From Tomato Pomaces Biorefinery to Biobased Shape-Memory Semicrystalline Polyester Networks

The development of new biobased polyester materials is of great interest. Seed-free and pulp-free peels provided by the biorefinery of industrial tomato wastes, i.e., pomaces, are rich in cutin, a polyester of hydroxy fatty acids. In this study, these fatty acids were recovered after alkaline hydrolysis, resulting in a crude brown-colored extract due to the coextracted phenolic compounds. Further purification drastically reduced the amount of these phenolic compounds, resulting in a pale yellow product containing about 95% (9/10)-16-dihydroxy hexadecanoic acid and 5% dicarboxylic fatty acids. Polymerization of the purified extract at 150 degrees C results in a weakly cross-linked polyester network with an estimated average number of 80 repeating units between nodes. Interestingly, the mechanical behavior of this material at 25 degrees C is determined by its semicrystalline structure. A necking phenomenon is observed during tensile tests, resulting in an apparent plastic deformation of 286% and a Young modulus of 72 MPa. In addition, this biobased polyester exhibits shape-memory properties with the ability to be hot or cold-programmed. This work highlights the significant impact of minor compounds related to the biochemical heterogeneity of agro-industrial waste products on the polyester properties and the potential of the biorefinery process to modulate the properties of biopolymers.