Optimizing mechanical performance in 3D printing through a benzoxazine monomer blend photosensitive resin formulation

The objective of this study was to enhance the mechanical properties of 3D printed specimens in commercial photosensitive resin (PS-resin) through blend-thermosets using a benzoxazine monomer based on bisphenol A and a commercially available resin. Specifically, a benzoxazine-based bisphenol A compound, 6,6-(propane-2,2-diyl)bis(3-cyclohexyl-3,4-dihydro-2H-benzo[e][1,3]oxazine), was successfully synthesized via the Mannich reaction. The synthesis involved paraformaldehyde, bisphenol A, and cyclohexylamine in a molar ratio of 4:1:2, respectively. To prepare the blend-thermosets, a stereolithography 3D printer (SLA) was utilized, combining the PS-resin with varying amounts of the benzoxazine (ranging from 0 to 8 parts per hundred of resin, phr). The printed specimens were then subjected to a polymerization process by heating them at various temperatures ranging from 120 to 160 degrees C in a hot air oven for 2 h, allowing the benzoxazine to undergo ring-opening reaction and form the thermoset structure. Characterization of all the materials obtained, including the PS-resin, benzoxazine, and the blend-thermosets before and after heating, was conducted using techniques such as FT-IR and DSC. This work also showcased a sample technique for verifying the ring-opening of the benzoxazine ring. Additionally, the mechanical properties of the blend-thermosets were evaluated through tests for tensile strength, elongation at break, modulus, and hardness. The addition of merely 2 phr of benzoxazine monomers and subsequent curing at 120(degrees)C resulted in a notable improvement in the mechanical properties.