Use of additive manufacturing technologies for functional rehabilitation ; Utilisation des technologies de fabrication additive pour la réadaptation fonctionnelle

Since 2016, the NGO Handicap International (HI) has been using 3D printing (Fused Filament Fabrication) to produce prostheses and orthoses in low-income countries. While the initial results are promising, importing polypropylene (PP) filaments from Europe poses logistical challenges and increases the manufacturing costs. Thus, this project aims to recycle plastic waste into 3D printing filaments to locally produce ankle-foot orthoses in Togo. A preliminary study was conducted on three polymers to identify the most suitable material: recycled PET (bottles), virgin PP (used by HI), and recycled TPU (production scraps from the footwear industry). Mechanical tests and numerical simulations showed that PP, due to its semi-rigidity, offered a good balance between comfort and support. Subsequently, the printability and properties of recycled PP-PEHD blends were studied. Adding 30 to 50% PEHD to the PP matrix improves stability during deposition. In-situ compatibilization during the process creates a fine morphology and satisfactory mechanical properties. Finally, recycled blends composed of 70% PP and 30% PEHD, derived from post-consumer food packaging waste and post-industrial scraps from orthopedic sheets, were processed into 3D printing filaments and used to print orthoses after optimizing process parameters. The durability of the orthoses was analyzed through accelerated aging tests on PP with different compositions (virgin, UV-stabilized, and recycled from post-consumer materials) and processes (3D printing, injection, and thermoforming) under conditions typical of Togo. On the one hand, recycled PP was found to be more sensitive to thermo- and photo-oxidation due to impurities and the lack of stabilizers, necessitating the addition of additives during recycling to prevent brittleness. On the other hand, 3D printing showed promise in improving aging resistance, as it limits degradation during the process. Finally, the rupture resistance of the orthoses was characterized using a test bench simulating walking. ...