Effect of a red-shifted benzotriazole UV absorber on curing depth and kinetics in visible light initiated photopolymer resins for 3D printing

• A red-shifted benzotriazole light absorber is proposed as 3D printing additive.
• The cure-depth under blue light is highly sensitive to the absorber concentration.
• With increasing absorber content the curing speed is moderately reduced.
• Optimizing the absorber concentration is vital for high accuracy in the built parts.

We have investigated the effects of a red-shifted UV absorber in projection-microstereolithography operating under blue visible light (405 nm). A 2-(2-hydroxyphenyl)-benzotriazole derivative (Tinuvin® CarboProtect®: CarboP) was introduced as an absorbing additive. A remarkable decrease of the curing depth from over 800 μm in the pristine resin to 65 μm at 0.2 mol% CarboP was observed, while the polymerization and build times were somewhat increased. Microfluidic channels were accurately fabricated with the modified resin whereas the pristine photopolymer did not form any precise patterns. This demonstrates potential applications of modified UV absorbers in visible light initiating resins for precise 3D printing.

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