(392d) Autonomic Self-Healing of 3D Printed Polymer Composites

One approach to a more sustainable materials ecosystem is through extending material lifetimes through self-healing behavior. While self-healing has utility across many applications, it is particularly important for components fabricated for hard to reach or hard to replace applications. Concurrently, the potential of additive manufacturing has grown tremendously in recent years and the benchmarking and exploration of new polymer materials and polymer composite materials for 3D printing applications is critical. Notedly, many 3D printed specimens tend to show inferior mechanical strength, and thereby increased potential for material damage and failure during fabrication and use, compared to traditional processing approaches. The inclusion of self-healing behavior is a promising approach to address the microcracks that can develop within the structure where fracture detection is difficult, and repair is almost impossible both during fabrication and in use. Moreover, many of the polymer material options for 3D printing are not intrinsically recyclable, requiring disposal if they suffer any damage or degradation, increasing environmental waste through the premature end of their useful life. Here, we incorporate self-healing properties towards extending the lifetimes of 3D printed polymeric objects. Inspired by biological self-healing, where a damage event triggers an autonomic healing response, microcapsules containing healing fluids are embedded within the 3D printed composites. Microcapsules rupture during a damage event release the healing agent, and heal the surrounding material by polymerization, entanglement, or cross-linking without external intervention increasing product life and improving material sustainability and long-term cost. Double shell wall polyurethane/poly (urea-formaldehyde) microcapsules are synthesized by in-situ-interfacial polymerization. Microcapsules with both solvent and monomer core fluids are prepared to investigate both solvent-healing and monomer self-healing mechanisms. Microcapsules, of varied size and at varied concentration, containing healing agents are either incorporated into the host polymer matrix (SLA 3D printing) or are coated onto 3D printing polymer filaments (FDM 3D printing). Microcapsule distribution within composites is visualized using X-ray Nano-CT imaging. Printed composite self-healing behavior is evaluated by their fracture toughness healing efficiency. Overall, we find the inclusion of autonomic self-healing behavior through this approach to be successful for both SLA and FDM 3D printing.