Sustainable additive manufacturing: predicting binder jettability of water-soluble, biodegradable and recyclable polymers

Additive manufacturing potentially generates customized polymeric objects with tailored geometry while reducing waste, employing biodegradable polymers and striving to use recyclable polymer feedstocks for a more sustainable future. Binder jetting additive manufacturing (BJ AM) creates 3D objects upon depositing liquid adhesive onto a powder bed, while a roller spreads powder over a build stage to form subsequent layers. Many factors affect jettability and printability including printhead design, binder material, binder solvent and powder characteristics. Material design for higher strength BJ AM parts using metals, ceramics or polymers exploits binders or particles that transform into thermosets or permanently shaped matrices through thermal or UV curing and sintering. While many BJ AM examples utilize biodegradable, water-soluble and recyclable polymers for biomedical and industrial applications, a wider array of opportunities exist to degrade, dissolve and reuse printed materials. Systematically shifting to these polymers will facilitate reuse and recycling of both binders and powders, but more studies to improve part strength are required. This review describes an overview of polymer jettability and a perspective into opportunities currently underutilized in transitioning BJ AM into a more sustainable AM platform.