Collaborative Research: Interfacial Photopolymerization (IPP): A Method For High-Resolution Digital Printing of Thermoplastics

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Additive manufacturing (AM) encompasses many technologies used to produce objects by successive addition of material in a layer-by-layer manner. Currently, AM techniques for thermoplastic polymers rely on local heating to melt and reshape the material. AM processes that form objects by photopolymerization rely on an intrinsic crosslinking mechanism in thermoset polymers. These photopolymerization AM methods can produce parts with superior surface finish and detail relative to the methods available for thermoplastics, but these attributes come at the expense of compatibility with large-scale recycling processes. This award will support research on the first AM technique for recyclable thermoplastic materials that utilizes photopolymerization, called Interfacial Photopolymerization (IPP). This work combines fundamental materials science and manufacturing scale-up to enable the digital production of intricate, high resolution thermoplastic objects using commercially available feedstock materials. This work will have economic and environmental benefits by opening new applications in automotive, aerospace, consumer, and medical device industries that use recyclable plastics, which is a vital contribution to the sustainability of our world. In IPP, the polymerization process and resolution are controlled by a LED light source, which is focused at the reaction zone located at or near a planar liquid-liquid interface. Realization of this technology requires a detailed investigation into fundamental transport and reaction kinetics, light management conditions, and chemical thermodynamics to elucidate the governing physical mechanisms for polymer formation and the role they play in final print quality (e.g., resolution, interlayer adhesion, mechanical properties). A macrokinetic model of the diffusion and precipitation at the interface will be developed to establish quantitative understanding of how single layers form in IPP and the fundamental limits and parameter tradeoffs, and a custom-built projector-based 3D printer will be used to fabricate demonstration objects. Data on process and material performance will be integrated into cost models to compare IPP to AM and injection molding methods for polymer manufacturing and evaluate the economic viability of IPP at industrial scale.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.