Polyurethanes as a viable route to valorise lignin

This work presents a study concerning the use of lignin as a macromonomer in polyurethane (PU) synthesis based on four lignin samples (Sarkanda (Granit SA), Indulin AT (MeadWestvaco), Curan 27-11P (BorregaardLigno Tech) and Alcell (Repap Enterprises)). The work started with lignin characterization, giving particular emphasis to hydroxyl groups’ determination. Therefore, lignin was used as a macromonomer in polyurethane synthesis, following two different approaches, namely: (i) its use as such without any purification or modification procedure and (i) its use after chemical modification (oxypropylation). A wide range of polyurethane materials (elastomers and rigid polyurethane foams) were prepared presenting properties which depended on the lignin type and content introduced. Briefly, for polyurethane synthesis purposes Alcell and Indulin AT were found to be the most viable raw-materials to be used as macromonomers. Alcell lignin presents high purity coupled with low molecular weight, while Indulin AT has the highest total hydroxyl content together with modest impurity content. Sarkanda and Curan 27-11P impurities and structural features constitute the main drawback for its application.Portuguese Foundation for Science and Technology (grant SFRH/BD/18415/2004) and the French-Portuguese Scientific Cooperation Programme (actions F-13/06 and F-32/08)