The crosslink density of the silica-filled NR vulcanisates
was determined by the FlorydRehner approach [Eq. (2)].
Fig. 4 shows the crosslink density of the vulcanisates at
room temperature. The addition of up to 5.0 phr of ALK into
the silica-filled rubber compound increased the crosslink
density, and further increases in the ALK loading decreased
the crosslink density. This observation is in line with that of
the torque difference (MHdML), which is an indirect
measure of the crosslink density of the rubber vulcanisates.