Preparation of flexible biobased non-isocyanate polyurethane (NIPU) foams using the transurethanization approach

A new process for the preparation of non-isocyanate polyurethane (NIPU) flexible foams has been implemented. Biobased amino-telechelic NIPU oligomers were prepared by an organo-catalyzed transurethane poly-condensation reaction of fatty biscarbamates with fatty diols and diamines. The obtained oligomers were reacted with a biobased multi-epoxide molecule as crosslinking agent, in the presence of a poly(hydromethylsiloxane) or its copolymer as foaming agent and surfactant. The crosslinking and foaming reactions were monitored by rheometric, volumetric and FTIR studies. The foams can be obtained in < 30 min at 100 degrees C or in 14.5 h at room temperature. The prepared foams displayed cell diameters in the range of 210 to 430 mu m associated with densities in the range of 130 to 400 kg/m(3). They also exhibited thermal stabilities above 300 degrees C, as well as a soft character attested by negative Tg values ranging from -10 to-28 degrees C, and low values of the Young modulus varying from 1.0 x 10(4) Pa to 6.3 x 10(4) Pa. The recovery time, hysteresis loss and the firmness of these foams were found to be dependent on their chemical structures.