Evaluating corn-based biochar as an alternative to carbon black in styrene-butadiene rubber composites

This study presents a characterization of corn-based biochar materials and examines their suitability as rein-forcing fillers in styrene-butadiene rubber (SBR) composites. The specific objectives were to determine whether there were significant differences in performance, depending on (1) the part of the plant they are sourced from and (2) how refined the feedstock was prior to processing. Corn cob, corn stover and the more highly refined corn starch feedstocks were pyrolyzed at 700 degrees C for 1 h, at a heating rate of 50 degrees C/min under nitrogen gas. Fillers were evaluated in terms of size, structure, and surface chemistry, which are the 3 primary areas contributing to filler reinforcement mechanisms. The cure, tensile and dynamic mechanical properties of the biochar SBR composites were also evaluated and compared to SBR composites filled with N772 grade carbon black. The results indicate that corn stover biochar has the highest reinforcing index in SBR, only 17.5 % lower than that of N772 in SBR. Biochar fillers from corn cob and corn stover had relatively similar characteristics, suggesting that they could be combined with minimal loss in performance. Starch biochar SBR composites were highly crosslinked but also significantly more brittle. Though all show promising reinforcing characteristics, corn-based biochar fillers are not yet on par with N772 carbon black, having poorer filler dispersion and lower reinforcement indexes. Further investigation and optimization of these alternative fillers is required before they can be considered for wide-spread use.