Rapid production of isocyanate-free, biobased polyurethane foams at ambient temperature is now a reality

Polyurethane foams (PU), produced for decades by the toxic isocyanate chemistry and currently under strict restrictions on use, are still essential materials in our everyday lives. Rigid PU foams are significant actors in the drastic reduction of our energy needs when used as thermal insulating panels on floors, walls, and roofs, as well as refrigerator doors. In their flexible versions, the foams are mainly used for comfort applications in mattresses, sofas, car seats, and soles of sports shoes, as well as for acoustic insulation or shock-absorbing materials.

Although various PU recycling strategies are currently being developed, the end-of-life management of PU foams still needs to be improved. In addition, many customers of the foam sector are looking for isocyanate-free and, ideally, bio-based materials. Alternatives for producing the foams by exploiting locally available resources while rendering them easy to recycle are intensively searched for. Developing such circular and more sustainable foams represents a major challenge, especially when the retrofit of existing industrial foaming infrastructures has to be considered.

"In 2022, we introduced the first recyclable isocyanate-free polyurethane foam (NIPU) manufacturing process using water to produce the foaming agent (CO2), the simplest and most economical system ever reported," explains Christophe Detrembleur, chemist at the CERM (Centre for Education and Research on Macromolecules. "This technology mimics the foaming of conventional PUs but without using toxic isocyanates. It is based on the use of water and a catalyst added to the formulation composed of cyclic carbonates and amines. Part of the cyclic carbonates is transformed into the blowing agent (CO2), which expands the matrix, and the other part contributes to its formation and hardening." Since this foaming process requires a thermal treatment to occur, it is very well suited to the manufacture of NIPU foams in heated moulds, i.e. for complex-shaped foams (car seats, shoe soles, etc). However, it is not adapted to the rapid foaming at room temperature demanded by many foam producers.

"In a new research project, for which a patent has just been filed, we are demonstrating how this process can produce NIPU foams from room-temperature formulations in record time, still using water to generate the foaming agent," explains CERM researcher Maxime Bourguignon. "The idea is to create cascade reactions that spontaneously and rapidly generate, thereby speeding up the manufacture of the NIPU matrix and its foaming by mimicking the traditional isocyanate-based process. Virtually all applications of PU foams, both rigid and flexible, can therefore be envisaged using this technology, without requiring the use of an external heat source for their manufacture. Moreover, foams with a high biobased content (70-90%) can easily be produced in less than two minutes," adds Maxime Bourguignon.

This innovative technology is simple, modular, robust and very easy to implement. "All that remains now is to convince PU foam producers, who are very conservative, to use this process for producing the next generation of foamed materials that are expected to answer the new legislative requirements, social needs and our sustainability imperatives," concludes Christophe Detrembleur.