Vat photopolymerization technologies are promising 3D printing techniques in the field of additive manufacturing, which requires high performance and affordable photoinitiating systems (PIS). In this paper, we introduce a complex PIS based on safranine as photosensitizer and two redox additives. The photocycling mechanism is explored via laser flash photolysis (LFP) and its reactivity is investigated through real-time Fourier transform infrared spectroscopy (RT-FTIR). A model which predicts with good accuracy the change in conversion with both time and light intensity is proposed. Cure depth experi-ments are conducted and the critical energy (Ec) and penetration depth (Dp) are established for the resin used. The relationship between these parameters and the corresponding RT-FTIR results was highlighted through the role of the conversion at the gel point, allowing optimization of the formulation. Finally, high resolution complex pieces are printed with the resin, whose composition was tailored in accordance with our studies, demonstrating the viability of this PIS in digital light processing (DLP) 3D printing.
This study provides insight into the relationship between the photochemical reactivity and the photonic parameters of an acrylate formulation usable in digital light processing (DLP) 3D printing. First the photoreactivity of riboflavin tetrabutyrate (RFT) used as a non‐toxic photoinitiator is assessed by laser flash photolysis in the absence and in the presence of an amine as co‐initiator. RFT alone is able to photopolymerize the acrylate formulation at a rate which is drastically increased when the co‐initiator is added. Then, the depth of light penetration (Dp) and the critical energy (Ec) to form a polymer film were measured and compared to those determined from the Bouguer‐Lambert‐Beer law for Dp and from the Stockmayer equation and photopolymerization experiments for Ec. A new proposed model is able to predict the in‐depth acrylate conversion within a printed part with a relatively low input of experimental parameters. Confocal Raman microscopy is used to discuss the effect of the photobleaching of RFT in the absence of co‐initiator on the photopolymerized films. Finally, it is shown that this formulation performs quite well for 3D printing with a resolution close to the best performance of the DLP printer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.