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Unraveling 3D Printing Dynamics
Scientists used ultrabright x-rays to uncover how the printing and curing process of a polymeric material influences the material's properties
November 30, 2020
The schematic shows the experimental setup to study the microscopic dynamics of the resin during 3D printing and simultaneous UV curing. Image credit: S. Coburn
Scientists reveal that higher UV intensity results in the faster curing of the resin, while the resin is less sensitive to directional forces during printing.
3D printing is a promising technique to rapidly produce polymeric materials; this work gives new insights about the fundamental nanoscale dynamics during 3D printing for optimization of material and processing parameters.
From cars and planes, to electronics and medical applications, many industries rely on creating precision 3-dimensional (3D) parts that are customized for their specific needs. Many of these industries started using a new, cost-effective method of making parts called additive manufacturing or 3D printing. While 3D printing offers many benefits, it also has a number of challenges that researchers need to face before industry can apply this technique to manufacturing parts with strict mechanical property requirements.
In this work, a group of scientists, together with industrial researchers, investigated how the printing and curing process of a polymeric material – a curable resin – affects the mechanical properties of the part. Specifically, they studied the evolution of dynamics of the material at the nanoscale during each step - printing, curing, and solidifying - of the printing process under industrial relevant conditions.
To resolve the evolution of the dynamics, the team used a technique called x-ray photon correlation spectroscopy (XPCS) to measure the change of the structure in space and over time. They focused their investigation on the printing speed and the intensity of the ultraviolet (UV) light during the curing the process. Both processes could be measured with XPCS using the Coherent Hard X-ray Scattering (CHX) beamline at the National Synchrotron Light Source II (NSLS-II). NSLS-II is a U.S. Department of Energy (DOE) Office of Science User Facility located at DOE’s Brookhaven National Laboratory and offers access to a wide range of materials characterization tools.
The team compared their XPCS results with the rheological behavior of the resin under comparable curing conditions. Rheology is the study of the flow of matter – mostly liquids and soft solids – and investigates deformation on such materials. They confirmed a correlation between the microscopic dynamics (by XPCS) and macroscopic material properties (by rheology), and identified the interplay between solidification mechanisms across a wide range of length and time scales.
They found that higher UV intensity results in faster curing of resin, slower dynamics between different layers, and that the printing speed impacts the overall dynamics of the structure. However, the dynamics induced by horizontal draw out and extension of the filament are not dramatic at the print speeds used in this experiment. The dynamics of the prepolymer and filler in the curable resins appear to be less sensitive to the directionally dependent forces than expected under these printing conditions. Understanding this process will eventually improve our understanding of interlayer adhesion resulting from the printing process and strengthen the 3D printed parts as whole.
This work proved that XPCS is a powerful technique to reveal the underlying processes during 3D printing and could provide essential insights to optimize the printing conditions for the creation of specific mechanical properties.
Stony Brook University
B. M. Yavitt, L. Wiegart, D. Salatto, Z. Huang, M. K. Endoh, S. Poeller, S. Petrash, T. Koga Structural Dynamics in UV Curable Resins Resolved by In Situ 3D Printing X-ray Photon Correlation Spectroscopy. ACS Appl. Polym. Mater. 2 (9), 4096-4108 (2020). DOI: 10.1021/acsapm.0c00716
B.M.Y. and T.K. acknowledge financial support from the Henkel Corporation and Brookhaven National Laboratory. Acknowledgment is made to the Donors of the American Chemical Society Petroleum Research Fund for partial support of this research. This work used resources of the Center for Functional Nanomaterials (CFN) and the National Synchrotron Light Source II (Beamline 11-ID), which are U.S. DOE Office of Science Facilities, at Brookhaven National Laboratory under Contract No. DE-SC0012704.
2020-18794 | INT/EXT | Newsroom