The maximum torque (S0
MH), minimum
torque (S0
ML), torque difference (S0
MHML), scorch time (ts2) and cure time (tc90) of
carbon-black-filled NR/EPDM or NR/R-EPDM blends increased with increasing weight ratio
of virgin EPDM or R-EPDM in the blend. SEM micrographs proved that, for low weight
ratios of virgin EPDM or R-EPDM, the blends exhibited high surface roughness and matrix
tearing lines. The blends also showed a reduction in crack path with increasing virgin
EPDM or R-EPDM content over 30 phr. This reduction in crack path could lead to less
resistance to crack propagation and, therefore, low tensile strength.