Green synthesis of flexible polyurethane foams from liquefied lignin

The present paper reports the innovative, sustainable, and green synthesis of soft foams from Kraft lignin. This research activity was performed in the EC project FORBIOPLAST grant agreement No. 212239 focused on the use and valorisation of forest resources which include lignin as by-products of wood industries and of bioethanol production. In order to produce flexible foams two types of chain extender were used in combination with liquefied lignin: polypropilenglycol triol and castor oil. The samples were produced with the "one shot" technique and the only blowing agent used was water. All samples were produced with a ratio NCO/OH less than one, because it is well known that it significantly reduces the degree of crosslink, resulting in higher flexibility of the material. Samples were produced in free and controlled rise expansion. The properties of these foams can be modulated by industrial producer, by the individuation of the most efficient chain extenders, thus introducing flexible chains in the macromolecular structure that can reduce the glass transition temperature of the materials and generate foams with higher flexibility. The quality of the foams are compatible with application in packaging, such as packaging of furniture, and for the interior part of car seats.