Flexible and Bio-Based Nonisocyanate Polyurethane (NIPU) Foams

The amine cure of cyclic carbonate blends, derived from renewable resources and carbon dioxide, in the presence of a liquid fluorohydrocarbon as physical blowing agent with no ozone depletion potential, enables the facile tailoring of flexible bio-based nonisocyanate polyurethane (NIPU) foams. Unlike conventional PU foams, neither isocyanates nor phosgene or aromatic amines are required as intermediates in NIPU foaming. Typically, rigid cyclic carbonates such as carbonated trimethylolpropane glycidylether (TMPGC) are blended together with the corresponding flexible cyclic carbonate such as ethoxylated TMPGC (EO-TMPGC) which lowers monomer viscosity and reactivity. This is reflected by higher pot life and gelation times for the cure with hexamethylene diamine (HMDA), improving NIPU foam processing. With increasing EO-TMPGC content, rigid TMPGC/HMDA-NIPU foams are rendered flexible and soft, as verified by simultaneously declining storage modulus and glass transition temperature. In this NIPU foam family, the TMPGC/EO-TMPGC (60 wt%/40 wt%) blend cured with HMDA in the presence of Solkane 365/227 affords flexible NIPU foams exhibiting low density, very good mechanical hysteresis, and tailored hardness, meeting the demands of various applications like automotive seating. Emission tests confirm the absence of critical compounds mentioned in the global automotive declarable substance list.