Technical characteristics of foamed polyurethane insulation materials

Editor:浙江振申绝热科技股份有限公司Zhejiang Zhenshen Insulation Technology Corp. Ltd. │ Release Time:2019-03-04 
Technical characteristics of foamed polyurethane insulation materials
  First, the main technical characteristics of on-site foamed polyurethane
  1.1 Adhesion: strong bonding ability, can be firmly bonded on concrete, masonry, wood, steel, asphalt, rubber and other surfaces;
  1.2 Thermal conductivity: can reach 0.017-0.022W/m.k, lower than building thermal insulation materials such as rock wool, glass wool, polystyrene board, extruded board;
  1.3 Water-repellent performance: the drowning rate is over 95%;
  1.4 Sealing performance: no cavity, no seams, completely enclose the building's outer protective structure, effectively preventing wind and moisture from flowing into and out of the building through the gap to achieve complete sealing;
  1.5 dimensional stability: dimensional stability less than 1%, with a certain degree of elastic deformation, elongation greater than 5%;
  1.6 Constant performance: Polyurethane is an inert material that does not react with acids and alkalis, and is not a food source for insects and rodents, and can maintain a constant material property and thermal insulation properties;

  1.7 Wind resistance: compressive strength>300Kpa, tensile strength>400Kpa, strong wind resistance, and its foaming can be drilled into the wall gap to increase its shear resistance;   

       1.8 Good flame retardancy: self-extinguishing from the fire 3S, surface carbonization can prevent combustion, and no droplets will be produced.

  Second, the requirements of on-site foamed polyurethane for the base layer
  The on-site foamed polyurethane outer wall thermal insulation layer has lower requirements on the wall base layer. The surface of the wall is free of oil, no floating ash, plastering or no plastering. If it is not plastered, the shearing ability is better.
  Third, the performance advantages and disadvantages of on-site foamed polyurethane (compared to glass wool / rock wool)
  3.1 Thermal insulation performance. Glass wool/rock wool is a loose fiber insulation material. Even if it has a low thermal conductivity, it can better block the heat loss caused by heat conduction. However, the heat transfer caused by heat convection is Powerless. According to the statistics of relevant departments, 40% of the thermal energy loss of buildings is lost through the gap in the form of heat convection.
  Polyurethane not only has a lower thermal conductivity, but also better blocks heat transfer, and has better sealing performance. It can completely wrap the building's outer protective structure, effectively prevent the generation of heat convection, and achieve better energy saving.
  3.2 mold. The fiber structure of the glass wool/rock wool will retain a large amount of dust and organic matter over time, and these impurities will produce a large amount of mold under conditions suitable for temperature and humidity. According to a survey conducted by the American Lung Health Association, the annual growth rate of adult asthma in the United States is 61%, and that of children is 72%. The direct cause of this consequence is indoor mold. The breeding of mold will seriously pollute the environment inside the building and greatly endanger the health of the building users. After the polyurethane insulation material is sprayed, a seamless continuous shell is formed, the surface of the shell does not absorb dust, and the foam has strong hydrophobic characteristics, which fundamentally blocks the conditions of mold production.
  3.3 Collapse after receiving water. After the glass wool/rock wool product is in contact with water, the moisture will reside in the gap of the fiber, the thermal insulation performance drops sharply, and the whole body sinks and sinks under the action of gravity, eventually leading to the overall failure of the thermal insulation layer.
  Polyurethane insulation materials have excellent water repellency, moisture does not reside in the foam body, and this phenomenon of collapse after water is not caused.
  3.4 insulation method. Polystyrene board/extruded board generally adopts a combination of adhesive anchoring and requires a large number of anchors. Tests have shown that an average of ф6 plastic anchors per square meter can increase the average heat transfer coefficient of the outer wall by 0.004. This will inevitably lead to a large increase in the amount of heat lost through the thermal bridge member, thereby greatly reducing the energy-saving effect of the theoretical calculation and failing to meet the expected energy-saving goal.
  Polyurethane construction does not require any metal anchors to be fixed to the wall, so this situation is completely eliminated, and the thermal conductivity correction coefficient is effectively reduced, so that the actual energy saving effect is basically consistent with the theoretical calculation value.
  Fourth, the heat bridge
  4.1 plate joint thermal bridge. The on-site foamed polyurethane insulation material is continuously sprayed and foamed in the field. There is no seam joint, which fundamentally eliminates the influence of this heat bridge and ensures better realization of energy saving goals.
  4.2 Anchor, pendant thermal bridge. The anchors and pendants of the polystyrene board/extruded board insulation system are the most difficult to handle thermal bridges in this system. Insulation materials for sheet metal are difficult to block this thermal bridge.
  4.3 crack thermal bridge. The thermal expansion and contraction coefficient of polystyrene board/extruded board and wall are different, and the elastic deformation ability of polystyrene board/extruded board is small. When the building wall is in thermal expansion and contraction or the building wall is creeping, it is very easy. The thermal insulation layer is cracked, the thermal insulation performance of the crack is lost, and the crack is easily permeable to air and water, which causes the polystyrene board/extruded board to fall off in a large area, which affects the function of the building.
  4.4 Combustion performance. The fire-retardant performance of on-site foamed polyurethane is higher than that of polystyrene board/extruded board. It will be extinguished after 3s from fire, no droplets will be formed, carbon deposits on the surface will prevent the flame from spreading, and the smoke generated during combustion will be less toxic. The main component is carbon dioxide.
  4.5 base layer processing. Before the construction of the polystyrene board/extruded board, in order to ensure the smoothness and bonding effect of the board surface, a cement mortar leveling layer should be made on the wall surface.
  V. Insufficient application of on-site foamed polyurethane in the construction field
  In China's current polyurethane products for building thermal insulation, most of the released ODP is not zero, it still has a destructive effect on the ozone layer, and in the process of use, volatilizes harmful organic gases, with the concept of environmental protection and energy conservation. This type of product will eventually be eliminated, and the true "environmentally friendly" polyurethane insulation material will be expected.
  Nowadays, polyurethane raw materials used for building insulation, only a few famous polyurethane brands are made of polyurethane for building insulation, which is directly packaged by the factory and transported directly to the project site for construction. It is not blended on site. Most of the polyurethane raw materials used for building insulation are purchased by the polyurethane insulation construction company from the polyurethane production company. The basic chemical materials are temporarily allocated according to actual needs, which lacks unified management and increases the uncertainty of the project quality.
  The polyurethane raw materials used for building insulation have been diversified, and the energy-saving detection technology of polyurethane is still very simple. There is no technical means for controlling the raw material of foamed polyurethane on site. The existing detection technology can no longer be suitable for the needs of building energy-saving on-site inspection. To some extent, it limits the standard development of building energy conservation work. The research and development of building energy-saving on-site detection technology has been particularly urgent and important.