Ground tire rubber filled low-density polyethylene: The effect of particle size

In the present study, we investigated the possibility of value-added recycling of ultrafine ground tire rubber (uGTR) produced from water jet milling, with an average particle size of a few tens of microns. Our goal was to compare the properties of blends with different uGTR and conventional fine ground tire rubber (fGTR) contents prepared by blending with low-density polyethylene (LDPE). We also aimed to explore the property changes caused by the larger specific surface area due to the size effect. Samples were prepared with a hydraulic press after internal mixing. In the case of ground tire rubber (GTR) filled mixtures, the tensile properties showed rubber-like characteristics: with a significant decrease in modulus, elongation at break remained high, and tensile strength slightly decreased. The fracture surfaces of the samples were analyzed by scanning electron microscopy (SEM), wherein the case of materials made with uGTR showed better adhesion between the phases. In order to investigate the interfacial adhesion between the GTR and LDPE, we performed dynamic mechanical thermal analysis (DMTA). The glass transition peak of the uGTR shifted to a higher temperature and the storage modulus was higher than in the case of samples containing fGTR. Finally, we determined the Shore D hardness of the materials, which decreased with increasing GTR content, but hardness was greater in the case of uGTR samples. The better mechanical properties of blends containing uGTR were explained by better interfacial adhesion between the two phases due to the significantly higher specific surface area compared to fGTR.