Poly(vinyl alcohol) (PVA) nanocomposites with pristine sepiolite and heat-treated (HT) sepiolites were prepared by the method of solution dispersion. The measurements of XRD, FTIR, TEM, and AFM were used for the characterization of the nanocomposites. Furthermore, thermal and optical properties were investigated by TG/DTG/DTA and UV-visible transmission spectra, respectively. Both the effects of sepiolite/polymer ratio and the structural changes in sepiolite on heating were examined in terms of changes in the properties of the nanocomposites. The addition of sepiolite/HT sepiolites into the PVA matrix resulted in a decrease in the thermal decomposition temperatures of the nanocomposites because of the fact that sepiolite and HT sepiolites facilitated the elimination of the water and acetate groups from the PVA in the second step based on the TG/DTG studies. The HT sepiolites-PVA nanocomposites had lower thermal stability and more influenced optical clarity than those of the sepiolite PVA, at the same filler levels.

Poly(ethyl methacrylate) (PEMA) and poly(2-hydroxyethyl methacrylate) (PHEMA) nanocomposites with sepiolite in pristine and silylated form were prepared using the solution intercalation method and characterized by the measurements of XRD, TEM, FTIR-ATR, TG/DTG, and DSC. The TEM analysis indicated that the volume fraction of fibers in sepiolite decreased and the fiber bundles dispersed in PEMA and PHEMA at a nanometer scale. These results regarding TEM micrographs were in agreement with the data obtained by XRD. The increase in thermal stability of nanocomposites of PEMA is higher than that of PHEMA according to the data obtained from TG curves. The DTG analysis revealed that sepiolite/modified sepiolite caused some changes, as confirmed by FTIR in the thermal degradation mechanism of the polymers. T g temperatures of PEMA and PHEMA usually increased upon the addition of sepiolite/modified sepiolite. In addition, modification of sepiolite with 3-APTS had a slight influence on thermal properties of the nanocomposites.

The effect of different chemical oxidation of multiwalled carbon nanotubes with H2O2, HNO3, and KMnO4on the change of electrical resistance of polyurethane composites with embedded oxidized nanotube networks subjected to elongation and bending has been studied. The testing has shown about twenty-fold increase in the electrical resistance for the composite prepared from KMnO4oxidized nanotubes in comparison to the composites prepared from the pristine and other oxidized nanotubes. The evaluated sensitivity of KMnO4treated composite in terms of the gauge factor increases with strain to nearly 175 at the strain 11%. This is a substantial increase, which ranks the composite prepared from KMnO4oxidized nanotubes among materials as strain gauges with the highest electromechanical sensitivity. The observed differences in electromechanical properties of the composites are discussed on basis of their structure which is examined by the measurements of Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscope. The possible practical use of the composites is demonstrated by monitoring of elbow joint flexion during two different physical exercises.

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In this study, the solution‐mixing method was used to prepare polymethacrylate derivatives' (PaMAs) nanocomposites with kaolinite. It was observed that the resultant materials could include exfoliated, intercalated, and undispersed kaolinite depending on their XRD patterns. TEM micrographs also revealed that platy and tube structures of kaolinite and their stacked form would disperse in the PaMAs. Therefore, they were called PaMAs–kaolinite materials with mixed morphology. The effects caused by different types of PaMA, solvent, and clay (sepiolite and kaolinite) on the thermal properties of these materials were examined. When the thermal stability of the materials was compared on the basis of the functional groups in the PaMAs, it was seen that the materials of the linear PaMAs with kaolinite usually had better thermal stability than that of the ring PaMAs and also seen that the thermal stability of Kao‐PaMAs increased from PMMA to poly(ethyl methacrylate) (PEMA) and poly(butyl methacrylate) for linear PaMAs. The solvent type affected the thermal stability and the glass transition temperature of the PaMAs. It was found that THF is the most suitable solvent for increasing thermal stability of the PaMAs in the presence of kaolinite; however, it is difficult to say the same about their Tg temperatures. In addition, the thermal stabilities of PEMA and poly(2‐hydroxylethyl methacrylate) were higher in the presence of kaolinite in comparison with sepiolite. The results obtained in this study were explained by the utilization of the relationships among their solubility parameters and of the interactions among the PaMAs, clays, the modifier (octadecylamine) and solvents. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

The atmospheric pressure plasma jet (APPJ) was used to enhance the sensitivity of industrially important polyaniline (PANI) for detection of organic vapors from amides. The gas sensing mechanism of PANI is operating on the basis of reversible protonation or deprotonation, whereas the driving force to improve the sensitivity after plasma modifications is unknown. Herein we manage to solve this problem and investigate the sensing mechanism of atmospheric plasma treated PANI for vapor detection of amides using urea as a model. The results from various analytical techniques indicate that the plausible mechanism responsible for the improved sensitivity after plasma treatment is operating through a cyclic transition state formed between the functional groups introduced by plasma treatment and urea. This transition state improved the sensitivity of PANI towards 15 ppm of urea by a factor of 2.4 times compared to the non-treated PANI. This plasma treated PANI is promising for the improvement of the sensitivity and selectivity towards other toxic and carcinogenic amide analytes for gas sensing applications such as improving material processing and controlling food quality.