Development of new materials based on polymers from natural resources: cutin and bacterial polyhydroxyalkanoates

As the negative aspects of conventional plastics become more apparent, the development of novel sustainable materials is essential. Bioplastics that are biobased and biodegradable are an ideal solution. This Thesis, developed inside the Horizon Europe AgriLoop project in collaboration with other partners, aims to obtain materials from agro-waste, with good barrier properties and bactericidal activity. These materials are designated for food packaging and films used in agriculture. Cutin, extracted from tomato and grape pomace, and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymers, produced by microorganisms, are employed in the development of these materials. Samples with different mol% of HV are provided: PHI003, a commercial PHBV from NaturePlast (with 1.5 mol% of HV units), PHBV with 16 mol%HV and with 57 mol%HV from Sapienza University of Rome. Initially, characterization of the copolymers was performed, to understand their properties and facilitate comparison. Cutin is an interesting biopolyester which revealed to have bactericidal activity when hydrolysed into its monomers and oligomers. In this work, cutin was firstly employed as a coating for PHBV films. Coating resulted to be homogeneous and the affinity with the surface was optimal after curing at 60°C for 24h. The resulting films were hydrophobic, especially when corona and curing treatments were applied. Barrier properties and antimicrobial tests are going to be performed to understand the applicability of these films. Furthermore, blends of PHBV and cutin with a ratio 95/5 (w/w) were produced and appeared homogeneous. Their tensile properties are comparable with those of PHBV with low HV content, proper of brittle and stiff materials. The use of PHBVs with a higher content of HV, synthesized at lab scale inside the Agriloop project, and a higher ratio of cutin, might improve these properties. Further studies are in progress to optimize the properties of both coated films and blends.