Cutting-edge development of non-isocyanate polyurethane (NIPU) foams: from sustainable precursors to environmental impact evaluation

Polyurethane (PU) foams represent a wide class of polymeric materials, having applications in different sectors ranging from automotive, packaging, and cushioning/bedding to construction. However, their synthesis requires the use of petrol-based components, which are mostly harmful and toxic isocyanates. Considering this, non-isocyanate polyurethane (NIPU) foams have been demonstrated to be promising alternatives to conventional PUs, which are obtained through “isocyanate-free” routes such as the aminolysis of cyclic carbonates with diamines. The building blocks of NIPU foams can be derived from different bio-sources, such as vegetable oils, sugars, and terpenes. Moreover, the final NIPU materials can be fully reprocessed and recycled owing to the presence of suitable functional groups that facilitate dynamic bond exchange. This review aims to comprehensively describe the current state-of-the-art concerning the synthesis and applications of NIPU and hybrid NIPU foams and is divided into three sections: (i) an outline of the synthesis of bio-based NIPU precursors, i.e. cyclic and linear carbonates, diamines and carbamates, from biomass-derived and waste sources such as vegetable oils and CO ₂ and via environmentally friendly approaches; (ii) analysis of the reprocessability and recyclability of NIPU and composite NIPU foams; and (iii) evaluation of the environmental impacts of NIPU precursors and foams using the life cycle assessment (LCA) technique, preliminary investigations of their techno-economic analysis (TEA), and description of future perspectives.