Progress in design and processing of polyhydroxyalkanoates (PHAs): Home compostable poly(3-hydroxybutyrate-co—3-hydroxyhexanoate) (PHBHHx)/polybutylene succinate-co-adipate (PBSA) blend

Abstract

Polyhydroxyalkanoates (PHA) are biodegradable linear polyesters mainly produced by bacterial fermentation. These materials are biocompatible, non-toxic, and have a low environmental impact, making them an excellent alternative to fossil-based plastics in food packaging. Despite their promising characteristics, PHAs have several disadvantages, such as brittleness, slow nucleation process, thermal instability and consequently poor processability. In this article, poly(3-hydroxybutyrate-co-3-hexanoate) (PHBHx), a copolymer belonging to the class of PHAs, was blended with polybutylene succinate-co-adipate (PBSA) and other process additives in order to improve its properties and realize a hot food container compostable in a domestic environment. The material in the pellet form was produced by reactive extrusion with a corotating twin-screw extruder. The compound was then processed by cast extrusion and the resulting film was thermoformed into a rectangular container. All the semi-finished products were characterized thermo-mechanically and with chemical–physical tests, demonstrating good processability, thermal resistance of 100°C, complete impermeability to oxygen, transmission of light radiation less than 30% and high toughness (<5 kJ/m2). In addition, the morphology of the blende was also investigated by SEM and XRD analysis.