Effect of Silica Phase on Certain Properties of Natural Rubber Based Composites Reinforced by Carbon Black/Silica Hybrid Fillers

Abstract

The paper reports on the effect that the silica phase has upon certain characteristics of hybrid fillers obtained via impregnation of two completely different types of conventional carbon black, namely oil absorption number, iodine adsorption, specific surface area, etc. The article also presents their dynamic mechanical and electrical properties, as well as the homogeneity of natural rubber based composites comprising those fillers. It has been found that, the silica phase, depending on its amount (3 or 7%), changes considerably both the main characteristics of the fillers (ash content, specific surface area, oil absorption number, iodine adsorption number, etc.) and their thermal behaviour. The increase in the amount of silica phase leads to a decrease of the storage modulus, while the mechanical loss angle tangent increases during the transition from the glass into rubbery state. The changes in those parameters are related first of all to the changes in the elastomer-filler and filler-filler interactions, to the mobility of elastomer chains and to the relaxation processes. The higher silica content, the higher the surface and volume resistivity of the composites are. On the other hand, the fillers homogeneity worsens depending on the grade of silica phase dispersion along the hybrid filler.