Sodium salt of lignosulforric acid (LS), which was obtained as a by-product of cooking process in sulfite pulping, was solved in diethylene-, triethylene or polyethylene glycol. Three series of polyurethane foams (LSPU) were synthesized by varying the LS content from 0 to 33 wt.%. Thermal properties of LSPU foams were studied by thermomechanometry (TMA) and differential scanning calorimetry (DSC). Main glass transition was observed in a temperature ranging from 80 to 140degreesC. Glass transition temperature (T-g) increased with increasing LS content and with decreasing oxyethylene chain length. T-g values obtained by TMA accorded well with those by DSC. (C) 2003 Elsevier B.V. All rights reserved.