Formaldehyde Free Renewable Thermosetting Foam Based on Biomass Tannin with a Lignin Additive

This study presents easily prepared free formaldehyde bio-based foam based on a prepared thermosetting resin comprising tannin-lignin-furfuryl alcohol-glyoxal (TLFG) via mechanical stirring in presence of ether as a foaming agent. The foam was developed through a co-polycondensation reaction of glyoxal and furfuryl alcohol with condensed tannin and lignin, which is a forest-derived product. Investigation using scanning electron microscopy (SEM) showed more closed-cell structure without cracks and collapse in the TLFG foam, with a higher apparent density with respect to tannin-furanic-formaldehyde (TFF) foam. Differential scanning calorimetry (DSC), dynamic thermomechanical analysis (DTMA), and thermogravimetric analysis (TGA) investigations revealed that the curing process of TLFG foam proceeds easily even at a lower temperature. Additionally, it acquired higher heat resistance than TFF foam. Moreover, TLFG has a more robust chemical network structure, which contributes efficiently to the mechanical strength and a lower pulverization degree compared with TFF-derived foam. Fourier transform infrared spectrometry (FTIR) and electrospray ionization mass spectrometry (ESI-MS) proved that the cross-inking reactions between tannin, lignin, furfuryl alcohol, and glyoxal have been proceeded efficiently.