Polyurethane rigid foam, polyurethane shell, polyurethane black and white material, polyurethane raw material polyurethane (ie, polyurethane, abbreviation PU) is a polymer compound containing many repeating -NHCOO groups on the main chain of the polymer. Polyurethane series products are generally polymer compounds obtained by polymerization of binary or polybasic organic isocyanates and polyols under the action of various auxiliaries. If both main materials contain only two or less hydroxy functional groups, The polymerization reaction obtains a compound having a linear structure. If one or both of the main materials have three or more functional groups, a polymer having a bulk structure can be obtained, and the properties are different due to the structure of the polymer. big difference. Just like steel, although it is iron-carbon alloy, the iron-carbon ratio is different, the heat treatment process is different, and its performance is completely different. Polyurethane raw materials are widely used in various industries. Due to the different industrial characteristics and products produced, the performance requirements of composite materials with polyurethane as the main raw material are also different. Polyurethane rigid foam (SPF), which is responsible for thermal insulation and waterproofing, is also completely different from polyurethane (PUR), which is only used for heat preservation in refrigerators and cold storages. Although their appearance looks very similar, as a building insulation and waterproofing integrated material, polyurethane Hard foam breaks the traditional building materials "target=_blank>The building materials have a single function, the waterproof is not insulated, the insulation is not waterproof, and the waterproof layer will leak if it leaks, and the insulation layer will lose the heat preservation function. It is compatible with other single-function insulation or waterproof materials. Compared with polyurethane rigid foam, it has obvious advantages:
1. Polyurethane rigid foam has a multi-purpose function, and has many functions such as heat preservation, waterproof, sound insulation and vibration absorption;
2. Excellent thermal insulation performance, is currently the lowest thermal conductivity of all building materials in China [ target=_blank> building materials (≤0.024, green environmental protection fluorine-free foaming technology), the highest thermal resistance material, thermal conductivity is only EPS foaming Half of the benzene board;
3. Polyurethane rigid foam continuous dense skin and nearly 100%% high strength interconnected wall closed pores, with ideal water impermeability. The spraying method is adopted to achieve continuous and seamless joint of waterproof and thermal insulation layer, forming a seamless roof and an integral outer wall thermal insulation shell, which is excellent in waterproof and impermeability;
4. Super self-adhesive performance (no need for any intermediate bonding material), strong adhesion to roof and exterior wall, good wind resistance and negative wind pressure resistance;
5. The overall spraying construction completely eliminates the “hot section†and the “cold bridgeâ€;
6. Flexible grading technology can effectively prevent cracking of waterproof layer;
7. Mechanized operation, automatic batching, uniform quality, short construction period;
8. It has stable chemical properties, long service life and no pollution to the surrounding environment;
9. It is self-extinguishing from the open flame, and it only carbonizes and does not drip when burning. The size and shape of the carbonized layer are basically unchanged, which can effectively block the entry of air, prevent the spread of fire, and have good fire safety performance.
The performance of the polyurethane rigid foam material itself has a major impact on the building safety, heat preservation function and waterproof function, and must be highly valued when selecting materials.
The performance difference between polyurethane rigid foam waterproof insulation material for construction industry and polyurethane rigid foam insulation material for cold storage and refrigerator is mainly reflected in four properties of elongation at break, closed porosity, dimensional change rate and bond strength. On the indicator.
One of the differences: elongation at break
The elongation at break is an important performance index to measure the resistance of polyurethane rigid foam to no permanent deformation. However, it is only used for heat preservation. The polyurethane rigid foam for non-waterproof refrigerators does not have any requirements for this key performance index.
The national building materials "target=_blank> building materials industry standard (JC/T998-2006) clearly stipulates that if the rigid polyurethane foam is used as a waterproofing and insulating integrated material for roofing and wall, it must meet the basic requirements of elongation greater than 10%%. Ensure the breakage, bulging and cracking of the waterproof layer caused by the change of ambient temperature, the shrinkage and swelling of the roof and the wall, the freezing and thawing damage of the winter and the uneven settlement of the building foundation. At the same time, fully demonstrate its reliable waterproof function, only polyurethane rigid foam with elongation rate meeting the above national industry standards can ensure that the building is warm in winter and cool in summer, the environment is comfortable, the roof dripping does not leak, and the outer wall never has the feeling of returning to the tide.
The second difference: the rate of change of size
Polyurethane rigid foam is affected by the change of ambient temperature, the size and volume will change, the size of the dimensional change rate and the type of raw materials, the structure of the foam, the density of the core material, the molding process and the type of foaming agent, etc. Regarding the polyurethane hard foam with good temperature difference resistance, the size should not change significantly at an ambient temperature of -20 degrees Celsius to +80 degrees Celsius. The closed cell rate of polyurethane rigid foam is up to 95%%. The gas pressure enclosed in the cell changes with the change of ambient temperature. If the structural strength of the bubble wall is small, the foam size will change due to the gas pressure in the closed cell. The deformation of low temperature shrinkage or high temperature expansion, the larger the relative deformation amount (ie, the dimensional change rate), the greater the probability that the polyurethane waterproof insulation layer will break or open.
The polyurethane rigid foam used in construction shall have a dimensional change rate of ≤1% according to the national industry standard JC/T998-2006, in order to adapt to the external wall finish system line type caused by sudden changes in temperature difference between day and night in the hot summer and cold season. Excessive size shrinkage and expansion. The dimensional stability is obviously closely related to the safe use of the exterior wall veneer system. The larger the value, the worse the safety. The rigid polyurethane foam with a dimensional change rate greater than 1%% is not in line with the national building materials "target=_blank> building materials industry standard required.
The third difference: closed cell rate
The closed cell ratio is an important index to measure the water absorption and thermal conductivity of the material. The water absorption and thermal conductivity of the hard foam with low closed cell ratio are high, which has a crucial influence on the heat preservation function and freeze-thaw resistance of the material. When using polyurethane rigid foam for construction as a roof waterproof insulation material, the foam closed cell ratio should be at least 95%%. When the closed cell ratio is lower than 70%%, short-term heavy rain will not cause roof leakage, but more During the continuous rainy season, due to the long-term immersion of hard foam in rainwater, the open-cell bubble absorbs more water, and the rainwater that penetrates into the bubble will enter the roof base layer through the string hole under the action of gravity, and will be sealed in the base layer and hard foam. Between the two, even if the weather is fine, it is difficult to discharge upward through the rigid foam insulation layer and the protective layer in the short term under the scorching sun. On the contrary, because the roof is exposed to sunlight, the upper layer is high in temperature and the lower layer is low in temperature, and the water migrates to the lower layer of the roof, causing anomalies in the rainy days and sunny seepage. This phenomenon is especially true in the southern yellow plum season.
The fourth difference: the impact of tensile strength and self-adhesive strength
The overall strength of the polyurethane rigid foam external insulation system depends on the tensile strength of the polyurethane base material (the weakest link of the system strength), so the tensile strength of the polyurethane rigid foam itself is actually the tensile strength of the entire exterior wall finishing system. Pull strength. For example, the tensile strength of polyurethane rigid foam is 200kpa, and the tensile strength of the entire external wall system is 200kpa; if this index is reduced to 100kpa, the tensile strength of the entire external wall system will be reduced to half of the original. The safety factor is also bound to plummet to half.
In addition, the construction of spray polyurethane hard foam in the construction industry should also fully consider the bonding strength requirements of the external insulation system when using materials, so it is required to have extreme materials for metal, concrete, masonry, wood, glass and other building materials. Good self-adhesive properties. National Building Materials "target=_blank> building materials industry standard JC/T998-2006 and recently passed the "polyurethane rigid foam exterior insulation engineering technical guidelines", all have mandatory indicators for the self-adhesive strength of polyurethane rigid foam, this It is also an important indicator that the sprayed polyurethane rigid foam has obvious advantages over the safety of the outer wall insulation system of foamed polystyrene board (EPS) and extruded insulation board (XPS). It is worth mentioning that the strength is the most rigid polyurethane foam. The important mechanical properties, its size directly determines the wind pressure resistance, impact resistance, strain resistance and the ability to carry the total weight of the exterior wall finishing system. It is the most important and direct evaluation of the safety of the external insulation system. Performance indicators.
In summary, when using polyurethane rigid foam as a building insulation and waterproof dual-function material, the user must extend the density, strength and fracture of the material according to the requirements of the national building materials "target=_blank> building materials industry standard JC/T998-2006. The rate, dimensional stability and closed cell ratio are strictly identified. As the only new building materials for thermal insulation and waterproof integration "target=_blank> building materials, the application of polyurethane rigid foam insulation materials in the domestic construction industry is still in the initial stage. Fortunately, in order to speed up the innovation of building insulation materials and promote the promotion and application of polyurethane rigid foam in the field of building energy conservation, the Ministry of Construction has also set up a “Polymer Building Energy Saving Application Promotion Working Groupâ€, which is highly valued and fully promoted by the Ministry of Construction. At present, the application of polyurethane rigid foam insulation materials in the domestic building energy-saving industry has made substantial progress.
Http://news.chinawj.com.cn Editor: (Hardware Business Network Information Center) http://news.chinawj.com.cn
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