The CycloCarb project set out to create formaldehyde‑free, bio‑based adhesives by exploiting multifunctional cyclic carbonates as cross‑linking agents. The research began with the laboratory synthesis of a range of cyclic carbonate monomers that are not commercially available. Starting from petro‑chemical or biobased epoxides, the team employed a basic, phase‑transfer catalyst system—tetra‑butylammonium bromide (TBAB) in combination with the non‑nucleophilic base DBU—to insert CO₂ into the epoxide rings at 170 °C under a continuous CO₂ flow. This approach yielded bifunctional carbonates such as poly(ethylene glycol) dipropylencarbonate (BCC) and ethylene glycol diglycidyl carbonate (BCC‑2), a trifunctional carbonate, trimethylolpropane tripropylencarbonate (TCC), and a highly functionalised carbonated soybean oil (CSBO) containing up to six carbonate groups. Spectroscopic confirmation was obtained by FTIR and NMR, while attempts to produce six‑ring cyclic carbonates proved unsuccessful and were discontinued.

With the monomers in hand, the next phase examined their ability to cross‑link both conventional novolak resins and renewable biopolymers such as lignin. Mixtures of 1:1 weight ratios of carbonate and novolak or lignin were heated with DBU at temperatures ranging from 170 °C to 200 °C. At 170 °C, the blends became insoluble within one hour, indicating rapid network formation; lower temperatures required longer reaction times. These cross‑linked products were then subjected to adhesive performance testing. Initial screening was followed by detailed evaluation using the Automated Bonding Evaluation System (ABES), which assessed bond strength, cure time, and processability. The results demonstrated that the cyclic carbonate cross‑linkers could replace formaldehyde‑based systems while maintaining comparable or improved mechanical properties, though further optimisation of component ratios and cure conditions was identified as necessary.

To move beyond proof‑of‑concept, the project scaled up the synthesis of the most promising carbonates. Pilot‑scale production maintained the same catalytic conditions but increased batch size, confirming that yields and product quality were preserved. Using these scaled‑up monomers, the team fabricated wood‑based composite samples and performed mechanical testing. The composites exhibited adequate adhesion and dimensional stability, illustrating the practical potential of the new adhesive formulations for timber products.

Throughout the project, collaboration with Prefere Resins GmbH was integral. Prefere supplied commercial novolak resins, provided expertise in resin chemistry, and assisted in the design of adhesive formulations. The partnership spanned the entire project duration, from initial synthesis to final product testing. The work was organised into six milestones (M1–M6) and ten work packages (AP1–AP10), covering synthesis, characterisation, cross‑linking studies, adhesive testing, scale‑up, and product evaluation. While the report does not specify a funding body, the project aligns with German research priorities aimed at reducing formaldehyde emissions and advancing bio‑based materials.

In summary, CycloCarb successfully demonstrated that multifunctional cyclic carbonates can serve as efficient, low‑toxicity cross‑linkers for both conventional and renewable resins, enabling the development of formaldehyde‑free adhesives. The project delivered new monomers, validated their reactivity with lignin and novolak, scaled up production, and produced viable wood‑composite samples, thereby laying a solid foundation for future industrial application of these green adhesive systems.