Research on nano-insulation insulation coatings for exterior walls

China Coatings Online News Information: At present, building energy-saving external wall insulation materials are divided into organic insulation materials (PU foaming, polystyrene foam, polymer phenolic resin foam, etc.); Inorgic insulation materials (loose inorgic fibers and products, porous lightweight particle insulation mortar, fiber and porous particles mixed insulation materials). The thermal conductivity of organic insulation materials is low and the insulation effect is good, but the fire safety is poor. The thermal conductivity of ordinary inorgestring materials is higher and the insulation effect is poor, but the fire safety is good. Inorgeable nano-porous insulation materials have low thermal conductivity, good high temperature resistance, often used as space insulation materials. The high-tech space insulation material into civilian, the development of a thin layer, insulation coating, is an important way for the future development of insulation materials technology.the composition and performance of
nanometer insulation coatings
nomes insulation insulation coatings with self-linked acrylic emulsions as film- and SiO2 aerogels, hollow glass microbeads, potassium hexa-titanium wafers, etc. as fillers, prepared with the cooperation of a variety of additives. Coatings with construction thin layer, nano-hole insulation, safety and fire prevention, environmental protection and energy saving, cost-effective and other advantages.
nometer insulation insulation coating insulation principle
heat transmission is always from the high temperature zone to low temperature direction, heat transfer has solid heat transmission, air ionizing heat transmission, radiation heat transfer 3 ways. Nano-insulation insulation coatings are characterized by the ability to effectively block or shield the above three thermal conduction pathways. Among the coating components, the key insulation is the nanoSiO2 aerogel, followed by potassium hexatanate and hollow glass microbeads. Nano SiO2 aerogel is a very good thermal insulation performance of lightweight nano-porous amorphoous solid material, its porosity rate of up to 80% to 99%, the typical size of the hole is 2 to 50nm, the average aperture is 20nm, than the surface area of 600 to 1000m2/g, the surface density is 0.003 to 0.35g/cm3, room temperature thermal conductivity can be as low as 0.013W/(m?k), even at high temperatures of 800 oC, its thermal conductivity is only 0.043W/(m?k), and high temperature does not break down, no harmful gases released, is pure green environmental protection materials, the disadvantage is low strength, brittleness, difficult to use alone. Mixing nanoSiO2 aerogel with aluminum silicate fiber and hollow glass microbeads can greatly improve the physical and mechanical properties of the coating under the cross-linking of elastic film.
1. Thermal insulation of SiO2 aerogel
solid thermal conduction: SiO2 aerogel is a nano-three-dimensional network skeleton structure formed by several Si-0-Si substations connected to each other, due to the existence of near-infinite multi-nanopores, solid heat transfer can only be carried along the hole wall, near-infinite porous wall constitutes a near "infinite path" effect, so that the solid thermal conductivity is reduced to almost the lowest limit.
convulsive thermal conduction: SiO2 aerogel has a median size of 2 to 50 nm, when the diameter of the pores in the material
radiant thermal conduction: radiation conduction heat is a non-contact heat transfer. Because the aerogel is a uniform nano-porous, and has a very low volume density, so that the number of pores inside the material tends to be "infinite", and each pore wall has the role of sun vises, resulting in nearly "infinite multi-sun visce" effect, so that radiation heat transmission down to the lowest limit.
2. Insulation of potassium hexatanate sachets
Potassium hexa-titanium-titanate crystals must be a chain tunnel structure with a loose density of 0.1 to 0.3g/cm3, a surface area of 11m2/g, and a median size of 0.8 to 1.8 to 1.8 2?m, length 30 to 50?m, low thermal conductivity (normal temperature 0.0534W/m?k), and has a negative temperature coefficient (the higher the temperature, the higher the thermal conductivity), 760 degrees C thermal conductivity of 0.0174W/(m?k); Infrared pass rate is small: in the wavelength range of 0.9 to 2.4?m, the thickness of 0.25?m potassium hettanate crystal must pass through the rate of only 8.4%. And non-toxic harmless, long service life, can withstand 1200 degrees C of high temperature, acid and alkali resistance, wear-resistant insulation, good electrical and physical performance.
six potassium titanate crystals set structural insulation, physical insulation, infrared reflection in one, infrared reflectivity > 95%.
3. Insulation of hollow glass microbeads
Hollow glass microbeads are a new type of lightweight material made of hollow thin wall ball powder and excellent performance, which is a silver-white glossy sphere, hollow, with a hard shell, inside the shell. N2 or CO2 inert gas, wall thickness of 8% to 10% of the diameter, thermal conductivity of 0.07W / (m?k) or so, with low density, large volume, low thermal conductivity, high pressure strength, low oil absorption rate, good self-mobility and other advantages. NanoSiO2 aerogel insulation coating with ultra-fine hollow glass microbeads, its coating film has a unique micro-hole structure, in order to maintain a small increase in thermal conductivity under the premise of significantly improving the anti-pressure strength of the coating, while having excellent thermal reflection and thermal radiation performance.
thermal conductivity of nano-insulation insulation coatings is 0.041W/(m?k). The thermal conductivity is an important parameter of the thermal insulation performance of the material, but it is not the only parameter, and the photothermal reflectivity and infrared radiation rate are the more important parameters for the nano-insulation material. When evaluating the thermal insulation performance of insulation materials, they should be evaluated according to the comprehensive factors of thermal conductivity, photothermal reflectivity and infrared radiation rate of the materials.
nano-insulation insulation coating insulation effect
homemade two steel plate test cases of the same form factor 1 and 2, steel plate thickness of 1mm, the form factor is: ×W× height s 1.2m ×0.6m×1.2m, 1 x box bread covered with an 8cm thick polybenzene foam plate, 2 x box six outer surfaces coated with 1mm thick nano-insulation insulation paint, maintenance drying. In summer, when the maximum temperature is 38 degrees Celsius, the two boxes are exposed to the outdoor sun until 15 p.m., while the internal temperature of the two boxes is detected. Test results: The internal temperature of the box is 27.5 degrees C, and the internal temperature of the 2-box is 27 degrees C.
In winter below zero degrees, the above 1 and 2 boxes are heated to 40 degrees C, closed and moved to outdoor freezing at the same time, 2h, the internal temperature of 2 boxes is tested, the results are as follows: the internal temperature of 1 box is 16.5 degrees C, 2 is 18 degrees C.
the above test results show that 1mm thick nano-insulation insulation coating than 8cm thick polybenzene foam plate insulation performance is good, summer insulation efficiency is 3% higher, winter insulation insulation efficiency is 9% higher.