Interpenetrating pectin-silica aerogel nanocomposite materials with improved thermo-mechanical properties

International audienceMonolithic silica / pectin aerogel nanocomposites were synthesized by dissolving a natural polymer, pectin, in an aqueous silicic acid solution, followed by gelation of each component, pectin coagulation, hydrophobization and supercritical drying. Monolithic, lightweight (0.12 - 0.18 g/cm3) and nanostructured aerogels were obtained. These materials displayed versatile morphologies and properties by varying the pH and aliquots of the components. The specific surface area, porosity, microstructural and mechanical properties as well as thermal conductivity and humidity uptake of these acid-catalysed aerogel nanocomposites were systematically studied. They exhibit high plastic deformation region (no rupture until at least within 80% strain) as well as greatly increased yield strength (2-15 MPa versus 0.3 MPa for silica aerogels) and compressive modulus 0.6 - 2.0 MPa. Aerogel composites are highly hydrophobic: their weight increases only by 4-12 % due to water vapor adsorption at 97 % RH and 23±2 °C for 7 days. New organic-inorganic composites are thermal superinsulating materials: their thermal conductivity is 14.2-17.0 mW/(m•K) which is comparable with that of pure silicic acid based aerogels (14.0-15.4 mW/(m•K))