Dual-curing polymer systems for photo-curing 3D printing

Photo-curing 3D printing technologies use a specific wavelength light source to trigger the polymerization of photosensitive resins, with the advantages of rapid curing and excellent spatial resolution. However, photo-curing materials based on the free radical polymerization suffer from brittleness and poor impact resistance, while those based on the cationic polymerization mechanisms are constrained by slow curing speed. Dual-curing materials are hybrid resins consisting of photosensitive and thermal curing resins that take into account fast curing speeds and excellent mechanical properties, which have been widely used in photo-curing 3D printing in recent years, and their application fields are gradually expanding. Herein, dual-curing materials used in photo-curing 3D printing are reviewed. The reaction mechanisms generally involved in photo-curing and thermal-curing are given first. Subsequently, the techniques of photo-curing 3D printing as well as UV-assisted 3D printing are summarized. By following, dual-curing with different sequential combinations of photo and thermal curing compositions are discussed in detail. Finally, recent progress on photo/thermal dual-curing materials for variety of applications are presented to further inspire the extensive development of dual-curing materials in 3D printing and future opportunities for post-print modification.