The devulcanization reaction of waste ethylene-propylene-diene monomer rubber (W-EPDM) during melt extruding process mixed with unvulcanized EPDM was investigated through a compound-induced reaction by increasing the screw rotation speed and being in the presence of different subcritical fluids in a twin screw extruder. The effects of subcritical fluids (water

ethanol/water mixture and propanol)

screw rotation speed and devulcanizaion accelerators (alkylphenol polysulfides 450 and DADS) on the gel content

mooney viscosity

FT-IR spectra of the sol of devulcanized blends (DEPDM/EPDM) and the mechanical properties of dynamically crosslinked thermoplastic elastomer((DEPDM/EPDM)/PP) prepared by devulcanization blends and PP were measured

and fracture surface morphology of dynamically crossinked thermoplastic elastomer (DEPDM/EPDM)/PP was also observed by SEM. The results show that subcritical ethanol/water mixture or propanol has a better selectivity on S—S bond cleavage

leading to increase of the cleavage reaction of crosslinked S—S bonds and decrease of cleavage reaction of the main bonds in crumb rubber crosslinked network. The size of unmelted particles in dynamically crosslinked thermoplastic elastomer becomes smaller. The mechanical properties of revulcanized material increased significantly. The devulcanization accelerator alkylphenol polysulfides 450 has significant role in promoting devulcanization. The tensile strength and elongation at break of dynamically crosslinked thermoplastic elastomer (DEPDM/EPDM)/PP reaches to 17.1MPa and 443% respectively when the screw rotation speed and devulcanization reaction temperatures exist optimum value (220℃

600rpm) in the presence of subcritical propanol. The mechanical properties and facture surface morphological structure of it was significantly better than those of the corresponding material obtained by conventional devulcaniztion tank.