SilicaePMMA nanocomposites with different silica quantities were prepared by a melt compounding\ud method. The effect of silica amount, in the range 1e5 wt.%, on the morphology, mechanical properties\ud and thermal degradation kinetics of PMMA was investigated by means of transmission electron\ud microscopy (TEM), X-ray diffractometry (XRD), dynamic mechanical analysis (DMA), thermogravimetric\ud analyses (TGA), Fourier-transform infrared spectroscopy (FTIR), 13C cross-polarization magic-angle\ud spinning nuclear magnetic resonance spectroscopy (13C{1H} CP-MAS NMR) and measures of proton spinlattice\ud relaxation time in the rotating frame (T1r(H)), in the laboratory frame (T1(H)) and cross-polarization\ud times (TCH). Results showed that silica nanoparticles are well dispersed in the polymeric matrix\ud whose structure remains amorphous. The degradation of the polymer occurs at higher temperature in\ud the presence of silica because of the interaction between the two components

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This article describes the results of an investigation on the influence of titania nanoparticles on the morphology and properties of vulcanized natural rubber (NR)/ethylene‐propylene‐diene monomer (EPDM) blends. The samples were prepared through roll‐milling and melt‐pressing and diphenyl guianidine was used as vulcanization accelerator. The transmission electron microscopy (TEM) and X‐ray diffraction (XRD) results show that the titania particles are concentrated in the NR phase, and that the presence of titania in EPDM seems to initiate the formation of crystals in the rubber phase. From the dynamic mechanical analysis (DMA) and tensile testing results it is clear that the presence of titania particles inhibited the vulcanization process in both the investigated rubbers, and that the mechanical properties of the nanocomposites were influenced by the interaction between the nanoparticles and the rubber, the reduced vulcanization of the two rubber phases, and the development of crystallinity in EPDM. The thermogravimetric (TGA) results show improved thermal stability of EPDM, and of the EPDM phase in the blend, for the samples containing titania nanoparticles. POLYM. COMPOS., © 2011 Society of Plastics Engineers.

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The properties of untreated sugar cane bagasse (SCB) and soft wood (SW) and their respective celluloses were investigated. The celluloses indicated improved crystallinity index values and decreased concentration of lignin and hemicellulose compared to their untreated counterparts. Three degradation models, Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (OFW), and Kissinger (KGR) methods were employed to determine apparent activation energy values. Generally, the thermal degradation processes of both sugarcane bagasse and soft wood included dehydration, degradation of hemicellulose and cellulose, whereas the lignin degraded from the degradation temperature of hemicellulose to the end of the cellulose. The apparent activation energy values obtained from the OFW and KAS models vary with the degree of conversion, and showed similar trends. The activation energies obtained by KGR were relatively lower than those obtained from the KAS and OFW methods.

Abstract. Zirconia nanoparticles were synthesized by means of a sol-gel method and embedded in poly(methyl methacrylate) (PMMA) by melt compounding. The zirconia was well dispersed in the PMMA matrix, with only a few clusters, especially for the highest investigated zirconia content. NMR results showed heteronuclear dipolar interactions involving the carbons and the surrounding hydrogen nuclei. The effect of the amount of zirconia, in the range of 1-5!wt%, on the thermomechanical properties and thermal degradation kinetics of PMMA was also investigated by means of dynamic mechanical analysis (DMA), thermogravimetric analyses (TGA), and Fourier-transform infrared spectroscopy (FTIR). The presence of zirconia showed a decrease in the storage and loss moduli at lower temperatures, probably due to a plasticization effect. The presence of zirconia in PMMA slightly increased its thermal stability, but the activation energies of thermal degradation for the nanocomposites were significantly lower, at degrees of conversion higher than 0.3, than those of pure PMMA.

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a b s t r a c tPolycarbonate/silica nanocomposites with different silica quantities were prepared by a melt compounding method. The effect of silica amount, in the range 1-5 wt.%, on the morphology, mechanical properties and thermal degradation kinetics of polycarbonate (PC) was investigated. Clusters of silica nanoparticles were well dispersed in the polycarbonate whose structure remained amorphous. NMR results showed intermolecular interactions involving the carbonyl groups of different polymeric chains which did not affect the intramolecular rotational motions. The presence of the lowest silica content showed a decrease in the storage and loss moduli below the glass transition temperature, probably due to a plasticization effect. However, an increase in the amount of silica increased the moduli. The presence of silica in PC slightly increased the thermal stability, except for the highest silica content which showed a decrease. The activation energies of thermal degradation for the nanocomposites depended on the amount of silica and on the degree of conversion.