Researchers at the UCLA Department of Mechanical & Aerospace Engineering have developed novel processing methods for polymer aerogels for thermal insulation and low thermal conductivity applications.
Thermal conductivity is the most important metric for high performance thermal insulation materials for applications in electronics, semiconductors, aerospace, energy and environmental engineering, and biomedicine. Great efforts have been made to develop ultralow thermal conductivity materials, such as the artificially made, disordered, layered WSe2 crystals and fullerene derivatives. However, these materials are limited for a wide range of applications due to their limited large-scale synthesis capability and extremely high cost. Porous materials, such as inorganic aerogels, including silica or silicon oxides based composite aerogels or ambigels are able to achieve very low thermal conductivity. However, the synthesis of aerogels involves supercritical drying process requiring high-pressure equipment, and the gel preparation reactions are limited to specific types of backbone materials.
Researchers at UCLA have developed a novel method of preparing high porosity and low thermal conductivity polymer aerogels. The mechanism of gelation is precipitation of polymer due to diffusion of insoluble liquid into solvent. This new processing method replaces supercritical drying processes with ambient drying, which produces poly vinyl chloride (PVC) aerogels with porosity as high as 92%. With such a high porosity and low intrinsic thermal conductivity of PVC, the PVC aerogel demonstrates thermal conductivity as low as 0.033 W/mK in air, and ~0.005 W/mK in vacuum.
Thermal insulation and low thermal conductivity applications:
The process method has been validated with PVC aerogel. The researchers are currently working on further minimize thermal conductivity of PVC aerogels in air by reducing the pore size and induce stronger Knudsen diffusion of air molecules.