Solvolysis of polyurethane and thermoplastic polymers for the recycle of post-industrial waste

The aim of this work is to apply different solvolysis techniques (glycolysis and acidolysis) to recycle shoe insoles made of different layers: a lower one of elastomeric polyurethane, an upper one of polyester (PET) fibers and between them a tie layer of hydroxyl polyurethane. Several operating parameters are explored in order to optimize the final products that are characterized through analysing viscosity, hydroxyl number, FT-IR spectrum and content of 4,4’-methylenedianiline (MDA). MDA is a hazardous aromatic amine formed by side-reactions of hydrolysis and thermal degradation of the polyurethane. At first glycolysis and acidolysis tests are applied only on the elastomeric PU part with and without the hydroxyl PU film, in order to establish the proper degradation mechanism and minimize the MDA formation by tuning the solvolysis conditions. In the second part of this work, with the intent to lower the MDA content under its legal limit of 1000 ppm, experiments are run with the addition of a thermoplastic polymer waste, the PC, whose depolymerization products can react with ammines. The following step of the research focuses on the identification of the best solvolysis techniques for the recycle of the whole PU insole, i.e. considering also its tie layer and the PET fibers layer. Even in this case, both glycolysis and acidolysis processes are considered and compared. The end part of the work consists in the realization of new foams for which mechanical properties and thermal conductivity are analysed.