Enhancing the Mechanical Properties of Inherently Brittle, Biobased and Biodegradable Polyhydroxybutyrate (PHB) Polymer by Cotton Fibre Reinforcement and Interfacial Grafting

Abstract The accumulation of fossil‐fuel‐based plastic waste drives the need for sustainable packaging materials. Stricter regulations and consumer demand for eco‐friendly products have expanded the biodegradable plastics market. Polyhydroxybutyrate (PHB), a microbial biopolymer, is biodegradable but inherently brittle. This study enhances PHB's strength and ductility by reinforcing it with polyvinyl alcohol (PVA)‐coated cotton fibres and further improving interfacial bonding through maleic anhydride (MA) grafting. Compared to neat PHB, incorporating PVA‐coated cotton fibres increases tensile strength and failure strain by 290% and 109%, respectively. MA grafting further enhances toughness (ninefold increase) and interlaminar fracture toughness (twofold rise), while reducing helium permeation to 60%. These enhancements stem from PVA's hydrophilicity and MA‐induced hydrogen bonding, highlighting the potential of PVA‐coated cotton fibre/MA‐grafted PHB composites as sustainable materials for packaging and biomedical applications.