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EPDM rubber was reinforced with titania in situ generated by using a nonhydrolytic sol-gel (NHSG) process starting from Ti[Cl.sub.4] as titania precursor and tert-butanol as oxygen donor. Titania particles in anatase form and with average diameter of 6 nm were synthesized via NHSG route and then the same procedure was adopted in presence of EPDM rubber to obtain composites containing up to 30 wt% of filler. Extraction and equilibrium swelling tests suggested an interfering effect of the NHSG reaction on the vulcanization process of the rubber resulting to a crosslink density which decreased in the presence of titania. Quasistatic and dynamic-mechanical characterizations indicated that the presence of titania as rigid filler in both the unvulcanized and vulcanized EPDM matrix led to a significant increase in stiffness and stress at break. The experimental values of modulus were systematically higher than the values predicted by classical equations suggesting an additional stiffening contribution deriving from the molecular interaction between the rubber and the filler., INTRODUCTION Organic-inorganic hybrid nanocomposites represent not only a new field of basic research but also, thanks to their remarkable new properties and multifunctional nature, hybrids offer prospects for many new [...]

This article is concerned with the preparation of a filled elastomer by means the nonconventional bottom-up approach to polymer composites, alternatively with the conventional mechanical compounding of preformed filler particles with rubber. EPDM rubber was modified with in situ generated silica particles prepared by means of a sol-gel process adopting a solution process. The used synthetic procedure permitted the preparation of highly filled rubbers (up to 40 wt % of silica) with silica particle dimensions ranging from 0.2 to 2 μm. Equilibrium swelling and extraction tests indicated a hindering effect of the presence of in situ generated silica on the vulcanization process which reduced the cross linking degree of the rubber matrix. Both tensile tests and dynamic-mechanical analysis showed a significant improvement in the mechanical properties due to the presence of the reinforcing filler, with an enhancement more significant than that expected from a simple hydrodynamic reinforcing mechanism. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]