Promising research findings with carbon fibre from lignin are presented in a new doctoral thesis by Ida Norberg
On 20 April, Ida Norberg defended her doctoral thesis “Carbon fibres from kraft lignin” at Innventia in Stockholm.
Her thesis shows that lignin, a substance that is found in wood but is removed during kraft pulp production, has great potential for use as a raw material for manufacturing carbon fibre. Carbon fibre is strong and light, with many applications. Today, demand is mainly limited by the high cost of production, with the petroleum-based raw material and fibre spinning accounting for around 50 percent of the cost. Thanks to LignoBoost technology*, the pulp mill can extract extremely pure lignin which could be used for carbon fibre, thus increasing access to a raw material for carbon fibre. According to studies reported on in Ida’s thesis, the cost of production could also be lowered by using lignin.
Ida carried out much of her doctoral work within the framework of the LigniCarb research project, with the aim of examining and demonstrating the possibilities of making carbon fibre from kraft lignin. One of the outcomes of this work was a brand new research environment at Innventia, where carbon fibre is now prepared on a laboratory scale.
“When I started this work six years ago, there was nothing except for a literature study by Elisabeth Sjöholm at Innventia,” explains Ida. “At that time, there were only three of us working on this project: Göran Gellerstedt from the Royal Institute of Technology, Elisabeth Sjöholm and me. Now there are lots of us involved, and there’s a great deal of interest from industry. It’s been exciting going from having nothing at all to now having lab equipment where we can actually produce carbon fibre. Hopefully, this work can lead to the full potential being realised and investment in larger scale, more advanced equipment.”
“There’s a lot to be gained from better equipment, such as the possibility of spinning a large number of fibres at the same time,” adds Elisabeth Sjöholm, who was Ida’s supervisor and is the project manager for LigniCarb. “But despite only having simple equipment, we can still show that kraft lignin has great potential as a raw material for carbon fibre. Building up knowledge is also extremely important in order to obtain expertise within what is a new area for us.”
In her studies, Ida has compared lignin from hardwood (birch and eucalyptus) and softwood (a mixture of spruce and pine). One important conclusion is that the differences in the lignin are reflected in the carbon fibre process. Softwood lignin has proven to be harder to liquefy and spin, but once lignin fibres have been produced they are easier to use later on in the process. The opposite is true with hardwood. A major breakthrough came when the team succeeded in spinning fibres from softwood lignin. This had previously been thought impossible, but is of particular interest to the forest industry in the northern hemisphere, such as the Nordic region and North America.
“This thesis is extremely interesting, and can be seen as another step towards the biorefineries of the future, where every component part of the wood is used based on its own unique properties, becoming raw materials for many different applications,” says Peter Axegård, Director of Business Area Biorefining at Innventia.