Eco-foaming lignin for innovative rigid foam

Abstract

Rigid lignin foam is prepared by a baking method using kraft lignin as the sole source. The eco-forming process involved cold-pressing kraft lignin powder into a solid block, heating the solid block to form lignin foam, and finally curing and cooling the lignin foam to obtain an open-cell, rigid foam. Both adsorbed water and water generated from the dehydration of hydroxyl groups in the lignin served as the blowing agent in this baking method. It was found that as the moisture content of lignin decreased, the foam densities increased, the mean bubble sizes decreased, and the bubble size distributions became narrower. Foam morphology showed an open cell structure and a wide cell volume distribution. The results suggest that controlling the moisture content in raw lignin allows for the control of the pore structure of the lignin foam. Based on their unique properties, lignin foam materials hold great promise in many applications especially as core insulation materials for structural insulated panels (SIPs).