Halfway into the project, r-LightBioCom has achieved significant success in developing an innovative recycling method for high-performance composites. Thermoset composites, made of aramid and phenolic resin, have been successfully recycled using supercritical carbon dioxide (Sc-CO2) co-solvent recycling. This innovative process nearly completely removed the resin from the composites, allowing the fibres to be recovered while retaining most of their original mechanical properties. The recovered fibres were reused to produce yarns, which are planned for use in the project’s infrastructure application – tunnel lining – to showcase their potential for applications in the construction industry.
Composite materials are valued for their outstanding properties. Unlike traditional materials such as metals or plastics, composites are made by combining two or more different materials, including fibres and resins, to achieve unique strength, durability, and performance. For this reason, they are valued in different industries such as aerospace, automotive, construction, sports equipment, maritime, medical and etc. However, recycling these materials presents a complex process due to their unique structure and composition. The difficulty lies in separating the tightly bonded components without damaging their properties. Conventional recycling methods often result in fibres with reduced mechanical strength and minimal reuse potential, while the resin is often either incinerated or discarded as waste. This limits the sustainability of composite materials and contributes to environmental concerns, as large quantities of composite waste can end up in landfills or be incinerated.
The r-LightBioCom project is addressing this issue by developing bio-based high-performance composites alongside sustainable manufacturing and recycling methods. Within the project, innovative recycling methods have been applied for ballistic helmet recycling and good results were achieved: Ballistic helmets, made of so-called thermoset composites and consisting of aramid fibres embedded in phenolic resin, were subjected to Sc-CO2 co-solvent recycling. This innovative recycling process resulted in the removal of 90% of the resin from the composites, while the fibres retained 90% of their original mechanical properties. This represents a significant improvement compared to mechanically recycled fibres. The fibres were successfully processed into yarns. As the project moves forward, the applicability of these yarns in tunnel lining will be demonstrated as part of r-LightBioCom’s infrastructure use case.
Yarn manufacturing from of obtained recycled aramid fibres done by AITEX:
This impressive recycling achievement was made possible through the multi-disciplinary collaboration of several European project partners, each playing a crucial role: Project partner FECSA supplied ballistic helmet pieces as the raw material for the Sc-CO2 co-solvent recycling process. They prepared the material by removing non-composite elements and cutting the helmets into smaller pieces. FeyeCon developed the Sc-CO2 co-solvent recycling process for these composites and carried out the recycling. Through thermogravimetric analysis (TGA), AITEX determined that 90% of the resin was successfully removed. Following this, AITEX successfully produced yarns from the recycled fibres using an innovative carding and spinning process, evaluated their properties in comparison with commercially available recycled fibres. Meanwhile, Hochschule Kaiserslautern (University for applied Sciences, HSKL) analysed the recycled fibres, comparing their mechanical characteristics to virgin aramid fibres. They also began to analyse the recovered resin fraction. The investigation is ongoing. Leibniz-Institut für Verbundwerkstoffe (IVW) has been exploring potential applications for the recovered resin, including its use in polyurethane and epoxy foams as well as epoxy composite, with this work still in progress.
This collaborative effort highlights the potential of combining innovative recycling technologies, such as Sc-CO2 co-solvent recycling, with sustainable composite material applications. By removing the resin with less damage to the fibres, their mechanical properties can be preserved. As a result, the fibres can be reused in high-performance applications, which reduces waste and contributes to making composite materials more sustainable, leading to a more efficient and sustainable lifecycle. r-LightBioCom will continue working to further enhance the sustainability of composite materials and their recycling processes.
Excurse: What is supercritical carbon dioxide (Sc-CO2) co-solvent recycling?
Supercritical CO2 (Sc-CO2) is a state of carbon dioxide achieved above its critical point, where it exhibits properties of both a gas and a liquid. In Sc-CO2 co-solvent recycling, Sc-CO2 penetrates deep into the composites and enhances effectiveness of the co-solvent to dissolve the resins from composite materials. This process is innovative, because it operates without the need for harsh chemicals and generates minimal waste. Furthermore, it offers a sustainable alternative to traditional recycling methods.
The above-mentioned breakthrough highlights the transformative potential of Sc-CO2 co-solvent recycling in achieving sustainability in high-performance composites. By effectively preserving the properties of materials and facilitating the recovery and reuse of both fibre and resin, this method is highly promising. It reduces waste considerably and promotes the circularity of high-performance composites, paving the way for more eco-friendly construction solutions.
