A cardanol modified epoxy polyol may be used for forming a polyurethane resin system for use in applications such as coatings and composites formed by filament winding. The polyurethane resin system includes an isocyanate-reactive component that has a first cardanol component and the cardanol-modified epoxy polyol, and includes an isocyanate component that includes at least one polyisocyanate. The cardanol-modified epoxy polyol is a reaction product of an epoxy component and an epoxy-reactive component at a ratio of epoxy groups to epoxy reactive groups from 1:0.95 to 1:5, and the epoxy-reactive component includes a second cardanol component.