Bio-based composite materials for high-performance applications
Wind turbine rotor blades, recreational boats or high-performance adhesives are based on epoxy resins, which are currently produced predominantly from fossil-based raw materials. As an alternative, researchers at the University of Oulu in Finland use chemicals recovered from biomass for producing fibre-reinforced epoxy and polyester resins. These alternative materials not only exhibit the same or even higher mechanical stability as fossil-based composite materials, but some are also easily recyclable.
Standard composite materials consist of a plastic matrix reinforced with glass or carbon fibres. Epoxy resins filled with fibres are known for their outstanding mechanical strength and resistance to salt water and UV light. These features make them best suited for being used in wind turbines. In conventional production of epoxy resins, bisphenol A diglycidyl ether (DGEBA) is a widely used raw material. The Chinese market research institute HDIN Research estimates the demand for epoxy resin for wind turbines at a minimum of 4,250 tonnes per gigawatt of electrical output.
Composite materials made from polyester resins with glass fibres are used, for example, in the construction of boats and caravans.
Behavior in combination with fibres
In a study recently published in the journal Composites Part B, two different furan-based epoxy resins were optimised for the upscaling of composite laminate production. One of the two furans developed resembled a BPA-like diol structure, whilst the second had a more atypical ester structure. These two molecules differ by only a few atoms. Glass and flax fibres were selected as the fibres for the composites produced from them. Glass fibres are widely used, cost-effective fibres that have proven themselves in composite plastics over decades. Flax fibres were selected as a sustainable, bio-based alternative. The various combinations of resin and fibre material were mechanically characterized through tensile, flexural and impact tests. Broken composite parts were examined morphologically and for their thermal stability.
The new composite materials exhibited good properties: in the case of the glass fibre composites, the measured mechanical strength values significantly exceeded those of the DGBEA-based material. Furthermore, composites were produced using flax fibres and furan-based resins that exhibited mechanical properties equivalent to or better than those of commercial materials.
In a further study on composite materials made from bio-based polyester and glass fibres, similarly good results were achieved:
“The biomass-based polyester resin we developed shows up to 76% higher tensile strength than a commercial fossil-based polyester resin.” says Mikka Salonen, doctoral researcher.
Bio-based materials should also be able to compete with fossil-based ones on price:
“Bio-based resins will not have a significant price difference compared to fossil resins,” says Senior Research Fellow Juha Heiskanen. “Once bio-based platform chemicals are produced, they can be processed using existing chemical industry production lines.”
What about recyclability?
Recycling fibre-reinforced plastics in such a way that both the fibre material and the matrix material can be kept in the cycle is a challenge. In the case of polyester resins, the authors had already carried out chemical recycling using methanol. A chemical route has also been developed for one of the ester-based epoxies, enabling the monomer used in its synthesis to be recovered and reused for resin production.
A chance for expanding bioeconomy
The raw materials for bio-based resins are hydroxymethylfurfural (HMF) and furfural. These substances can be obtained from cellulose and hemicellulose, and thus from forestry and agricultural residues.
Whilst the forestry industry (in Finland) has traditionally focused on pulp production, newer technologies now enable a wider range of options for using biomass components such as lignin.
“Upgrading bio-based raw materials into high-performance materials and products offers a significant opportunity to expand the bioeconomy,” says Heiskanen, who leads a seven-member research team developing biomass-based materials.
Three patents have already been filed, and the team is currently seeking partners to move into pilot-scale production.
Given that less than two per cent of global oil reserves are located in the EU, Finnish researchers consider the expansion of bio-based chemical production to be of significant strategic importance, particularly when it comes to materials whose use can help achieve climate targets and support the circular economy.
The development of bio-based epoxy resins took place as part of the FurBio flagship project, funded by Business Finland, which also involved partners from Italy and Sweden.
The development of bio-based polyester resins is taking place within the Interreg Aurora project SUSBICO (Sustainable Biocomposites) in collaboration with researchers from Luleå University of Technology in Sweden. Initial results from the ongoing project were published in ACS Sustainable Chemistry & Engineering in November 2025.
Featured image: Logga Wiggler / Pixabay