Preparation of Lignosulfonate‐Based Phenol Formaldehyde Foam with Excellent Thermal Performance

Abstract

AbstractAn efficient route for the synthesis of lignin phenol formaldehyde (LPF) foams through the foaming process of LPF resin is described. The one‐pot method is used to prepare the resin. To obtain the resin, lignosulfonate is phenolic modified under alkaline conditions. The resin is obtained by incorporating the modified lignosulfonate with phenol via phenol‐formaldehyde condensation. Subsequently, the LPF resin is subjected to a foaming process that yields LPF foam, and the thermal properties of the foam are investigated. The results of 1H nuclear magnetic resonance (1H‐NMR), Fourier transform infrared (FT‐IR) spectroscopy, and gel permeation chromatography (GPC) analyses indicate that compared with lignosulfonate, the molecular weight of phenolated lignin decreases significantly, and the content of phenolic and aliphatic hydroxyl groups increases. Thermogravimetric, thermal conductivity, and limiting oxygen index analyses are also conducted. The results reveal that the maximum carbon residue rate (43.76% at 800 °C), maximum thermal conductivity (0.0344 W m−1 K−1), and maximum oxygen index (39.1%) occur for the LPF foam with 20 wt% lignin. These results demonstrate that lignosulfonate is a promising candidate for the use of phenol modification in preparing LPF foam. Furthermore, this study provides a new direction for the modification and application of lignin.