Effects of the Heat Treatment in the Properties of Fibrous Aerogel Thermal Insulation

Abstract

Nowadays, besides the use of conventional insulations (plastic foams and wool materials), aerogels are one of the most promising thermal insulation materials. As one of the lightest solid materials available today, aerogels are manufactured through the combination of a polymer with a solvent, forming a gel. For buildings, the fiber-reinforced types are mainly used. In this paper, the changes both in the thermal performance and the material structure of the aerogel blanket are followed after thermal annealing. The samples are put under isothermal heat treatments at 70 °C for weeks, as well as at higher temperatures (up to 210 °C) for one day. The changes in the sorption properties that result from the annealing are presented. Furthermore, the changes in the thermal conductivity are followed by a Holometrix Lambda heat flow meter. The changes in the structure and surface of the material due to the heat treatment are investigated by X-ray diffraction and with scanning electron microscopy. Besides, the above-mentioned measurement results of differential scanning calorimetry experiments are also presented. As a result of using equipment from different laboratories that support each other, we found that the samples go through structural changes after undergoing thermal annealing. We manifested that the aerogel granules separate down from the glass fibers and grow up. This phenomenon might be responsible for the change in the thermal conductivity of the samples.

Influence of thermal annealing on structural properties of silica aerogel super insulation material

“…In this case, the temperature in the dryer was varied between 70 °C and 210 °C with about 30-50 °C steps for 1 day. After both experimental series, different types of equipment were used to reveal any changes [6,23]. The results presented in this paper are a continuation of previously published research; therefore, it is indispensable to highlight those results.…”

“…This is an amorphous SiO 2 aerogel embedded in a glass net. In our previous works, the properties are well highlighted, but due to the nature of the paper what is the presentation of the analysis of the chemical contaminants and chemical bonds we should highlight the main declared components [4,6,23]. As the declaration file of the manufacturer, this material contains approximately 40-50% of amorphous SiO 2 , about 10-20% methylsilylated silica, polyethylene terephthalate (PET) and fibrous glass (textile grade) each, while in scattered form 0 to 5% magnesium oxide and synthetic graphite [27].…”

“…The results presented in this paper are a continuation of previously published research; therefore, it is indispensable to highlight those results. In recent papers in Ref [4,6,23], different experiments were executed on aerogel samples after thermal annealing. It was showed that thermal aging (heat treatment) has significant consequences both in the material and in the thermal properties.…”

“…It was showed that thermal aging (heat treatment) has significant consequences both in the material and in the thermal properties. Structural modifications were detected by registering the sorption isotherms, where we deduced the changes through the modifications in the shape of the curves, see Ref [23]. Through SEM images, increase in the grain size was revealed.…”

“…The tested aerogel material contains not only silica, but different organic groups as methyl, OH and carbon. It was shown earlier that due to heat treatments structural changes can happen, which could lead to loss the thermal stability and increase their thermal conductivity [23]. First of all, it could be connected with the poor thermal stability of methyl groups [24].…”