Effects of Ground Rubber Loading on Rubber Compounds Studied by the Hyphenated Rheo‐NMR and the Palierne Model

This article investigates the effect of ground rubber (GR) loading of rubber compounds using the unique hyphenated Rheo-NMR setup. This setup is used to quantify the effects on the rheological behavior as an emulsion-like blend as well as of the further vulcanization of the GR particle due to sulfur diffusion. The GR as a sustainable component of rubber compounds affects engineering properties. This can be explained by the diffusion of free sulfur from the rubber matrix into the GR particles, resulting in a change in cross-link density (CLD) in the matrix and the GR particles. Another effect that occurs is the emulsion-like blend of GR particles within the rubber matrix describable by adequate constitutive emulsion models. Rubber compounds of styrene-butadiene rubber (SBR) and natural rubber (NR) were used both for the rubber matrix and the self-produced GR. The predictions by the Palierne model describe the rheology with a deviation of up to 15%. NMR results of the GR particle show an increase of 100% in CLD for NR, while SBR shows a decrease of around 13%. Such results have not covered in the literature so far and are of great importance to optimize recycling of rubber materials.