• Natural polyols
• Thermal properties
• Mechanical properties
• Lignin
• Flexible foams
• Biobased polyurethanes

In this work was presented a synthetic pathway to valorise lignin wastes to make a product that was more environmental friendly and economically viable than the polyurethanes produced by current synthetic processes.
The usage of lignin with suitable chain extenders, as a potential replacement to petroleum polyols, in the production of flexible foam polyurethanes, was investigated. Advantages of lignin is that it is a renewable resource, cheap and easily available and it is a waste material from the wood and pulp industries. Two different kind of lignin were employed, one from kraft and one from soda process, also the soda lignin was subjected to chemical modification process to improve its reactivity.The cell structure as well as physico-mechanical and thermal properties were characterized to compare with commercial analogues. It was investigated that liquefied lignin foams had high content of open cell, density, physico-mechanical and thermal properties were comparable with foams made with commercial petroleum based polyols. The properties of these foams was modulated introducing flexible chains in the macromolecular structure that can reduce the glass transition temperature of the materials and generate foams with higher flexibility.