RESUMEN
In this study, the effect of the post-curing process as well as the long-term weathering behavior were studied for three different three-dimensional printable, pigmented (black), nonstabilized, ultraviolet (UV) cure resin formulations (A and B being thiol-ene chemistry, and C being acrylate chemistry). To study the effect of the post-cure process, the printed parts were post-cured using one of five different processes: no post-cure, UV-only, heat-only, UV+heat, and electron beam (EB) post-curing. Bulk tensile properties and nanohardness were measured for each of the systems and post-cure conditions. For weathering studies, the parts were post-cured using the recommended UV-only process and exposed using the ASTM D7869 exterior weathering protocol. The results show that the post-cure process had a significant effect on the final mechanical properties of the resins and was dependent on the underlying resin chemistry. Thermal post-curing was not as effective as UV curing for Resin C compared with the two other resins, which could both undergo thermal polymerization. In addition, Resin B showed the smallest change in mechanical properties before and after post-curing, regardless of the type of post-curing process. EB post-curing, even at very low dosages, that is, from 0.05 to 1 Mrad, resulted in considerable post-cure cross-linking to the point of embrittlement and a significant drop in percent elongation at break for dosages above 0.5 Mrad. Although Resins A and C outperformed Resin B in photooxidation performance, all three resins demonstrated that promising results considering no hindered amine light stabilizers were used in the formulations.
RESUMEN
OBJECTIVE: Gel nail polishes represent an advanced class of nail polishes, with the ability to cure under ultraviolet (UV) radiation, and consequently demonstrate improved properties and greater durability compared to conventional nail polishes. Most gel nail polishes available today are based on petrochemical resources, making them unsustainable. Bio-based materials are excellent renewable resources, with high potential for meeting final-product performance, cost, and environmental needs. In addition, bio-based materials can be modified to make them amenable to being cured by advanced Light Emitting Diode (LED) resources that consume low energy and are safer for human exposure compared to conventional UV-mercury lamps. Consumer preference for use of products made from bio-based sources has been clearly growing. On the other hand, according to the U.S. Department of Energy (DOE) technology roadmap, a considerable amount of basic chemical building blocks should be derived from plant-based renewable materials in near future. However, to the best of our knowledge, bio-based nail products have not been sufficiently explored. Therefore, to keep pace with environmental regulations and consumer preference, there is an unmet opportunity to develop novel, sustainable nail gel polishes with considerable bio-renewable content. In this study, two sustainable UV-LED curable gel nail polish prototypes-one high-solids zero-volatile organic content (VOC) and the other waterborne, both with considerable bio-renewable content, were designed. METHODS: Both formulations were cured under both UV-mercury and UV-LED radiation sources in order to evaluate their curing efficiency under a UV-LED source. Also, their performance was compared with a commercial petro-based benchmark. RESULTS: The high-solids formulation demonstrated promising performance, exceeding that of the benchmark in opacity, chemical properties, gloss, and pendulum hardness, while the waterborne formulation met most of the desirable requirements with some significant technical benefits, including low odour and higher renewable raw material content. CONCLUSION: These novel gel nail polishes are greener alternatives to the current products in the market with high potential for promising consumer acceptance.
