Dynamic damping properties of thermoplastic elastomers based on EVA and recycled ground tire rubber

Abstract
Recycling waste tires being important for both economical and environmental reasons, ground tire rubber can be blended to other polymers, modifying their properties. In order to characterize and explain these modifications, an experimental study was carried out concerning the improvement on the dynamic damping properties when adding recycled ground tire rubber (GTR) fillers to an elastomeric matrix (Ethylene Vinyl Acetate EVA). To evaluate the influence of both the ground tire rubber and the porosity in a GTR/EVA composite, three samples have been elaborated by injection: the EVA matrix alone, a GTR/EVA composite and a GTR/EVA porous composite. Dynamic measurements of the samples were performed using Dynamic Mechanical Thermal Analysis ‘DMTA’. The Young's modulus and loss factor of these materials are estimated by using the frequency-temperature equivalence introduced by Williams-Landel-Ferry (WLF) expanding the measurement of the dynamic properties over a wider range of frequencies. This method showed that in low frequency bandwidth the loss factor has been improved by the addition of GTR to the EVA matrix. The α-relaxation activation energy showed lower activation energy for both of the GTR filled composites leading to the conclusion that the mobility of the polymer chains has been improved by addition of GTR. The impact behavior study carried out using a weight drop-test experiment also concluded to better impact energy absorption for the GTR filled composites at the expense of a larger maximum strain.