Silica aerogels play a role in the preparation of thermally insulating coated fabrics

Thermal insulation coated fabric is a coating with thermal insulation effect on the surface of the fabric, by blocking, reflecting or radiating solar energy, to achieve the purpose of reducing the internal temperature of the fabric covering and reducing energy consumption, it has a wide range of applications in the textile industry prospect.

According to the thermal insulation mechanism, fabric thermal insulation coatings can be divided into three types: barrier type, reflective type and radiation type. Barrier thermal insulation coating is a passive cooling coating that achieves thermal insulation through the resistance of heat transfer. In order to obtain good thermal insulation effect, it usually has the characteristics of relatively low bulk density, low thermal conductivity, and low dielectric constant. Reflective thermal insulation coating isolates sunlight energy through reflection. Commonly used reflective materials include ceramic micropowder, aluminum powder, titanium dioxide and ATO (antimony-doped tin dioxide) powder.

Common barrier fabric thermal insulation coating agents are divided into chemical structures, mainly including polyvinyl chloride (PVC), polyacrylate (PA), polyurethane (PU), silicone, rubber emulsion and PTFE Ethylene, etc., among which PA and PU are widely used; according to the medium used, they can be divided into two types: solvent type and water dispersion type.

As an amorphous nanoporous material, SiO2 aerogel has a controllable structure and a continuous three-dimensional network structure. And its density is adjustable between 3-500mg/cm3, it is a solid material with the lowest density in the world, the porosity can reach 80%-99.8%, the pore size is between 1-100nm, and the specific surface area can be as high as 1000m2/ g. Due to the unique nanoporous structure, its thermal conductivity is extremely low, and the thermal conductivity is as low as 0.017W/(m·K) under normal temperature and pressure, which is the lowest thermal conductivity of solid materials known so far. Since the structural units constituting the aerogel skeleton are smaller than the wavelength of visible light, it also has better light transmission properties. At the same time, it is an inorganic material with non-combustible or flame-retardant effect, and has wide application prospects in the field of thermal insulation.

According to statistics, in recent years, the compound annual growth rate of the global aerogel market size is 36.4%, while the compound annual growth rate of the domestic aerogel market is as high as 61.1%. Its application in thermal insulation fabrics can not only reduce the weight of thermal protective clothing, make it lighter and thinner, but also greatly reduce work loss during use.

For example, SiO2 aerogel can be added to PA or PU adhesives according to a certain proportion to obtain a thermal insulation coating agent, and the cotton fabric can be directly coated, and then the process of drying and baking can be carried out. Preparation of SiO2 Aerogel Thermal Insulation Coated Fabrics. Compared with the original fabric, the thermal insulation performance of the coated fabric with SiO2 aerogel is significantly improved, and when the amount of aerogel added in the coating agent is less than 10%, the thermal insulation effect of the fabric increases with the amount of SiO2 aerogel added. increases and gradually improves.

In addition, glass fiber SiO2 aerogel felt can also be selected as the material of the fabric insulation layer. Its thermal protection performance is greater than 60, and it can withstand high temperature flame combustion at 450 ° C for 50s, which significantly improves the thermal protection performance of the fabric, and can resist firefighting. instantaneous high temperature.

SiO2 aerogel has the characteristics of high porosity and low thermal conductivity, making it a new type of super insulating material. However, the flexibility and integrity of SiO2 aerogels are poor, and the thermal conductivity of aerogels prepared by drying at room temperature increases rapidly at high temperatures, which greatly limits the application of SiO2 aerogels. In recent years, SiO2 aerogel composite thermal insulation materials prepared by in-situ sol-gel method and molding method have improved their toughness, integrity and high-temperature thermal insulation performance to a certain extent, making SiO2 aerogels. It is possible as a single block insulation material.