A novel robust and flame-retardant photosensitive branched prepolymer for 3D stereolithography printing

To advance the application of stereolithography (SLA) 3D printing in demanding environments, there is an urgent need for photopolymers that simultaneously achieve flame retardancy and structural robustness. In this study, a photosensitive branched prepolymer (TTH) with phosphorus-sulfur co-synergistic flame suppression and rigid heat-resistant heterocyclic ring structure was synthesized through molecular topology design, followed by its application in SLA printing. The branched structure endows TTH with substantial photosensitivity, which not only imparts superior 3D printing performance to the photosensitive resin but also enhances its mechanical properties and flame retardancy upon incorporation. The tensile strength, impact strength and storage modulus of photosensitive resin containing 80 wt% TTH are 187 %, 84 %, and 346 % higher than those of commercial photosensitive resin matrix (TTH-0). Meanwhile, the optimized resin achieved a limiting oxygen index (LOI) of 27.2 %, UL-94 V-0 rating, and 74 %/27 % reductions in peak heat release rate (PHRR)/total heat release (THR) compared to TTH-0. These results demonstrate that the TTH system combines branched molecular design with dual fire-safety reinforcement, positioning it as a high-performance candidate for functional 3D-printed components requiring stringent flame and mechanical compliance.