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Hart, A. John Tumkur Mahesh, Prajwal Massachusetts Institute of Technology. Department of Mechanical Engineering 2024-08-01T19:01:07Z 2024-08-01T19:01:07Z 2024-05 2024-06-13T16:49:12.086Z https://hdl.handle.net/1721.1/155850 https://orcid.org/0000-0002-5128-0503 Conventional light-based processes used in additive manufacturing (AM), such as vat polymerization, yield non-recyclable thermoset polymers, which pose sustainability issues at scale. This thesis studies a method for photopolymerization 3D printing of the common polymers polyacrylonitrile (PAN) and polymethyl methacrylate (PMMA) to address the growing demand for low-waste production of high-resolution polymer parts with complex geometries in industrial-scale manufacturing. This new approach not only produces directly recyclable linear thermoplastic polymers but also enables the light-based printing of polymers soluble in their own monomer. It was previously demonstrated by Chazot et al. that photo-defined layers of polyacrylonitrile (PAN) can be formed at a liquid-liquid interface; this technique was named interfacial photopolymerization (IPP). In this thesis, which focuses on multilayer 3D printing (3D-IPP), the resolution and stability of layers formed by IPP are improved using a light-absorbing dye while incorporating a water-soluble polyethylene glycol binder to improve yield, printing speed, and mechanical properties. Joint initiation using commercial water-soluble photoinitiators V-50 and LAP, along with the addition of HCL and CaCl2, further enhances printing performance by producing dense layers and reducing voids. Post-processing techniques are devised to preserve part geometry after printing, including controlled air drying, thermal post-processing with PEG infiltration, and the inclusion of compatible polymeric binders in the printing composition to minimize cracking and shrinkage. Additionally, hardware is developed to integrate the IPP process into a commercial projector-based 3D printer, demonstrating compatibility of the proposed chemistry with off-the-shelf hardware. The capability to digitally manufacture high resolution 3D structures with IPP is demonstrated and the physical properties of the resulting composite polymer are characterized. While 3D-IPP cannot yet directly rival conventional manufacturing methods, the benign aqueous chemistry as well as recyclability and circularity of produced parts offers a promising path towards sustainable and resource-efficient AM as the technology matures. S.M. Massachusetts Institute of Technology Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) Copyright retained by author(s) https://creativecommons.org/licenses/by-sa/4.0/ Method for Photopolymerization 3D Printing of Recyclable Thermoplastic Polymers Thesis application/pdf Master Master of Science in Mechanical Engineering Publication unknown unknown <Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="baee9d66-0fcd-4149-bf01-427c0c318886"> <Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type> <Title>Method for Photopolymerization 3D Printing of Recyclable Thermoplastic Polymers</Title> <PublishedIn> <Publication> </Publication> </PublishedIn> <PublicationDate>2024-05</PublicationDate> <Authors> <Author> <DisplayName>Tumkur Mahesh, Prajwal</DisplayName> <Affiliation> <OrgUnit> </OrgUnit> </Affiliation> </Author> </Authors> <Editors> </Editors> <Publishers> <Publisher> <DisplayName>Massachusetts Institute of Technology</DisplayName> <OrgUnit /> </Publisher> </Publishers> <License>https://creativecommons.org/licenses/by-sa/4.0/</License> <Abstract>Conventional light-based processes used in additive manufacturing (AM), such as vat polymerization, yield non-recyclable thermoset polymers, which pose sustainability issues at scale. This thesis studies a method for photopolymerization 3D printing of the common polymers polyacrylonitrile (PAN) and polymethyl methacrylate (PMMA) to address the growing demand for low-waste production of high-resolution polymer parts with complex geometries in industrial-scale manufacturing. This new approach not only produces directly recyclable linear thermoplastic polymers but also enables the light-based printing of polymers soluble in their own monomer. It was previously demonstrated by Chazot et al. that photo-defined layers of polyacrylonitrile (PAN) can be formed at a liquid-liquid interface; this technique was named interfacial photopolymerization (IPP). In this thesis, which focuses on multilayer 3D printing (3D-IPP), the resolution and stability of layers formed by IPP are improved using a light-absorbing dye while incorporating a water-soluble polyethylene glycol binder to improve yield, printing speed, and mechanical properties. Joint initiation using commercial water-soluble photoinitiators V-50 and LAP, along with the addition of HCL and CaCl2, further enhances printing performance by producing dense layers and reducing voids. Post-processing techniques are devised to preserve part geometry after printing, including controlled air drying, thermal post-processing with PEG infiltration, and the inclusion of compatible polymeric binders in the printing composition to minimize cracking and shrinkage. Additionally, hardware is developed to integrate the IPP process into a commercial projector-based 3D printer, demonstrating compatibility of the proposed chemistry with off-the-shelf hardware. The capability to digitally manufacture high resolution 3D structures with IPP is demonstrated and the physical properties of the resulting composite polymer are characterized. While 3D-IPP cannot yet directly rival conventional manufacturing methods, the benign aqueous chemistry as well as recyclability and circularity of produced parts offers a promising path towards sustainable and resource-efficient AM as the technology matures.</Abstract> <Access xmlns="http://purl.org/coar/access_right" > </Access> </Publication>