The aim of our study was to develop biocomposite and bionanocomposite films based on polyvinyl alcohol (PVA) with the addition of a reinforcing component – cellulose nanofibrils (CNF) and different types of biologically active tannins – along with tannic acid (TA), gallic acid (GA) and chestnut tannin (KT). CNF was added in a weight percentage of 2%, while TA, GA and KT had a weight percentage of 4% in relation to PVA. The addition of 4% TA to the PVA matrix resulted in a biocomposite film with more than 25% higher tensile strength compared to the neat PVA film. By adding 2% CNF and 4% TA to the PVA matrix, a bionanocomposite film (P2C4T) with an improved elastic modulus and higher tensile strength was obtained. At the same time, the flexibility of this bionanocomposite was greatly increased, as the elongation at the breaking of the final formulated film (P2C4T) was more than 50% higher than the elongation at break of the neat PVA film. The surface hydrophilicity of the two-component PVA films was lower, while that of the three-component films was higher.
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