Among 3D printing photosensitive resins, epoxy resin has excellent mechanical properties, chemical stability, high/low-temperature resistance, low shrinkage, and low cost.
From the molecular point of view, the curing process of photosensitive resin is a process of changing from small molecules to long-chain macromolecules, and its molecular structure has changed greatly, so a shrinkage in the curing process is inevitable. The shrinkage of resin mainly consists of two parts, one is curing shrinkage, and the other thermal expansion and cold contraction caused by temperature change when a laser scans the surface of liquid resin. At the same time, the area of temperature rise is very small, so the shrinkage caused by temperature change is extremely small and can be ignored.
The influence of the volume shrinkage of photosensitive resin in the light curing process on the precision of parts can not be ignored. Shrinkage leads to shrinkage stress, which leads to a warpage of parts. When the acrylic resin is cured, the polymerization reaction of the carbon-carbon double bond breaks, which leads to larger volume shrinkage, while when epoxy resin for 3d printing is cured, a ring-opening reaction occurs, so the volume shrinkage is relatively small.
Because cycloaliphatic epoxy resin has the advantages of low viscosity, excellent weather resistance, low curing shrinkage, high crosslinking density, and high reactivity, the photosensitive resin printed in SLA 3D is widely used and is one of the most important matrix oligomers.
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