The detailed formulations used in this study are shown
in Table 2. Mixing of raw materials was done using conventional
laboratory-sized two roll mill (model XK 160).
The total mixing time was less than 20 min to avoid premature
vulcanisation of excess heat generated during
compounding. Also, the mixing sequence was kept constant
for all of the mixes. The curing characteristics such as,
scorch time (ts2), cure time (tc90) and maximum torque
(MH) of filler-filled natural rubber compounds were determined
by Monsanto Moving Die Rheometer (model MDR
2000) according to ISO 3417 at 150 C, followed by,
compression moulded at 150 C according to their respective
tc90 values. Moulded sheets were conditioned in desiccators
for 24-h prior to further testing.