Research on Building Thermal Insulation Coatings and Composite Technology of Chinese National Core Journals ZHANG Xueqin S Korea Min S. Zhou Genquan 2 (Hangzhou Institute of Design and Construction of China New Building Materials Industry, Hangzhou 310003, China; 2. Amethyst Real Estate Co., Ltd., Hangzhou 310009, Zhejiang, China) Good Performance Functional building coatings are often the result of the synergistic effect of two or more thermal insulation mechanisms. Therefore, composite technologies can be used to take into account both the insulation effect of the insulation system and the need for external surface insulation, making full use of various types of insulation. The characteristics of the paint, avoiding weaknesses, and complementing each other's advantages, develop composite heat insulation coatings with excellent performance. At the same time, according to the climate characteristics of different regions and building energy-saving requirements, a composite application of different types of building thermal insulation coatings or other exterior wall thermal insulation materials can be used to make an external thermal insulation system that is both thermal insulation and thermal insulation. Or make the external insulation system based on heat insulation to meet the building energy saving and thermal insulation requirements in hot summer and cold winter and hot summer and warm winter areas.
New Building Materials 2008.10 0 Foreword Building energy efficiency has received widespread attention from the whole society. In order to promote energy conservation, improve energy efficiency, protect and improve the environment, and promote comprehensive and coordinated economic and social development, the “Energy Conservation Law of the People's Republic of China†(below The "Energy Law" for short) was implemented on April 1, 2008. The “Energy Law†states: “Saving resources is the basic national policy of our country. The state implements the energy development strategy that combines conservation and development and puts conservation first.â€
China's building energy consumption accounts for about 30% of the country's total energy consumption, so building energy efficiency is one of the important contents of China's energy conservation work. The “Energy Law†has made special provisions for building energy conservation: “The construction, design, construction and supervision units of construction projects shall abide by building energy-saving standards. Construction projects that do not meet the building energy-saving standards shall not be approved for construction by the construction department; construction has started. If it is built, it shall be ordered to stop construction and be corrected within a time limit, and if it is completed, it may not be sold or used.The State encourages the use of new wall materials and other energy-saving building materials and energy-saving equipment in the energy-saving renovation of new buildings and existing buildings, installation and use of solar energy, etc. Renewable Energy Utilization System.†The Ministry of Housing and Urban-Rural Development has implemented the “Energy Law†in order to fulfill the role of public supervision. On June 26, 2008, it formulated the “Measures for the Public Display of Energy-saving Information for Civil Buildings†(hereinafter referred to as “Measuresâ€). , and implemented on July 15, 2008. The Measures stipulate: “Newly built (reconstructed, expanded) and civil buildings that carry out energy-saving renovations shall publicize the building energy-saving information. The public information content of building energy-saving information includes energy-saving performance, energy-saving measures and protection requirements.†In order to strengthen the management of civil building energy-saving, promote public Institutional energy conservation, on August 1, 2008, State Council Decree No. 530 and Decree No. 531 issued the “Regulations for the Energy Conservation of Civil Buildings†and the “Regulations for the Energy Saving of Public Institutionsâ€, which were implemented from October 1, 2008.
With the promulgation and implementation of a series of laws, regulations, standards and standards such as the “Energy Lawâ€, the laws, regulations, and standards system for building energy conservation in China have been further improved. This will strengthen the management of building energy conservation, ensure the quality of building energy conservation projects, and achieve energy efficiency in buildings. The goals and requirements, etc., have important significance and roles.
1 Main categories and problems of exterior insulation of exterior wall JGJ144-2004 "Technical specification for external insulation of exterior wall" stipulates 5 types of exterior insulation systems, followed by EPS (expanded polystyrene) plate and thin plastering. Exterior Insulation System, Plastic Powder EPS Granule Insulation Mortar Exterior Insulation System, EPS Board In-situ Concrete Exterior Insulation System, EPS Steel Wire Frame In-situ Concrete Exterior Insulation System and Mechanical Fixed EPS Steel Wire Frame Board exterior insulation system. In May 2007, the Ministry of Construction issued the "Technical Guidelines for External Thermal Insulation of Polyurethane Hard Foam Exterior Walls". The polyurethane rigid foam external wall external insulation system is used as a new type of external wall external insulation system, and it has also achieved a comparative advantage in the field of building energy conservation in China. Wide range of applications. In the above-mentioned several types of exterior wall thermal insulation systems, the application of EPS board thin plaster external wall external insulation system and EPS powder particle insulation slurry external wall external insulation system is the most common, and the application technology is also relatively mature.
However, the above-mentioned several kinds of heat preservation systems also have their own shortcomings, such as the EPS (expanded polystyrene) board thin plaster exterior wall external insulation system construction is cumbersome, the construction is not easy to crack and fall off, the fire performance is not good, not suitable for complex shaped complex structure Construction, and there are a large number of board seams in the entire system, easy to form thermal bridges, etc.; thermal insulation performance of external insulation system of rubber powder EPS particle insulation slurry external insulation system is not good, it is not easy to achieve energy saving 65% of the requirements of the single use; Polyurethane hard foam site Spraying the exterior wall insulation system can achieve seamless insulation, and it is also suitable for the construction of complex and complex structures. However, on-site spraying construction has higher requirements on the environment and climate, there is also a certain degree of environmental pollution, and the surface of the insulation system is poor in flatness. There are generally two kinds of measures to solve the problem of building energy conservation: one is thermal insulation; the other is reflective thermal insulation. Therefore, in the wall insulation system, it is necessary to consider not only the insulation effect of the insulation system but also the insulation of the exterior surface of the insulation system.
This provides a broad space for the development of composite multifunctional building exterior thermal insulation coatings. The following mainly introduces the building thermal insulation coatings and their composite technologies.
2 Classification, Characteristics and Development of Thermal Insulation Coatings for Buildings According to the heat transfer mechanism, insulation coatings for external walls of buildings can be divided into barrier type building thermal insulation coatings, reflective building thermal insulation coatings and radiation-based architectural thermal insulation coatings. For three categories, these three types of coatings have different adiabatic mechanisms, and their applications and results are also different.
2.1 Barrier-type building insulation coatings 2.1.1 Characteristics of Barrier-type Building Insulation Coatings The insulation mechanism of barrier-type building insulation coatings is achieved through heat transfer resistance, which requires low thermal conductivity of the coating. Coefficient, and have a certain thickness, in order to maintain high thermal resistance.
22 Development of Barrier-Type Building Thermal Insulation Coatings Development of barrier-type thermal insulation coatings in China began in the 1980s with silicate thermal insulation coatings as the main application. They are mainly used for thermal insulation of pipelines and equipment surfaces. Inorganic material (such as cement, water glass, etc.) as the base material, asbestos fiber, expanded perlite, sepiolite powder and expanded vermiculite inorganic silicates made of thermal insulation filler, the performance of this type of coating in line with GB /T17371-1998 "Silicate composite thermal insulation coating" requirements. Although these thermal insulation coatings have low thermal conductivity and low cost, they have disadvantages such as long drying cycle, weak impact resistance, large drying shrinkage, large moisture absorption, low bonding strength, and poor decorative effect.
With the development of exterior wall thermal insulation technology, external wall thermal insulation coatings have gradually attracted people’s attention. The powdery building thermal insulation coatings that the construction industry used to call “insulation mortar†and “light insulation mortar†also got Extensive application, construction industry standards JG 158-2004 "plastic powder polystyrene external wall insulation system" promulgated and implemented, this type of material called polystyrene powder polystyrene insulation slurry, but in the early stages of development and application of Call it a thermal insulation coating. In recent years, domestically developed organic polymer (elastic) emulsions (including pure acrylic emulsion, styrene-acrylic emulsion and silicon-acrylic emulsion) as base materials, expanded polystyrene particles, vitrified microspheres, and hollow glass Micro-beads, expanded perlite, expanded vermiculite, mineral rock wool, etc. are heat-insulating aggregates, and polypropylene fiber, wood fiber, etc. are external wall thermal insulation coatings for crack-resistant modified materials. They have achieved good results through composite technology. Apply effects. The main physical properties of commonly used insulation aggregates are shown in Table 1. Table 1 Main Physical Properties of Commonly Used Insulating Aggregates Insulation Aggregate Density At Room Temperature Thermal Conductivity / (kg/m) / Structural Features Expanded Polystyrene Particles About Honeycomb The closed pore structure of the expanded perlite is bubble-like, the porous structure of the vitreous microspheres has a porous hollow structure, the appearance of the closed hollow glass microspheres hollow microspheres, the shell of the hard expanded meteorites thin laminated structure, filled with microscopic gaps between The average diameter of rockwool short fibers is about 7 2.2 2.2 Reflective Building Thermal Insulation Coatings 2.2.1 Insulation Principle of Reflective Building Thermal Insulation Coating In the solar radiation that can be received on the earth, infrared heat radiation and visible light are about It accounts for 45%, while the infrared thermal radiation is mainly concentrated in the 0.78~2.5 band, and the proportion of the radiant energy greater than 2.5 is less than 5%. The solar radiation incident on the coating is absorbed, transmitted or reflected, and the absorption rate is transmitted. The relationship between the rate p and the reflectance t is as follows: Since the coating film is opaque, the transmittance P is approximately 0. Therefore, only by increasing the reflectance T of the coating can the coating surface absorb less. The amount of the coating reduce the amplitude of the temperature rise. Reflective architectural thermal insulation coatings are made of highly transparent resins and highly reflective fillers to produce highly reflective coating films for the purpose of reflecting light and heat. Reflective building thermal insulation coatings use high reflectivity of the coating film for light and heat, so that most of the energy that the sun shines on the coating film is reflected instead of being absorbed by the coating film; at the same time, the thermal conductivity of the coating film itself is very high. Small, very good thermal insulation, which prevents the conduction of heat through the coating. Because reflective building thermal insulation coating has high reflectivity and low thermal conductivity, when the coating film exceeds a certain thickness, its reflection performance is only related to the reflectance of the coating film surface, but has nothing to do with the thickness of the coating film.
2.2.2 Composition and Preparation Technology of Reflective Building Thermal Insulation Coatings The base material of reflective building thermal insulation coatings should be selected based on reflectance, absorption rate and weatherability of the coating. The resin used in reflective architectural insulation coatings absorbs visible and near-infrared light as little as possible, usually requires high transparency of the resin (light transmittance should be above 80%), low solar heat absorption, and structure As little as possible contain an energy-absorbing group such as C-O-C-, C=O, and OH.
To obtain a high-reflectivity coating, high-reflectivity fillers must be used. Glass hollow microspheres are also called multi-functional hollow additive for coatings. The particles are round or nearly circular in shape. The surface is a smooth, hard, dense structure of glass, almost no absorption of various liquid media, can reflect light and heat well Incident waves. Hollow glass hollow microspheres have a low density, low thermal conductivity, and good heat transfer and insulation properties. These properties make it very suitable as a reflective filler for reflective thermal insulation coatings. Table 2 shows the technical performance of several German hollow glass bead products.
Table 2 Technical characteristics of several glass hollow microspheres from Germany MOLUS Corporation View of white fine powder Gray fine powder (surface pressure bubble treatment) Particle morphology Rigid hollow sphere composition Borosilicate ceramic Borosilicate About average particle size /pm about 35 bulk density / (kg / m) melting point / °C Mohs hardness glass hollow bead function filler mixed in the coating, one of which is the use of spherical structure of hollow microspheres to reflect sunlight, reduce the base layer to the sun The absorption rate of light; the second is the use of air in the hollow microspheres in the coating can form an effective thermal barrier, hinder the heat conduction, so that the solar heat barrier in the paint. In addition, the spherical filler has the characteristics of small specific surface area and low oil absorption, which can reduce the amount of base material and improve the leveling and smoothness of the coating. Under the same conditions, the comparison of the solar heat reflectance of functional fillers such as hollow borosilicate glass microspheres, ceramic microspheres, and fly ash floating beads is shown in Table 3. Table 3 Microspheres and ordinary fillers against solar heat Reflectivity Comparison Items Common Fillers Cordierite Fly Ash Floating Beads Glass Beads Ceramic Beads Note: Visible light and near-infrared light with a wavelength range of 400-1800 nm are measured.
Color has a great influence on the reflectivity of reflective building insulation coatings.
To achieve a high thermal reflectivity, pigments with a high refractive index must be selected, and the color of the coating film can be easily achieved by using white or light colors, or using spectrally selective materials to form a certain color. One of the keys to formulating colored heat-insulating reflective coatings is to select pigments with lower absorption. The U.S. military standard specifies that the reflectance of dark paint should be above 50%.
Tongji University and Shanghai Academy of Building Research have studied the effect of colorants on the thermal reflection properties of heat-reflective insulation coatings, adding different concentrations of iron red, iron yellow, indigo blue, and indigo green, respectively, into two shades of depth and lightness. The color paints, including light red, light yellow, light blue, light green, dark red, dark yellow, dark blue, dark green, a total of 8 species. The results show that with the deepening of the added colorant concentration, the reflectance in the visible light range of the reflective building thermal insulation coating is most affected. In the near-infrared range of 780 to 900 nm, the colorant concentration has a great influence on the reflectivity. In the near-infrared range of 900~1200nm, the influence of colorant concentration on the reflectance began to decrease, while within the range of 1200~2500nm, the colorant concentration had little effect on the reflectance. Of the four colorants tested, the addition of iron yellow to the thermal barrier coating had minimal effect on the reflectance.
2.2.3 Insulation performance of reflective building thermal insulation coatings) The requirements for the thermal insulation properties of building reflective insulation coatings are shown in Table 4. Table 4 Thermal insulation properties of building reflective insulation coatings Performance indicators Roof reflective insulation coatings Wall Reflective Heat Insulation Coatings Solar Reflectance (White) Hemispherical Reflectance Thermal Insulation/C Thermal Insulation Temperature Decay (White Note: Thermal Insulation Temperature Differences and Thermal Insulation Temperature Difference Attenuation Indicators To Be Determined.
2.3 Radiant Building Thermal Insulation Coatings There is a saddle-shaped phenomenon in heat absorption and radiation in the atmosphere (see below). In the wavelength range of 8~13.5 pm, there will be heat radiation greater than absorption, and radiation-based building thermal insulation coatings using infrared radiation materials. It can increase the heat radiation in this area, and transmit the sunlight and heat absorbed by the building into the air with a certain wave, so as to achieve the effect of heat insulation and cooling, and can make the surface temperature of the coating lower than that of the environment. Emissivity. This type of paint is different from barrier and reflective thermal insulation coatings, because these two types of coatings can only slow down but not block the transfer of thermal energy. During the day, solar energy passes through roofs and walls coated with heat-insulating paint and is continuously introduced into indoor spaces and structures. These incoming heat energy passes through the outdoor air temperature coating in the atmospheric environment where heat absorption and radiation are reduced after saddle-shaped phenomenon, and then passed in reverse. The rate of heat transfer from the roof and wall coated with thermal insulation coating is also very slow. Radiant building thermal insulation coatings can radiate the absorbed heat in the form of heat radiation, thereby stimulating indoor and outdoor cooling at the same rate, and thus have a higher cooling rate. Radiant building thermal insulation coating can be used in hot summer and warm winter and hot summer and cold winter areas to improve living comfort.
According to the US Standard ASTMC1483*04 “Standard Specification for Solar Radiation Control Coatings for Architectural Exterior Useâ€, the infrared emissivity of solar radiation control coatings at ambient temperature should not be less than 80%. Currently, the application of these coatings in the field of building thermal insulation is still at Research phase.
3 Composite technology of building thermal insulation coating The above three types of building thermal insulation coatings have their own advantages and limitations. A functional building coating with good thermal insulation properties is often a combination of two or more thermal insulation mechanisms. result. Therefore, composite technology can be used to make full use of the characteristics of a variety of thermal insulation coatings, avoid weaknesses, complement each other, and develop a composite thermal insulation coating with excellent performance to meet the needs of the development of exterior insulation of the external walls of buildings. The composition of the composite elastic building insulation coating is shown in Table 5. Table 5 Composite elastic building thermal insulation coating formula Raw material mass fraction Silicone-acrylic emulsion Enamel glass bead Hollow glass beads Infrared radiant filler Expanded gangue rock wool Short fiber Auxiliary amount of deionized water to make up the balance In addition, according to the different regions of the climate characteristics and building energy-saving requirements of different types of building insulation coatings or thermal insulation materials with other composite applications, made of both insulation and insulation The external wall insulation system, or made of external insulation insulation system, in order to meet the hot summer and cold winter and hot summer and warm winter areas of building energy-saving insulation requirements. In particular, some cities and regions have taken the lead in raising the standards for building energy efficiency, which also provides a good space for the development of composite applications of exterior wall thermal insulation coatings.
(1) Composite application of barrier type exterior wall thermal insulation coatings and reflective exterior wall thermal insulation coatings Powdered polystyrene particles External wall exterior insulation systems are suitable for the thickness of rubber powder EPS particle insulation slurry calculated according to building energy-saving requirements The use of this system alone does not exceed 100 mm, making it difficult to achieve 65% of building energy efficiency.
If it is combined with reflective outer wall thermal insulation coatings on its surface, it can improve the energy-saving and thermal insulation performance of the wall and obtain the effect of insulation and heat insulation.
(2) Composite application of expanded polystyrene board thin plaster exterior insulation system and reflective exterior wall insulation coating Flexible reflective outer wall thermal insulation coating and expanded polystyrene board thin plaster outer wall Insulation composite applications, on the one hand, can form an external insulation system with both thermal insulation and thermal insulation. At the same time, it can overcome the disadvantages of easy cracking and poor aging resistance of the polyphenylene plate system, and can prolong the use of exterior thermal insulation systems. life.
(3) Composite application of self-insulating wall and reflective exterior wall thermal insulation coatings When a single self-insulating wall body is used, it is difficult to meet the higher standards of building energy conservation requirements. If it is combined with a reflective exterior wall thermal insulation coating, it can be Further improve the energy-saving insulation effect of the wall and the thermal comfort of the living room.
4 Conclusion With the country's mandatory implementation of building energy conservation, the building energy-saving requirements of the continuous improvement and the external wall insulation system in the practical application of the gradual emergence of problems, the application of building insulation coatings will be paid attention to, and Will get rapid development.
Barrier-type, reflective-type and radiation-type 3 types of building thermal insulation coatings have their own advantages and limitations. Using composite technology, a good performance of the building insulation can be obtained by selecting appropriate base materials, thermal insulation aggregates, and pigments and fillers. Hot paint. On the other hand, the thermal insulation coatings for buildings can be combined with other thermal insulation materials for the climate characteristics of different regions and building energy-saving requirements, and the external thermal insulation systems with insulation and heat insulation can be made or separated. The heat-based external wall insulation system meets the building energy-saving and heat preservation requirements in the regions of hot summer and cold winter and hot summer and warm winter, and further improves the energy-saving insulation and heat insulation effects of the wall and the thermal comfort of the living room.
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