A team of researchers at Windesheim University of Applied Sciences (the Netherlands) have developed an industrial methodology to generate new structural materials from End-of-Life (EoL) thermoset composites. The work was carried out in close cooperation with a large consortium of over 50 SMEs, government bodies and multinationals including global resin manufacturer AOC and waste management professional SUEZ, thus bringing together a diversity of experience and skills from the industry.
Traditional recycling technologies aim at separating a material into its original components, but this method machines EoL composite products into strips or flakes with a large L/D-ratio, which can be embedded as reinforcing elements in new composite articles and components. The strong points of composites, for example mechanical strength, stiffness and water resistance, remain unimpaired and are transferred to the new product.
Full scale demonstrators
To prove the viability of the method, full-scale demonstrators were developed and installed since 2017 at various locations in the Netherlands: for example retaining walls (Almere), furniture (Zwolle), guiding beams (Delfzijl) and crane mats (Lexmond).
When is a boat not a boat?…….Answer: when it becomes a guide beam, furniture or crane mat
Albert ten Busschen, associate Professor for Polymer Engineering and project leader says:
“The composite industry needs to make End-of-Life recycling integral to product design. Now that circularity has become a qualifier, the thermoset industry must change. It is no longer possible to rely solely on outstanding mechanical properties, as an industry we have to transform ourselves and rethink and learn to re-use these long-lifespan materials”.
Testing for safe use
The infrastructure industry has to be convinced of the safe use of the embedded strips and flakes with respect to the potential leaching of chemicals and metal ions from the re-used polyester products . Therefore a major test programme was established and carried out by an independent laboratory, SGS Intron, to investigate the effects of leaching in the presence of groundwater and or rainwater.
End-of-Life composite from obsolete boat hulls was selected from a scrapyard. On purpose, strips of material were chosen from the engine room (possible diesel and oil contaminations), and in a variety of colours and coatings (“old” pigments and anti-fouling coatings). These materials were machined into strips and flakes and embedded in a synthetic resin (SynoliteTM 1967-G-9 from AOC) and new composite panels were manufactured.
The outcome was very encouraging. Huub Creuwels from SGS Intron:
“Composites are strong and durable, but when re-using old parts you have to be sure of the quality. When we evaluated the leaching from the test panels however, we were extremely pleased to find everything measured far below the maximum allowable limit. We even took the tests one step further by inflicting damage to the panels to simulate impact by boats to guide beams that can occur in real life situations”.
The diffusion tests show that the method of reused EoL composite can be safely used to create civil engineering structures according to the Dutch Soil Quality Decree, as materials that pass the EN 16637-2/NEN7375 tests are considered safe to use for 100 years.
Thermosets go Circular
Dr. Jaap van der Woude, EuCIA:
“This is a major step forward for the thermoset composites industry. Re-use of End-of-Life materials has been made possible, while retaining its intrinsic properties, effectively closing the loop. Thermoset composites enable extraordinary structures like very large blades for windmills, but it can now also take responsibility for End of Use applications”.
The project ‘Structural Reuse of End-of-Life Composites” was funded by SIA, the province of Overijssel and Compoworld.