Mechanical and Water Barrier Properties of Biopolyester Films Prepared by Thermo-Compression

Four different biopolyester films, two aliphatic polyesters including polylactides (PLA) and poly(3-hydroxy-butyrate-co-3-hydroxyvalerate (PHBV), and two aliphatic-aromatic copolyesters including Ecoplex and Biomax, were prepared using by thermo-compression, and their tensile and water barrier properties were determined. Among the films tested, PLA film was the most transparent (T: 95.8%), strongest, and stiffest (TS, 40.98 MPa; E, 1916 MPa), however it was rather brittle. In contrast, Ecoplex film was translucent while being the most flexible and resilient (EB, 766.8%). Biomax film was semitransparent and was the most brittle film tested (EB, 0.03%). All biopolyester films were water resistant exhibiting very low water solubility (WS) values ranging from 0.0.3 to 0.36%. PHBV film showed the lowest water vapor permeability (WVP) value ($1.26{\times}10^{-11}\;g{\cdot}m/m^2{\cdot}sec{\cdot}Pa$) followed by Biomax, PLA, and Ecoflex films, respectively. The water vapor barrier properties of each film were approximately 100 times higher than those of carbohydrate or protein-based films, but about 100 times lower than those of commodity polyolefin films such as low-density polyethylene (LDPE) or polypropylene (PP).