Montmorillonite nanoclay filler effects on electrical conductivity, thermal and mechanical properties of epoxy-based nanocomposites

Epoxy-based nanocomposites with 2, 5, and 7 wt% of montmorillonite (MMT) nanoclay were prepared using high shear melt mixing technique. The microstructural features of the nanocomposites were investigated by transmission electron microscopy (TEM). The thermal and mechanical properties were measured using differential scanning calorimetry (DSC), thermogravimetric analyzer (TGA), and dynamic mechanical analyzer (DMA). Further, the effect of voltage, temperature, sea-water aging on the electrical conductivity (sigma(DC)) of the nanocomposites was also measured. To understand the free volume behavior upon filler loading, and to observe the connectivity between microstructure and other properties, positron annihilation lifetime spectroscopy was used. The TEM results revealed that MMT nanoparticles were uniformly dispersed in the epoxy matrix. Experimental results showed that the inclusion of 2 wt% MMT nanofiller increased the T-g, electrical conductivity, thermal stability, modulus, free volume of the epoxy nanocomposite significantly. This is well explained from the results of T-g (DSC and DMA), thermal stability, TGA residue, free volume analysis, and electrical conductivity. POLYM. ENG. SCI., 51:1827-1836, 2011. (C) 2011 Society of Plastics Engineer

Influence of nanopores on molecular polarizability and polarization currents in epoxy nanocomposites

Epoxy resin based nanocomposites with silica (SiO2), alumina (Al2O3) and zinc oxide (ZnO) as nano fillers were fabricated to investigate the relationship between the polarization and depolarization current. The polarization and depolarization current, charge carrier mobility, absorption current and nano size free volume cavities of nano dielectric epoxy composites and their interrelation are discussed. It is observed that the current magnitude increases in the three nanocomposites with loading of nano SiO2, Al2O3 and ZnO and the peak width of each composite is greater than that of pure epoxy. Free volume studies are carried out using positron annihilation lifetime spectroscopy (PALS). From the results it is observed that molecular polarizability decreases and charge carrier mobility increases with the incorporation of SiO2, Al2O3 and ZnO loading. This trend is typical in Al 2O3, whereas in case of SiO2 the molecular polarizability is unaffected and with ZnO, molecular polarizability and charge carrier mobility decrease above 10 wt% filler. The Al2O3 nanofillers are structurally different as compared to SiO2 and ZnO fillers. It is observed that Al2O3 has more influence on polarizability of the composite

Preparation and characterisation of Isophthalic-Bi2O3 polymer composite gamma radiation shields

Bi2O3 filled Isophthalic resin based polymer composites of different weight (0, 5, 10, 20, 30, 40, 50 & 60) were fabricated by open mould cast technique. Gamma attenuation study was carried out using NaI (Tl) gamma ray spectrometer for Cs-137. The shielding parameters such as attenuation coefficient, HVL & λ were investigated. The distribution of the filler within the matrix was studied using Scanning Electron Microscopy. X ray diffractometer and Fourier Transform Infrared Spectroscopy were employed to study the structural changes if any. The thermal stability and mechanical strength of the composites were investigated using TGA & UTM respectively. Dielectric properties and AC conductivity were also studied using LCR meter. The composites are found to be thermally stable upto 200°C. There were no such structural changes observed and all the composites show very low conductivity. The mechanical strength of the composites was found to increase upon adding the bismuth oxide with a slight decrease when the concentration of the filler exceeds 40wt. Attenuation results reveal that, the shielding efficiency increases with the increase of the filler wt and are comparable to those of the conventional shielding materials. Hence, Bi2O3 filled composites can be used for gamma shielding applications