The automotive industry has made significant progress in replacing traditional materials with lightweight natural fibre composites
Flax, hemp and recycled textiles are now widely used in interior trim, door panels and non-structural components. However, these materials still rely on synthetic polymer resins to bind the fibres together, limiting their recyclability and reducing their environmental benefits.
Researchers at the University of Leeds believe they have developed a solution that removes synthetic polymers altogether.
The team’s patented all-cellulose composite is manufactured entirely from natural cellulose fibres, creating a material that combines high mechanical performance with genuine circularity. Made using flax, hemp, cotton, recycled textiles or even agricultural waste, the material contains no epoxy, resin or adhesive, offering manufacturers a potential route towards replacing conventional plastics in a range of automotive applications.
Professor Mike Ries, who leads the research, was keen to emphasise the material’s credentials: “It’s not 99.99% natural. It is genuinely 100% natural. There is no glue, no epoxy, no resin or other synthetic polymer. This material is 100% flax.”
CHARGING FORWARDS WITH CELLULOSE
Unlike conventional natural fibre composites, where cellulose reinforcement is embedded within a petrochemical matrix, the University of Leeds’ process uses cellulose as both the reinforcing fibre and the matrix material. The concept builds on earlier work at the university involving single-polymer composites, where synthetic fibres were partially melted to create a matrix while retaining the fibre core for reinforcement. Because cellulose cannot be melted, the researchers developed an alternative approach using a recyclable ionic liquid solvent.
Rather than melting the fibre surface, the solvent selectively dissolves the outer layer of the cellulose fibres. Under pressure, the dissolved cellulose flows between the remaining fibres before the solvent is removed using water. The regenerated cellulose then solidifies, creating a rigid composite consisting entirely of the same natural polymer.
The manufacturing process operates at relatively low temperatures and uses a single solvent that can be recovered and reused, reducing both energy consumption and waste compared with conventional composite production.
SIGNIFICANCE LIES IN SUSTAINABILITY
Today’s natural fibre composites still present recycling challenges because fibres and polymer matrices must be separated, often requiring thermal processing that destroys the natural reinforcement.
“Even today a natural composite still uses a synthetic polymer thermoset resin, which means if you want to recycle that composite at end of use, you have to burn away the natural polymer to recover the synthetic polymer,” Ries explains. “That means that plant captured all that CO2, took it into your material, and to recycle it, you have to release all that CO2 back into the environment. This is a different way of doing that.”
Because every component of the new composite consists of cellulose, the material can simply be dissolved back into the original processing solvent and remanufactured into new products. The researchers have already demonstrated the complete recycling loop, converting composite panels back into cellulose fibres before spinning them into yarn, weaving new fabrics and manufacturing entirely new composite components.
“We have a true circular material. Not just a circular economy, but a circular material. And it can undergo this process again and again,” Ries says.
FREEDOM AND FLEXIBILITY
Material flexibility is another notable advantage. The process has been successfully demonstrated using virgin flax, hemp and cotton, alongside recycled denim and textile waste. Agricultural residues also represent a potential feedstock, opening opportunities to utilise biomass that would otherwise remain underused.
Ries notes, “In agriculture, only about 10% of what you grow is what you eat, the other 90% is waste. That waste is full of biomolecules that you can use to make composites and other things with cellulose.”
The process also offers significant design freedom. Components can be compression moulded into complex three-dimensional geometries while preserving woven textures, colours and decorative patterns. Embroidered fabrics, coloured textiles and laser-cut finishes remain intact after consolidation, enabling both structural and aesthetic applications.
In terms of mechanical performance, the material exhibits a modulus of between six and 10GPa with tensile strength approaching 100MPa, placing it within the performance range required for many semi-structural automotive components. The composite also demonstrates good peel strength, impact energy absorption and thermal stability, retaining its mechanical properties at temperatures between 200°C and 250°C.
Importantly for vehicle engineers, the material properties can be tailored during manufacture, Ries says: “We can alter the weave and processing time to give manufacturers the properties they require.”
DEMONSTRABLE PROGRESS
Current development has reached Technology Readiness Level 4, with prototype components already produced for several automotive manufacturers. Among the demonstrators is a steering wheel developed for the Waste2Race Le Mans programme in collaboration with the UK’s National Composites Centre, illustrating the material’s suitability for demanding transport applications.
Although further industrial scale-up remains necessary, the technology has already secured patent protection across Europe, and also in Japan and the United States.
Looking ahead, Professor Ries believes the material offers manufacturers a compelling combination of sustainability, performance and circularity: “We have a material that is genuinely 100% natural. You can use virgin sources, recycled materials, textile waste, agricultural waste, and so on. It’s a low temperature and low energy manufacturing process. And not only does the material have high chemical and thermal resistance, but it has ease of recycling at end of use, and ultimately at end of life it is biodegradable.”
