Properties of Gluten Foam Composites Containing Different Fibers and Particulates

Gluten-based foam composites containing various additives were produced to develop materials derived from mostly renewable resources. The fillers included walnut shells, torrefied walnut shells, paraffin wax, milkweed fibers, hemp fibers, and cotton fibers. The effects of the fillers on the foam composites’ properties were determined using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis, compression testing, and water uptake measurements. SEM results showed that most of the fillers were well dispersed in the gluten matrix except for the cotton fibers, which produced agglomerated fiber bundles. FTIR results indicated that foams had a more aggregated structure with higher β-sheet contents than gluten powder. In general, foam composites containing fibers had larger compressive modulus values than those containing particulates. The sample containing 10 wt% milkweed fibers had the highest value of 67.03 ± 12.01 MPa. Also, composites containing torrefied walnut shells had higher compressive strength values than those containing raw walnut shells, indicating better compatibility with the gluten matrix. Moreover, the water uptake values of the foam composites varied from 110 to 270%, with the samples containing milkweed fibers having the largest values.