By-Products from Food Industry as a Promising Alternative for the Conventional Fillers for Wood-Polymer Composites

The present paper describes the application of two types of food-industry by-products, brewers' spent grain (BSG), and coffee silverskin (LK) as promising alternatives for the conventional beech wood flour (WF) for wood-polymer composites. The main goal was to investigate the impact of partial and complete WF substitution by BSG and LK on the processing, structure, physicochemical, mechanical, and thermal properties of resulting composites. Such modifications enabled significant enhancement of the melt flowability, which could noticeably increase the processing throughput. Replacement of WF with BSG and LK improved the ductility of composites, which affected their strength however. Such an effect was attributed to the differences in chemical composition of fillers, particularly the presence of proteins and lipids, which acted as plasticizers. Composites containing food-industry by-products were also characterized by the lower thermal stability compared to conventional WF. Nevertheless, the onset of decomposition exceeding 215 degrees C guarantees a safe processing window for polyethylene-based materials.

Automated summary

This study investigated the potential of using food-industry by-products such as brewers' spent grain and coffee silverskin as alternatives for conventional wood flour in wood-polymer composites. The results showed that partial or complete substitution of wood flour with these by-products improved melt flowability and ductility of the composites, but had an impact on their strength and thermal stability. The presence of proteins and lipids in the fillers acted as plasticizers, affecting the mechanical properties of the composites.