Comparison of soft foam polyurethane and rigid foam polyurethane
发布时间： 2018-09-07 09:21 Author: Polyurethane foam machine Source: http: //motokone.com
Published: 2018-09-07 09:21
1. Different foaming mechanisms
Rigid foam polyurethane is a two-component liquid (commonly known as black and white materials). After fully mixing, it produces a rapid chemical reaction and cures (tens of seconds to minutes). It foams under the action of additives such as foaming agents, catalysts, foam stabilizer It forms a lightweight foam with a high closed cell ratio> 90% and a reticulated structure, which is a thermoset foam.
Polystyrene foam (EPS, XPS) is a foam body that is swelled by heating of granules or powders, and the foaming agent vaporizes. The foam is formed by a mold or an extrusion machine. It has a granular structure and belongs to thermoplastic foam. Higher sensitivity, potential for secondary foaming.
2. Different physical and chemical properties of foam
① Thermal insulation performance
Polystyrene foam has better thermal insulation, but λ value is still relatively large compared to rigid foam polyurethane, such as EPS board λ≈0.04w / k · m, XPS board λ≈0.031 w / k · m, and PUR board λ≈0.022 w / k · m. Under the premise of the same energy saving index, the thickness of the insulation board can be reduced, and the quality stability of the insulation system can be improved.
② Thermal stability
The thermal stability of rigid foam polyurethane can be as high as 120 ℃, while the styrene board is only 70 ℃. In summer in China, the temperature of the external surface of the external wall is generally 70 ° C or more. Such a temperature can easily cause the secondary foaming of the benzene board, resulting in cracks in the board seam.
③ Surface binding energy
Polyurethane molecular chains have a certain -OH bond, that is, a hydrophilic gene, which is easy to bond with cement-based slurry, while polystyrene has no -OH bond, which is a hydrophobic material, and its surface is difficult to bond with cement-based slurry, etc. Inorganic materials are fused, which is also one of the main reasons for cracking, bulging, and falling of the benzene board external insulation system.
④, combustion theory
Rigid foam polyurethane is a thermosetting material, which will form a carbonized layer after being heated and burned, blocking the further penetration of heat and oxygen, hindering the further combustion of the foam, and is unlikely to cause fire spreading accidents. Polystyrene foam is a thermoplastic material, which shrinks and melts after being heated, and then drips and burns. It cannot produce a carbonization barrier layer, and it is easy to cause flame spread and blaze accidents.
⑤, corrosion resistance
Polyurethane is resistant to water, oil and solvents. Polystyrene is resistant to water but not to solvents. It is extremely sensitive to benzene and ester solvents and is prone to rapid corrosion.
3. Different application methods
Polystyrene foam can only be molded and extruded in the factory state, while rigid foam polyurethane can be sprayed, poured and factory foamed. Therefore, the application methods and application fields are more diverse and convenient than polystyrene foam. .
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