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Published in:
2021 | OriginalPaper | Chapter
Experimental Study on Depth of Cure During UV-Post-Curing of Photopolymers Used for Additive Manufacturing
Authors : Jan Nitsche, Tristan Schlotthauer, Florian Hermann, Peter Middendorf
Published in: Advances in Automotive Production Technology – Theory and Application
Publisher: Springer Berlin Heidelberg
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Abstract
For the production of automotive interior parts, there is a high demand regarding the surface quality combined with large production rates. These requirements can potentially be achieved by using Stereolithography (SL).
This work concerns the dimensional limitations of depth of cure during UV-post-curing of parts made of urethane acrylates by Digital Light Processing (DLP). Due to absorption of the UV-light in the photopolymer, the penetration depth is limited. A better understanding of the depth of cure is necessary to define optimal post-curing parameters and potential limits of the wall thickness. To investigate the depth of cure, green-state specimens are irradiated unidirectionally by UV-light with a wavelength of 365 nm and 405 nm. Subsequent hardness measurements according to Shore D are used to determine the corresponding depth profiles. Thereby the influence of photoinitiator concentration, irradiation dose and wavelength on depth of cure is analysed. Additional transmission measurements during post-curing contribute to a better understanding of the penetration depth of the UV-light for optimal production times.
For a non-pigmented photopolymer, the measured depth of cure is between 0.59 mm and 8.58 mm. The highest depth of cure is obtained by a low photoinitiator concentration of 0.75%wt, long wavelength of 405 nm and high irradiation dose of 70 J/cm\(^2\).