No abstract

No abstract

ABSTRACT:In this study, bleached Eucalyptus fibers obtained by a Kraft pulping process were characterized prior to and after chemical modification with a silane coupling agent, vinyltriethoxysilane, for use as an alternative additive in composites based on silicone. The presence of a silane coating on the fiber surface was observed by infrared, energy dispersive, and X-ray photoelectron spectroscopies. The morphology of the fibers was investigated by field emission scanning electron microscopy. The untreated fibers were ribbon-shaped and had a rough surface, due to the presence of fibrils. The coating reaction conducted in ethanol gave rise to loose fibrils and a more rough surface compared with those of untreated fibers. A smoother surface was observed when fibers were modified in tetrahydrofuran. The surface topography of the fibers was also examined by atomic force microscopy.

In this investigation, the preparation and characterization of partially pyrolyzed membranes based on poly(dimethylsiloxane) (PDMS) are described. These membranes were obtained by the crosslinking of silanol‐terminated PDMS with multifunctional nanoclusters derived from the reaction of pentaerythritoltriacrylate with 2‐aminoethyl‐3‐aminopropyltrimethoxysilane and the in situ polycondensation of tetraethylortosilicate, followed by the thermal treatment of the resulting membranes at different temperatures. The partially pyrolyzed membranes were characterized with infrared spectroscopy, thermogravimetry, elemental analyses, dynamic mechanical analysis, small‐angle X‐ray scattering, and scanning electron microscopy. The membranes exhibited improvements in the thermal stability and mechanical strength. Even with distinct compositions with respect to the Si/O and Si/C ratios, the flexibility of these materials was maintained. The flux rates of the gases through the membranes were measured for N2, H2, O2, CH4, and CO2, at 25 °C. The permeability of the membranes changed with increases in the pyrolysis and oxidation temperatures. These membranes could be described as PDMS chains separated by inorganic clusters. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 299–309, 2007.

Silicone composites reinforced with short eucalyptus pulp fibers were obtained. The composites were prepared with untreated fibers and with fibers modified with a silane coupling agent, vinyltriethoxysilane, with tetrahydrofuran or ethanol as a solvent. The surface treatment improved the adhesion at the fiber-matrix interface, and vinyltriethoxysilane was suitable for forming a covalent and nonhydrolyzed interface in the composites. The thermal stability of the composites was lower than that of the silicone matrix, with a distinct mechanism of degradation, because of the presence of the cellulosic fibers in the composite. The tensile properties of the composites depended more on the fiber dispersion in the matrix than on the nature of the interface.

Os basaltos são rochas vulcânicas abundantes provenientes de extensos derrames de lava. A tecnologia de fiação contínua produz filamentos de basalto na forma de fios micrométricos amorfos. Neste trabalho são apresentados resultados da caracterização térmica e morfológica de fibras longas de basalto, de diâmetro micrométrico. Estas fibras apresentaram excelente estabilidade térmica, resultando em alterações de massa menor que 1% sob aquecimento até a temperatura de 1000 ºC, em atmosfera inerte ou oxidante. Por outro lado, a ~ 800 ºC ocorreu a cristalização parcial das fibras de basalto, com a formação de fases cristalinas de silicatos e alumino-silicatos, como a anortita, da classe dos plagioclásios. A morfologia das fibras, aquecidas a 1000 ºC, foi alterada devido à fusão e cristalização das fases presentes.

No abstract

No abstract