Chapter 15: Applications of Polysaccharide and Protein Based Aerogels in Thermal Insulation

In this chapter, the main focus is the thermal insulation properties of the polysaccharide and protein based aerogels. After giving insights about the thermal insulation context, several existing thermal insulation materials are briefly described. Then, cellulose, alginate, starch and chitosan, which are the main polysaccharides extensively used to produce biobased aerogels for thermal insulation applications, will be described. Their specific properties such as non-toxicity, renewability, mechanical stiffness, large aspect ratio and flexibility make them interesting candidates for the design of new materials such as aerogels. The main aerogel preparation protocols and the thermal insulation properties of the produced materials are summarized with their possible applications. Similar to silica aerogels, some of the polysaccharide based aerogels possess super thermal insulating properties. For example, pectin, cellulose nanofiber and chitosan based aerogels showed a thermal conductivity of 0.016, 0.015, and 0.022 W (m K)⁻¹, respectively. In addition, the chitosan and pectin aerogels have better mechanical properties compared to traditional silica aerogels. It has been demonstrated that the thermal conductivity of the aerogels mainly depends on the density, morphology, pore size, pore volume, and surface area. A few attempts have been carried out with proteins, they will be discussed in this chapter. Many studies highlighted challenges (e.g., overcoming the radiative effect, improving hydrophobicity, being resistant to fire and having good mechanical stability) to develop successful polysaccharide and protein based aerogels for insulation applications. To overcome these challenges, some possible routes are briefly discussed in this chapter.