Binder jetting is a versatile additive manufacturing (AM) technique that can form parts from a variety of powdered materials including metals, ceramics, polymers. Binder jetting utilizes inkjet printing to selectively bind these powder particles together to form complex geometries of hybrid materials. We report the discovery of an exceptionally versatile high-performance binder, hyperbranched polyethyleneimine (PEI) for binder jetting. The PEI binder enables (1) exceptionally strong green parts with silica sand, higher than unreinforced concrete, (2) reactive infiltration to provide further 8-fold increase in flexural strength, exceeding any known polymer sand composites and building materials such as masonry, and (3) washout functionality. The printed sand bridge with infiltration (6.5 cm length) can hold 300 times its own weight, which is analogous to 12 Empire State Buildings sitting on the Brooklyn bridge. We elucidate that PEI forms a corrugated interfacial structure of hydrogen bonding at the PEI-sand interface and the residual amines in PEI can initiate reactive infiltration. Furthermore, PEI binder is washable, allowing to serve as sacrificial tools (i.e. washout tooling) that can be broken down and removed from complex lightweight composite structures. The strong printed parts coupled with the ability for sacrificial washout presents potential to revolutionize AM in various applications including construction and tooling.

Polyethyleneimine binder in binder jetting enables exceptionally strong silica sand structures

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.