New composite advances lignin as a renewable 3-D printing material

December 19, 2018 by Kim Askey, Oak Ridge National Laboratory
A new composite of lignin and nylon is easily extruded during 3D printing and exhibits good mechanical strength in finished products. Credit: Oak Ridge National Laboratory

Scientists at the Department of Energy's Oak Ridge National Laboratory have created a recipe for a renewable 3-D printing feedstock that could spur a profitable new use for an intractable biorefinery byproduct: lignin.

The discovery, detailed in Science Advances, expands ORNL's achievements in lowering the cost of bioproducts by creating novel uses for lignin—the material left over from the processing of biomass. Lignin gives plants rigidity and also makes biomass resistant to being broken down into useful products.

"Finding new uses for lignin can improve the economics of the entire biorefining process," said ORNL project lead Amit Naskar.

Researchers combined a melt-stable hardwood lignin with conventional plastic, a low-melting nylon, and to create a composite with just the right characteristics for extrusion and weld strength between layers during the printing process, as well as excellent mechanical properties.

The work is tricky. Lignin chars easily; unlike workhorse composites like acrylonitrile-butadiene-styrene (ABS) that are made of petroleum-based thermoplastics, lignin can only be heated to a certain temperature for softening and extrusion from a 3-D-printing nozzle. Prolonged exposure to heat dramatically increases its viscosity—it becomes too thick to be extruded easily.

Using as much as 50 percent lignin by weight, a new composite material created at ORNL is well suited for use in 3D printing. Credit: Oak Ridge National Laboratory

But when researchers combined lignin with nylon, they found a surprising result: the composite's room temperature stiffness increased while its melt viscosity decreased. The lignin-nylon material had tensile strength similar to nylon alone and lower viscosity, in fact, than conventional ABS or high impact polystyrene.

The conducted neutron scattering at the High Flux Isotope Reactor and used advanced microscopy at the Center for Nanophase Materials Science—both DOE Office of Science User Facilities at ORNL—to explore the composite's molecular structure. They found that the combination of lignin and nylon "appeared to have almost a lubrication or plasticizing effect on the composite," noted Naskar.

"Structural characteristics of lignin are critical to enhance 3-D printability of the materials," said ORNL's Ngoc Nguyen who collaborated on the project.

Scientists were also able to mix in a higher percentage of lignin—40 to 50 percent by weight—a new achievement in the quest for a lignin-based printing material. ORNL scientists then added 4 to 16 percent carbon fiber into the mix. The new composite heats up more easily, flows faster for speedier printing, and results in a stronger product.

ORNL scientists have created a new composite material for additive manufacturing that makes use of lignin, a biofuels byproduct. Credit: Oak Ridge National Laboratory
"ORNL's world-class capabilities in characterization and synthesis are essential to the challenge of transforming byproducts like lignin into coproducts, generating potential new revenue streams for industry and creating novel renewable composites for advanced manufacturing," said Moe Khaleel, associate laboratory director for Energy and Environmental Sciences.

The -nylon composite is patent-pending and work is ongoing to refine the material and find other ways to process it.

Explore further: Team develops lignin-based thermoplastic conversion process

More information: Ngoc A. Nguyen et al. A path for lignin valorization via additive manufacturing of high-performance sustainable composites with enhanced 3D printability, Science Advances (2018). DOI: 10.1126/sciadv.aat4967

Related Stories

Team develops lignin-based thermoplastic conversion process

November 30, 2012

(Phys.org)—Turning lignin, a plant's structural "glue" and a byproduct of the paper and pulp industry, into something considerably more valuable is driving a research effort headed by Amit Naskar of Oak Ridge National Laboratory.

Lignin waste modified for industrial bio-oil use

September 11, 2017

Lignin, a waste product in biomass and ethanol production, now finds new value as bio-oil in new products. At the University of Borås, Sweden, a team of researchers has investigated methods to extract and refine lignin for ...

New measuring technique can save pulp mills millions

October 5, 2018

New research at Karlstad University shows that pulp mills can save millions by using a new measuring technique. This new technique enables control of the pulping process, thus reducing the demand of chemicals, water and energy. ...

Spinning plant waste into carbon fiber for cars, planes

August 23, 2017

Using plants and trees to make products such as paper or ethanol leaves behind a residue called lignin, a component of plant cell walls. That leftover lignin isn't good for much and often gets burned or tossed into landfills. ...

Recommended for you

Fish-inspired material changes color using nanocolumns

March 20, 2019

Inspired by the flashing colors of the neon tetra fish, researchers have developed a technique for changing the color of a material by manipulating the orientation of nanostructured columns in the material.

Researchers shed new light on the origins of modern humans

March 20, 2019

Researchers from the University of Huddersfield, with colleagues from the University of Cambridge and the University of Minho in Braga, have been using a genetic approach to tackle one of the most intractable questions of ...

One transistor for all purposes

March 20, 2019

In mobiles, fridges, planes – transistors are everywhere. But they often operate only within a restricted current range. LMU physicists have now developed an organic transistor that functions perfectly under both low and ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.