Carbon Coated Silica For Elastomer Reinforcement
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Carbon Coated Silica For Elastomer Reinforcement D. Kohls1, G. Beaucage1,*, S.E. Pratsinis2, H. Kammler2, G. Skillas1,2 1 Department of Materials Science and Engineering, University of Cincinnati, Cincinnati, OH 45221-0012 USA 2 Institute of Process Engineering, ETH Zentrum ML F26, CH-8092 Zürich, Switzerland *Author to whom correspondence should be addressed. Key words: carbon coated silica, elastomer reinforcement, fractal, scattering ABSTRACT Carbon coated silica made by flame synthesis was investigated for reinforcement of styrene-butadiene (SBR) rubber. These composite silica/carbon fillers were examined through small angle x-ray scattering (SAXS), TEM, and AFM showing that these fillers have a rough fractal surface and have fractal aggregate structures. The carbon coated silica fillers were compounded with elastomers and their effect on reinforcement was measured using dynamic mechanical analysis and tensile testing. These fillers were also compared to commercial fumed silica, carbon black, and carbon black/silica composite fillers. INTRODUCTION Filled elastomer systems have been studied extensively over the past several decades, especially in application to tire performance. During this time, many attempts have been made to explain reinforcement of an elastomer when fillers are added. These reinforced properties include enhanced strength, modulus, abrasion resistance, and dynamic mechanical properties. Several approaches have been used to separate the contributing influences and to explain how they work. The majority of these approaches look at the structure and property relationships of the fillers and rubbers independently and as a synergistic combination. These approaches have evolved into the following major areas: filler structure, hydrodynamic reinforcement, and interactions involving fillers and elastomers. The majority of these studies focused on conventional carbon black with more recent studies focusing on silica as an alternative filler for reinforcement. Recently a series of studies was performed by Wang1,2,3 on the use of a new carbon black/silica hybrid filler referred to as Ecoblack or carbon-silica dual phase fillers. These fillers consist predominately of carbon black with a low percentage of silica (3-5%). By introducing a small percentage of silica into the carbon black, the filler-polymer interaction is decreased compared to a blend of carbon black and silica while the filler-filler interaction is decreased compared to conventional carbon black. It was shown that this leads to a decrease in hysteresis at higher temperature for the carbon-silica filled compounds.4 Studying the morphology and structure of fillers requires several techniques that probe a broad size scale (nm-µm) and describes different structural features. Fillers are made up of primary particles at the smallest size scale, Ångstrom to micron, which are bonded to other primary particles to form an aggregated structure. The aggregates range from the nanometer to micron size range and these can interact with other aggregates th
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