3D printing formulation comprising thiol compound and vinyl polymer using SLA technology

Abstract

The study of thiol-ene liquid resins for use in stereolithography 3D printing is highly promising due to low shrinkage properties and highly homogenous polymer networks which are largely desirable for applications such as fabrication of optical devices. However, there are still certain drawbacks in thiol-ene resins namely low shelf storage stability. Radical stabilizer systems are required to inhibit premature gelation from occurring and increase shelf storage stability. This project aims to devise a formulation of thiol-ene resin that is suitable for use in stereolithography printing. For a thiol-ene resin to be a suitable resin for stereolithography printing, it must have exhibit good curing behavior as well as possess good shelf storage stability. Three different radical stabilizers (Hydroquinone, TEMPO, Trimethyl) were experimented with to evaluate the overall effectiveness in terms of shelf storage stability. Curing tests were performed on the formulations with systematic combinations of radical stabilizer and photo-initiator with to evaluate its curing behavior. The printability, polymer conversion rate and thermal properties would then be investigated once both conditions were satisfied. The experimental results showed that Trimethyl was greatly ineffective at preventing premature gelation from occurring within the thiol-ene formulations while TEMPO and Hydroquinone was very effective. In terms of exhibiting curing behavior, optimal weight percentages of radical stabilizer (Hydroquinone, TEMPO) and photo-initiator was found. However, for formulation containing the radical stabilizer (Hydroquinone), it displayed poor printability conditions but with radical stabilizer (TEMPO), it displayed great printability conditions. Therefore, the radical stabilizer (TEMPO) with the optimal weight percentage of photo-initiator used was suitable for use in stereolithography 3D printing. Lastly, the conversion rate and thermal properties of the resin formulation containing radical stabilizer (TEMPO) were studied for future optimization.