Plant-Based 3D Printing Material Developed by ORNL
Michael Molitch-Hou posted on July 09, 2018 |

The power of 3D printing lies in the materials used and no one knows this better than Oak Ridge National Laboratory (ORNL), which is currently researching both carbon fiber and metal 3D printing technologies. Now ORNL can lignin to its repertoire of material expertise.

A composite made up of 40 percent lignin. (Image courtesy of Ngoc Nguyen/Oak Ridge National Laboratory, U.S. Dept. of Energy.)
A composite made up of 40 percent lignin. (Image courtesy of Ngoc Nguyen/Oak Ridge National Laboratory, U.S. Dept. of Energy.)

In the journal Applied Materials Today, ORNL researchers outline their patent-pending process for developing 3D printable lignin, an organic polymer found in the walls of plant cells as well as a common byproduct in the production of biofuels. The study’s authors explain that, given the unrenewable and polluting nature of ubiquitous petroleum-based plastics, it’s necessary to find a sustainable replacement based on renewable sources, such as lignin, which provides plans and some algae with their structure.

Lignin-based composites are often difficult to process, making it possible only to produce objects using compression molding or casting. Therefore, ORNL sought to find a new method for processing the material in such a way that would yield more practical and scalable applications. For this reason, the team turned to fused deposition modeling (FDM) 3D printing.

To create a 3D printable lignin composite, ORNL combined Organosolv hardwood lignin with several different materials, including acrylonitrile-butadiene rubber (NBR41), acrylonitrile-butadiene-styrene (ABS) and carbon fiber. The composites were then formed into 3D printer filament and printed using a LulzBot TAZ 3D printer.

The researchers found that “A high loading (40 wt.%) lignin-ABS composite has a similar tensile Young's modulus (1.82 ± 0.08 GPa) to that of pristine ABS (1.91 ± 0.32 GPa). However, the addition of lignin commonly results in a very brittle structure.” The addition of NBR41 increased the tensile strength, while a further addition of chopped carbon fiber made the composite stronger and more printable.

A micrograph showing a cross-section of the weld area between two 3D-printed layers of the lignin-based composite material. (Image courtesy of Christopher Bowland/Oak Ridge National Laboratory, U.S. Dept. of Energy.)
A micrograph showing a cross-section of the weld area between two 3D-printed layers of the lignin-based composite material. (Image courtesy of Christopher Bowland/Oak Ridge National Laboratory, U.S. Dept. of Energy.)

In the study, the authors note the following: “The lignin-based composites exhibited equivalent or even better mechanical performance in comparison to regular petroleum-based thermoplastics. For example, the ABS-NBR41-Lignin-CF-5131 [one combination, created by the authors] had a tensile strength of ∼65 MPa and a tensile Young's modulus of ∼2.6 GPa. The percolation of CFs contributed significantly to the improvement of the composites’ mechanical properties. The combination of ABS, NBR41, and lignin revealed a promising route to utilize high loading of lignin as a sustainable feedstock for additive manufacturing.”

This is just one example of a material relying on abundant organic polymers. Javier Gomez Fernandez, assistant professor at the Singapore University of Technology and Design (SUTD), has also developed a unique natural material that is 100 percent biodegradable. In SUTD’s case, the material does not include any petroleum-based materials. Though that may not be true for ORNL, the lab has demonstrated what is possible when waste material is not discarded but converted into useful materials.


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