Biobased and compostable trilayer thermoplastic films based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and thermoplastic starch (TPS)

Abstract

Food preservation is crucial in safeguarding the global food supply and security. Current regulations do not encourage the use of chemical food preservatives. Therefore, creating a physical barrier in the form of packaging remains a necessary measure to prevent food contact with biological and physical contaminants. This work presents a novel biodegradable thin trilayer assembly of two sandwiching layers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and a core layer composed of thermoplastic starch (TPS), maleated TPS, or their blends with PHBV (80/20). Scanning electron microscope (SEM), and optical microscopy images showed the samples' consistent film formation. The tensile test revealed that the sample with a core layer of a blend of maleated TPS and PHBV was the strongest, with a modulus of 178 MPa. The water vapor transmission rates were as low as 20.2 g/(m2·d). The oxygen permeation rate was below the detection limit of the test. Most importantly, the samples pass the biodegradation (28 °C) disintegration test in less than six weeks. The study confirmed that a trilayer structure with two outer layers of PHBV, and a middle layer of TPS-PHBV blend provides excellent barrier properties in conjuncture with its biodegradability making it an appealing, sustainable food packaging material option.