The dissertation covers the development and preparation of biocomposite films based on a poly(vinyl alcohol) matrix reinforced with different types of cellulose nanofibrils and tannins. Unmodified cellulose nanofibrils, lignocellulosic nanofibrils, and TEMPO-modified cellulose nanofibrils were employed. To obtain biologically active composites, tannic acid, gallic acid, chestnut tannin, and a hydrophilic knotwood extract of silver fir (Abies alba Mill.) were incorporated into the polymer matrix. During the preparation of the biocomposite films, the proportions of the different cellulose nanofibrils and tannins in the poly(vinyl alcohol) matrix were varied, and the influence of the type and content of the fillers on the final properties of the formulated polymer biocomposite films was subsequently investigated. All types of cellulose nanofibrils used were found to be suitable for the reinforcement of poly(vinyl alcohol), as biocomposite films with improved mechanical properties were obtained. Through the simultaneous addition of unmodified cellulose nanofibrils or lignocellulosic nanofibrils together with tannic acid, three-component biocomposite films with enhanced thermal stability, increased glass transition temperature, and improved water resistance were prepared. Incorporation of tannic acid and the hydrophilic knotwood extract of silver fir (Abies alba Mill.) into the polymer led to the formation of biocomposite films exhibiting antioxidant activity and antibacterial performance against both Gram-positive and Gram-negative bacteria.
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