The effect of pressure on carbon‐black/elastomer powders. Part I: Density measurements on haf‐black/sbr‐powders at pressures up to 19 kbar

Carbon‐black/elastomer powders were prepared by spray‐drying mixtures of aqueous dispersions of high abrasion furnace (HAF) black with styrene‐butadiene rubber (SBR) latex. The HAF/SBR ratio was varied in the range 100/0, 95/5, 75/25, 67/33, 50/50, 33/67 and 0/100 parts by weight. The powders were subjected to pressures up to 19 kbar in a piston‐cylinder apparatus. The density of the powders was measured at different pressures and it was found that an interaction between carbon‐black and polymer occurs which results in the formation of coherent samples. They exhibit a pressure dependent degree of porosity the magnitude of which was calculated from their density and compared to the porosity determined experimentally from the methanol uptake of the samples. At higher carbon‐black loadings the specimen become increasingly porous with a corresponding decrease in density. Density measurements on the three‐phase system (HAF/SBR/pores) permitted to determine the density of the HAF‐black at 19 kbar as 1.97 g/cm 3 . Density and porosity at 0 kbar of the pressed specimen are a function of the pressure at which they were prepared. The density increases with increasing pressure whereas the porosity decreases due to stronger interaction between carbon‐black and elastomer.