Flexible polyurethane foams modified with bio-based polyols: synthesis and physical/chemical characterization

Abstract

A series of flexible polyurethane foams with different polyol compositions were synthesized through the replacement of aportion of the petroleum-based polyether polyol with biobased polyols, namely, glycerol (GLY) and hydroxylated methyl ester(HMETO). HMETO was synthesized by the alkaline transesterification of tung oil (TO; we obtained GLY as a byproduct) and the subsequenthydroxylation of the obtained methyl esters with performic acid generated in situ. IR spectroscopy, 1H-NMR, and different analyticalprocedures indicated that the hydroxyl content increased significantly and the molecular weight decreased with respect to those ofthe TO after the two reaction steps. The characterization of the obtained foams, achieved through the measurement of the characteristicreaction times, thermal and dynamic mechanical analysis, scanning electronic microscopy, and density measurements, is reported anddiscussed. The most important changes in the modified foams were found with the addition of GLY to the formulation; this led to anincreased foam density and storage rubbery modulus, which were associated with a higher crosslinking density because of the decreasein the chain length between crosslinking points.