Physicochemical, mechanical properties, and biodegradation studies of poly(3-hydroxybutyrate) composites reinforced with bacterial nanocellulose or wood flour

The results of the study of plastic composites from degradable poly(3-hydroxybutyrate) P(3HB) and cellulose-containing natural materials of various origins are presented. For the first time, P(3HB) composites filled with bacterial nanocellulose (BNC) or wood (Pinus sibirica) flour (WF) were produced by melt pressing at 170 °C and 2000 Pa. The influence of the filler type and amount (30, 40, 50, 70 and 90 wt%) on the physicochemical and mechanical properties of the composites and their degradability in soil laboratory microcosms was revealed. The P(3HB)/WF composites compared with P(3HB)/BNC ones were thermally stable; their thermal degradation temperatures were 266 and 227 °C, respectively. Both composites had lower values of Young's modulus and fracture strength compared to P(3HB). As BNC content was increased, Young's modulus and fracture strength of the composites increased from 1831 to 14 MPa to 3049 and 19 MPa, in contrast to P(3HB)/WF, where the values decreased by a factor of 1.5–2.0. The half-life of composites with BNC and WF in soil was 180 and 220 days, respectively. Changes in the structure of the microbial community were determined as depending on the filler type; primary destructors among bacteria and fungi were isolated and identified. Environmentally friendly and completely degradable composites show promise as cellulose-plastic materials for practical application.