Fast, catalyst-free room temperature production of isocyanate-free polyurethane foams using aromatic thiols

Abstract

Non-isocyanate polyurethane (NIPU) foams of the polyhydroxyurethane (PHU)-type are promising greener alternatives to their conventional isocyanate-based polyurethane counterparts that dominate the foam market. Recently, the concomitant organocatalyzed aminolysis and S-alkylation of the cyclic carbonates of PHU formulations offered a facile way to produce CO2 self-blown PHU foams. However, this process was limited to the production of foams of rather low Tg (commonly up to room temperature) and suffered from a slow foaming (i.e. 30 min.) at 120 °C, thus still far away from the foaming timeframes (1-10 min) and room temperature (r.T.) needed for adaptation on industrial foaming equipment’s. In this work, we elaborate strategies to accelerate the thiol-assisted NIPU foaming in order to be complete in 5 to 10 minutes from r.T. reactive formulations under catalyst-free conditions. This is achieved by substituting aliphatic thiols by more acidic aromatic ones, and by adding epoxides as heat release promotors that will accelerate both the foaming and curing rates. Moreover, flexible, semi-rigid and rigid foams are easily accessible by the choice of the amine comonomer and epoxide additive. This work draws general and simple concepts for strongly speeding-up the self-blowing NIPU process, a crucial step toward decreasing the energetic and production costs, offering potential retrofitting of existing foam production plants.