Incorporating Interlayer Crosslinks in Fused Filament Fabrication: Insights into Post Deposition Reactions

3D printed objects exhibit low interlayer adhesion and defects that result in anisotropic mechanicalproperties. In this presentation, we will describe the introduction of covalent bonds between filaments to enhance interlayer adhesion by the reaction of multi-amines with oxygenated functional groups on the recently deposited filament. Interfacial fracture energy evaluation and infrared (IR) spectroscopy indicate the successful formation of interlayer bonds and strengthening of interlayer adhesion with a variety of multi-amine materials. More importantly, the spectroscopy results also reveal the relative reaction rates of each multi-amine with the oxidized filament. The results show that crosslinking reactions occur rapidly at elevated temperatures immediately following filament deposition. Data also indicates that amine reactivity is not the prevailing factor in the observed interfacial strength improvement, as crosslinker aromaticity also plays an essential role. Therefore, these results offer important foundational information that can foster the use of similar protocols in other extrusion additive processes and materials.