Photopolymer resin is a liquid, UV-curable material — typically acrylic or epoxy monomers combined with photoinitiators — that solidifies layer by layer under ultraviolet light in SLA, DLP, and other resin 3D printing processes.
Photopolymer resins are liquid formulations built from acrylic, methacrylic, and epoxy monomers and oligomers, combined with photoinitiators that trigger polymerization, plus diluents, dispersants, pigments, and UV blockers that tune viscosity, color, and cure depth. When exposed to ultraviolet light, the photoinitiators generate reactive species that crosslink the monomer chains, converting the liquid into a rigid solid through a process called vat photopolymerization.
In resin 📝3D printing, the material sits in a vat and is cured selectively one layer at a time: stereolithography (SLA) traces each cross-section with a UV laser, while digital light processing (DLP) flashes an entire layer at once using a projected image. Because curing is defined by light rather than a mechanical nozzle, photopolymer processes reach finer feature detail and smoother surfaces than filament-based extrusion.
Formulations are engineered for specific outcomes — standard, tough, flexible, castable, and dental or biocompatible grades — each balancing resolution, mechanical strength, and shrinkage. Printed parts emerge only partially cured, or "green," and require washing to remove excess resin followed by post-curing under additional UV light to reach full mechanical properties. Uncured liquid resin is an irritant and is generally handled with gloves and ventilation.