Abstract
Fused Filament Fabrication (FFF) allows rapid prototyping of custom-made, complex 3D shapes from thermoplastic filaments, reducing design-to-production times and costs[1]. Similarly, Fused Granulate Fabrication (FGF) is an extrusion-based printing technique that starts from granulates[2]. In FGF, the preprocessing step of extruding the polymer into a filament with constant diameter is avoided, as a screw extruder is directly built into the printer head. The pellets are fed to the printer head by the screw and deposited onto the print bed in the same way as starting from a filament. FGF allows the printing of softer materials compared to the commercial thermoplastics and it can also be used for composites[3].
Self-healing polymers based on thermoreversible Diels-Alder (DA) bonds have recently been introduced to FFF [4]. These dynamic covalent networks can be printed at temperatures close to their gel transition temperature (Tgel). When heated above Tgel, the dynamic equilibrium shifts towards the dissociation of the DA crosslinks until the polymer network degels, allowing the resulting polymer to flow through the nozzle as a viscous melt. Once in contact with the printing bed at a temperature below Tgel, the dynamic equilibrium shifts back to the formation of the DA adducts, reforming the network structure.
Commercial thermoplastics allow printing of complex structures, while this proves difficult with the pure Diels-Alder network due the drastic change to low viscosity upon degelation. The viscosity in the melt state of the dissociated network is increased by the addition of fillers and allows to print more complex structures with higher accuracy[5]. Different fillers, filler loadings and different mixing techniques are evaluated and compared. The printed part has extended lifetime upon damage thanks to the self-healing ability of the Diels-Alder crosslinks, it can be reprocessed/recycled. Different polymer composites are used in multimaterial printing for the creation of a self-healing touch sensor. Different designs are investigated and optimized to obtain a higher sensitivity.
Self-healing polymers based on thermoreversible Diels-Alder (DA) bonds have recently been introduced to FFF [4]. These dynamic covalent networks can be printed at temperatures close to their gel transition temperature (Tgel). When heated above Tgel, the dynamic equilibrium shifts towards the dissociation of the DA crosslinks until the polymer network degels, allowing the resulting polymer to flow through the nozzle as a viscous melt. Once in contact with the printing bed at a temperature below Tgel, the dynamic equilibrium shifts back to the formation of the DA adducts, reforming the network structure.
Commercial thermoplastics allow printing of complex structures, while this proves difficult with the pure Diels-Alder network due the drastic change to low viscosity upon degelation. The viscosity in the melt state of the dissociated network is increased by the addition of fillers and allows to print more complex structures with higher accuracy[5]. Different fillers, filler loadings and different mixing techniques are evaluated and compared. The printed part has extended lifetime upon damage thanks to the self-healing ability of the Diels-Alder crosslinks, it can be reprocessed/recycled. Different polymer composites are used in multimaterial printing for the creation of a self-healing touch sensor. Different designs are investigated and optimized to obtain a higher sensitivity.
Original language | English |
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Publication status | Published - 14 Nov 2022 |
Event | Belgian polymer group (BPG) annual meeting 2022 - Duration: 14 Nov 2022 → 15 Nov 2022 |
Conference
Conference | Belgian polymer group (BPG) annual meeting 2022 |
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Period | 14/11/22 → 15/11/22 |