Exploring the potential of resorcinol-formaldehyde xerogels as thermal insulators

The contribution to the total thermal conductivity of porous materials depends mainly on the operating conditions and on its type of porosity. Accordingly, the thermal insulating capacities of several resorcinol-formaldehyde (RF) xerogels synthesized by microwave heating were investigated. First, the operating conditions were optimized, since the thermal conductivity measurements were to be performed both before and after the degassing of the organic xerogels and with various particle sizes, ranging from 3 mm to below 212 μm. Special attention was paid to the influence of the porous properties, particularly density and pore size, on the total thermal conductivity. A minimum thermal conductivity value of 0.035 W m−1 K−1 was obtained for an organic xerogel with a bulk density of 0.248 g cm−3 and a mean pore size of 144 nm. The results obtained suggest that RF xerogels would be highly suitable candidates for thermal insulation applications as their thermal conductivity values are comparable to those of commercial materials, such as expanded polystyrene (0.034 W m−1 K−1).The authors gratefully acknowledge the financial support of the Ministerio de Economía y Competitividad of Spain, MINECO (Projects IPT-2012-0689-420000, CTQ2013-49433-EXP, CTQ2014-54772-P). NRR also acknowledges a predoctoral research grant from MINECO.Peer reviewe