Mechanical and thermal properties of rigid polyurethane foams derived from sodium lignosulfonate mixed with diethylene‐, triethylene‐ and polyethylene glycols

Abstract Sodium salt of lignosulfonic acid (LS), which was obtained as 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%. Apparent density (ρ) of LSPU foams ranged from 0.08 to 0.18 g cm−3 and was affected by both LS content and oxyethylene chain length. Glass transition temperatures increased with increasing amount of LS and with decreasing oxyethylene chain length. Thermal gravimetry analysis indicated that the LS component decomposes first and that the thermal stability increases with decreasing oxyethylene chain length. Compression strength and compression modulus increased linearly with increasing apparent density. It is concluded that LS is successfully utilized as a hard segment of rigid PU foams, whose thermal and mechanical properties can be tuned by changing the amount of LS and the length of soft oxyethylene chains.