Lignin-derivable non-isocyanate polyurethane foams with tunable density, stability, and compressive mechanics

• Thomas Downey, Chemical Engineering, University of Delaware

• LaShanda Korley, Material Science, University of Delaware

Due to their potentially safer building blocks sourced from renewable
feedstocks, lignin-derivable non-isocyanate polyurethane (NIPU) foams offer a class of greener
alternatives to the isocyanate-based polyurethane (PU) foams used in our everyday lives. NIPU
foam networks are synthesized by reacting a difunctional amine (diaminodecane [DA-10]) with
varying ratios of a petroleum-derived tricyclic carbonate (trimethylolpropane tricyclic carbonate
[TMPTC]) and lignin-derivable tricyclic carbonate (LTCC). Foaming is induced via water-driven
cyclic carbonate hydrolysis to generate CO 2 gas, mimicking traditional water-blown PU
chemistry without the need for toxic isocyanates. By systematically varying the aromatic (LTCC)
to aliphatic (TMPTC) cyclic carbonate ratio, this work investigates how monomer architecture
dictates pore morphology, foam density, and thermomechanical performance while leveraging
the sustainability benefit of a renewable monomer feedstock. Thermogravimetric analysis (TGA)
demonstrates that increases in LTCC content can modulate thermal stability (T d5% : 200–270 °C),
improve hydrolytic stability (moisture uptake: 10–6 wt%), and increase flame retardance (char
yield: 5–17%). With increased LTCC: TMPTC content, the expansion ratio of resulting foams
increases (~2:1–5:1), and the foam density decreases (0.38–0.25 g/cm 3 ), indicating applicability
in PU foam sectors across construction, automotive seating, packaging, and apparel. Scanning
electron microscopy (SEM) images further demonstrate tunability in foam cell size,
homogeneity, and type (i.e., open, closed), while compression testing demonstrates changes in
compressive strength with varying cyclic carbonate ratios. Overall, the use of lignin-derivable
monomers in NIPU foam production shows promise in replacing toxic, petroleum-derived foams
currently used in the industry while allowing for tunability in thermomechanical performance.