Carboxymethylated lignin incorporated chitosan aerogel as thermal insulator
Saba Khodavandegar, Rozita Zare, Pedram Fatehi
Abstract
Aerogels have been used in many applications, including thermal insulation. However, most of these aerogels were produced using petrochemical materials with adverse environmental footprints. Biodegradable materials, such as chitosan (CH) and lignin, can promote the green manufacturing of sustainable aerogels. In this work, aerogels were produced from carboxymethylated lignin (CM). The NMR and XPS confirmed the crosslinking of CM and CH, as indicated by an increase in the intensity of the O C–N bond in the lignin-chitosan composite network. This work assessed a hypothesis that carboxymethylated lignin derivatives would improve the critical characteristics of aerogels required for insulation purposes. As the charge density of CM increased, the crosslinking bond between CM and CH intensified, reducing porosity and compression strength while increasing thermal conductivity. In addition, the increment in the charge density of CM increased the elasticity and hardness of the induced aerogels. The least charged CM (CM1) fabricated aerogel with a surface area of 211.2 (m 2 /g), pore volume of 0.198 (cm 3 /g), and pore size of 1.9 (nm). This aerogel had the lowest thermal conductivity, 0.035 (W/mk), and the highest compression strength, 3.87 (MPa). Moreover, the addition of CM increased the biodegradability of the aerogels. The results of this work present a promising strategy for fabricating a sustainable and biodegradable aerogel using only green materials and employing water-based, environmentally friendly processes that eliminate the use of toxic organic solvents.