Blends of ultrasonically devulcanized and virgin carbon black filled ethylene–propylene–diene monomer rubbers

Ultrasonically devulcanized ethylene–propylene–diene monomer (dEPDM) rubber was blended with virgin ethylene–propylene–diene monomer (vEPDM) rubber. The properties of these blends were investigated and compared with those of blends of ground ethylene–propylene–diene monomer (gEPDM) and vEPDM. The dynamic properties and curing characteristics were studied. The dynamic properties of the uncured blends showed that the gEPDM/vEPDM compounds were more elastic than the dEPDM/vEPDM compounds at a low frequency range, whereas the opposite trend was observed at a high frequency range. In contrast, the dynamic properties of gEPDM/vEPDM vulcanizates were less elastic than those of dEPDM/vEPDM vulcanizates at a low frequency range. The curing characteristics of the blends indicated that an increase in the dEPDM content in the dEPDM/vEPDM blends reduced the scorch time and the maximum torque and increased the minimum torque. A similar but more pronounced tendency was also found for the gEPDM/vEPDM blends. The tensile properties of the dEPDM/vEPDM vulcanizates were much better than those of the gEPDM/vEPDM vulcanizates, indicating the significant benefit of ultrasonic devulcanization.