Exploring Urea Phase Connectivity in Molded Flexible Polyurethane Foam Formulations Using LiBr as a Probe

Lithium bromide (LiBr) was incorporated in formulations based on molded flexible polyurethane foams in order to alter systematically the phase separation behavior and thus give insight into urea phase connectivity. The formulations of the materials generated were similar to those of molded flexible polyurethane foams except that a surfactant and a low molecular weight cross-linking agent (such as diethanol amine) were not used. The resulting materials were evaluated by using the techniques of atomic force microscopy (AFM), SAXS, and DSC. Atomic force microscopy and SAXS were used to demonstrate that the materials with and without LiBr were microphase separated and possessed average interdomain spacings of ca. 90 A, typical of flexible polyurethane foams. AFM phase images also showed that incorporation of LiBr reduced the urea phase aggregation, which is known to take place in flexible polyurethane foams, and led to a more homogeneous distribution of the urea microdomains in the soft polyol phase....