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Since polyol is one of the major components in polyurethane foam synthesis, introducing renewably sourced polyols in the foam formulation leads to materials with high renewable carbon content. A series of flexible polyurethane foams with variations in polyol composition were synthesized with castor oil based Lupranol Balance ® 50 polyether polyol and corn based polytrimethylene ether glycol mixtures. Water was used as the unique and eco-friendly blowing agent. The effect of the relative amount of each polyol on the structure and properties was analyzed by optical microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, tensile and compressive tests, dynamic mechanical analysis and atomic force microscopy. The average molecular weight and hydroxyl number of the polyol components showed to influence the foaming reaction and hence the structure and properties of the polyurethane foam. The newly developed peak force quantitative nano-mechanics technique was used to map the elastic modulus values of foam cell struts and it seemed to be adequate to assess the purity of the different phases.

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Sorbitol arises to be a strong candidate for renewably sourced polyol synthesis. Moreover, processes for extracting sorbitol directly from cellulosic materials are effective, and materials such as agroforestry residues could be used as green sorbitol sources. Rigid polyurethane foams were successfully synthesized by using mixtures of a sorbitol based high functionality polyol and a corn based diol. Microstructure and properties of the rigid polyurethane foams were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, thermal conductivity measurements, compression tests, and dynamic mechanical analysis. Results showed that the cross-linking density of the formed polymer network was directly modified by polyol mixture ratio, and microstructure and properties also changed in consonance. The incorporation of different amounts of a diol with longer chain length between hydroxyl groups allowed fixing the rigidity of the foams, opening the door to the possibility of designing rigid polyurethane foams with tailored properties.