Conversion Mapping by Raman Microscopy and Impact of Slice Overlap in Additive Manufacturing

Abstract

Improved materials designed specifically for 3D printing are required before the technology becomes ubiquitous; however, trial and error printing parameter development is hindering progress. We describe an innovative Raman data analysis method to map conversion through cross-sectioned 3D printed layers. The method alleviates two common complications present in Raman spectroscopy, varying baselines and normalization of spectra, resulting in high quality chemical maps showing the monomer to polymer conversion profile throughout a 3D printed part. The conversion profile is used to demonstrate the impact of “overlap” between slices (layer thickness) on the providing sufficient structural strength during printing while also maintaining resolution. A simple printing process using “infinite cure” to determine the layer thickness that can be cured to a sufficient level to become solid has been identified as a means to optimize photoinitiator and photoabsorber levels, exposure, and time.

Influence of Postprinting Conditions on Morphologies in a Three-Dimensional Printable Dual-Cure Interpenetrating Dimethacrylate/Epoxy Polymer Network

“…The main relaxation for the fully cured epoxy–amine is relatively narrow with a width at half height of 14 °C and shows a weak secondary transition at approximately −50 °C, which is consistent with previous reports and typical for many polymers. , The primary transition for the 9G is very broad with a width at half height of 40 °C. This behavior has been observed previously and is attributed to the random distribution of the number of ethyleneoxide units in this monomer …”

“…This behavior has been observed previously and is attributed to the random distribution of the number of ethyleneoxide units in this monomer. 26 The primary relaxation in the 50:50 mixtures that have been postcured for 1 and 3 h occurs between the main relaxations for the two pure components, indicating some miscibility of the dimethacrylate and epoxy phases. There is evidence of a second phase present, although the relaxation is at 5 °C, indicating that there is also a pure 9G phase present.…”