Particle size and particle-particle interactions on tensile properties and reinforcement of corn flour particles in natural rubber

Authors: Jong, Lei

Submitted to: European Polymer Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2015
Publication Date: 1/1/2016
Citation: Jong, L. 2016. Particle size and particle-particle interactions on tensile properties and reinforcement of corn flour particles in natural rubber. European Polymer Journal. 74:136-147.

Interpretive Summary: The particle size of corn flour was significantly reduced to ~300 nm by chemical dissociation of corn flour particles. These small particles were used to significantly increase the strength of natural rubber. Natural rubber composites have a wide variety of applications such as machine belts, seals, hoses, gaskets, etc. We found that dissociated corn flour yielded better mechanical properties than undissociated corn flour. This development will create new markets for corn products, and will be beneficial to corn grower and processing industries.

Technical Abstract: Renewable corn flour has a significant reinforcement effect in natural rubber. The corn flour was hydrolyzed and microfluidized to reduce its particle size. Greater than 90% of the hydrolyzed corn flour had an average size of ~300 nm, a reduction of 33 times compared to unhydrolyzed corn flour. Compared to unhydrolyzed corn flour composites, the composites filled with 10-40% hydrolyzed corn flour had a significant increase in tensile strength at break (29-48%), Young’s modulus (16-74%), and toughness at break (33-55%), but a decrease in the elongation at break (4-29%). The 300% modulus also increased 2-3 fold. Particle agglomeration at higher filler concentration observed by a swelling study was significantly reduced after corn flour was oxidized to introduce particle-particle repulsion with negatively charged carboxylic acid functional groups. The oxidized corn flour was also found to interfere with the sulfur crosslinking process and behaved like a scorch retarder. The reinforcement factor at the linear viscoelastic region was fitted with a mechanical model for non-spherical particles and the result indicates the shape of the corn flour particle aggregates in the composites was anisotropic. The aspect ratio of the corn flour aggregates also decreased as the temperature increased, indicating a softening of polymer chains that connected the particles.