The effects of ALK on the cure characteristics of the
silica-filled NR compound can be seen in Fig. 3 and Table 5.
Fig. 3 shows that the scorch and the cure times decreased
with increased ALK loading. It was observed that there was
an enhancement in the cure characteristics, indicating that
ALK could act as a co-curing agent or secondary accelerator
in the curing process of the silica-filled NR compounds. The
cure enhancement can be attributed to the amine content
of the ALK. Amine is an alkaline substance which will increase
the pH of the rubber compound and, in most instances,
enhance the cure rate. Any material that makes the
rubber compound more basic will enhance the cure rate
since acidic materials tend to retard the effect of the
accelerator [8]. Increasing the ALK loading has the same
effect as increasing the amount of amine in the silica-filled
NR compound. Hence, it can be said that the higher the ALK
loading, the greater the amount of amine and the shorter
the cure rate.