Carbon fibre – carbon atoms bonded together to form a long chain — is a modern material of choice in structural design, prized for bicycles, wheelchairs, buses, and electric vehicles, products that require strength and durability while remaining lightweight. The predominant precursor for carbon fibre is polayacrylonitrile[1] – or PAN. To a lesser extent, carbon fibre is also made from petroleum pitch. Could it also be manufactured from petroleum waste products, including asphaltenes from Alberta bitumen? That question sparked the Carbon Fibre Grand Challenge sponsored by Alberta Innovates and the Clean Resource Innovation Network to accelerate carbon fibre development via this alternative pathway.
Nineteen teams from across Canada, the United States and Australia participated in Phase I. At the University of Alberta, three research teams are among the dozen that have advanced to Phase 2. A team led by Kevin Hodder at the University of Alberta Chemical and Materials Engineering Department with chemists Robin Hamilton, David Scott and Jeff Stryker has developed a process to pre-treat asphaltene before spinning it into carbon fibre. Details are scant because the process is proprietary. However, Hodder says, “we’re basically purifying the asphaltenes… so you get a better product after it’s spun.”
Having proven that their process works on a lab-scale, his team is now “turning some knobs, pushing some buttons to make it a little bit better than what it has been and trying to push those mechanical properties even higher,” and working to make it scalable, says Hodder.
Also in phase II is University of Alberta chemical and materials engineer and team lead Zhi Li. His team, including Department of Chemical and Materials Engineering professor Ken Cadien, is focused on single carbon nano-tubes – the tiny ones, aiming for a small fibre with a diameter of a few hundred nanometres.
Their aim was to create ultrathin carbon fibre by applying “an electro-spinning process” he says, using electrical field to help line up the molecules. The challenge, says Li, “is to produce high performance without high cost.” Underlining that their work is still at an early stage, they are aiming to improve their product’s mechanical strength.
For mechanical engineering professor Cagri Ayranci, a University of Alberta phase II competition contender, this work is a departure from his usual focus. “My students usually call me a tree hugger,” says Ayranci, referencing his prior work with biomaterials. Almost a decade ago, he initiated a project to derive carbon fibres from lignin – a class of polymers found in plants. “Lignin has a very messy, mixed, chemical composition,” he says. But asphaltene is complex too, he explains. Like lignin, it is difficult to process, but Ayranci and the team were up for the challenge.
Initially, applying the same tactics developed for lignin was unsuccessful. But employing the learnings from lignin led to new methods. His team, including eight hard working graduate students plus University of Alberta mechanical engineering professors Tian Tang and Jason Carey, and chemistry professor Mark McDermott, has achieved a different way of obtaining carbon fibres. How it works is something he can’t yet elaborate on since his team will be applying for a patent.
Calling the competition a “grand challenge” is fitting because whereas PAN is a well-defined molecule with known properties, asphaltene is not. PAN is “a polymer chain derived from petrochemicals that has undergone a lot of processing…so you know what to expect from it in manufacturing carbon fibre,” says Joanna Wong, mechanical and manufacturing engineering professor at the University of Calgary. Asphaltene’s rheology — its flow properties – are poorly understood. Analogous to the way cholesterol clogs up human arteries, asphaltene, as a component of bitumen, can settle inside pipes, clogging them up. So it’s often removed.
High in the aromatic compounds essential for carbon fiber strength, asphaltene tends to contain impurities including sulphur and vanadium. Do these need to be removed to make carbon fibre? “That’s one of the big questions,” says Wong. It’s something those in the competition, including her own University of Calgary team, are trying to find out.
Could an unwanted waste product be given a new purpose? That’s the hope. In a news release Laura Kilcrease, Chief Executive Officer of Alberta Innovates, articulated that “Carbon Fibre is a real and practical alternative to traditional uses for Alberta’s vast bitumen reserves.”
[1] https://www.materialsciencejournal.org/vol14no1/carbon-fibres-production-properties-and-potential-use/