Stockholm University scientists have developed a lignin inspired material to replace fossil fuel-based plastics and adhesives.
According to the scientists, their new lignin derived material behaves like thermosets but can be thermally reprocessed.
They used lignin as the renewable raw material in a catalyst-free reaction with a non-toxic chemical derived from ethylene glycol.
“We were amazed by the performance of the new materials, and one of the striking aspects of our results is the simplicity and material-efficiency of the synthetic process,” notes Stockholm University’s Dr. Adrian Moreno.
“In contrast to earlier examples we do not need any chemical modification or fractionation of the lignin but can simply cook it with the cross-linker in a one-pot reaction”
According to Moreno, the end result is a black and plastic-like material that could be casted to various shapes using conventional technology such as injection moulding.
The new lignin-based materials can be used several times, which is central to future’s circular materials.
To demonstrate this, the scientists measured mechanical strength of the pristine material as such and again from the same material that was repossessed from the fractured sample.
Tests show that the mechanical strength was comparable to that of engineered plastics and remained unchanged after the reprocessing.
The scientist also discovered that the material performance could be tailored from hard and brittle to soft and tough simply by changing the amount of lignin used in the formulation.
“The ability to tune the material properties opens many opportunities to commercial applications,” notes PhD student and study author Mohammad Morsali.
“For example, the formulation containing 50 percent of lignin by weight is an excellent adhesive for several types of soft and hard materials.”
“It is possible to recover the adhesive or simply detach the material and glue it again at mild temperatures comparable to those that are used in the kitchen oven”.
“This is an excellent demonstration of the possibilities that lignin holds as a valuable feedstock,” opines assistant professor Mika Sipponen.
“The material that we developed is perfectly in line with the current move towards sustainable circular materials.”
“Owing to its design consisting of so-called dynamic covalent bonds, the material can be formed over and over again by relatively mild heating.”
Image and content: Mika Sipponen/Stockholm University