Constructing long-lasting antibacterial starch blown films via multi-functional epoxy micro-crosslinking effect

The widespread pollution arose from petroleum-source non-degradable plastics has driven urgent demand for biodegradable green packaging materials. Starch is an attractive feedstock because of its low cost, renewability, and complete biodegradability, but its poor melt processability and low mechanical strength hinder practical applications, particularly in blow molding. Herein, we report a micro-crosslinked pure starch film fabricated via reactive extrusion and blow molding using cassava starch, antibacterial hexamethylene guanidine hydrochloride and a multi-epoxy functional aromatic copolymer (AE) as a crosslinking agent. The micro-crosslinking network effectively enhances melt strength at low shear rates, enabling stable blow molding of pure starch films. With 0.5 wt% AE content, the film exhibits optimal mechanical properties, achieving a tensile strength at 5.71 MPa, 262% elongation at break, and 583% increase in Young's modulus. Notably, the starch film exhibits outstanding long-lasting bactericidal efficacy, even following a four-week aqueous immersion, it retains more than 98.4% growth suppression toward Escherichia coli and Staphylococcus aureus, corresponding to a 74.3% conjugation yield. Moreover, the incorporation of rigid benzene ring segments slows down the degradation rate, which decelerate the degradation rate and thus prolong the service life, with ultimate biodegradation taking place afterwards. This study provides a feasible strategy to prepare high-strength, long-lasting antibacterial pure starch films via micro-crosslinking and blow molding, promoting sustainable packaging applications.