The design of an insulation coating resistant to high temperature and light radiation is discussed

China Coatings Online News News
Li Zhiqiang (Aerospace Science and Technology Group Meiling Chemical Plant, Zunyi, Guizhou 563003)
Abstract: A design concept combining radiation resistance with high temperature insulation has been developed High-temperature insulation coating, the resulting thermally controlled coating within 850 degrees C /5 min, insulation temperature of less than 200 degrees C, at the same time, the coating anti-photothermal radiation hem emission rate ≥ 0.85.
key words: photothermal radiation, thermal conduction, high temperature insulation coatings
in the figure classification number: TQ 637.6 document identification code: A article number: 1009-1696 (2013) 02-0046-03
insulation is for thermal energy Insulation measures taken by conduction, radiation and reflow, in some high temperature environment to control the transfer of heat, especially with high temperature insulation coating for insulation protection research more, has been used high temperature insulation coating as some products insulation coating, its heat-resistant temperature in a certain period of time more than 1,000 degrees C, at the same time has a good insulation effect. Similarly, there is a lot of research on special coatings that are resistant to photothermal radiation, and different radiation-resistant coatings are used for different radiation-resistant needs, such as polished reflective layers, chemically converted reflective layers, coating reflective layers, etc. However, when the product needs both high temperature insulation and anti-light heat radiation, it is necessary to use the combination of radiation and heat insulation design concept, high-temperature insulation coating and anti-light heat radiation layer combined, so that it can play a role in both anti-light radiation and high temperature insulation.
coating film-forming substances usually choose organic or inorganic resins with high heat resistance temperature, choose combinations according to the requirements of insulation and radiation resistance, and use different filling (pigment) materials to achieve thermal insulation and radiation resistance purposes.
1. The basic composition of thermally controlled coating coatings
1.1 resin, filling (pigment) material selection
the choice of silicone modified acrylic resin, which has the characteristics of maintaining more than 20 h at temperatures of about 850 degrees C does not change its basic properties, weather resistance, light preservation, high temperature resistance is excellent.
After calculating the theory of granularity, thermal migration and heat absorption and combining resin phase change and curing reaction system analysis, it was determined that hollow ceramic (glass) microbeads, titanium dioxide, mica powder and other filling (pigment) material combinations with low thermal conductivity and high heat resistance characteristics were determined. Epoxy resin is used to improve the process of the main resin, and the curing agent is determined by construction characteristics.
1.2 flame retardant, thinner selection
In order to ensure the effectiveness of the coating system, the choice of flame retardant is necessary, combined with coating system analysis, insulation insulation coating formulation design selected compound flame retardant. A special thinner specially designed for diluents.
1.3 Basic ingredients combination
silicone modified acrylic resin, 57%; epoxy resin, 7%; Hollow ceramic microbeads, 11%; Titanium white powder, 7%; asbestos powder, 4%; mica powder, 3%; gas-phase silicone, 3%; other functional components, 8%; flame retardants, functional additives, compounding agents. m (base material): m (curing agent) s 10: 3.
2 The basic performance of thermally controlled coatings
test results of thermally controlled coatings can be found in Table 1.
Note: Test sample substrate selected 1 mm steel plate, after oil removal and rust removal treatment with spraying or brushing method to prepare a model (both sides and all around the coating), cured coating thickness of 0.05 to 0.1 mm; The temperature display of the Mafu furnace or other high-temperature equipment (temperature range 0 to 1,000 degrees C) as a heat source, the cured model at room temperature into the high-temperature equipment, starting equipment heated to 900 degrees C, maintain 15 min after the removal of the model, cooling, visual coating surface. Requires coating: no foaming, no cocking, no shedding.
3. Thermally controlled coating insulation performance detection
3.1 model preparation and treatment
substrate selected aluminum magnesium alloy plate, thickness (1.2±0.15 mm, form factor 100 mm ×100 mm, surface cleaning oil removal, anode treatment. The coating is evenly coated on the side of the substrate by spraying or brushing, after a coating needs to be dried after the next coating, and finally make the coating layer thickness of more than 1.0 mm, room temperature construction, temperature curing 24 h or more or 120 degrees C baking 4 h, so that the coating is completely cured.
3.2 detection instrument
meter: stopwatch, PT-100 thermal resistance, temperature digital display (0 to 1 000 degrees C).
heat source: heating heat source with temperature controller resistance furnace (1,000 to 3,000 W), furnace with insulation material modified to upper mouth size: 65 mm×65 mm, lower port size: 1 The 30 mm×130 mm heating channel (channel height (65±5) mm), the lower port is close to the resistor furnace, and the upper port is covered with alloy steel plates (70 mm×70 mm ×1.5 mm).
detection method: the test end of the PT-100 thermal resistor two probes is fixed in the center of the model (or alloy steel plate) detection surface, the other end is fixed to the transferor to the temperature digital display, the temperature controller is used to adjust the temperature in the resistance furnace.
3.3 Environmental requirements
ambient temperature: (25±5) degrees C;
3.4 Insulation measurement
(1) heat source calibration: after starting the resistance furnace, set the control temperature, use alloy steel plate to detect the furnace temperature, control the resistance furnace temperature, so that the surface temperature of the alloy steel plate is guaranteed to be within (850±10) degrees C (remember T0), maintain more than 5 min.
(2) Back temperature (insulation temperature T1) determination: the detection model coated with a coating layer side facing the heat source channel, while pushing open the alloy steel plate in parallel, and finally make the model completely cover the resistance furnace, the PT-100 thermal resistance detection probe placed in its central position, with a stopwatch to record the heating time, record 5 min when the surface temperature of the sample T1.
(3) Repeat calibration of the heat source: repeat the above (1) and (2) steps, replace the model with alloy steel plate, detect the temperature T2 at the center of the alloy steel plate, T2 value should be in the T0 range (no more than (850±10) degrees C), otherwise it should be re-labeled and tested.
3.5 Test Results
see Table 2.
4. The detection index of the anti-photothermal radiation performance of the thermally controlled coating
the detection index of the anti-photothermal radiation performance is referenced by the hetero-emission rate, and its hetero-emission rate is ≥ 0.85 (the actual detection value is 0.9).
5 Results Discussed
5.1 Main Resin
Resin as a film-forming material, its role in addition to the functional material and substrate combined, itself needs to have heat resistance and reflective photothermal radiation function, the use of silicone modified acrylic resin, designed to reduce the C-O structure in the resin (e.g. C-O-C, C-O, O-H, etc.) and other heat-absorbing groups, so that it is replaced by Si-O structure, enhance the resin's heat resistance and reduce the resin's absorption of space photothermal radiation, a variety of resins (with titanium dioxide as a filler) on the absorption rate of solar heat see Table 3.
can be seen from Table 3: acrylic resin on the absorption rate of sunlight heat is only 0.24, and with silicone modified to 0.19, has a better anti-light heat radiation capacity. The modified resin can maintain more than 20 h without changing its basic performance at a temperature of about 850 degrees C, and has the characteristics of better weather resistance, light preservation and high temperature resistance. Its reflectivity to solar thermal radiation is greater than 80%.
5.2 combination function filler
thermally controlled coating filler selected hollow ceramic (glass) microbeads, titanium white powder, mica powder and other pigments with low thermal conductivity, high heat resistance characteristics. Hollow ceramic (glass) microbeads form a hollow spherical barrier after the coating is cured, like a "miniature" foam material, and is a "closed-hole bubble", heat transfer by the table and the inner coating, closed-hole "foam" formed by the low heat conductivity gas slows down the heat transfer rate, filler combination after the actual detection of its thermal conductivity is less than 0.2 W/ (m. K), with good thermal insulation. Hollow ceramic (glass) microbeads with low accumulation density, high temperature resistance, high strength, low shrinkage, acid-base corrosion and insulation, sound insulation, insulation, low water absorption rate and so on, can significantly improve the thermal control coating insulation, anti-photothermal radiation performance, as well as the mechanical properties of the coating.
high temperature insulation coating developed by
, with heat-resistant conduction and anti-photothermal radiation properties, as well as good insulation properties, the application prospects are broad.
References
, Xu Na. Solar Thermal Reflection Insulation Coatings and Their Trends. Modern Coatings and Coatings, 2009 (02): 19-23.
. Li Zhiqiang. Talk about the use of hollow fillers in high temperature insulation coatings. Shanghai Coatings, 2010 (11): 25-27.
. Performance detection of a high temperature insulation coating. Modern coatings and coatings, 2010 (08): 30-31, 36.