As seen from Fig. 8 and Table 4, the tan d value shows a
marked decrease in the presence of filler that corresponds
with the trend: carbon black < silica < OPA. This can be a
consequence of fillers carrying greater stress hence less
energy dissipation occurs in the filler-filled vulcanizates.
Also, the tan d shows the amount of matrix material that is
capable of relaxation, depending on the filler content and
the restriction of chain mobility within the interphase of
NR matrix and reinforcing filler [16], thus resulting in the
tan d value for OPA being higher than silica-filled vulcanizates.
The Tg of gum NR vulcanizates (78 C) was
increased when filled with silica (73 C) and carbon black
(71 C). The positive shift toward higher temperature may
be linked to strong filler-rubber interaction. However