Design and Processing of Novel PBS/PVOH Blown Films for Food Packaging: Effect of PVOH Phase Structuring on Morphology and Functional Performance

Biodegradable polymer blends are promising materials for flexible packaging films with tunable properties. In this work, poly(butylene succinate)/poly(vinyl alcohol) (PBS/PVOH) blown films were produced by twin-screw melt compounding followed by film blowing, and the effect of PVOH content on phase organization, processability, morphology, and functional performance was investigated. The blends showed phase-separated morphologies and composition-dependent structural evolution. DSC indicated that both polymers largely retained their crystallization ability, although the crystallinity decrease was more evident for PVOH. Rheological analysis revealed limited compatibility and increasing elastic response at higher PVOH contents, consistent with the formation of structured PVOH insoluble gel-like domains. SEM confirmed droplet–matrix morphologies, becoming coarser and more heterogeneous at high PVOH content, with film-blowing instability for PBS/PVOH 20/80. PVOH incorporation improved oxygen and water-vapor barrier properties and increased stiffness, but progressively reduced ductility. Model fitting supported the structure–property correlations, relating film performance to blend composition, morphology, and PVOH phase organization. Among the processable formulations, PBS/PVOH 80/20 showed the best balance between improved barrier properties and acceptable extensibility for food packaging application. Overall, PBS/PVOH blown films are promising biodegradable systems for flexible food packaging, provided that PVOH phase structuring is properly controlled.