Fused Filament Fabrication 3D Printing of Self-Healing High-Impact Polystyrene Thermoplastic Polymer Composites Utilizing Eco-friendly Solvent-Filled Microcapsules

Fused filament fabrication (FFF) is a widely used additive manufacturing process that is increasingly adopted for prototyping and is growing in popularity for manufacturing. Simultaneously, there is increasing consideration of material lifecycles in choosing and designing materials and material processing techniques. One approach to extending material lifetimes is enabling the recovery of material properties after damage through an autonomous self-healing behavior. Here, we investigate the microcapsule-solvent-based self-healing of high-impact polystyrene (HIPS), a common thermoplastic polymer, toward increasing FFF three-dimensional (3D) printed specimen lifetimes and improving material sustainability by fabricating robust materials. Double-walled self-healing microcapsules filled with an environmentally friendly ethyl phenylacetate solvent are synthesized using in situ interfacial emulsion polymerization and coated on polymer filaments prior to FFF 3D printing. The ability of these microcapsules to sustain the FFF 3D printing process is demonstrated, and the self-healing performance of FFF 3D printed HIPS composites is evaluated via quantification of mechanical properties and healing efficiency (up to 81% healing efficiency is achieved).