Sawdust offers up recyclable composite resins

Researchers in Finland have developed bio-based polyester and epoxy resins that can replace conventional oil-based materials in composite products, without compromising strength, cost or industrial scalability.

Polyester resins are widely used in fibreglass composite structures such as boats and caravans. Epoxy resins, meanwhile, are essential in adhesives and high-performance composites used in sports equipment and industrial components.

Forestry waste

A team at the University of Oulu says new epoxyand polyester resins, sourced from forestry and agricultural waste streams such as sawdust and straw, match or even outperform their fossil-based counterparts.
Doctoral researcher Mikko Salonen says the results are striking: ‘The biomass-based polyester resin we developed shows up to 76% higher tensile strength than a commercial fossil-based polyester resin.’

Senior research fellow Juha Heiskanen adds that the new bio-based resins will not have a significant price difference compared to fossil resins. ‘Once bio-based platform chemicals are produced, they can be processed using existing chemical industry production lines.’
The new resins also offer chemical recyclability. Unlike conventional composite materials, such as those used in wind turbine blades, the new materials can be chemically broken down and reused as raw materials.

Bioeconomy boost

While the forest industry has traditionally focused on pulp production, new technologies now enable broader utilisation of biomass components such as lignin.
‘Upgrading bio-based raw materials into high-performance materials and products offers a significant opportunity to expand the bioeconomy,’ Heiskanen argues.
Three patents have already been filed and the team is seeking partners to move into pilot-scale production.

The research involved collaborators from Italy and Sweden and was carried out under the Business Finland-funded FurBio project.