Light scattering and transmission studies of nanofiller particulate size, matrix cavitation, and high strain interfacial dewetting behavior in silica-elastomer composites.

The effect of silica nanofiller surface chemistry on compounded particle size and high strain particle dewetting in a semitransparent nanosilica-filled elastomer composite was determined using backscattered visible light and transmitted light, respectively. The integrated intensities of backscattered light from the samples were collected at various visible wavelengths for thin-film composites using ultraviolet-visible spectrometer with an integrating sphere. The data revealed strong Rayleigh-type scattering from compounded filler particles. Size information was extracted and found to broadly correlate with scanning electron microscopy image analysis of fracture surface. Incorporation of a siloxane surface treatment chemical during compounding resulted in a reduced average filler particle size in the cured composite. On extension of the samples, an optical transition was observed only in the filled composites. At high strains, the semi transparent samples displayed an abrupt drop in transparency becoming opaque. This was quantified using a simple light transmission-sample extension technique. Strain-induced crystallization was discounted as the cause for the transition by X-ray diffraction analysis. The onset yield stress for the optical transition was found to be filler surface-chemistry-dependent with the siloxane-treated filler exhibiting a greatly increased onset stress value. These observations were discussed and rationalized in terms of filler particle-matrix dewetting and cavitation at high strains. Matrix-filler dewetting was distinguished from matrix cavitation by comparison with Beer-Lambert behavior derived from unstrained samples. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011. [ABSTRACT FROM AUTHOR]