2.2 Sample prep3ration
The NR/CB master batch was prepared by mixing in
an internal mixer (YFM: 3 L) with a mixing time of about [
hour to ensure the homogeneity of the composites. The NR/
CB mixtures, curative chemicals and the additional conductive
fillers were compounded on a typical two-roll mill for a
period of time (about 30 minutes). Compounds were kept in
a desiccator for 24 hours before molding at a temperature of
I50aC under a pressure of 3,000 psi for vulcanization and
forming into composite slaps. The time period for molding
was obtained from the Moving Die Rheometer (MDR 2000).
Samples were prepared at different thicknesses of2, 4.5 and
5.5 mm. For determining mechanical and electrical properties
of composites, the average value was deduced from two
repeated measurements at different locations of each composite
obtained from three reproducible mixing batches.