Study on curing shrinkage and mechanism of DHOM‐modified epoxy‐acrylate‐based UV‐curing 3D printing materials

UV‐curing 3D printing technology is one of the technologies with the highest molding efficiency and accuracy in the field of 3D printing. At present, the main problems of UV‐curing 3D printing materials include the high curing shrinkage and the low toughness. In this work, free radical/cation hybrid curing system was developed, the effects of expansion monomer (DHOM, 3,9‐diethyl‐3′,9′‐dihydro‐xymethyl‐1,5,7,11‐tetraoxaspiro[5,5]undecanone) on the curing shrinkage, toughness, and other properties of the epoxy acrylate‐based UV‐curing 3D printing materials were investigated. The results showed that when the added amount of DHOM was 15 wt%, the best comprehensive performance of UV‐curing 3D printing materials was obtained. At this time, the curing shrinkage rate decreased from 6.13% to 3.47%. The main reason was that DHOM undergoes ring‐opening polymerization under the action of cationic photoinitiator, resulted in volume expansion. The impact strength increased from 9.61 to 12.13 KJ/m2, which was because that the ring‐opening reaction of DHOM reduced the curing shrinkage of the resin system and released the internal stress between the resin molecules. In the curing process of photosensitive resin, the single bond of carbon and oxygen in expansive monomer was broken due to ring‐opening polymerization, which changed the covalent bond length to van der Waals distance between carbon and oxygen atoms, and manifested as volume expansion on the macro level. This property can effectively resist volume shrinkage caused by photosensitive resin curing crosslinking during DLP 3D printing.