Thermal conductivity/structure correlations in thermal super-insulating pectin aerogels

Sophie Groult; Tatiana Budtova

doi:10.1016/j.carbpol.2018.05.026

Thermal conductivity/structure correlations in thermal super-insulating pectin aerogels

Carbohydr Polym. 2018 Sep 15:196:73-81. doi: 10.1016/j.carbpol.2018.05.026. Epub 2018 May 9.

Authors

Sophie Groult¹, Tatiana Budtova²

Affiliations

¹ MINES ParisTech, PSL Research University, Center for Materials Forming (CEMEF), UMR CNRS 7635, CS 10207, 06904 Sophia Antipolis, France. Electronic address: Sophie.Groult@mines-paristech.fr.
² MINES ParisTech, PSL Research University, Center for Materials Forming (CEMEF), UMR CNRS 7635, CS 10207, 06904 Sophia Antipolis, France. Electronic address: Tatiana.budtova@mines-paristech.fr.

PMID: 29891326
DOI: 10.1016/j.carbpol.2018.05.026

Abstract

Pectin aerogels were synthesized via dissolution-solvent exchange-drying with supercritical CO₂. The goal was to correlate thermal conductivity with aerogel morphology and properties in order to understand how to obtain a thermal super-insulating material with the lowest possible conductivity. Polymer concentration, solution pH and presence of bivalent ions were varied to tune pectin gelation mechanism and the state of matter, solution or gel. For the first time for bio-aerogels, a U-shape curve of thermal conductivity as a function of aerogel density was obtained. It shows that to reach the lowest conductivity values, a compromise between density and pore sizes is needed to optimize the inputs from the conduction of solid and gaseous phases. The lowest value of conductivity, 0.015 W/m K, was for aerogels from non-gelled pectin solutions. Calcium-induced gelation leads to pectin aerogels with very low density, around 0.05 g/cm³, but with many macropores, thus reducing the contribution of Knudsen effect.

Keywords: Aerogel; Density; Pectin; Specific surface area; Thermal conductivity.