Packaging related properties of commercially available biopolymers - An overview of the status quo

Several commercially available thermoplastic biopolymers were processed in a continuous extrusion line. The molecular weight, crystallinity, and mechanical and permeation properties of the cast films were determined in order to evaluate the status quo of biopolymers currently commercially available. The biopolymers that were evaluated were polylactic acid (PLA), several polyhydroxyalkanoates (PHAs) (Poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (PHBHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)), thermoplastic starch (TPS), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polycaprolactone (PCL) and biobased polyethylene (BioPE). Due to its potential for biobased production, thermoplastic polyurethane elastomer (TPU) was also analysed. Mechanical analysis showed the PLA and PHA films had high strength and extremely low elongation at break. These were also the materials with the highest molecular weights. Films made of TPU, PCL, TPS, PBAT and BioPE had a significantly lower Young's modulus and significantly higher elongation at break; these films had comparatively low molecular weights. Permeation measurements showed that PHA films, and particularly PHBV, had the lowest oxygen and water vapour permeability of the biopolymers that were analysed. The biopolymers BioPE, TPS, PCL, TPU and PBAT were highly permeable to oxygen, and had comparatively low molecular weight. The biopolymers TPU, PBS, PBAT, PCL and TPS were highly permeable to water vapour.