Silica aerogels with low density and low thermal conductivity are useful in the preparation of thermal insulation coating fabrics

Thermal insulation coated fabric is a layer of coating with thermal insulation effect applied to the surface of the fabric. By blocking, reflecting or radiating solar energy, it can reduce the in...

Thermal insulation coated fabric is a layer of coating with thermal insulation effect applied to the surface of the fabric. By blocking, reflecting or radiating solar energy, it can reduce the internal temperature of the fabric covering and reduce energy consumption. It has broad applications in the textile industry. prospect.

Fabric insulation coatings can be divided into three types: barrier type, reflective type and radiation type according to the insulation mechanism. Barrier type thermal insulation coating is a passive cooling coating that achieves heat insulation through the resistance of heat transfer. The heat insulation mechanism is relatively simple. Generally, a composition with low thermal conductivity is used or a material with extremely low thermal conductivity is introduced into the coating film. Air, in order to obtain good thermal insulation effect, usually has the characteristics of small packing density, low thermal conductivity and small dielectric constant. Reflective thermal insulation coatings isolate solar energy through reflection. Commonly used reflective materials include ceramic powder, aluminum powder, titanium dioxide and ATO (antimony-doped tin dioxide) powder.

Common barrier fabric insulation coating agents are divided according to their chemical structures, mainly including polyvinyl chloride (PVC), polyacrylate (PA), polyurethane (PU), silicone, rubber emulsion and polytetrafluoroethylene. 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-dispersed 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 and 500 mg/cm3. It is a solid material with the lowest density in the world. Its porosity can reach 80% to 99.8%, and its pore size ranges from 1 to 100nm. time, the specific surface area can be as high as 1000m2/g. Due to its unique nanoporous structure, its thermal conductivity is extremely low, with the thermal conductivity as low as 0.017W/(m·K) at normal temperature and pressure. It is the currently known solid material with the lowest thermal conductivity. Since the structural units constituting the airgel skeleton are smaller than the wavelength of visible light, it also has good light transmission properties. At the same time, it is an inorganic material, non-flammable or flame-retardant, and has broad application prospects in the field of thermal insulation.

According to statistics, the global aerogel market has grown at a compound annual growth rate of 36.4% in recent years, while the domestic aerogel market has grown at a compound annual growth rate of 61.1%. Its application in thermal insulation fabrics can not only reduce the weight of thermal protective clothing, making it lighter and thinner, but also greatly reduce work losses during use.

For example, SiO2 airgel can be added to a PA or PU adhesive in a certain proportion to prepare a thermal insulation coating agent, which can be directly coated on cotton fabrics, and then dried and The preparation of SiO2 airgel thermal insulation coating fabric can be achieved through baking and other processes. Compared with the original fabric, the thermal insulation performance of the coated fabric with SiO2 airgel is significantly improved, and when the amount of airgel in the coating agent is less than 10%, the thermal insulation effect of the fabric It gradually becomes better as the amount of SiO2 airgel increases.

In addition, you can also choose glass fiber SiO2 airgel felt as the fabric insulation layer material. Its thermal protection performance is greater than 60, and it can withstand high-temperature flame burning at 450°C for 50 seconds, which significantly improves the thermal protection of the fabric. Performance, can withstand instantaneous high temperatures such as fire fighting.

SiO2 aerogel has the characteristics of high porosity and low thermal conductivity, making it a new super thermal insulation 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 SiO2 sub>Applications of airgel. In recent years, SiO2 airgel composite insulation materials prepared through in-situ sol-gel method and molding molding method have improved its toughness, integrity and high-temperature insulation to a certain extent. Thermal properties make it possible for SiO2 airgel to be used as a separate bulk thermal insulation material.

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