Unsaturated polyester resins (UPR) are solutions of unsaturated polyesters dissolved in a low-viscosity monomer (such as styrene). Through a chemical reaction with the monomer and organic peroxides (hardeners), these resins become solid and durable. UPRs are frequently used in conjunction with glass fibers, carbon fibers, or aramid fibers (FRP) to produce strong and lightweight materials. They find applications in various industries, including construction, automotive, and water sports.