Scientists at Oak Ridge National Laboratory have developed a new polymer, PEI, to bond and harden quartz sand. The resin can be used to print sandy structures with complex geometries and exceptional strength.

To create the objects, the team used polyethyleneimine, a synthetic polymer that doubled the strength of sandy parts compared to conventional binders.

For example, scientists presented a toy sand bridge that was printed using a new polymer. With a height of 6.5 cm, it withstood a weight that was 300 times its own.

The researchers printed porous parts using inkjet printing. Scientists soaked them with an adhesive, cyanoacrylate, which filled in the gaps in the composition. This provided an eight-fold increase in strength and made the polymer-sand composition stronger than other building materials. The impressive strength of the binder polymer is due to its interaction with cyanoacrylate during curing.

“Few polymers are suitable for use as a binder for porous material. We were looking for specific properties, such as solubility, that would give us the best possible result. But the key discovery lies in the unique molecular structure of our polyethyleneimine binder. It interacts with cyanoacrylate and this is what gives us exceptional strength, ”said Tomonori Saito, lead researcher on the project.

The new method allows the creation of 3D structures from a variety of powder materials. The concept is based on inkjet printing, but instead of ink, the printer head releases liquid polymer.

The polymer can be used in inkjet and 3D printing, and industrial plants use it to prototype and manufacture parts.