EPDM rubber reinforced with titania generated by nonhydrolytic sol-gel process

EPDM rubber was reinforced with titania in situ generated by using a nonhydrolytic sol-gel (NHSG) process starting from TiCl4 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 sug- gested 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. Quasi- static and dynamic-mechanical characterizations indicated that the presence of titania as rigid filler in both the unvul- canized 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 val- ues predicted by classical equations suggesting an addi- tional stiffening contribution deriving from the molecular interaction between the rubber and the filler.