CHARACTERIZATION OF FLEXIBLE SLABSTOCK FOAMS CONTAINING LITHIUM-CHLORIDE

Characterization of a series of flexible polyurethane foams that conta in LiCl in their formulation is discussed. These foams were developed in order to provide an alternative method to produce foams without phy sical blowing agents and still attempt to maintain specific important physical properties. Three high water content foams of varying LiCl co ntent have been characterized by utilizing several morphological techn iques as well as by their viscoelastic behavior. From a morphological standpoint, it appears that by adding LiCl to the formulation, there i s less formation of urea-rich aggregates that occur when LiCl is absen t. Also, the hard segments are more dispersed as single units within t he network. The cellular texture of the LiCl-containing foams also sho ws a greater amount of cellular window material than the same foam wit hout LiCl. Both of these changes due to LiCl addition are believed to bring about a significant increase in the amount of viscoelastic decay . This decay has been observed in tensile stress relaxation, compressi on load relaxation, and compressive creep studies. Temperature also ha s a more significant effect on the compression load relaxation behavio r of foams with LiCl in their formulation than when absent. These diff erences in viscoelastic behavior between foams with and without LiCl i n their formulation are attributed to the greater mobility of the hard segments in the presence of the LiCl additive serving as a localized ''hard segment'' plasticizer that also promotes more phase mixing in t he foams. (C) 1994 John Wiley & Sons, Inc.