Room-temperature foaming of carbonated soybean oil into biobased non-isocyanate polyurethane foams via a substrate-decoupled cascade exotherm

Carbonated soybean oil (CSBO) is a soybean-oil-derived cyclic carbonate platform, but its internally substituted carbonate groups are sterically hindered and exhibit low reactivity, limiting room-temperature foaming. Conventional cascade-exotherm strategies generally rely on more reactive terminal cyclic carbonates to initiate the early-stage reaction cascade and are therefore not readily applicable to CSBO. Herein, we report a substrate-decoupled cascade-exotherm strategy for self-foaming initiated at room temperature of CSBO-based formulations. Rapid epoxy–amine ring opening supplies heat independently of CSBO aminolysis, raising the internal temperature to a maximum of 171.1 °C within minutes and thereby facilitating CSBO aminolysis, hydrolysis-mediated CO 2 evolution, and early-stage network formation. Spontaneous self-foaming initiated at room temperature without external heating, followed by thermal post-curing at 80 °C for 12 h, yields hybrid non-isocyanate polyurethane (NIPU) foams. By varying the epoxy-to-carbonate molar ratio, amine structure, and water dosage at a fixed KOH ratio, the compressive modulus can be tuned from 0.021 to 9.79 MPa and T g from 19.7 to 37.1 °C. Replacing petroleum-derived trimethylolpropane triglycidyl ether (TMPTE) with biobased glycerol triglycidyl ether (GTE) increases the theoretical formulation-based biobased content to 93.28 wt% while retaining room-temperature foamability. The foam prepared at H 2 O/5CC = 0.15 exhibits nearly complete elastic recovery under 40% cyclic strain and retains 60.7% of its first-cycle peak stress after ten cycles at 90% strain, demonstrating substantial mechanical retention under repeated large deformation. This strategy provides a route to soybean-oil-derived NIPU foams with high biobased content; the compressive recovery and energy dissipation observed here indicate potential for cushioning applications, although dynamic impact performance and long-term service behavior remain to be established.