In its natural state, lignin is a tightly cross-linked organic polymer that plays an important role in giving plants and trees their rigidity. But when these resources are converted into paper, the manufacturing process leaves huge amounts of lignin on the scrapheap. Scientists in Germany have developed a technology that could give the organic polymer a new lease on life, converting the waste product into the basis for a biopaste fit for 3D printing.
A number of research groups have looked at ways to recycle lignin for use in other products, demonstrating techniques that put it to use in carbon fiber, stronger concrete and even cheaper batteries. As it stands, however, the majority is still incinerated to produce bioenergy as part of the paper manufacturing process, leaving plenty of opportunities for new methods of recycling and re-use.
“This is why we’re researching into alternative possibilities for making better use of this raw material in future,” says Professor Dr. Marie-Pierre Laborie from the University of Freiburg, who led the research.
The team was experimenting with a biopaste material which had been investigated by another research team in the 1980s. This material was made of liquid crystals based on cellulose, another key component of biomass, and lignin. Through their investigations, the researchers found that the crystals could provide the strength of the paste, while the lignin acts as glue that holds it all together.
By experimenting with the makeup of this biopaste, the researchers also found that they could tweak its characteristics, making it more rigid or more flexible depending on the orientation of the lignin and the ratio of the materials. The upshot of the scientists’ work was a viscous biopaste made of half lignin and half cellulose that is easy to process and sets quickly, making it ideal for lightweight structures produced by 3D printing.
So far, the team has used lignin from beech trees to produce its biopaste, and notes that were it sourced from other plants the characteristics of the end material could be slightly different. Among the next steps for the team’s research is to investigate how lignin as a waste product from the paper industry can be incorporated into the process.
A paper describing research was published in the journal Applied Bio Materials.
Source: University of Freiburg