Insights into the properties of bio-based packaging materials containing poly(3-hydroxybutyrate) with ethyl cellulose and lignin - a sustainable approach toward the green economy

Abstract Sustainable bio-based packaging materials derived from natural resources offer significant potential to enhance the sustainability and environmental performance of packaged products through biodegradability, thereby reducing waste while maintaining product quality and safety. This study aimed to fabricate bio-based films containing poly(3-hydroxybutyrate) (PHB), ethyl cellulose (EC), and lignin (L), and to evaluate their properties for potential packaging applications. Lignin was extracted from winery waste streams using two pretreatment methods: with sodium hydroxide (NaOH) and with deep eutectic solvents (DES). Various blend ratios were selected to ensure homogeneous dispersion within the film matrix. NaOH-treated lignin was processed with ethylene glycol to form lignin particles, whereas DES-treated lignin was used as obtained. The blends were prepared using an oil-in-water Pickering emulsion approach to disperse lignin in PHB or PHB-EC matrices. The effects of the additives and their relationships with crystallinity, microstructure, thermal, and mechanical properties were investigated in detail. The properties of the blends were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and mechanical testing. Morphology was analyzed via confocal microscopy, and surface roughness was quantified using optical profilometry. The addition of lignin increased crystallinity by up to 37% (from 44.0% for pure PHB to 60.3% for PHB-8%L NaOH ), confirming its role as a nucleating agent. Ethyl cellulose reduced surface roughness by up to 92% (from 6.22 μm for PHB-2%L NaOH to 0.47 μm for PHB-EC-L DES -74:20:6), enhancing compatibility. However, the mechanical properties decreased, with tensile strength reduced by 29% (from 20.19 MPa for pure PHB to 14.30 MPa for PHB-EC-80:20) due to poor interfacial adhesion between PHB and lignin. Understanding the interactions between the PHB matrix and bio-additives through comprehensive property evaluation is critical for optimizing the processability of these films. The increasing adoption of bio-based materials for packaging offers environmental benefits, including reduced waste, lower greenhouse gas emissions, and accelerates the transition to a circular economy.