More than just a beer – Brewers' spent grain, spent hops, and spent yeast as potential functional fillers for polymer composites
[ 1 ] Instytut Technologii Materiałów, Wydział Inżynierii Mechanicznej, Politechnika Poznańska | [ 2 ] Wydział Inżynierii Mechanicznej, Politechnika Poznańska | [ 3 ] Instytut Inżynierii Materiałowej, Wydział Inżynierii Materiałowej i Fizyki Technicznej, Politechnika Poznańska | [ P ] employee | [ SzD ] doctoral school student
[2.8] Materials engineering[2.9] Mechanical engineering[7.6] Chemical sciences
2024
scientific article
english
- Poly(ε-caprolactone)
- Brewers' spent grain
- Spent hops
- Spent yeast
- Brewery waste
- Recycling
EN Beer is among the most popular beverages in the world, with the production distributed uniformly between the biggest continents, so the utilization of brewing by-products is essential on a global scale. Among their potential recipients, the plastics industry offers extensive range of potential products. Herein, the presented study investigated the application of currently underutilized solid brewing by-products (brewers' spent grain, spent hops, spent yeast) as fillers for highly-filled poly(ε-caprolactone)-based composites, providing the first direct connection between spent hops or spent yeast and the polymer composites. Comprehensive by-product characterization revealed differences in chemical composition. The elemental C:O ratio, protein content, and Trolox equivalent antioxidant capacity varied from 1.40 to 1.89, 12.9 to 32.4 wt%, and 2.41 to 10.24 mg/g, respectively, which was mirrored in the composites' structure and performance. Morphological analysis pointed to the composition-driven hydrophilicity gap limiting interfacial adhesion for high shares of brewers' spent grain and spent hops, due to high hydrophilicity induced by carbohydrate content. Phytochemicals and other components of applied by-products stimulated composites' oxidative resistance, shifting oxidation onset temperature from 261 °C for matrix over 360 °C for high spent yeast shares. Simultaneously, spent yeast also provided compatibilizing effects for poly(ε-caprolactone)-based composites, reducing complex viscosity compared to other fillers and indicating its highest affinity to poly(ε-caprolactone)due to the lowest hydrophilicity gap. The presented results indicate that the proper selection of brewing by-products and adjustment of their shares creates an exciting possibility of engineering composites' structure and performance, which can be transferred to other polymers differing with hydrophilicity.
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