Flexible and Bio‐Based Nonisocyanate Polyurethane (NIPU) Foams

Abstract

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.

Polymers Based on Cyclic Carbonates as Trait d'Union Between Polymer Chemistry and Sustainable CO2 Utilization

“…The main chemical blowing agent for polyurethane foam is carbon dioxide, formed by the reaction between isocyanate groupsa nd water presenti nt he polyol mixture. [185] Additionally,t he presence of EO-6d increased the swellingo ft he foams in water and toluene (Table 1), increased the thermals tability, and decreased the storage modulus and T g of the foams, owing to its flexible structure. To compensate for this absence, severalb lowinga gentsw ere investigated (Table 1).…”

“…[134,184] The use of 6d as cross-linker has been known since the early works on PHUs. [185] 6e has been recently used for the synthesis of thermoresponsive PHUs. [114d, 186] An ethoxylated version of 6d (EO-6d)w as pre-pared by allowing the growth of short oligo(ethylene oxide) chains on each hydroxy group of 6d followed by capping with ECH and carbonation.…”

“…Isocyanate-free foams Soft and hard polyurethane foams have applications as construction materials, in the automotive industry,a nd in mattresses, owing to their excellent acoustic and thermalinsulative properties. [185] The PHUs were prepared by the reactiono fh examethylene diamine (HMDA) with 6d and EO-6d at 80 8Cf or 14 h, followed by heating at 100 8C for 4h to obtain full conversion of the carbonate groups. Physical blowing agents are solvents with al ow boiling point that evaporate owing to the exothermic polymerization during the foaming process.…”

“…[114c] Foams exhibitedo penc ells with sizes ranging from 200 to 1000 mm. [185] This approach is very promising because it requires few steps and mild experimental conditions in term of pressure and temperature, as well as relatively short preparation time. Indeed, shorter molecular weights increased the density of the foams and decreased their flexibility,t herefore inducing a larger stress on the strain applied to the foams.T he glass transition temperature (T g )d ecreased with larger molecular weight of PPOBC and increased slightly with increasing concentration of 6d because the foams were more rigid.…”

“…[114d, 186] An ethoxylated version of 6d (EO-6d)w as pre-pared by allowing the growth of short oligo(ethylene oxide) chains on each hydroxy group of 6d followed by capping with ECH and carbonation. [185] 6e has been recently used for the synthesis of thermoresponsive PHUs. [184] Trimethylolpropane and pentaerythritol, used as reagents for the synthesis of 6d and 6e,respectively,can be prepared by the reactions of formaldehyde with n-butyraldehyde or acetaldehyde.…”