Recycling 3D printed and laser-sintered plastics, physically foamed recycled PET, plasma treatment enhancement of adhesion to polycarbonate and use of gluten as a toughening additive for polylactic acid (PLA) are among recent and current research projects at KuZ Kunststoff-Zentrum in Leipzig, Germany.
Announced at the end of August and running until June 2022, the "ReUp-3D-Printwaste" project uses chemical additives to improve additive manufacturing waste plastic quality. These include support structures and faulty printed parts in PLA from fused deposition modeling (FDM), and selective laser sintering (SLS) polyamide 12 powder. These "upcycled" materials save costs while benefiting the circular economy by use in additive processes from which they originate.
When added to PLA waste, chain extenders, hydrolysis stabilizers and antioxidants enable extrusion into new FDM filaments, and chain shortening and antioxidant additives in PA12 waste powder results in new SLS material. KuZ says it also focuses on combined SLS-FDM and FDM recycled materials.
Material costs take the largest share of additive process operating costs. Virgin PLA filaments cost 25-30 euros ($28-$34) per kilogram, virgin nylon 12 powder 80-120 euros ($92-$138) per kg. So there is plenty of material available for upcycling, as FDM generates 20-30 percent waste, SLS 50-70 percent.
In a "RecySchaum" recycled foam project, KuZ uses PET from post-consumer packaging waste as a basis for recycled PET thermoplastic foam injection molding lightweight automotive components. A recycled PET foam model achieved 40 percent weight saving over an equivalent real application reference part.
Recently concluded with Sandersdorf-Brehna, Germany-based contract compounder Compraxx GmbH, the "Gluplast" project involved wheat gluten as a naturally reoccurring additive in PLA to reduce inherent brittleness and improve low plastic deformability and impact strength, previously only achieved by blending PLA with conventional petroleum-based polymers such as thermoplastic polyurethane or ethylene copolymer.