Liège, Belgium – Scientists at the University of Liège have developed a method for creating self-blown non-isocyanate foams at ambient temperatures that they believe will work in existing production plants. It also the potential to improve the environmental credentials of the foams.
Their earlier process to make water-induced self-blowing foams from a system involving a CO2-based tricyclic carbonate, diamine, water and a catalyst required elevated temperatures, and while it is appropriate for foaming in heated moulds, this limited its wider application. Now, they have modified the process so that foaming occurs at ambient temperatures.
This was achieved via the creation of cascade exotherms, by adding a highly reactive triamine and an epoxide to the formulation. The exotherms, along with the rapid cross-linking of the triamine and epoxide, quickly increase the temperature to the foaming threshold. Hybrid NIPU foams are formed within five minutes, with potassium hydroxide as the catalyst.
By tuning the selection of monomers, foams with a range of properties can be created, they said. Biobased content of up to 90% is also possible. The foams can also be upcycled into polymer films, raising the potential of reuse at end of life.
“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,” said Maxime Bourguignon, who led the project.
“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.”
A patent has been applied for, and the work has been published in the Journal of the American Chemical Society.