Reactive biodegradable extruded blends of thermoplastic starch and polyesters

Poly(butylene succinate) (PBS) and poly(butylene adipate co-terephthalate) (PBAT) are biodegradable polymers applied as alternative materials to non-biodegradable plastics. They have adequate mechanical properties to be used on an industrial scale, but their high cost is a limiting factor. Using thermoplastic starch (TPS) as the main component of the matrix is an alternative to producing low-cost materials. This work aimed to develop PBAT/PBS/TPS biodegradable films by blown extrusion, combining the most attractive properties of each polymer: the ductility of PBAT, the tensile strength of PBS, and the biodegradability and low cost of TPS. PBS/PBAT/TPS (20/10/70 wt%) sample achieved the best balance between hardness, ductility, and strength, with an elongation at break of 32%, a tensile strength of 6 MPa, and Young's modulus (YM) of 56 MPa. Citric acid acted as a multifunctional compound, increasing tensile strength and elongation at break and decreasing YM for all films. It increased the opacity and degree of crystallinity of the films but did not influence the color. FTIR did not indicate chemical reactions between the constituents, and the SEM showed higher compatibility between TPS/PBAT than with PBS. Our work proposed a well-known manufacturing process that allows scaling up the production of biodegradable films