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.