Foam stability and segmented polymeric phase morphology of polyurethane foams synthesized partially and completely from castor oil are investigated. Preliminary analysis of the impact of alterations in the polymeric phase on macroscopic stress dissipation in foams is also carried out. The stability and morphology show unique trends depending on the concentration of castor oil used in foam synthesis. While low and intermediate concentrations of castor oil does not significantly affect the foaming process; at high concentrations, the volumetrically expanding liquid matrix remains in a nonequilibrium state during the entire foaming period, resulting in significant foam decay from top. This increases the final foam cell density and decreases the plateau border thickness at bottom. In the polymeric phase of castor oil based foams, the fraction of monodentate urea increases at the cost of non-hydrogen bonded urea. These monodentate urea domains undergo flocculation in foams synthesized completely from castor oil, thus prominently modifying the segmented morphology. The glass transition temperature of soft segments of partially substituted foams shows moderate increase, with indications of phase mixing between the polyether and castor oil generated urethane domains. Foams synthesized entirely from castor oil have significant sol fraction due to unreacted oligomers. The microscopic alterations in polymeric phase reduce the elastic recovery of partially substituted castor oil foams compared to its viscous dissipation under an applied stress. V C 2014Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40668.
We report a simple, serendipitous, two step mediation that overcomes the polyaddition threshold of castor oil during polyurethane formation. The mediation facilitates formation of polyurethane systems directly from castor oil without triricinolein chain extension or the use of supplementary hydroxyl compounds. The mediation involves refluxing castor oil with n-Butyl lithium in the presence of a solvent followed by water addition. We demonstrate the effectiveness of this mediation by successfully generating two important polyurethane systems (foam and coating) from castor oil. We identify that the mediation introduces two new compounds in castor oil namely, a lithiated diglyceride and a lithium salt of fatty acid. We characterize the new polyurethane synthesized for their hard-soft segmented morphology, glass transition temperature, and thermomechanical properties. V C 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43964.
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