Improving the properties of reclaimed waste tire rubber by blending with poly(ethylene-co-vinyl acetate) and electron beam irradiation

Non-degradable waste tire generation around the world is growing at an alarming rate. Diversifying the recycling route of these waste tires is essential to solve the problem. One way is to incorporate them into polymers and convert them into new products. However, incorporation of ground tire rubber into thermoplastics has been hampered due to lack of toughness and adhesion between phases. To address the issue, this study utilized reclaimed waste tire rubber (RTR) instead; and evaluated the properties of RTR and poly(ethylene-co-vinyl acetate) (EVA) blends. The properties of the RTR/EVA blends were further enhanced by compatibilization and electron beam irradiation. Processing, mechanical, thermal and dynamic mechanical properties of RTR were tremendously improved by blending with EVA. However, the interfacial adhesion was found to lack in the blends. Compatibilization by reactive, physical and combination strategies were explored utilizing (3-Aminopropyl)triethoxy silane (APS), liquid styrene butadiene rubber (LR) and maleated EVA (MAEVA), respectively. APS and MAEVA were found to be the most and least favourable compatibilizer, respectively. Apart from functioning as reactive compatibilizer, APS also reclaimed the RTR phase further. These lead to improved dispersion of smaller RTR phase in EVA matrix and enhanced the interfacial adhesion. Electron beam irradiation revealed the presence of radical stabilizing and scavenging additives within RTR which retards the crosslinking process in RTR and RTR/EVA blends. Though chain scissions were predominant; study showed the replacement of S-S and S-C bonds with stronger and stiffer C-C bonds ensures the retention of RTR and RTR/EVA blends properties upon irradiation. Compatibilization of RTR/EVA blend by APS (50RTR/5APS) also improved the crosslinking efficiency. However, the blend still suffered from oxidative degradation from irradiation in air. Radiation sensitizers, trimethylol propane triacrylate (TMPTA), tripropylene glycol diacrylate (TPGDA) and N,N-1,3 Phenylene Bismaleimide (HVA2), were used to accelerate the irradiation induced crosslinking in RTR and 50RTR/5APS blends. Presence of radiation sensitizers leads to simultaneous improvement in toughness and tensile strength of RTR and 50RTR/5APS blends. Elastic capacity of RTR phase was restored and interfacial adhesion enhanced in the presence of radiation sensitizers.