Insulation performance analysis Polyurethane net According to the general rules of equipment and pipe insulation technology, insulation material is a material with a thermal conductivity less than 0.14 W/(m*K) when the average temperature is 623K (350 degrees Celsius) or less. Insulation materials are usually characterized by light weight, looseness, porosity, and low thermal conductivity. Generally used to prevent thermal equipment and pipeline heat loss, or in the freezing (also known as Pu cold) and low temperature (also known as cryogenic) use, so in our country insulation material is also known as insulation or cold materials. At the same time, because the porous or fibrous structure of the thermal insulation material has a good sound absorption function, it is also widely used in the construction industry.
1 Classification methods There are many kinds of insulation materials, and they can generally be categorized according to materials, operating temperature, shape, and structure.
According to the material can be divided into organic insulation materials, inorganic insulation materials and metal insulation materials three categories.
Thermal insulation materials used in thermal equipment and pipelines are mostly inorganic thermal insulation materials. This kind of material has the characteristics of no rot, no burning, high temperature resistance and so on. For example: asbestos, diatomaceous earth, perlite, glass fiber, foamed glass concrete, silicic acid, etc.
The cold insulation materials used in Puro are mostly made of organic thermal insulation materials. Such materials have extremely low thermal conductivity, low temperature resistance, and flammability. For example: polystyrene foam, polyvinyl chloride foam, urethane foam, cork and so on.
According to the form can be divided into porous thermal insulation tear material, fibrous thermal insulation material tear tear, powder insulation and layer insulation materials four. The porous insulation material, also called foam insulation material, has the characteristics of light weight, good thermal insulation performance, good elasticity, dimensional stability, and poor stability. Mainly foamed plastic, foamed glass, foam rubber, calcium silicate, lightweight refractories and so on. Fibrous insulation materials can be divided into organic fibers, inorganic fibers, metal fibers, and composite fibers. In the industry, the main material used for thermal insulation of tears is inorganic fibers. Currently, the most widely used fibers are asbestos, rock wool, glass wool, silicate ceramic fibers, and crystalline alumina fibers. Powdered insulation materials mainly include celadon, expanded perlite and its products. These materials have a rich source of raw materials and are inexpensive, and are widely used as efficient heat insulation materials in construction and thermal equipment.
2 performance indicators and general selection principles as the thermal conductivity of tear-off material, thermal conductivity should be the smaller the better, generally should use thermal conductivity of less than 0.14W/m * K as a cold insulating material, higher thermal conductivity requirements.
The bulk density of the bulk density insulation material should generally be lower than the 600kg/m bulk density of the building materials, and the thermal conductivity of the tearing factor is also generally small, but at the same time the mechanical strength is also reduced, so it should be a reasonable choice.
Mechanical strength: In order to make the insulation material not deformed and damaged under its own weight and external force, its compressive strength should not be less than 3kg/cm. Water absorption rate: The heat insulation material not only will greatly reduce the thermal insulation performance, but also accelerate the corrosion of metal. It is very harmful. Therefore, choose a heat-insulating material with low water absorption.
Heat resistance and use temperature: According to the temperature of the place of use, choose different thermal insulation materials. The "maximum use temperature" is the basis of the heat resistance of the insulation material.
In addition to the above principles, factors such as construction, price, and transportation should also be considered when selecting insulation materials.
2. Development Status of China's Insulation and Thermal Insulation Materials Currently, there are more than 1,000 production companies of insulation and thermal insulation materials in China. There are more than ten categories and hundreds of varieties of products. The adaptable temperature range is from -196 to 1000 degrees Celsius, and the technology and equipment level There is also a trap increase. Currently used insulation materials mainly include the following.
Foam insulation materials mainly include two major types of polymer foam insulation materials and foam asbestos insulation materials. The polymer foamed insulation material has the advantages of small absorption rate, stable thermal insulation effect, low thermal conductivity, no dust flying during construction, and easy construction. It is in the period of popularization and application. Foam asbestos heat insulation material also has the characteristics of small density, good heat preservation performance and convenient construction, promotion and development are relatively stable, and the application effect is also good. However, there are also certain drawbacks: For example, foamed cotton is susceptible to moisture, easily immersed in water, and has a small coefficient of elastic recovery. It cannot be used in contact with flames and in places where wall pipes are used.
2.2 Composite silicate insulation materials Composite silicate insulation materials have the characteristics of strong plasticity, low thermal conductivity, high temperature resistance, and low drying shrinkage of the slurry. The main types of magnesium silicate, silicon magnesium aluminum, rare earth composite insulation materials. The sepiolite thermal insulation materials that have emerged in recent years as a leader in composite silicate thermal insulation materials have attracted great attention from the construction industry due to their good thermal insulation properties and application effects, showing strong market competition. Power and broad market prospects. Sepiolite insulation material is a special non-metallic mineral-a sepiolite as the main raw material, supplemented by a variety of metamorphic mineral raw materials, additives, using a new process by foaming the composite surface. The material is non-toxic and odorless. It is a gray-white static inorganic paste, and after drying and molding, it is a gray-white closed mesh structure. Its distinctive features are low thermal conductivity, wide temperature range, anti-aging, acid and alkali, light weight, sound insulation, flame retardant, easy construction, and low overall cost. It is mainly used for thermal insulation of building roofs, walls, indoor ceilings at room temperature, and thermal equipment of petroleum, chemical, electric power, smelting, transportation, light industry and national defense industries, thermal insulation of pipes, chimney inner walls, and furnaces. Kiln shell insulation (cold) works. This thermal insulation material will create a new situation of thermal insulation and energy conservation with its unique properties.
2.3 Calcium silicate insulation products Insulation materials Calcium silicate insulation products In the 80's, insulation materials have been recognized as the best one of the block hard insulation materials, characterized by small density, high heat resistance, low thermal conductivity, The flexural and compressive strength is high and the shrinkage is small. However, since its introduction in the 1990s, its use has seen a downturn. The main reason is that many manufacturers use pulp fibers. Although the above measures have solved the problem of asbestos-free, due to the high temperature of the pulp fiber, the high-temperature resistance of the heat-insulating material is affected, and the breaking rate is increased. The heat-insulating material is not economical when it is used at a low-temperature portion of the low-temperature material, although the performance is not affected.
The market share of fiber insulation in the early 1980s was due to its excellent fire protection and insulation properties. The main application of insulation materials for building walls and roof insulation. However, due to the large investment, there are not many manufacturers, which limits its promotion and use, and thus the current market share is low.
3. Development trend of thermal insulation materials 3.1 Water repellency is the ability of insulation materials to have an adverse effect on the important development direction performance. In the “terminology definition†of the International “Insulation Material Water Repellent Test Methodâ€, it is defined as a performance index reflecting the water permeation resistance of a material, and the volume percentage of the impervious portion in the sample has been specified after the water spray of a mode and a certain flow rate. Indicated. At present, the modified silicone type water-repellent agent is a general-purpose high-efficiency water-repellent agent for heat-insulating materials. Its water-repellent mechanism is to effectively change the strong chemical affinity between the organic silicon compound and the inorganic silicate material. The surface characteristics of the silicate material make it hydrophobic. It has the characteristics of good stability, low cost, simple application process and so on. For example, fiber insulation materials, such as mineral rock wool products, and off-work cotton products, basically do not drown, but after drowning treatment, the drooling rate can reach 90% or even higher. Ordinary foam asbestos is not water-repellent, and its water absorption rate is extremely high. However, after the “gas-phase absorption method†is used for secondary treatment, it can be made into elastic water-dropped foam asbestos products. The use effect is much better than ordinary asbestos. The water absorption rate of the material is in use. An important factor that should be considered when considering the insulation material is that the coefficient of thermal conductivity of water at room temperature is 23.1 times that of air. Insulation material absorbs not only greatly reduces its tear-off performance, but also accelerates the corrosion of metals, which is very harmful. The void structure of the insulation material is divided into connected, closed, and semi-enclosed types. Other insulation materials, regardless of the void structure, have their own water absorption, and the capillary penetration of connected voids absorbs water, so the overall water absorption rate is high. At present, most of the insulation and heat insulation materials in China are not water-repellent, and the water absorption rate is high. As a result, the waterproof requirement of the outer jacket is ten, which increases the cost of the outer layer. BS
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