Researchers combined a melt-stable hardwood lignin with a low-melting nylon and carbon fiber to create a composite with excellent mechanical properties as well as with the right characteristics for extrusion and weld strength between layers during the printing process.
Lignin can only be heated to a certain temperature for softening and extrusion from a 3D-printing nozzle, but when the researchers combined lignin with nylon, they found that the composite’s room temperature stiffness increased while its melt viscosity decreased. The lignin-nylon material had tensile strength like nylon alone and lower viscosity.
The scientists were able to mix in a higher percentage of lignin—40 to 50 percent by weight, then added 4 to 16 percent carbon fiber. The new composite heats up more easily, flows faster for speedier printing, and results in a stronger product.
“ORNL’s world-class capabilities in materials 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 lignin-nylon composite is patent-pending, and work is ongoing to refine the material and find other ways to process it.