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Canola meal (CM), a by-product of canola oil extraction, was modified by poly (styrene-co-glycidyl methacrylate) (PSG) and could potentially be used as a sustainable natural composite. Infrared analysis indicated that PSG could efficiently react with the proteins in CM and become covalently bonded. DSC results revealed that the modified CM composites showed new glass transition temperatures ( T g ) decreasing with the introduction of PSG, which were attributed to the disruption of intermolecular association. Torque curves and melt flow index tests showed the flow property of the modified CM composites increased due to interference by PSG of the hydrogen and disulfide bonding among the protein species. DMA results showed greater amorphous character for the modified CM composites and new glassy plateaus with increased storage moduli, indicating a change in molecular structure and enhancement in mechanical property and usability below T g . Furthermore, the thermostability, the tensile strength, and the elastic moduli of the modified CM composites increased because of the formation of cross-linked proteins in the CM composites, which will potentially increase the application value in some fields, such as single-use agricultural planting containers replacing high-impact polystyrene (HIPS) containers, and food or coffee trays. [ABSTRACT FROM AUTHOR]

Cross-linked canola protein isolate (CPI) films were prepared using a bisepoxide as a chain extender by wet cast followed by heat compression. By DSC measurements, it was verified that the cross-linking reaction took place in the CPI matrix and was completed in 10 min at 90 °C. FTIR analysis confirmed that the chain extenders were covalently bonded with CPI chains. The reaction led to the formation of a cross-linked architecture which was revealed by an increase in molecular weight of the modified CPI films. The newly formed chain architecture increased the thermostability of CPI as evaluated by TGA; furthermore, the thermostability increased with the increase in cross-linking degree of the modified CPI films. DMA results of the unmodified CPI film showed that microcosmic phase separation occurred between two major proteins, cruciferin and napin in CPI; however, the extent of phase separation decreased with the increase of chain extenders and finally disappeared because of the increased compatibility between cruciferin and napin. Elastomeric mechanical behavior was observed with the introduction of cross-linked architecture in the modified CPI films. At low humidity of 55%, the cross-linked CPI films showed an increase in tensile strength and a decrease in elongation at break. At high humidity of 98%, the increase in hydrophobicity of cross-linked CPI matrix resisted the decreasing tensile strength seen in unmodified films. [ABSTRACT FROM AUTHOR]