ABSTRACT:Two organofunctional silanes and a copolymer were used to increase the interfacial adhesion in glass fiber polypropylene (PP) reinforced composites. The performance of the coupling agents was investigated by means of mechanical property measurements, scanning electron microscopy (SEM), and dynamic mechanical analysis. The increased adhesion between the glass fibers and PP matrix observed with SEM resulted in an improvement of the mechanical and dynamic mechanical properties of the composites. Coupling achieved with the copolymer poly(propylene-g-maleic anhydride) (PP-g-MA) proved to be the most successful compared with 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane. The combination of PP-g-MA with the silanes resulted in further property improvements because of the ability of the MA groups to react with the amino groups of the silanes.

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Two organofunctional silanes and three functionalized copolymers were used as adhesion promoters in glass fiber/polyethylene-reinforced composites. The performance of the coupling agents was investigated by mechanical property measurements, scanning electron microscopy, and dynamic mechanical analysis. Coupling achieved with the poly(ethylene-g-maleic anhydride) copolymer proved to be the most successful compared with the other copolymers (ethylene/vinyl alcohol, ethylene/acrylic acid) and silane agents (␥-methacryloxypropyltrimethoxy, cationic styryl). The combined coupling performance of the silanes and copolymers examined in this study appears to be controlled by the coupling performance of the copolymer. Effective coupling was reflected in increased mechanical properties. Increased fiber/matrix adhesion is not always associated with effective coupling because structural changes occurring at the interface region can result in a deterioration of the material property.

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An experimental study of the effect of surface roughness and crystallinity on the light scattering of polyethylene tubular blown films is reported. Several films were prepared by varying the raw polyethylenes and the extrusion temperature. Other processing variables were maintained constant. We have made a statistical analysis of data and we have obtained multiple regressions between light scattering for a given wavelength of incident light and a given film thickness (30 pm, 50 pm, and 70 pm) and the independent variables average surface roughness and degree of crystallinity. It was demonstrated that, for the polymeric films studied, the surface texture evaluates better than crystallinity the variation of light scattering, but crystallinity has also some importance.

A study is reported on the effect of the filler size and concentration on the electrical resistivity, density, and hardness of composites made of copper powder embedded in nylon 6 matrix by means of compression molding. The electrical resistivity of the composites is > 1011 ohm·cm unless the metal content reached the percolation threshold, beyond which the resistivity decreased markedly by as much as 1012. The percolation concentration was found to decrease with a decrease in the average particle diameter. The density of the composites was measured and compared with values calculated assuming different void levels within the samples. However, there is no sharp variation in the density due to the onset of percolation. Furthermore, it is shown that a percolation concentration can be also defined in the hardness/metal concentration curves as the intercept of linear regression curves of the low and high metal content regimes, respectively.

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