Biocomposite of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), wood fibres and additives: physicochemical properties and processability through different techniques

Abstract Bio-based composites are a promising substitute for fossil-based plastics and aim to reduce their negative environmental impact. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) is a bio-based and biodegradable thermoplastic whose properties are comparable to those of commonly used plastics, such as polypropylene (PP) and polyethylene (PE). In this study, we propose different blends of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with bio-based fillers and additives, including wood fibres, poly(butylene-co-adipate terephthalate) grafted with either maleic anhydride or glycidyl methacrylate and calcium carbonate as an alternative to fossil-based plastics. Fourier transform infrared spectroscopy results showed that no significant new bonds were formed. The X-ray scattering data revealed that the presence of additives did not significantly influence the crystallinity of the composites. In terms of thermal stability, the formulation containing the poly(butylene-co- adipate terephthalate) grafted with glycidyl methacrylate demonstrated increased degradation temperature which was reduced by the presence of wood in the blends. Additionally, this formulation presented the highest melting temperature of 175.1 °C. Mechanical properties were decreased with the addition of wood fibres, in terms of tensile strength and elongation at break but increased in terms of Young modulus for all composites containing wood. The functionalisation of the wood with tannic acid and iron resulted in improved elongation at break (3.78 ± 0.14%), ultimate strength (29.28 ± 1.12 MPa) and, especially, Young modulus (1060 ± 19.59 MPa). The PHBV/wood TA.Fe/CaCO 3 formulation presents comparable results to those of neat PHBV, with higher values for Young modulus. The overall aim of this study is to develop and characterise different fully bio-based composites that could be used in injection moulding and additive manufacturing techniques, such as fused granular fabrication.