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.