Self-Healing Photocurable Resin with Epoxy-Loaded Melamine–Urea–Formaldehyde Microcapsules for Molds Fabricated by Liquid Crystal Display 3D Printing

Abstract

Additively manufactured resin molds are susceptible to thermomechanical failure and accumulated damage during molding processes, severely limiting their service life. To address this, a thermally stable self-healing photocurable resin was developed for liquid crystal display (LCD) 3D printing. Microcapsules (MCs) comprising a commercial E51-grade epoxy resin core and a melamine–urea–formaldehyde (MUF) shell were incorporated into the photocurable matrix together with an amine curing agent to enable crack repair. At 7 wt % MCs, the optimized formulation showed a healing efficiency of 68.97% after healing at 60 °C for 12 h. It exhibited a 5% mass-loss temperature of 372.1 °C, a maximum mass-loss-rate temperature of 428.1 °C, and short-term shape retention after treatment at 240 °C for 4 h. Open-ended internal channels were fabricated and demonstrated room-temperature flow connectivity. Representative molds were further printed and used for silicone molding, demonstrating the potential of the optimized formulation for repairable LCD-printed resin molds requiring short-term heat resistance.