Cure Depth Effects on Photopolymer Reactivity in Stereolithography 3D Printing

The quality of 3D printed polymers produced by stereolithography (SLA) 3D printing depends heavily on the characteristics of the liquid photopolymer resin. Layer delamination may occur if a resin reacts too quickly upon UV irradiation, resulting in a failed print. Monomer conversion upon UV irradiation will be minimal if a resin reacts too slowly, which leads to the same result. Several characteristics of SLA resins show an ideal range within which print conditions are optimal. Resin characteristics may be tuned within this zone to achieve consistent 3D printing and desirable mechanical properties. These characteristics include monomer conversion, rate of polymerization, and photopolymerization onset time as a function of curing depth. This study seeks to investigate the effect of photoinitiator concentration on these characteristics. Resin reactivity will be monitored via real-time Fourier infrared spectroscopy by attenuated total reflectance (RT-FTIR ATR). Two photoinitiatiors will be employed as an additive to a commercial SLA resin and the reactive species in an original resin. A monochromatic UV LED will be employed at varying intensity as the UV source. Prints will be attempted with varying photoinitiator content and mechanical properties will be studied by tensile testing.