Ternary blends of thermoplastic starch (TPS) with poly(lactic acid) (PLA) and poly(butylene succinate-co-adipate) (PBSA): Design and processing

This paper studies a ternary blend of thermoplastic starch (TPS) with bio-derived polyesters, such as polylactic acid (PLA) and polybutylene succinate-co-adipate (PBSA). The compounds were obtained by means of a co-rotating twin screw extruder and were then reprocessed by cast extrusion and thermoforming in order to obtain films and semi-rigid containers. Semi-finished products (compounds and films) and thermoformed products were characterized by evaluating their thermo-mechanical, physical and chemical properties. The films showed good mechanical strength (Ey∼ 600 MPa, σb∼ 15 MPa), adequate stiffness / toughness (Ɛ ∼ 2.5 J) compromise and fair impermeability to oxygen (<30 cm3/m2day). Furthermore, tests show a high disintegration rate of the designed material with considerable mass loss in ambient composting conditions. On the other hand, the thermoformed containers showed inadequate thermal resistance, performing well up to 80°C and failing to endure direct contact with hot liquids at 100°C.