Polyurethanes are largely employed in various fields such as building, insulation and adhesive industries, but there is the constant need to develop sustainable formulations using "green" components and feasible processes. Here, a new series of sustainable castor oil and epoxidized castor oil-based (CO/EpCO) polyurethane networks was synthetized and characterized. The added epoxy functions react with isocyanates forming oxazolidinone linkages in the gels' network, reducing the gelation time from over 3 hours up to 0.5 hours, increasing thermal resistance from 385 °C to 400 °C, tuning the gels' chemical affinity to organic solvents, and modulating some of their structural features at the nanoscale (