The low torque value for the blends is associated
with the low viscosity of the PS phase compared to NR. Unattached
PS chains can also reduce the cohesion of the rubber matrix by hindering
the sulphur crosslinks although at some stage the grafted
copolymer may attain somewhat higher torques because of the
interlinking of different polymer chains. The latter effect is presumably
of low magnitude considering that NR exhibits a still
higher value of torque.