The effects of corn zein protein coupling agent on mechanical properties of flax fiber reinforced composites

• Zein protein was shown to be an effective coupling agent for flax fiber in composites.
• Corn gluten meal and distillers dried grains with solubles were also investigated.
• An optimal zein concentration on flax fiber was shown to provide the best performance.
• Findings were substantiated through mechanical testing and characterization.

The aim of this study was to investigate the effect of zein protein treatments on the mechanical performance of flax fiber/thermoset resin composites. Flax fibers treated with corn zein protein to improve compatibility with epoxy and vinyl ester resin were processed into composites and tested under tensile, flexural, and short beam shear loadings. Pure zein treatments were tested at 1, 2.5, and 5% concentrations. Zein was also introduced to flax fibers through treatments with Corn Gluten Meal (CGM) and Dried Distiller Grains with Solubles (DDGS). The addition of zein protein increased the strengths of the composite for all three tests. Results demonstrated that the 2.5% pure zein treatment produced the largest gains with an increase of tensile strength by 8%, flexural strength by 17%, and short beam shear strength by 30% compared to untreated samples. To further investigate the effectiveness of zein treatments, Fourier Transform Infrared Spectroscopy (FTIR), chemical analysis, and Scanning Electron Microscopy (SEM) techniques were used. Results showed promise of using zein protein as an all-natural, environmentally friendly, coupling agent for flax fiber composites.