Building energy consumption has accounted for more than 1/3 of the total energy consumption of the whole society, and it has become the industry with the highest energy consumption ratio. Therefore, it is necessary to develop green building materials to reduce building energy consumption and save energy. It is the most important means to achieve building energy efficiency. Insulation and energy-saving wall generally refers to the building wall constructed with building materials with low thermal conductivity. Due to the low thermal conductivity of the material itself, the heat transfer coefficient of the whole wall is very low, which can achieve good thermal insulation effect. . At present, the thermal insulation materials applied to the external walls of buildings are mainly organic thermal insulation materials, such as EPS (Expanded Polystyrene, molded polystyrene foam), XPS (Extruded Polys 1: yrene, extruded polystyrene foam), PU (Polyurethanes, polyurethane foam). , PF (Phenolicfoam, phenolic foam), etc., these materials have the advantages of low density, low water absorption, good thermal insulation properties, etc., which can be used for building exterior walls to achieve good thermal insulation and energy saving effects.
At the same time, these organic thermal insulation materials also have problems of poor bonding performance, low dimensional stability, aging, and easy burning. In particular, the fire events caused by this occur sometimes, and several fires have occurred in recent years. The casualties and property losses caused various people to think about the fire safety performance of building insulation materials. Building exterior insulation materials can be divided into three categories according to different materials: organic, inorganic and organic/inorganic composites. This paper reviews several commonly used building exterior wall insulation materials, and analyzes their research and application and their existing deficiencies in terms of thermal insulation performance, safety performance, anti-aging performance and dimensional stability. Inorganic thermal insulation materials are excellent for their comprehensive synthesis. Performance will be the first choice for building insulation materials in the future.
1 Commonly used building exterior wall insulation materials Currently, the insulation materials commonly used in exterior walls of buildings include: organic EPS, XPS, PU and PF; inorganic rock wool, foam glass (ceramic), foam concrete and newly developed inorganic hollow spheres. foam.
EPS is a molded polystyrene foam, abbreviated as a molded polystyrene board or an expanded polystyrene board. The EPS board is a foamed plastic sheet having a fine closed cell structure which is made of expandable polystyrene particles as a raw material, preheated by heating, and heat-molded in a mold. The foam consists of about 98% air and 2% polystyrene. The honeycomb hole has a diameter of 0.20.5 mm and a wall thickness of 0.001 mm. It is divided into two types: normal type and flame retardant type. Table 1 is the performance index.
Like the EPS board, the main raw material of the XPS board is also polystyrene. It was invented by Dow Chemical Company of the United States in 1941. It is a hard material made of polystyrene resin, added with flame retardant and other materials. The material has a tight closed cell honeycomb structure inside, and Table 2 is the performance index of the XPS board.
EPS/XPS board has the advantages of small apparent density, light weight, low thermal conductivity, low water absorption, easy processing and low price. It is currently the most widely used building insulation material. EPS/XPS boards also have a lack of use temperature of 75 ° C, low oxygen index, and easy burning of open flames. Therefore, people have done a lot of research work on flame retardant treatment. The flame retardant method of polystyrene includes bulk flame retardant, halogen flame retardant, phosphorus flame retardant, inorganic flame retardant, intumescent flame retardant, clay flame retardant, etc. Bulk flame retardant refers to the introduction of flame retardant on the polystyrene molecular chain. The effect of nitrogen, phosphorus, halogen elements, to achieve the effect of flame retardant, other flame retardant methods are added flame retardant.
Table 1 Physical properties of EPS board Specifications Performance index Apparent density kg/m3 Compressive strength / kPa Thermal conductivity W / (m dimensional stability /% water vapor transmission coefficient ng / (Pa water absorption rate (volume) /% oxygen index / % combustion grade reaches B2 level Note: Normal type EPS does not require combustion performance Table 2 XPS board physical performance index performance index item without belt skin compressive strength / kPa water absorption rate (volume) water vapor transmission coefficient ng / (Pams) heat conduction Coefficient / (W / (m size stability /% oxygen index /% combustion classification to achieve B2 grade halogen flame retardant high flame retardant efficiency, is a traditional flame retardant, which is dominated by bromine system, such as six Bromocyclododecane (HBCD), 2,4,6-tribromophenyl allyl ether, decabromodiphenyl ether, tetrabromobisphenol A, etc., but halogenated flame retardants will generate a large amount of human body when burned And environmentally harmful smoke, corrosive gases and toxic gases. With the increasing awareness of environmental protection around the world, various countries have introduced various regulations and prohibit the use of halogen-containing flame retardants. Therefore, from the perspective of long-term development, Halogen flame retardant is the main direction of future development of flame retardants.
Intumescent flame retardant and inorganic flame retardant have developed rapidly in recent years. Jia Juanhua studied the flame retardant effect of polyphosphate (APP), pentaerythritol (PER) and melamine (MEL) mixtures on polystyrene. The results show that: high temperature The next three synergistically form a layer of bulky porous carbon layer, which blocks heat transfer and 2 diffusion, achieves the purpose of flame retardant, reduces the release of combustible gas and smoke, and prevents the polymer from burning to produce molten dripping. Aluminium hydroxide and magnesium hydroxide are the main inorganic flame retardants. Together with the use of inorganic flame retardant modifiers, they can achieve good flame retardant effect. Polyurethane CPU) is the abbreviation of polyurethane, which is composed of polyhydric alcohol and polyisocyanate. A general term for a polymer having a repeating -NHCOC- group on a main chain prepared by the reaction. Polyurethane foam is made of polyether polyol, polyester polyol and polyisocyanate or modified isocyanate prepolymer, adding a certain proportion of foaming agent, catalyst, foam stabilizer, etc., under certain temperature conditions, mixed A foam material obtained by uniformly foaming. In the 1940s, Bayer (a foam produced by a company with a density of 140 kg/m3) was very unfavorable for reducing the thermal conductivity, which in turn increased the thermal conductivity, so the reduction in density could not be at the expense of thermal performance.
SEM topography of foam concrete 2 Conclusion The application of building insulation materials is becoming more and more extensive, and the promotion of its application has become the main measure of building energy conservation in China. Therefore, the performance requirements for insulation materials are getting higher and higher. In particular, in recent years, fire accidents caused by building insulation materials have gradually increased, causing more and more attention to the safety of building insulation materials. The traditional organic thermal insulation material has excellent thermal insulation performance, and the flammable nature of the organic material is difficult to change, and does not meet the requirements for safety and fireproof performance of the building thermal insulation material, while the commonly used inorganic thermal insulation material has a high fireproof rating and safety. The property is good, but there is also a shortage of thermal insulation performance and high thermal conductivity. Therefore, it is urgent to develop a new inorganic thermal insulation material with low thermal conductivity. The author uses a light inorganic hollow sphere as the main raw material and adopts the direct foaming process to prepare an inorganic hollow sphere foam insulation material with a secondary closed-cell structure. The inorganic thermal insulation material has the advantages of low thermal conductivity and good safety performance. A new type of inorganic insulation material will surely become the first choice for building insulation materials.
(Finish)
Pdlc Smart Glass,Switchable Glass,Intelligent Glass,Pdlc Switchable Electrochromic Glass
Shenzhen YuGuang New Material Co.,Ltd , https://www.ygsmartfilm.com