The influence of carbonization temperature on vulcanization behavior and cross-link density of filled NR compounds

Abstract

Investigation into the effect of carbonization on the rheological properties and crosslink density of natural rubber compounds using rubber seed shell carbon as filler was carried out. The samples of rubber seed shell carbonized at 100, 200, 300, 400, 500, 600,700,and 800oC were characterized in terms of pH, moisture content, bulk density, loss on ignition, conductivity, metal content and surface area. The rheological properties as well as the crosslink density of the vulcanizates were measured as a function of filler carbonization and loading and compared with the values obtained using commercial grade carbon black (N330). The rubber seed shell carbon showed good processing safety in terms of torques, and scorch. The results of the cure characteristics showed that the cure times, and the torque gradually increased, while scorch times decreases with increasing filler content for rubber seed shell carbon-filled natural rubber. The filler obtained at carbonizing temperature of 600°C tend to show optimum cure indices. Equilibrium swelling properties of the natural rubber vulcanizates in organic solvents; toluene, acetone, diesel and kerosene were determined and provided estimates of the dispersability of the particulate fillers derived from the rubber seed shell carbon in the natural rubber. The crosslink density of the vulcanizates increased with filler loading. The reinforcing potential of the carbonized rubber seed shell carbon was found to increase markedly for the filler obtained at the temperature range 500-600°C and then decrease with further increase in temperature.