Measurement of rubber-filler interactions
The rubber-filler interaction was determined by
swelling the cured compounds in toluene according to ISO
1817. Test pieces with dimensions of 30 mm 5 mm
2 mm were prepared from the moulded sheets. The
initial weights were recorded prior to testing. The test
pieces were then immersed in toluene and conditioned at
25 C in a dark environment for 72 h. After the conditioning
period, the weights of the swollen test pieces were recorded.
The test pieces were then dried in an oven at 70 C for
15 min and allowed to cool at room temperature for
another 15 min before the final weights were recorded. The
Lorenz and Park equation has been applied in this study
[17]. The swelling index was calculated according to
Equation (1):
Qf =Qg ¼ aez þ b (1)
where the subscripts f and g refers to filled and gum
vulcanisates, respectively, z is the ratio by weight of the
filler to the rubber hydrocarbon in the vulcanisates and
a and b are constants. Higher Qf/Qg values reflect weaker
interactions between the filler and matrix. In this study, the
weight of toluene uptake per gram of rubber hydrocarbon
(Q) was calculated according to the following relation:
Q ¼ ½swelled weight dried weight=½initial weight
100=formula weight