Polymer exposure gives 3D-printed sand superpower

Polymer exposure gives 3D-printed sand superpower

A new polymer developed at Oak Ridge National Laboratory strengthens sand for additive production applications. A 6.5-centimeter 3D-printed sand bridge, shown here, held 300 times its own weight. Credit: Dustin Gilmer / University of Tennessee, Knoxville

Researchers at the Oak Ridge National Laboratory of the Department of Energy have designed a new polymer to bind and reinforce silica sand for bonding additive manufacturing, a 3D printing method used by industries for prototyping and part production.

The printable polymer enables sand structures with intricate geometries and exceptional strength — and is also water-soluble.

The study, published in Natural communications, shows a 3D-printed sand bridge that at 6.5 centimeters can hold 300 times its own weight, a feat analogous to 12 Empire State Buildings sitting on the Brooklyn Bridge.

The link jet printing process is cheaper and faster than other 3D printing methods used by industry and makes it possible to create 3D structures from a variety of powder materials, offering advantages in cost and scalability. The concept comes from inkjet printing, but instead of using ink, the printer head ejects liquid polymer to bind powdery material, such as sand, building a 3D design layer after layer. The bonding polymer is what gives the printed sand its strength.

The team used polymer expertise to adapt polyethyleneimine, or PEI, a binder that doubled the strength of sand parts compared to conventional binders.

Parts printed by link casting are initially porous when removed from the print bed. They can be reinforced by infiltrating the design with an additional superglue material called cyanoacrylate, which fills in the gaps. This second step provided an eight-fold fortification in addition to the first step, making a polymer sand composite stronger than any other and any known building materials, including masonry.

“Few polymers are suitable to serve as a binder for this application. We were looking for specific features, such as solubility, that would give us the best result. Our key finding was in the unique molecular structure of our PEI binder, which makes it reactive. with cyanoacrylate to achieve exceptional strength, “said Tomonori Saito of ORNL, lead researcher on the project.

Parts formed by conventional binders become denser with infiltrated materials, such as superglue, but none reach close to the performance of the PEI binder. The impressive strength of the PEI binder comes from the way the polymer reacts to bond with cyanoacrylate during curing.

Polymer exposure gives 3D-printed sand superpower

Oak Ridge National Laboratory scientist Tomonori Saito shows a 3D-printed sandcastle at the DOE Manufacturing Demonstration Facility at ORNL. Credit: Oak Ridge National Laboratory scientist Tomonori Saito shows a 3D-printed sandcastle at the DOE Manufacturing Demonstration Facility at ORNL.

One possible application for the overpowering sand is to advance gear for compound production.

Silica sand is a cheap, readily available material that has interested in the automotive and aerospace sectors to create composite parts. Lightweight materials, such as carbon fiber or fiberglass, are wrapped around 3D-printed sand cores, or “tools,” and cured by heat. Silica sand is attractive for gear because it does not change dimensions when heated and because it offers a unique advantage in washable gear. In composite applications, using a water-soluble bond to form sand tools is significant because it enables a simple wash step with tap water to remove the sand, leaving a hollow compound shape.

“To ensure accuracy in tool parts, you need material that doesn’t change shape during the process, so silica sand was promising. The challenge was to overcome structural weakness in sand parts,” said Dustin Gilmer, a University of Tennessee Bredesen Center student and principal author of the study.

Current sand molds and cores have limited industrial use because commercial methods, such as elevating gear, apply heat and pressure that can cause sand parts to break or fail on the first attempt. Stronger sand parts are needed to support large-scale manufacturing and enable rapid part production.

“Our high-strength polymer sand composite elevates the complexity of parts that can be made by bonding jet methods, enabling more complicated geometries, and broadens applications for fabrication, tooling, and construction,” Gilmer said.

The new link won a 2019 R&D 100 Award and was licensed by industry partner ExOne for research.

The journal article is published as “Additional fabrication of strong silica sand structures enabled by a polyethylene bond.”

Engineers invent ultra-fast production technology, eliminating need for polymeric bonds

Additional information:
Dustin B. Gilmer et al, Additional fabrication of strong silica sand structures enabled by polyethylene bond, Natural communications (2021). DOI: 10.1038 / s41467-021-25463-0

Provided by Oak Ridge National Laboratory

Quote: Polymer discovery gives 3D-printed sand superpower (2021, November 12) taken November 13, 2021 from https://phys.org/news/2021-11-polymer-discovery-3d-printed-sand-super .html

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