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

Abstract

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°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°C resulted in a notable improvement in the mechanical properties.