Tetrahydrofuran-based recycling of furan–lignin foams: comparative characterization of regenerated and virgin foams

Abstract

Foams are used widely in furniture, construction, automotive, and related industries because of their mechanical performance and durability. However, the poor recyclability of conventional polyurethane (PU) foams has raised environmental concerns because of their persistence and contribution to solid-waste accumulation. Bio-based furan-lignin foams (FLFs) offer a promising alternative because they are derived from renewable feedstocks and may provide improved end-of-life options. This study investigated the recycling of rigid FLFs through solvent-assisted dissolution. Virgin foams were prepared from furfuryl alcohol, used as a cross-linker, and lignin-based polyol obtained from corn husks and palm fruit shells, respectively. Glyoxal was used as a hardener and diethyl ether as a blowing agent. Eight solvents were evaluated for their dissolution indices and recyclability potential. Tetrahydrofuran (THF) gave the highest dissolution index (93.24%), followed by ethylene glycol and polyethylene glycol-400, whereas water gave the lowest value (1.10%). Four recycled furan-lignin foams (RFLFs) were then produced from the THF-derived dissolution product, which was used as recycled polyol. Comparative characterization showed that RFLF2 produced the highest char residue (24.45%), whereas RFLF4 showed the highest degradation temperature (556.80 oC), compressive stress, and density (0.876 g cm-3). The regenerated foams retained, and in some cases improved, the mechanical and thermal performance of the virgin FLFs.