Development of extrusion blown films of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) blends for flexible packaging

Abstract

Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) is a biodegradable polymer with significant potential for use in food packaging. However, its limited melt strength poses a challenge when employing film‐blowing techniques to produce flexible packaging. To overcome this obstacle, we developed blends consisting of 70 wt% PHBV and 30 wt% poly(butylene‐co‐succinate‐co‐adipate) (PBSA). Organic peroxides such as dicumyl peroxide and 2,5‐dimethyl‐2,5‐di‐(tert‐butylperoxy)hexane, were utilized as reactive compatibilizers to enhance the interfacial adhesion between the polymers. Additionally, acetyl tributyl citrate (ATBC) was employed as a plasticizer to improve processability and ductility. The inclusion of organic peroxides resulted in the formation of long‐branched structures, as confirmed by the van‐Gurp‐Palmen plot. The melt flow index decreased from 30 to 9.8 g/10 min without ATBC and 15.5 g/10 min with ATBC. Successful production of blown PHBV/PBSA films was achieved on a pilot scale (bubble height 180 cm). These films exhibited heat‐sealing capability and increased impact strength (7.7 kJ/m2). Moreover, the films maintained a maximum elongation at break of 4% during a 3‐month storage experiment with frozen food. Food safety was assessed through overall migration experiments, and the non‐plasticized films received approval. In conclusion, the compatibilized PHBV/PBSA blends demonstrate great potential as materials for manufacturing film‐blown flexible packaging.