With the rapid development of China's economy, the construction speed and scale of various buildings have reached an unprecedented height. In order to enable buildings to meet the requirements of environmental protection and energy conservation, it is necessary to install insulation boards for the exterior walls of buildings. As an economical, high-efficiency, fire-resistant and practical insulation material, rock wool has been widely used in the production of thermal insulation panels for exterior walls of buildings.
Rock-wool is defined in China's standards: a mineral wool made mainly of dissolved natural igneous rock called rock wool. Rock wool is made of selected basalt or diabase as a main raw material, plus a certain amount of auxiliary materials, which are sprayed by high-temperature melting and centrifugal injection (3.3%). There are three main methods for producing rock wool: injection, centrifugation, and centrifugal injection.
1 Research status of rock wool for thermal insulation materials at home and abroad In China, rock wool has been used as a Class A fireproof material for exterior insulation systems, but it has not been popularized, and its application technology is still under discussion. However, it has been in Europe for decades, with mature product standards and system certification guidelines. Rock wool is applied to exterior wall insulation, which can be used in the whole wall using rock wool insulation (using rock wool board, fibers parallel to the wall), and also has the effect of external wall fire protection; it can also be used with other insulation materials, among which Rockwool belts act as fire barriers (called barriers, fibers perpendicular to the wall).
At present, there are more than 200 rock mineral wool manufacturers in China, but most of them use slag as raw material or main raw material. The acidity coefficient of the product is generally below 1.5, and it belongs to rock wool according to the acidity coefficient of 1.6 (also proposed 1.5 or 1.7). According to a standard, these products are not rock wool products, but slag wool products, whose performance is far from the technical requirements of European standards. The performance of domestic major rock wool products is shown in Table 1. Table 1 The performance of domestic major rock wool products The domestic rock wool can not meet the technical requirements. The tensile strength of the board perpendicular to the surface (kPa) 500-2003 building exterior wall thermal insulation composite Mineral wool specification for system use, water absorption (Partial immersion EN13162-2001 Specification for artificial mineral wool for building insulation 07 Determination of tensile strength of building insulation products 1609 Partial insulation of building insulation products for short-term water absorption 2972 Standard Specification for Bonded Synthetic Mineral Fiber Board Requirements Test Method European Model of Tensile Strength Wall External Composite System Vertical to EOTA, ETAG004 Plastered External Surface After Ageing >50 Degrees Retention Rate Assessment Guide Mineral Cotton Thermal Insulation The materials generally include rock wool, slag wool and glass wool. The raw materials for the production of rock wool and slag wool are mainly natural rock and slag. The proportion of natural rock used in the production of rock wool is generally greater than 70% 75%, while 70% of slag wool raw materials. More than % is blast furnace slag. In practice, according to the chemical composition of the fiber melt, acidic oxides (S+AOd and basic oxides (CaO ratio, ie the characteristic value of acidity coefficient, Rock wool and slag wool can be discriminated.
2 Rockwool performance 2.1 Chemical stability and water absorption Rock wool is an inorganic fiber such as basalt and diabase that has been melted by high temperature and centrifugally sprayed. The inorganic matter accounts for over 98%, and its acidity coefficient is greater than 1.6, which makes rock wool very chemically stable, it does not contain active elements and corrosive components, and does not contain solvents, oily substances or softeners that affect the building. The water absorption rate is only 0. 1kg/m2. The water absorption rate is only 0. 1kg/m2. The water absorption rate is only 0. 1kg/m2. The water absorption rate is only 0. 1kg/m2 after the long-term immersion test (test period 28d). The rock wool fiber with no capillary permeability and high acidity coefficient has strong chemical durability and hydrolysis resistance due to low alkali metal oxide content. Corrosive impurities that may be contained in slag wool products dissolve in water and corrode steel plates and metal anchors. Under humid or watery conditions, alkali metal or alkaline earth metal ions such as K+, Na+, B3+, Ca2+, Mg2+ on the surface of the slag cotton fiber are easily absorbed and precipitated, and hydrolysis occurs, thereby causing damage to the fiber structure and causing fracture. And powdered. It can be seen that the slag wool is not drowned and has strong water absorption. Therefore, a good rock wool insulation board, under reasonable installation and construction conditions, does not require maintenance. According to the application experience of the European exterior insulation system, rock wool can achieve the same life as the construction.
2.2 Thermal stability Rock wool has long-lasting thermal insulation performance, and its thermal conductivity does not change with time; the size of rock wool outer wall panel can maintain long-term stability, and the expansion ratio is very low. At normal temperature, it is only 1X10-6. According to ASTM C356, at the maximum service temperature of 650 °C, the line shrinkage of 24h will not exceed 1%. Therefore, the rock wool will not be meshed with mortar and mortar on the surface due to thermal expansion and contraction. Produces additional stress. In addition, under high temperature conditions, the slag cotton fiber begins to devitrify at 500C600C, the fiber shrinks and produces coarse yellow feldspar crystal, embrittlement and agglomeration, easy to chip and powder; and the melting temperature of rock wool products exceeds 1000 2.3 The slag cotton fiber is short and brittle, and contains many impurities in the slag ball. The slag and dust are easy to break and fall off during construction cutting or installation, feel itching and tie, and easily enter the body through the respiratory tract. The rock wool melt with higher acidity coefficient is beneficial to produce high-quality fibers with slender softness, which is not easy to break and generate dust. At the same time, rock wool does not contain toxic or carcinogenic components such as CFC, HFC, HCFC or asbestos. The radioactivity and free aldehyde content of rock wool meet the standard requirements and are an environmentally friendly external wall insulation material.
2.4 Mechanical properties Fiber quality and fiber structure will affect the mechanical properties of roof insulation boards, such as compressive strength, compressive modulus, point load, tensile strength and shear strength. After the improvement of the production process, rock wool for exterior wall insulation can have better mechanical properties, which are mainly manifested in two aspects: First, compressive strength, tested according to EN826 or GB/T19686-2005: rock wool board >40kPa , rock wool strip>100kPa. Second, tensile strength, according to EN1607 test, rock wool board >10kPa, rock wool strip>80kPa. 2.5 thermal insulation properties Because rock wool is a porous fibrous material, it has very good Insulation and thermal insulation performance, according to national standards GB/T19686 and EN13162, the thermal conductivity of rock wool board (25 °C) should be no more than 0 K) When there is a nominal value, it should not be greater than its nominal value. The thermal capacity of rock wool at 25C is 084K/(kgK). It can be seen that the rock wool has good thermal insulation performance, and the use of rock wool board as the building exterior wall thermal insulation material can achieve the purpose of energy saving.
2.6 Fire performance Rock wool has a high melting point and is resistant to high temperature shrinkage. It can be used in building structures to form an effective fire barrier and prevent the spread of fire. It does not burn or produce toxic fumes, and is a "A" grade (or "A1" grade) fireproof building material. In the single-layer roofing system with steel plate as the base layer, rockwool can separate the heat flow for the internal or external fire source, prevent the temperature of the backfire surface from rising, and cause other combustible materials to burn. Tested according to the fire temperature rise-time curve contained in the ISO8 34 standard, the use of rockwool insulation material in the construction of the building can achieve a 14 h fire endurance limit. The maximum temperature of rock wool is above 650C, and its melting point exceeds 1000C. In the event of fire, the rock wool insulation board will not cause smoke or cause Mars, nor will it drip, causing the fire to spread, even at high temperatures. It releases gases that are harmful or harmful to the environment and the human body. Therefore, as a thermal insulation material for building exterior walls, rock wool is also very superior in fire resistance.
27 Water resistance The water resistance and moisture resistance of mineral wool products are the main obstacles applied to building walls. When the performance is insufficient, the strength of rock wool products is reduced under the action of moisture, forming a natural fall. The engineering performance is commonly known as “垮†The waistband is analyzed for its causes. First, the relationship between fiber structure and water resistance is studied. The rock wool component belongs to the Ca-Al203-say 02 system. It is found that the composition of the existing rock wool is located in the crystallization zone (ie CS-C2AS-C2S zone) of the wollastonite H-aluminum sulphate of Ca-Al2. Among them, although aluminum stellite and wollastonite do not react with water, among the three crystal forms of dicalcium silicate, except for the Y-structure, the a- and å©-structural properties are similar, and both can be hydrated with water. reaction. It is not desirable to have these two structures in rock wool, and conditions should be created to convert the a-, - structure to the direction of 7-C2S to improve its water resistance. However, a-C2S and p-C2S can only be converted to y-C2S when they are slowly cooled from high temperature to below 675 °C. In the actual fiber-forming process, the melt is not slowly cooled but is rapidly cooled, and its viscosity rapidly increases with the sudden drop of temperature. At this time, the ion movement is hindered, and it is impossible to continue to regularly arrange and suppress the growth of the crystal. The silicon and oxygen ions are connected into a continuous and irregular grid, which retains the morphology of the 匚23 variant at low temperatures, forming a larger amount of glassy å©-C2S, which means that it will form under the action of the aqueous solution. More hydrated silicates and hydrated aluminates reduce the stability of slag wool fibers in humid environments.
When the rock wool composition point should fall within the wollastonite-aluminum beryl feldspar crystal action zone (ie CS-C2AS-CAS2g), the three crystal phases must be left in the solid phase due to wollastonite and aluminum. Both the beryl and the anorthite do not have the hydraulic characteristics, and the change after the water is small, so that the rock wool has good water resistance.
2.8 Strength performance In the external thermal insulation system of the external wall, the strength performance requirements are improved due to the self-weighting shearing action and wind pressure of the rock wool board. The strength properties of rock wool have the following characteristics: First, the strength of the thermal insulation board is related to the composition, and the fiber in the CS-C2AS-CAS2 region is affected by the change of the structure due to the absence of calcium disilicate and its hydration. The intensity will be greatly improved. At the same time, the high acidity coefficient means that the alkali content is small, the silicon-oxygen bond breakage in the fiber is reduced, the network of the bridge oxygen bond is increased, and the strength is improved. In addition, the alkali metal ions are also easy to adsorb moisture in the air, so that the microcracks expand, and the alkali content can be lowered to reduce the adverse effect of the factor on the strength.
Second, the fiber diameter, the smaller the diameter of the fiber, the greater the strength. Therefore, reducing the fiber diameter in the range of process allowability and controllability of the material is advantageous for increasing the fiber strength.
Third, it is closely related to the adhesive and its curing conditions. The purpose of the adhesive is to form the fibers into a spatial three-dimensional interlacing point and fix the structure by a curing process. Since material cracking always starts at the weakest point, the uniformity of the curing agent has a great influence on the strength. Therefore, how to spray the adhesive uniformly in the case of high-speed fiber forming requires constant adjustment of the glue dispensing system.
Increasing the amount of binder can increase the joint strength between the fibers, but the binder is an organic material, and the excess binder will make the material's burning performance less than Class A.
Fourth, the tempering process of the heat preservation board, the purpose of pleating the cotton sheet is to superimpose the surface of the cotton sheet to increase the tensile strength perpendicular to the board surface. From the current state of strength failure, the depth of pleating needs to be further improved. In this way, the oscillating felting technique is studied, the oscillating mechanism is optimized, and a continuous skeining belt is formed, including the determination of the process parameters of the oscillating felt, and the forming process of the lap.
3 Conclusions The above analysis shows that the standard rock wool insulation board has good thermal insulation and fireproof functions, and its chemical stability, water resistance, strength performance, mechanical properties and thermal stability make it a building exterior wall. A good choice for insulation.
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