Eco-Friendly and Ready-To-Market Polyurethanes: A Design of Experiment-Guided Substitution of Toxic Catalyst and Fossil-Based Isocyanate.

In this contribution, we tackle the replacement of the Hg-based catalyst and fossil-derived isocyanate precursors toward the formulation of a more sustainable polyurethane thermosetting resins (PUs), emulating the performance of a fully fossil-based one employed in industrial encapsulation of optoelectronics. A mixed Bi-Zn catalyst and a 71 % bio-based isocyanate are exploited at this aim through multivariate chemometric approaches, namely Design of Experiment (DoE). DoE allows us to investigate the effect of different formulation factors on selected parameters, such as the film flexibility and transparency or the gel time. More in detail, it is found that a low amount of Zn-rich catalytic mixture leads to a ready-to-market polyurethane only when a fossil-based isocyanate is used. Differently, PUs formulated with bio-based isocyanate, albeit showing a higher bio-based content, present an insufficient optical purity, jeopardizing their market acceptability. Nevertheless, adding a negligible amount of a specific long chain fatty acid as reactivity modulator in the formulation leads to a bubbles-free and ready-to-market resin showing an impressive 65 % w/w content of circular and bio-based components.