No abstract

Ethylene vinyl acetate rubber (45% vinyl acetate content, EVA-45) and organomodified clay (12Me-MMT) composites were prepared by solution blending of the rubber and the clay. A combination of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy studies showed that the composites obtained are on the nanometer scale. The measurements of the dynamic mechanical properties for different compositions over a temperature range (Ϫ100 to ϩ100°C) showed that the storage moduli of these rubber-clay nanocomposites are higher above the glass to rubber transition temperature compared to the neat rubber. The tensile strength of the nanocomposites is about 1.6 times higher than that of the EVA-45.

ABSTRACT:The filler action of dodecylamine (12C) intercalated montmorillonite (MNT) referred to as organomodified montmorillonite (12C-MNT) up to 4 wt % on natural rubber (NR) and styrene butadiene rubber (SBR) was studied and findings were compared with respect to the unmodified Na-MNT. X-ray analysis was used to calculate the interchain separation (R and RЈ), degree of crystallinity (X c ), and distortion factor (k). It is noted that R and RЈ showed the opposite trend, whereas X c as well as k showed overall increasing trend with an increasing amount of 12C-MNT on both NR and SBR. For Na-MNT (1 wt %) filled NR and SBR, the corresponding magnitude of R and R Ј and X c showed nearly no change, whereas k c increased significantly. The crosslinking density (v c ) does not show any significant changes in NR, whereas for SBR, it increases with increasing 12C-MNT as filler. Interestingly, in the case of 1 wt % pure Na-MNT used as filler for both NR and SBR, v c was lower compared to the virgin rubbers. Both swelling index (s i ) and sol fraction (Q) do not show any significant variation for NR composites, whereas these decrease for SBR composites with increasing concentration of 12C-MNT filler. On the contrary, NR and SBR with 1 wt % of Na-MNT filler show greater magnitude of s i and Q corresponding to the pure ones. Measurements of mechanical properties showed a significant increase in tensile strength and elongation at break for NR-12C-MNT (4 wt %) when compared with either virgin NR. In addition, modulus at the elongation at 100 and 200% in general increases with increasing loading of 12C-MNT filler in NR. Similar observations were also noted in the case of SBR. Interestingly, when only pure Na-MNT is used as filler, the strength of NR and SBR decreases drastically. Scanning electron microscopic studies were also to used support the mechanical behavior of NR-12MNT and SBR-12CMNT composites.

Abstract. Structural, thermal and electrical behavior of polymer-clay nanocomposite electrolytes consisting of polymer (polyethylene oxide (PEO)) and NaI as salt with different concentrations of organically modified Na + montmorillonite (DMMT) filler have been investigated. The formation of nanocomposites and changes in the structural properties of the materials were investigated by X-ray diffraction (XRD) analysis. Complex impedance analysis shows the existence of bulk and material-electrode interface properties of the composites. The relative dielectric constant (εr) decreases with increase in frequency in the low frequency region whereas frequency independent behavior is observed in the high frequency region. The electrical modulus representation shows a loss feature in the imaginary component. The relaxation associated with this feature shows a stretched exponential decay. Studies of frequency dependence of dielectric and modulus formalism suggest that the ionic and polymer segmental motion are strongly coupled manifeasting as peak in the modulus (M″) spectra with no corresponding feature in dielectric spectra. The frequency dependence of ac (alternating current) conductivity obeys Jonscher power law feature in the high frequency region, where as the low frequency dispersion indicating the presence of electrode polarization effect in the materials.

No abstract

The solid polymer electrolyte films based on polyethylene oxide, NaClO 4 with dodecyl amine modified montmorillonite as filler, and polyethylene glycol as plasticizer were prepared by a tape casting method. The effect of plasticization on structural, microstructural, and electrical properties of the materials has been investigated. A systematic change in the structural and microstructural properties of plasticized polymer nanocomposite electrolytes (PPNCEs) on addition of plasticizer was observed in our X-ray diffraction pattern and scanning electron microscopy micrographs. Complex impedance analysis technique was used to calculate the electrical properties of the nanocomposites. Addition of plasticizer has resulted in the lowering of the glass transition temperature, effective dissociation of the salt, and enhancement in the electrical conductivity. The maximum value of conductivity obtained was ∼4.4×10 −6 S cm −1 (on addition of ∼20% plasticizer), which is an order of magnitude higher than that of pure polymer nanocomposite electrolyte films (2.82×10 −7 S cm −1 ). The enhancement in conductivity on plasticization was well correlated with the change in other physical properties.

The present work deals with the dehydration transformation of Ca-montmorillonite in the temperature range 30°°-500°°C. Thermal, infrared (IR), and X-ray diffraction (XRD) analyses were used to describe the thermal transformation. The microstructural and layer disorder parameters like crystallite size, r.m.s. strain (〈 〈e 2 〉 〉 1/2 ), variation of interlayer spacing (g), and proportion of planes which were affected by the defect (γ γ), have all been calculated from the (001) basal reflection using the method of variance and Fourier line shape analysis. These investigations revealed that sample underwent transformation from hydrated phase to dehydrated phase at 200°°C, and as a consequence, its basal spacing collapsed from 16⋅ ⋅02 Å (30°°C) to around 10 Å (200°°C). This transformation occurred through a wide range of temperature, i.e. within the range 120°°-200°°C. The crystallite size was maximum at room temperature (30°°C), however, the size decreased with increasing temperature in the hydrated phase, whereas the size increased with increasing temperature for the dehydrated phase. The g, γ γ and 〈 〈e 2 〉 〉 1/2 of the hydrated and the dehydrated phase increased and decreased, respectively with increase of heating temperature.

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