3D printing has demonstrated tremendous growth in recent years, making it one of the fastest-growing technology in the medical manufacturing industry. The significant contribution of the technology has been extraordinary, as it has completely transformed many medical manufacturing industries such as those providing devices for dental prosthetics and hearing aid. In terms of 3D printing techniques, stereolithography is one of the most commonly used. We analyzed the effect of UV and thermal processing on UV-curable polymers fabricated by 3D printing, and modeled the properties of these materials. Polymers used were proprietary Formlabs resins based on methacrylates (strength methacrylate monomer-based resin), and samples were produced directly in printed geometrical configurations.&nbsp;Using the ASTM D638 standard, four different types of resin from Formlabs were tested under tension to obtain an estimate of their mechanical properties. The resins that were tested in this investigation were Clear, Tough, Durable, and High-Temperature resins. After post-processing was accomplished by using a custom-built curing oven, the experiment results were compared with those of non-post processed control samples.Young's modulus and Poisson's ratio, as well as yield stress measurement, were conducted at room temperature in uniaxial tension. Additional exposure to UV light and higher temperature "soaking" (in various combinations) has been utilized in post-processing. It has been observed that post-processing is likely to affect the mechanical properties significantly, especially of those resins that present a more flexible behavior when at the green state.&nbsp;As an example, It was found that the Tough and Durable resins performed similarly when green (TG, DG), but the post-processing treatment made the&nbsp; Tough Resin (TC) change its behavior from an elastomer-like to rigid plastic. There could be seen a significant change in the relation between the strain and stress as it became progressively more linear.&nbsp; The Durable resin (DC) kept behaving like an elastomer. The ultimate strength for TC is 33 MPa, while the ultimate strain for DC is 0.05 mm/mm. For DC, the ultimate strength is 20 MPa, while the ultimate strain was 0.2 mm/mm.&nbsp;Compared to the materials that were not treated, the post-processing treatment combination of UVA irradiation and thermal soaking significantly improved the strength of the materials under tension by a factor of two to more.&nbsp;Furthermore, the treatment increases the stiffness of the material up to eightfold. For the Durable resin, the elastic modulus increased from 66 MPa to 433 MPa, while for the Tough resin, the elastic modulus increased from 200 MPa to 800 MPa. On the other hand, our results have lower values than the elastic modulus measured in tensile reported by the manufacturer of 1.7 and 2.7GPa,&nbsp; for the Tough resin and&nbsp; 0.45 GPa and 1.26 GPa for the Durable resin.

Irradiation and Thermal Post-Processing for Vat-Polymerization Additive Manufacturing: Tensile Properties of Four Formlabs Resins

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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