Bio-based non-flammable foams with a circular end-of-life based on the self-foaming process

For conventional polymeric foams, over-utilization of harmful precursors and the problem with waste management are driving scientists to develop sustainable foaming methods and make polymeric foams from renewable precursors. This study developed a self-foaming system to create a lignin carbonate foam (LCF) from two non-toxic carbon storage precursors: lignin and ethylene carbonate (EC). Specifically, kraft lignin, in its isolated salt form, referred to as lignophenolate, is copolymerized with EC via the anionic ring-opening polymerization. Under the optimal condition, the gelation and solidification of the copolymers could coincide with trapping in-situ generated CO2 blowing gas from the copolymers to make the foams. Its unique composition endows the materials with comparable performances with those benchmark plastic foams (for example polyurethane foam, expanded polystyrene) considering the mechanical performances, thermal stability, shape fidelity, and non-flammability. Moreover, the carbonate linkages in LCFs render them to be reshaped or depolymerized with valuable precursors for end-of-life recycling. This study opens new avenues to fabricate polymeric foams from carbon storage precursors through a self-foaming process for applications in the construction industry.