Transforming waste cooking oil into a mechanically enhanced photocurable resin for 3D printing

Waste cooking oil (WCO), a substantial urban waste stream, holds untapped potential for synthesizing high-value materials. This study introduces a sustainable approach to convert WCO into a mechanically enhanced photocurable resin for three-dimensional (3D) printing through a sequential epoxidation-hydrolysis-blending process. Initially, WCO is transformed into WCO-based hydroxy fatty acids (WHFA), featuring a linear chain with multiple hydrogen-bonding sites, via epoxidation and hydrolysis. WHFA is then blended with triethylene glycol dimethacrylate (TEGDMA) to create photocurable resins. The resin demonstrates outstanding dimensional accuracy during light-curing 3D printing (penetration depth = 0.168 mm, dimensional deviations < 0.2%). WHFA serves as a dual-functional modifier in the WHFA/TEGDMA system, plasticizing the network while forming a dynamic hydrogen-bond network that acts as a physical crosslinker. This unique mechanism results in unprecedented mechanical properties among WCO-derived resins. In the optimized formulation (TEGDMA:WHFA = 15:1), the WHFA/TEGDMA resin exhibits a high tensile strength of 35.48 MPa (4.2 times higher than pure TEGDMA) and improved impact toughness (5.92 kJ/m2, 3 times that of pristine TEGDMA). This work offers a scalable, high-value pathway for WCO upcycling and highlights the crucial role of molecularly tailored WCO derivatives as functional additives for advanced 3D printable materials.