Ground tire rubber (GTR) surface modification using thiol-ene click reaction: Polystyrene grafting to modify a GTR/polystyrene (PS) blend

In this work, a thiol-ene click reaction was used to graft polystyrene (PS) chains onto the surface of ethylene propylene diene monomer-based ground tire rubber (GTR). A thiol-terminated PS (11 kg mol−1) was selected, due to its commercial availability, to modify a postconsumer GTR. The resulting PS-grafted GTR (GTR-g-PS) particles were analyzed via Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) to detect surface changes on treated samples. An increase in aliphatic and aromatic carbon atoms was observed by FTIR and XPS, while grafted material was observed by SEM on the GTR surface, confirming that grafting took place. Then, composites were prepared from these GTR-g-PS particles and from PS by solution evaporation, at 50 wt%. A significant increase in tensile (20%) and storage moduli (from 80% at 65°C to 510% at 95°C) was observed by dynamic mechanical thermal analysis when compared to composites prepared with untreated GTR. In addition, GTR samples showed improved thermal resistance, as attested by the shift in degradation temperature for 10% mass loss (from 400°C for GTR to 450°C for GTR-g-PS). This increases the possible range of processing temperature and service temperature (applications) for introduction of GTR in other polymer matrices.