Additive manufacturing of a self-healing thermoplastic polyurethane

Abstract

Additive manufacturing of smart polymers is a rapidly growing field. Additive manufacturing presents a versatile, low-waste manufacturing method for functional materials. Self-healing polymers are a type of smart polymers that are able to mend damage, either by the incorporation of an encapsulated healing agent or by intrinsic polymer design. Beside this ability to repair damage, certain types of self-healing polymers have also shown to improve interlayer adhesion of 3D printed parts due to the formation of reversible cross-links. This thesis demonstrated the additive manufacturing of a self-healing polyurethane (CR1) by fused deposition modelling. A protocol was established in order to print with this self-healing polyurethane while minimising material loss. Measurable polymer properties that were relevant to fused deposition modelling were identified and measured in order to establish the processing window of the polymer. CR1 was synthesised, processed into a filament using a commercial filament maker and successfully printed using a modified commercial 3D printer. The elastomeric nature of the polymer combined with its high sensitivity to temperature, resulted in a narrow printing window. Beside the ability to 3D print the polymer into rectangular bars, the self-supportability of the 3D printed CR1 was demonstrated by the printing of a single-wall structure. Printing at 230 °C and 20 mm/s resulted in the most regular sample, with a very low void concentration in its cross-section. The mechanical response of 3D printed CR1 showed good resemblance to that of the bulk. Furthermore, the test showed that the polymer retained its self-healing ability after printing.