Developing thermoplastic corn starch composites filled with brewer's spent grain for applications in biodegradable films

Despite the growing interest in utilizing starch-based biodegradable films, their low mechanical properties generally limit them from being widely used. On the other hand, brewer's spent grain (BSG) is an abundant by-product that does not yet have high added-value industrial use. This study proposes the development of starch-based composites filled with BSG for applications in biodegradable films. Different contents (1-5 wt%) of BSG fibers of different sizes (35, 60, and 100 mesh) were used aiming to identify the film compositions with better mechanical and thermal properties. The composites were produced by casting and had their mechanical, morphological, and thermal properties evaluated. The composites with the most promising mechanical properties contained 2.5 wt% BSG with 35 mesh and 1 wt% BSG with 100 mesh. Lower amounts of smaller BSG fibers resulted in balanced mechanical properties because of their higher surface area-to-volume ratio and higher aspect ratio. Results revealed that incorporating BSG may slightly improve the tensile strength and thermal stability of pure TPS, thus acting as a promising active filler due to the compatibility with the polymer matrix and increased polymer crystallinity. The developed films contribute to the circular economy and might be a promising low-cost option for application in conventional packages or mulch films.

Automated summary

This study proposes the development of starch-based composites filled with brewer's spent grain (BSG) to improve mechanical and thermal properties. By using different sizes and contents of BSG fibers, it was found that lower amounts of smaller BSG fibers can enhance the mechanical properties of the composite films.