Improvements of Nanofiller-Elastomer Systems by Filler Modification and Tailored Mixing Techniques

Abstract

Elastomers are a unique material group due to their ability of high reversible deformation under stress. In actual practice, the mechanical properties of pure rubbers are not sufficient for everyday applications and their performance is typically improved by reinforcing fillers such as carbon black and silica. Nevertheless, these conventional fillers have some drawbacks, which can be overcome by developing new filler systems. Nano-size fillers result in high reinforcing potential for different polymers. The improvements in properties are mainly due to the large surface areas of tiny particles. Due to difficulties in mixing them into an elastomeric matrix, full reinforcing potential cannot be utilized yet. Therefore, research on nanofiller systems and related mixing techniques is required.<br/><br/>The objective of this thesis was to study the ability of the new filler systems to tailor the properties of elastomeric materials for applications requiring good mechanical and dynamic properties, in this case tyre tread. The experiments were performed by replacing the small amounts of carbon black by layered silicates, halloysite nanotubes and carbon nanotubes. The effect of replacement on the dispersion of the filler system and on the vulcanization, mechanical and dynamic properties of rubber was analysed. The approach was to improve the compatibility of filler and polymer by the surface modification of nanofillers.<br/><br/>It was observed that the partial replacement of very reinforcing carbon black by the nanofillers using traditional mixing techniques has only minor effect on the mechanical properties of rubber. Therefore, nanoclays and carbon nanotubes have a comparable reinforcing effect to carbon black, but additionally the partial replacement of carbon black by those reduces stiffness and improves dynamic properties such as the loss factor of rubber. Moreover, it was found that a blend of two fillers improves the dispersion and distribution of fillers, and that, with these hybrid fillers, sufficient dispersion of nanofiller loadings up to 5 phr can be achieved by traditional mixing methods. Masterbatch mixing is a way to facilitate the dispersion of carbon nanotubes and to prevent health and environmental risks possible during the mixing of nanoparticles.