldimethylammonium chloride (DODMAC) through an intercalation and ion exchange reaction in alkane solvents. Optical micrographs show that in situ organo-modification with surfactant DODMAC significantly improves the dispersibility of Na-MMT in alkane solvents. Changes in the structure and surface properties of the organophilic montmorillonite (OMMT) formed in octane, a volatile alkane, were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), thermogravimetric analysis (TGA/DTG) and Fourier transform infrared spectroscopy (FTIR). It is shown that organo-modification of Na-MMT surfaces based on ion exchange reaction in alkane solvents results in dispersion of the hydrophilic Na-MMT in the organic medium. And most importantly, viscosity curves of the clay suspensions suggest a potential method to control the rheological behavior of dispersions in alkane solvents instead of using organophilic montmorillonites. Furthermore, dispersion approaches and mechanism presented here will be useful for choosing compatibilizer and optimizing processing conditions especially in developing pristine-clay polymer nanocomposites.

Ionic supramolecular bonds preserve mechanical properties and enable synergetic performance at high humidity in water-borne, self-assembled nacre-mimetics

Although tremendous effort has been focused on enhancing the mechanical properties of nacre-mimetic materials, conservation of high stiffness and strength against hydration-induced decay of mechanical properties at high humidity remains a fundamental challenge in such water-borne high-performance materials. Herein, we demonstrate that ionic supramolecular bonds, introduced by infiltration of divalent Cu(2+) ions, allow efficient stabilization of the mechanical properties of self-assembled water-borne nacre-mimetics based on sustainable sodium carboxymethylcellulose (Na(+)CMC) and natural sodium montmorillonite nanoclay (Na(+)MTM) against high humidity (95% RH). The mechanical properties in the highly hydrated state (Young's modulus up to 13.5 GPa and tensile strength up to 125 MPa) are in fact comparable to a range of non-crosslinked nacre-mimetic materials in the dry state. Moreover, the Cu(2+)-treated nacre-inspired materials display synergetic mechanical properties as found in a simultaneous improvement of stiffness, strength and toughness, as compared to the pristine material. Significant inelastic deformation takes place considering the highly reinforced state. This contrasts the typical behaviour of tight, covalent crosslinks and is suggested to originate from a sacrificial, dynamic breakage and rebinding of transient supramolecular ionic bonds. Considering easy access to a large range of ionic interactions and alteration of counter-ion charge via external stimuli, we foresee responsive and adaptive mechanical properties in highly reinforced and stiff bio-inspired bulk nanocomposites and in other bio-inspired materials, e.g. nanocellulose papers and peptide-based materials.

First Evidence of Singlet Oxygen Species Mechanism in Silicate Clay for Antimicrobial Behavior

ABSTRACTThin silicate nanoplatelets, derived from the exfoliation of natural Sodium montmorillonite (Na+-MMT) clays, show an unexpected antimicrobial property. A physical trapping mechanism has been proposed because the clay nanoplatelets can indiscriminately inhibit the growth of a broad spectrum of bacteria, including drug-resistant species such as methicillin-resistance S. aureus (MRSA) and silver ion-resistant E. coli. The ability to generate singlet oxygen species was first observed for the clay platelets that showed a high-aspect-ratio geometric shape and the presence of surface ionic charges. By comparison, the pristine clay with a multilayered structure failed to generate any singlet oxygen species. The ability to emit singlet oxygen species provides direct evidence for the antimicrobial ability of clay through a non-chemical mechanism, which opens the potential for medical use.

Morphology, thermal and mechanical properties of PVC/MMT nanocomposites prepared by solution blending and solution blending + melt compounding

Two types of montmorillonite (MMT), natural sodium montmorillonite (Na-MMT) and organically modified montmorillonite (OMMT), in different amounts of 1, 2, 5, 10 and 25 phr (parts per hundred resin), were dispersed in rigid poly (vinyl chloride) by two different methods: solution blending and solution blending + melt compounding. The effects on morphology, thermal and mechanical properties of the PVC/MMT nanocomposites were studied by varying the amount of Na-MMT and OMMT in both methods. SEM and XRD analysis revealed that possible intercalated and exfoliated structures were obtained in all of the PVC/MMT nanocomposites. Thermogravimetric analysis revealed that PVC/Na-MMT nanocomposites have better thermal stability than PVC/OMMT nanocomposites and PVC. In general, PVC/MMT nanocomposites prepared by solution blending + melt compounding revealed improved thermal properties compared to PVC/MMT nanocomposites prepared by solution blending. Vicat tests revealed a significant decrease in Vicat softening temperature of PVC/MMT nanocomposites prepared by solution blending + melt compounding compared to unfilled PVC. The mechanical properties of the PVC/MMT nanocomposites were, in general, greatly improved compared to unfilled PVC. Nanocomposites with 2 phr and 5 phr of OMMT have demonstrated enhanced results in Young’s modulus, tensile strength and elongation. The Mori–Tanaka method along with an orientation distribution function was used to predict the effective stiffness of the PVC/OMMT nanocomposites prepared by solution blending + melt compounding method. Experimental values for 1 and 2 phr are larger than the calculated values which directly suggest that the MMT particles are exfoliated.

Segregated Networks of Carbon Black in Poly(vinyl acetate) Latex: Influence of Clay on the Electrical and Mechanical Behavior

AbstractFilms were prepared from mixtures of PVAc latex, CB, and natural sodium montmorillonite clay. In the absence of clay, these composites exhibit a percolation threshold of 1.2 vol.‐% CB, which is nearly an order of magnitude lower than that observed for composites prepared using PVAc solution. SEM images reveal a segregated CB network that is the result of excluded volume created by the much larger polymer particles in the latex. With the addition of 0.2 wt.‐% clay, the percolation threshold is reduced to 0.9 vol.‐% carbon black due to clay‐induced networking. The storage modulus is also enhanced by the presence of clay, although higher clay concentration appears to adversely affect electrical and mechanical behavior of these composites.magnified image

Structure and properties of styrene-butadiene rubber/ pristine clay nanocomposites prepared by latex compounding method

AbstractStyrene- butadiene rubber (SBR)/ clay nanocomposites were prepared by mixing the SBR latex with aqueous clay dispersion and co-coagulating the mixture. Tapping mode AFM and XRD were applied to characterize the structure of nanocomposites. It was found that fully exfoliated structure could be obtained by this method only when the low loading of layered silicate (< 10 phr) is used. With increasing the clay content, both non-exfoliated (stacked layers) and exfoliated structures can be observed simultaneously in the nanocomposites. The results of mechanical tests on the vulcanized pure SBR and SBR/ clay nanocomposites showed that the nanocomposites presents better mechanical properties than clayfree SBR vulcanizate. Furthermore, initial modulus, tensile strength, tensile strain at break, hardness (shore A) and tear strength increased with increasing the clay content, indicating the nanoreinforcement effect of clay on the mechanical properties of SBR/ clay nanocomposites. Compared to the clay free SBR vulcanizate, the nanocomposite vulcanizates exhibit a lower tanδ peak value, higher storage modulus and higher tanδ value at the rubbery region (0-60 °C) which indicate that the elastic responses of pure SBR towards deformation are strongly influenced by the presence of nanodisperced natural sodium montmorillonite layers especially completely exfoliated silicate layers.

Thermoplastic elastomeric nanocomposites from poly[styrene–(ethylene‐co‐butylene)–styrene] triblock copolymer and clay: Preparation and characterization

AbstractThermoplastic elastomer (TPE)–clay nanocomposites based on poly[styrene–(ethylene‐co‐butylene)–styrene] triblock copolymer (SEBS) were prepared. Natural sodium montmorillonite (MMT) clay was organically modified by octadecyl amine to produce an amine‐modified hydrophobic nanoclay (OC). Commercially available Cloisite 20A (CL20) and Cloisite 10A, tallow ammine modified nanoclays, were also used. The intergallery spacing of MMT increased on amine modification as suggested by the shifting of the X‐ray diffraction (XRD) peak from 7.6 to 4.5 and 3.8° in the cases of OC and CL20, respectively. The latter demonstrated no XRD peak when it was used at 2 and 4 parts phr in the SEBS system. Transmission electron microscopy studies showed the intercalation–exfoliation morphology in SEBS containing 4 parts of CL204–SEBS, agglomeration in SEBS having 4 parts of MMT, and mixed morphology in SEBS with 4 parts of OC systems. Locations of the clay particles were indicated by the atomic force micrographs. Mechanical and dynamic mechanical thermal analysis studies confirmed the best properties with the CL204–SEBS nanocomposites. Significant improvements in mechanical properties such as tensile strength, modulus, work to break, and elongation at break were achieved with the CL204–SEBS in polymer‐layered silicate nanocomposites. Dynamic mechanical studies further showed the affinity of the organoclays toward both segments of the TPE and a compatibilization effect with CL20 at a 4‐phr loading. Atomic force microscopy showed distinctly different morphologies in nanocomposites prepared through solution and melt processing. Comparisons of the mechanical, dynamic mechanical, and morphological properties of the nanocomposites prepared by melt and solution intercalation processes were done. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2040–2052, 2006