ARS | Publication request: Evaluating corn starch and corn stover biochar as renewable filler in carboxylated styrene-butadiene rubber composites

Submitted to: Journal of Elastomers and Plastics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 26, 2011
Publication Date: January 1, 2012
Citation: Peterson, S.C. 2012. Evaluating corn starch and corn stover biochar as renewable filler in carboxylated styrene-butadiene rubber composites. Journal of Elastomers and Plastics. 44(1):43-54.

Interpretive Summary: In this research renewable corn starch and corn stover biochar (biochar is the charred corn stover left over as crop residue) were examined as possible substitutes for carbon black, the most common rubber composite filler in industry. Carbon black is a byproduct of the petroleum industry and reducing or substituting it completely with renewable materials will help us sustain needed industrial products in the future. Starch does a good job of reinforcing rubber composites but the resulting material tends to be brittle. The corn stover biochar does not have as favorable reinforcement properties as starch but does make composites that are less brittle. Blends were made of these components to see if the final composites would be less brittle and still retain the positive reinforcement characteristics present from the starch. Although most of the composites did not have better material properties than the carbon black control, it was found that at low concentration (10% by weight), the corn starch and a blend of 3:1 corn starch:biochar-filled rubber composites had better material properties across the board than the corresponding carbon black control sample. This is promising and means that applications needing softer, rubbery composites may be good opportunities for using these renewable filler materials.

Technical Abstract: Corn starch, corn flour, and corn stover biochar were evaluated as potential renewable substitutes for carbon black as filler in rubber composites using carboxylated styrene-butadiene as the rubber matrix. Previous work has shown that starch-based fillers have very good reinforcement properties at the expense of brittleness in the final rubber composite. In an attempt to alleviate this, starch was blended with corn stover biochar; the biochar does not have as good reinforcement properties but makes composites that are less brittle. It was found that carboxylated styrene-butadiene rubber composites filled with 10% (by weight) corn starch or a 3:1 blend of corn starch:biochar had better reinforcement, tensile strength, elongation, and toughness than the corresponding carbon black-filled control sample. These renewable fillers therefore show good potential in replacing carbon black filler for applications utilizing more ductile styrene-butadiene rubber composites.