Rheological Properties of Carbon Black/Silica Hybrid Filler in Acrylonitrile Butadiene Rubber

Abstract

Filler is a common additive added into rubber vulcanizate to achieve reinforcing performance. Typically, filler is compounded via two-roll mill which results in filler agglomeration and lower reinforcing efficiency. To gain higher reinforcing efficiency, filler agglomeration must be minimized via masterbatch preparation. This study investigates colloidal stability of carbon black/silica (CB/SiO2) hybrid filler and effectiveness between typical compounding and masterbatch process for NBR vulcanizate production. CB/SiO2 hybrid filler was fixed at 20 wt.% with ratios of 100/0, 75/25, 50/50, 25/75 and 0/100 were dispersed separately in sodium hydroxide (NaOH) via ball milling. The zeta potential, particle size and viscosity results showed CB and SiO2 dispersions stabilized after 48 hours of ball milling. NBR masterbatch with 50/50 ratio has highest flow resistance. SiO2 reinforced NBR masterbatch showed higher flow resistance compared to CB due to finer silica particle size. However, scorch and cure time for SiO2 reinforced NBR is slower than CB reinforced NBR as silica deactivate the accelerator. CB/SiO2 at 50/50 has highest Tmax and ΔT while 100/0 and 0/100 has insignificant differences. As conclusion, CB and SiO2 dispersions were stable based on zeta potential analysis and particle size reduced as ball milling time increased.