The tradition of adding straw and other natural fibres to mud to strengthen earthen bricks and reduce their cracking is a construction technique that dates back to time immemorial. The contemporary world has largely eschewed the use of such ancient techniques and materials, creating urban skylines of steel, glass and concrete, as well as vehicles that incorporate oil-based rubber and plastic. However, the escalating development of natural fibre bioproducts as additives for such modern materials could improve the performance of contemporary structures while reducing their environmental impact.
Performance BioFilaments, a research and development business formed in 2014 as a joint venture between Canadian firms Mercer International and Resolute Forest Products, is gearing up to open a manufacturing facility next year to produce multipurpose cellulose bioproducts that could optimize the strength, stability, flexibility and longevity of composite materials, plastics, concrete, as well as paint and other consumer products.
Gurminder Minhas, the managing director of Performance BioFilaments, is part of a team currently scoping out potential locations for the commercial plant; ideally, he says, it will be close to one of its parent companies’ existing facilities in Canada. While that search continues — an announcement is expected by the end of this year — the company is driving development of its core technology with a small R&D group at the University of British Columbia that is exploring how to enhance the characteristics of cellulose filaments for commercialization, says Minhas, who is an industrial chemist with an executive MBA.
Although created from one of the most common and ubiquitous building materials ever known — wood, which is about two-thirds cellulose — the filaments have become one of the “world’s most exciting new biomaterials,” Minhas says. Cellulose filaments belong to a broader category of nanofibrillated cellulose created from traditional kraft pulp composed of 95 percent cellulose and five percent hemicellulose. In wet form, the pulp looks similar to white polyester pillow stuffing. However, by applying either chemical or mechanical energy to the pulp, the cellulose fibres break down into individual, nano-sized filaments or fibrils through a process called delamination. Performance BioFilaments has licensed a mechanical grinding process created by FPInnovations, a Pointe-Claire, Que.-based forest products company, to make their cellulose filaments.
Gurminder Minhas Keith Gourlay
In the past decade, FPInnovations has also done extensive research into the development of nanocrystalline cellulose (NCC), which is created using commercial bleached pulp that is broken down using strong acids. As wood cellulose is composed of both crystalline and non-crystalline parts, chemicals like sulphuric acid purify the tiny grains of the crystalline portion. When mixed into plastics or other composite materials, these grains can confer enhanced strength and other desirable properties. The cellulose filaments that Performance BioFilaments is developing, however, are slightly different. NCC particles are typically five to 10 nanometres wide and a few hundred nanometres long. Fibrils, on the other hand, can range up to several micrometres in length. This gives them different properties, especially from a rheological perspective.
Performance BioFilaments’ reason for selecting a mechanical grinding process over chemical treatment is improved economy, says Minhas, adding that researchers at FPInnovations developed the process in about 2000 but kept the discovery internal for another decade while securing patents and scaling from lab to pilot plant. With mechanical grinding, kraft pulp is put between two spinning plates, breaking down the fibre and peeling filaments off, similar, says Minhas, to unravelling rope licorice candy. “The material is very thin yet very long, which allows us to excel in certain applications such as reinforcing other materials.” When chemicals like sulphuric acid are used, some of the wood cellulose is hydrolyzed, converting it to sugar and reducing overall yield. Not only does the mechanical process allow for a higher yield but the process itself is relatively low cost, making scale-up more economical. As an added bonus, the fact that mechanical grinding doesn’t require acids reduces the environmental impact, Minhas adds. He expects the new plant, when finished, will be able to produce from 20-40 tonnes of cellulose filaments a day.
In addition to their ongoing efforts to improve the manufacturing process, Performance BioFilaments is also conducting research on potential applications. The biggest contenders so far are the reinforcing of plastics and concrete and rheology additives for industrial paints and coatings. The potential of these markets is what attracted Mercer International and Resolute Forest Products, both of which have been looking to diversify their existing printing and writing grade paper markets, Minhas says. The partnership is a win-win for all involved. “We’re a new company that is well backed by two very strong partners with good operational and engineering experience.”
Performance BioFilaments is particularly focused on injection-moulded plastics that are geared towards the automotive sector and driven by environmental regulations. For example, in the United States, cars will have to attain 55 miles to the gallon by 2025, which is nearly double the minimum standard today, as a way to cut greenhouse gas emissions. (Canada tends to harmonize national emission standards with the US Environmental Protection Agency federal standards.) European standards are based upon how many grams of carbon dioxide are emitted per kilogram driven. The European Commission has set a target of 95 grams of CO2 emitted per kilometre by 2021 in all new cars, which is a 40 percent reduction from the 2007 average. These new regulations mean that auto manufacturers in both North America and Europe are looking to use lighter plastics to reduce vehicle weight to help meet future fuel efficiency standards. To maintain safety standards, however, the plastic needs to be reinforced by a lightweight material — cellulose biofilaments could well fit the bill.
As for paints and coatings, this is where the unique rheological properties come into play. Cellulose fibrils exhibit a property known as thixotropy, meaning that they become viscous and resistant to flow under normal conditions. But when agitated or otherwise subjected to stress, their viscosity drops significantly. By mixing cellulose nanofibres with paints or coatings, manufacturers could fine tune the flow properties of their product and improve performance.
Keith Gourlay, a University of British Columbia-based biochemist who is involved in R&D for Performance BioFilaments, confirms that three of the application areas under development include thermoset and thermoplastic reinforcement, concrete reinforcement and rheology modification to alter the viscosity of solutions. Each of these areas has unique challenges that are being overcome either by tailoring the production process — generally by altering the amount of refining energy used — or by performing a complementary process following production of the cellulose filament. Gourlay’s industrial postdoctoral fellowship with Performance BioFilaments is co-sponsored by Mitacs, a not-for-profit organization that builds partnerships between academia and industry. The products created by Performance BioFilaments will be sold in different forms, depending upon how it is being used. For example, with concrete, the cellulose filament can be directly added as a reinforcement. “We think it bridges microcracks and prevents them from forming,” Gourlay says. This bridging ability could play a key role in developing concrete for buildings located in earthquake zones, however research by Performance BioFilaments into this phenomenon is still underway.
One of the key issues is ensuring optimum dispersal of filaments throughout the material. Minhas says that Phase 1 of a research project in conjunction with UBC Civil Engineering into high performance concrete reinforced with cellulose filaments has just wrapped with “very, very good results.” The amount of cellulose filaments is small, only about one half to one percent of the concrete material. Such data, Minhas says, allows the company to pursue joint development partnerships that further additional research into this area.
It is more challenging to get proper distribution of cellulose filaments within plastics and especially thermoplastics, says Gourlay. He expects that the most efficient way to disperse filaments within plastics is to sell batches of plastic pellets containing a “higher concentration of the filament than you would want in your final product.” When these pellets are mixed in the right ratio with traditional plastic pellets, the final melted plastic will contain the desired concentration of cellulose fibres. Another key challenge is compatibilization of the filaments with the matrix polymer. “We’ve been working on a number of different processes both for enhancing dispersion within thermosets and thermoplastics, as well as modifying the surface properties of the filaments to enhance the bonding between the matrix polymers and the cellulose surface,” says Gourlay.
With plastics, the main goal is to replace the glass fibres currently used for reinforcement. Gourlay points out that since cellulose is less dense than glass, composites that incorporate cellulose fibres are lighter weight than what is on the market today. This is “particularly desirable for applications in the automotive, aerospace and sporting equipment sectors, where the weight of the components is a major concern.” He admits that plastics are just one component of a car or airplane and there will have to be many incremental improvements undertaken to reduce the overall weight of vehicles, such as new metal alloys and more efficient motors in order to meet the new emission standards set by governments in Europe and the US. Still, replacing glass fibre in plastics with cellulose filaments is “important to get these cars lighter weight,” Gourlay says.
Minhas says that lighter vehicles are also important for improved performance in electric vehicles, as the less heavy the car, the longer the battery will last. Lightweighting also holds true for trains and buses. Even the Boeing Company, which designs, manufactures and sells airplanes, rotorcraft, rockets and satellites, is looking into amalgamating biomaterials into its products.
The ultimate dream, says Gourlay, is to make vehicles that are biodegradable. Indeed there are some projects underway by Performance BioFilaments that are focusing on producing 100 percent renewable or bio-based composites for the automotive sector. However, for the time being, Performance BioFilaments needs to work with non-biodegradable plastics as that’s what industries are currently using. Hence, while researching the use of cellulose filaments to reinforce biodegradable plastics is a “longer term” project, nonetheless this is an “area that we’re very interested in,” Gourlay says.
Finally, for rheology modification — tailoring the viscosity of the material for specific applications, such as paints, cosmetics and coatings — Gourlay is researching altering the rheology profiles of the cellulose filaments. Enzymatic processes are yielding positive results and he expects this will be the “most promising route going forward.” This process is cheaper in comparison to chemical processes, as acid-resistant equipment isn’t required. The use of enzymes can have “dramatic effect on the fibre and filaments characteristics.”
Keeping the global economy moving and thriving involves not only the expansion of urban areas but the use of vehicles: cars, buses, semi trucks, tankers and planes, which run off petroleum and are largely made of fossil fuel-derived materials. Performance BioFilaments is helping to change that, forging a more sustainable future by providing not only environmentally friendly but better-performing alternatives to the materials that make up our modern world.