PHB/PLA plasticized by olive oil and carvacrol solvent-cast films with optimised ductility and physical ageing stability

Abstract

Polylactic acid (PLA) is a bio-based polyester, widely used in various compostable food packaging film applications. Polyhydroxybutyrate (PHB), the most commercialised polymer of the PHA polyesters family, is one of the preferred bio-based polymers for food packaging, mainly because of its biodegradability in natural and controlled environments, and its good gas barrier properties. PHB, being a rather brittle polymer, is suitable for rigid packaging applications, mainly through injection molding processes. PHB may also be used for manufacturing flexible packaging by film casting and film blowing extrusion, through blending or co-extrusion with selected bio-based polymers such as PLA and additives. The potential development of blends of PHB with selected bio-based polymers that may be used for food packaging film applications was investigated in this work. Films made of various blends of PHB with other bio-based biodegradable polymers and additives were produced by the solvent casting method at laboratory scale and evaluated in terms of their mechanical properties and stability, used as “pass-fail” selection criteria. Following the development and evaluation of a second series of selected PHB/PLA blends suitable for films production, it was possible to achieve optimised compositions of PHB/PLA (10/90) blends with olive oil (OO) and carvacrol (CAR) as plasticizing and stabilising additives. The excellent mechanical performance of the selected blends with high ductility and stability against physical ageing, was analysed in depth in terms of their chemical structure and thermal behaviour.