Sustainable Sheep Wool/Soy Protein Biocomposites for Sound Absorption

The wool fibers of the Latxa sheep breed were combined with a soy protein isolate (SPI) matrix to develop sustainable biocomposites with acoustic properties, adding value to Latxa sheep wool, which is currently considered a residue. Samples with 7, 10, 15, and 20 wt % wool were prepared by freeze drying in order to develop porous structures, as shown by SEM analysis. Additionally, XRD analysis provided the evidence of a change toward a more amorphous structure with the incorporation of wool fibers due to the interactions between the soy protein and keratin present in wool fibers, as shown by the relative intensity changes in the FTIR bands. The biocomposites were analyzed in a Kundt's tube to obtain their sound absorption coefficient at normal incidence. The results showed an acoustic absorption coefficient that well-surpassed 0.9 for frequencies above 1000 Hz. This performance is comparable to that of the conventional synthetic materials present in the market and, thus, sheep wool/SPI biocomposites are suitable to be used as acoustic absorbers in the building industry, highlighting the potential of replacing not only synthetic fibers but also synthetic polymers, with natural materials to enhance the sustainability of the building sector.

Automated summary

This study developed sustainable biocomposites using Latxa sheep wool fibers and a soy protein isolate (SPI) matrix, which showed excellent acoustic properties. The SEM and XRD analysis confirmed the porous structure and the interaction between soy protein and keratin in wool fibers. The biocomposites demonstrated a high sound absorption coefficient above 0.9 for frequencies above 1000 Hz, comparable to conventional synthetic materials. These findings suggest that sheep wool/SPI biocomposites have the potential to replace synthetic materials in the building industry, enhancing sustainability.