Fig. 6 portrays rubber-filler interaction values of gum
vulcanizates and vulcanizates filled with oil palm ash, silica
and carbon black that were calculated in accordance to the
Lorenz and Park equation [9] based on the data gathered
from the sweeling experiment. All the filler-filled NR vulcanizates
indicated lower Qf/Qg values in which reinforcing
fillers (i.e. carbon black, OPA, and silica) had developed a
strong rubber-filler interaction [13] and therefore restricted
the toluene to penetrate into NR vulcanizates. The experimental
results support our previous tensile results that
carbon black-filled vulcanizates show the lowest Qf/Qg
values.