Tailoring bionanocomposite film functionality using cellulose nanofibrils and bioactive wood extractives

Abstract The aim of the study was to produce biologically active biocomposite films with improved mechanical properties compared to pure poly(vinyl alcohol) (PVA) film. In a first step, two-component films were produced, namely PVA with the addition of nanocellulose. Unmodified cellulose nanofibrils (CNFs), TEMPO cellulose nanofibrils (TCNFs), and lignocellulose nanofibrils (LCNFs) were used as reinforcement, and the performance of these nanofillers with respect to the properties of PVA-based biocomposites was compared. All nanofillers improved the mechanical properties of PVA, with TCNFs providing the greatest reinforcement. The PVA biocomposite with 6% TCNF showed a 55% higher modulus of elasticity and 58% higher tensile strength than the reference film. The most thermally stable bionanocomposite among the PVA-nanocellulose biocomposites was PVA with 6% CNF; thermal degradation (T onset ) started at a temperature 4 °C higher than the reference. In order to achieve antibacterial activity of the produced three-component films, a hydrophilic extract of silver fir knotwood was added to the PVA/nanocellulose system. In addition to the antibacterial properties, the effects of the hydrophilic extract on the mechanical and thermal properties of the three-component films were also investigated. The extract led to a shift in the T onset towards higher temperatures, with the higher content having an even greater effect. The addition of 4% extract to the LCNF-reinforced biocomposite increased the tensile strength by 10% compared to the PVA-LCNF biocomposite. Graphical abstract