Self-blowing, hybrid non-isocyanate polyurethane foams produced at room temperature

Abstract

Self-blowing polyurethane foams are essential for several everyday applications, yet their traditional production involves fossil-derived products and hazardous isocyanate compounds. Thus, research into isocyanate-free polyurethane foams is receiving considerable attention. However, current approaches often rely on external blowing agents, and/or high temperatures with long polymerization times. This research presents a rapid, self-blowing, partially bio-based non-isocyanate polyurethane (NIPU) foams at room temperature, specifically poly(hydroxy-thio-urethane), with both rigid and flexible configurations. The method involves the partial conversion of an epoxy resin to an oligomer mixture composed of 85% bio-cyclic carbonate and 15% of non-converted epoxide. This oligomer undergoes a fast process, through reactions between the epoxy groups and the reactive components, that is then followed by simultaneous aminolysis and decarboxylation reactions, arising from the interaction of an amine and cyclic carbonate. An in-situ blowing agent (CO₂) is generated from the interaction between thiols and cyclic carbonate. The glass transition temperature is modulated by the thiol/amine content in rigid foams and by the addition of aliphatic long chains in flexible foams. With almost 30% renewable carbon content, these foams provide a sustainable alternative to traditional isocyanate-based pathways. The resulting porous materials possessed densities between 0.158 and 0.201 g/cm³. Finally, the foams can be transformed into films, enhancing recyclability and sustainability at the end of their lifecycle. Thus, this development has the potential to facilitate the production of eco-friendly, recyclable polyurethane foams.