Filler Phase Distribution in Rubber Blends Characterized by Thermogravimetric Analysis of the Rubber-Filler Gel

Abstract

Abstract The analysis of the rubber-filler gel of carbon black filled rubber compounds and blends provides useful information about the mixing process taking place inside the internal mixer. A new measure technique named wetting rate was introduced to describe the wetting behavior of the rubber onto the filler. Natural rubber (NR)/styrene-butadiene rubber (SBR) blends has been used for experimental investigation. NR shows a significantly higher wetting rate than SBR. The wetting rate does not only depend on the viscosity of rubber but strongly on the functionalization of it. Using the data determined from the thermogravimetric analysis (TGA) of rubber-filler gel, a new method was developed to characterize the kinetics of carbon black (CB) localization in the phases of heterogeneous rubber blends. During the first mixing stage, the CB localization is affected strongly by the wetting rate ratio of the blend components. In the second mixing stage, the rubber-filler interaction dominantly influences the distribution kinetics of the filler to the phases. Because of the higher wetting rate of the NR component, in the investigated NR/SBR blends more CB is found in the NR phase than in the SBR phase. The effect of the matrix viscosity and polarity on the phase specific CB distribution was systematically investigated.