Sustainability aspects of composite filament fabrication for 3D printing applications

The usage of plastics has become an inherent part of human life due to low cost, light weight, flexibility and ease of production. The degradation time for plastics is one of the major concerns currently the world is facing. According to the United Nations Sustainability Development (UNSD), a major percentage of currently available plastic must be either recycled or reused for a sustainable ecosystem. In this systematic review a methodology is presented to recycle the discarded plastics, metal, and ceramic scrap for the fabrication of composite filaments for material extrusion based 3D printing. The capabilities and recent progress in material extrusion based metal additive manufacturing are reviewed to identify the potential recyclable resources. The sustainable and entrepreneurial opportunities for recyclable materials for composite filament fabrication are discussed. It is observed that the composite filament must contain a minimum of 40 vol% reinforcement infill to make the printed parts eligible for sintering. The applications of the material extrusion based metal and ceramic additive manufacturing are detailed. The limitations, future directions and the possible improvements are explained. From this comprehensive review, it is expected that the reader will attain a proficient understanding of the sustainable process involved in fabricating metal and ceramic particle filled polymer composite filaments.