Thermoplastic dynamic vulcanisates containing LDPE,rubber, and thermochemically reclaimed ground tyre rubber

Abstract

Thermochemically devulcanised ground tyre rubber (GTR^DL) was added to fresh rubber compositions, which were then melt blended with low density polyethylene (LDPE). Styrene/butadiene rubber (SBR), natural (NR), and ethylene/propylene/diene (EPDM) rubbers were selected as the fresh rubbers. During blending, dynamic curing was achieved using sulphuric, phenolic, and peroxide curing agents. Some of the GTR was decomposed in the presence of 6 phr Regen^TM Agent-S reclaiming compound before being incorporated into the blends. The resulting thermoplastic dynamic vulcanisates had constant compositions, namely LDPE/rubber/GTR=50:25:25. Sulphuric and phenolic curing agents proved to be most suitable for dynamic curing. The thermoplastic dynamic vulcanisates with the best mechanical performance contained SBR and EPDM rubbers. The observed improvements in mechanical performance were attributed to chain entanglement and co-crosslinking in the interphase between the GTR^DL particles and the surrounding matrix (i.e. with the fresh rubber and/or LDPE). The phase morphology, which was assessed using scanning electron microscopy on the etched surfaces of cryogenically fractured thermoplastic dynamic vulcanisate compositions, is discussed.