Polymeric Binders for Metal Binder Jetting Additive Manufacturing: A Review

In metal Binder Jetting Additive Manufacturing (BJAM), the polymeric binder is often treated as a temporary, almost incidental consumable — yet it silently governs nearly every outcome of the process, from droplet ejection to the properties of the final sintered part. This review reframes the binder as a central design variable and examines it through a polymer-science lens, tracing its influence along the complete BJAM process chain. We first dissect binder chemistry and architecture, organizing aqueous, solvent-based, and reactive systems by carrier medium and bonding mechanism, and linking molecular features — functional groups, chain entanglement, and crosslinking — to printability, green strength, and clean thermal removal. We then follow the binder into the powder bed, where rheology, droplet dynamics, and capillary migration dictate spreading, penetration, and shape fidelity; into the green part, where adhesion and particle bridging set mechanical integrity; and through debinding and sintering, where decomposition chemistry, residual carbon, and densification determine final quality. A survey of automotive, energy, aerospace, biomedical, and tooling applications highlights where binder limitations still constrain industrial adoption. Throughout, we emphasize the recurring trade-offs — jettability versus green strength, penetration versus saturation, and burnout cleanliness versus chemical composition — that any next-generation binder must resolve, and we outline design criteria toward predictive, application-specific binder development.