Abstract: The effects of screw rotation speed, extrusion temperature and the addition of devulcanizing agents (2butyl alcohol, nbutyl amine, and alkyl phenol disulfide 420 or 450) on the various behavior of mixtures of ground tire rubber (GTR) and PEHD were investigated. The high shear stress during melt extruding induced chain scission and oxidative degradation of the crosslinking network of the ground tire rubber, leading to the decrease of the gel content of the devulcanized blends, the increase of their melt flow rate, and the decrease of the size of gel grain in dynamic vulcanized PEHD thermoplastic elastomer. The four devulcanizing agents all accelerated the devulcanization reaction during the extruding process, especially the alkyl phenol disulfide 450 and nbutyl amine achieved a better accelerating effect. In the best devulcanization condition (240 ℃ and 1000 r/min and in presence of nbutyl amine), the tensile strength and elongation at break of a dynamically vulcanized devulcanized blends/EPDM thermoplastic elastomer reached 12.5 MPa and 440.6 %, respectively.

Key words: ground tire rubber, stress-induced reaction, devulcanization, dynamic vulcanized, thermoplastic elastomer