Published 18 Poly(hydroxyl butyrate-co-valerate) (PHBV) is a biopolymer synthesized by microor-19 ganisms that is fully biodegradable with improved thermal and tensile properties with 20 respect to some commodity plastics. However, it presents an intrinsic brittleness that 21 limits its potential application in replacing plastics in packaging applications. Films made 22 of blends of PHBV with different contents of thermoplastic polyurethane (TPU) were 23 prepared by single screw extruder and

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... ir fracture toughness behavior was assessed 24 by means of the essential work of fracture (EWF) Method. As the crack propagation 25 was not always stable, a partition method has been used to compare all formulations 26 and to relate results with the morphology of the blends. Indeed, fully characterization 27 of the different PHBV/TPU blends showed that PHBV was incompatible with TPU. 28 The blends showed an improvement of the toughness fracture, finding a maximum with 29 intermediate TPU contents. 30