Steven C. Peterson

Utilization of low-ash biochar to partially replace carbon black in styrene–butadiene rubber composites:

A biochar made from woody waste feedstock with low-ash content was blended with carbon black (CB) as filler for styrene–butadiene rubber. At 10% total filler concentration (w/w), composites made from 25% or 50% biochar showed improved tensile strength, elongation, and toughness compared with similar composites filled with CB. This demonstrates the potential to use renewable biochar as a partial substitute for CB in flexible, low-filler rubber composite applications.

Evaluating corn starch and corn stover biochar as renewable filler in carboxylated styrene–butadiene rubber composites

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.

Effect of Shearing on the Reinforcement Properties of Vital Wheat Gluten

An aqueous dispersion of vital wheat gluten and styrenebutadiene rubber was subjected to high-shear mixing in an attempt to reduce the aggregate size and enhance filler—matrix interactions with the goal of improving contributions of the reinforcement to the overall composite properties. Composites were formulated using 10—40% vital wheat gluten by mixing aqueous suspensions of the gluten and rubber, then freeze-drying and compression molding the resulting composite. Rheological experiments indicated that vital wheat gluten reinforced the rubber up to a factor of roughly 30. Subjecting the gluten suspension to high shearing reduced the particle size from approximately 5.2—4.5 µm, and 16 min was the optimum shearing time since shearing the dispersions longer did not result in any additional size reduction. Composites with 10% vital wheat gluten have good potential in applications requiring high elasticity since they were equal to or better than the carbon black control in terms of Young’s modulus, percent elongation, and toughness. Isolated vital wheat gluten was studied in order to determine its relative merit as one of the two reinforcing components of wheat flour (the other being wheat starch), and vital wheat gluten’s reinforcing ability was a factor of 10 weaker than wheat flour, indicating that wheat starch is a much more effective biomaterial filler in terms of rigidity, but vital wheat gluten may be more suitable for applications requiring more elasticity.

Improved hydroxypropyl methylcellulose (HPMC) films through incorporation of amylose-sodium palmitate inclusion complexes

Polymer film blends of hydroxypropyl methylcellulose (HPMC) and amylose-sodium palmitate inclusion complexes (Na-Palm) were produced with no plasticizer, and were observed to have improved physical and gas barrier properties as compared with pure HPMC. The crystalline amylose helices incorporating the hydrophobic sodium palmitate ligand decreased the water vapor permeability of a 50/50% blended film of HPMC/Na-Palm by 40% and decreased oxygen permeability by 96%. The incorporation of 25% Na-Palm into HPMC films resulted in improved elongation, Youngs modulus and toughness. Addition of the amylose-complexes produced relatively smooth, high clarity films which had reduced solubility in neutral and acidic solutions. Increasing concentrations of Na-Palm increased film thermal resilience and increased storage modulus at high temperatures. The heat deflection temperature of the films also increased with increasing concentrations of amylose-complex; HPMC/Na-Palm film blends with >50% Na-Palm displayed almost no material deformation up to 250 °C.

Effect of spray drying on the properties of amylose-hexadecylammonium chloride inclusion complexes ☆

Water soluble amylose-hexadecyl ammonium chloride complexes were prepared from high amylose corn starch and hexadecyl ammonium chloride by excess steam jet cooking. Amylose inclusion complexes were spray dried to determine the viability of spray drying as a production method. The variables tested in the spray drying process were the% solids of the amylose-hexadecyl ammonium chloride complex being fed into the spray dryer, feed rate and the spray dryer outlet temperature. The amylose-inclusion complexes remained intact in all spray drying conditions tested as determined by X-ray diffraction. The rheological properties of solutions of the spray dried amylose-complexes remained unchanged when compared with the freeze dried control. Particle density and moisture content decreased with increased outlet temperature while particle size increased. X-ray diffraction and DSC analysis confirmed the formation of type II amylose inclusion complexes. Spray drying is a high throughput, low cost continuous commercial production method, which when coupled with excess steam jet cooking allows for the industrial scale production of cationic amylose-hexadecyl ammonium chloride complexes which may have value as flocculating and filtration enhancing agents and other aspects of paper production.

Using heat-treated starch to modify the surface of biochar and improve the tensile properties of biochar-filled styrene–butadiene rubber composites

Heat-treated starch (HTS) is a renewable material that can be used to modify the surface chemistry of small particles. In this work, HTS was used to coat hydrophilic biochar particles in order to make them more hydrophobic. Then, when added as filler to hydrophobic styrene–butadiene rubber (SBR), the coated biochar dispersed more easily and had enhanced filler–matrix interactions, which were reflected in the tensile properties of the final composites. Biochar particles modified with 5% (weight) HTS showed increases of 59% in the ultimate tensile strength, 49% in elongation percentage, and 79% in fracture toughness of SBR composites compared to unmodified biochar particles. This shows that HTS can be used to improve the tensile properties of composites filled with biochar and potentially other hydrophilic filler materials.

Co-milled silica and coppiced wood biochars improve elongation and toughness in styrene-butadiene elastomeric composites while replacing carbon black

Carbon black (CB) is a petroleum by-product with a million ton market in the US tire industry. Finding renewable substitutes for CB reduces dependence on oil and alleviates global warming. Biochar is a renewable source of carbon that has been studied previously as a replacement for CB in styrene-butadiene rubber (SBR) composites. However, biochar typically has lower carbon content, higher ash content, and larger particle size, which are all significant detractors to making biochar a viable drop-replacement for CB. In this study, high carbon and low ash biochars made from fast-growing Paulownia elongata and Populus tremuloides were co-milled with small amounts of silica in order to reduce the particle size, and the biochar/silica blends were then used to partially replace CB in SBR composites. Using this method both Paulownia and poplar biochars were able to replace 30% of the CB filler and improve elongation and toughness with virtually no loss of tensile strength, compared to the 100% CB-filled control composite.