2. Experimental
2.1. Preparation of rubber/clay composite
Concentrated natural rubber latex (60% dry rubber
content, high ammonia) and the clay (Na-montmorillonite), with a cationic exchange capacity of 119 meq/100 g were used to prepare the rubber/clay composite. Concentrated NR latex was diluted with water to 30% dry rubber
content. The amount of clay used was calculated such that
the dried natural rubber would contain 6 phr of clay. The
clay suspension was prepared before mixing with NR latex.
The clay was added into the excess water (2 g per 100 ml of
water) and was stirred vigorously for 4 h in order to achieve
good dispersion of the silicate layers in the medium. Then,
the mixture of clay suspension and NR latex was stirred
gently for 30 min. Thereafter, the mixture was cast in
a stainless steel tray and left at room temperature for a day.
Finally, it was further dried in an oven at 50 C. The rubber/
clay obtained was further mixed with other ingredients to
prepare the rubber compound