Full Bio-Based Aerogel Incorporating Lignin for Excellent Flame Retardancy, Mechanical Resistance, and Thermal Insulation

Aerogels have drawn a lot of interest as prospective insulation materials in the construction industry due to their low thermal conductivity. However, the combination of excellent mechanical properties and flame retardancy is a fundamental issue with the majority of bio-based aerogels. By utilizing the ability of the alginate solution to gel in mildly acidic environments, sodium alginate (SA)/sodium lignosulfonate (LS)/phytic acid (PA) aerogels were fabricated in a quick and facile method. To solve the issue of inorganic additives being incompatible with the bio-based substrate, we introduced lignin to it as a structural reinforcer and char-forming agent, significantly improving the mechanical strengths of the aerogels, which has increased their compressive modulus by nearly 30 times. The inclusion of lignin dramatically boosted the ability of aerogels to suppress smoke while simultaneously reducing its fire index and then providing outstanding fire resistance. A superhydrophobic flame-retardant aerogel with a water contact angle of 150° was then obtained by chemical vapor deposition of methyltrichlorosilane (MTCS), further broadening its application potential. This work offers a fresh idea for the high-value utilization of lignin, and the obtained aerogels have enormous application potential in the fields of construction and transportation.