1. What is polyurethane spraying?
Polyurethane spraying uses isocyanate and polyether as the main raw materials. It is a high molecular polymer that is foamed on-site through high-pressure spraying under the action of various additives such as foaming agents, catalysts, and flame retardants, mixed through special equipment. Polyurethane rigid foam is a new synthetic material with thermal insulation and waterproof functions. Its thermal conductivity is low, only 0.022~0.024W/(m².k). It is equivalent to half of the extruded board and has the lowest thermal conductivity among all current insulation materials. Polyurethane spray flame retardant grades B1 and B2 can be used.
Polyurethane rigid foam is generally foamed at room temperature. Its molding process is relatively simple. In our refrigeration industry Generally, polyurethane rigid foam spraying is used.
Black material and white material ：
The scientific name of black material is polyisocyanate, because it is a black viscous liquid, so it is commonly known as black material. Among them, MD is a kind of polyisocyanate, which is used in the production of refrigerator polyurethane foam.
White material is the industrial production of refrigerator polyurethane foam, usually the polyether polyol is combined , catalyst foam stabilizer, the mixture is a white viscous liquid.
2. Application and product features of polyurethane spraying
Polyurethane spraying is widely used in all walks of life, and is mainly used in our refrigeration and HVAC industry：
Exterior wall cold storage spray insulation;
Pipe insulation;
Cold storage board insulation;
Solar insulation;
refrigerator freezer insulation;
Reefer container insulation;
Cold storage insulation We usually use polyurethane sandwich double-sided color steel cold storage insulation boards, or directly spray polyurethane facades on the wall for insulation. In southeastern China In the south, polyurethane sandwich double-sided color steel cold storage insulation boards are mostly used, while in the northwest, polyurethane facade spraying is mostly used for insulation.
Advantages of polyurethane spraying:
Good thermal insulation performance, low thermal conductivity, better than polystyrene board, it is currently a better thermal insulation material .
Good waterproof performance, sealing rate 95%, no rainwater Seep through the holes.
Polyurethane spraying has dimensional stability, high production efficiency, fast molding speed and high efficiency,
Spraying construction can directly implement spray foaming processing on substrates of various shapes;
The service life is as long as 30 years, and the performance will not change greatly;
Can be prefabricated, can be foamed on site, can be poured, can be sprayed, and the construction method can be changed as needed;
Disadvantages of polyurethane spraying:
atThe foaming rate will decrease below 10 degrees, and the product is limited by external conditions during use.
Spraying is fast and difficult to spray very flat, and unevenness is normal;
Polyurethane spray that comes into direct contact with black and white materials for a long time may cause dizziness, headache, nausea and vomiting, etc. Severe cases may suddenly collapse.
3. Polyurethane spraying process and FAQ
polyurethane spray The performance indicators should comply with the requirements of JC/T998-2006 “Spray Polyurethane Rigid Foam Insulation Materials”. During on-site spraying operations, the ambient temperature should not be lower than 10°C, the wind force should not be greater than 5m/s (level 3 wind), the relative humidity should be less than 80%, and no construction is allowed on rainy days.
If the foam appears abnormally during spraying, the blast holes are large, and the black material is excessively foamy Too much black or white material will turn white and soft. You can refer to the reasons:
The mixing is not good, there is an interlayer in the middle of the foam, and it shrinks locally;
Out of proportion, organized and shrunk;
The temperature is not suitable, the foaming is too small or the fire is too high;
Solution: When manually foaming, control the mixing effect of the mixing head and keep the diameter to 2/3 of the mixing container. When foaming by machine, pay attention to managing abnormal changes in pressure. Check whether the piping system and mixing head are blocked and clean them.
face=”宋体”>Spray forming is fast, and it is not easy to spray it very flat, and unevenness is normal;
Polyurethane spraying Direct contact with black and white materials for a long time may cause dizziness, headache, nausea and vomiting, etc. Severe cases may suddenly collapse.
3. Polyurethane spraying process and FAQ
polyurethane spray The performance indicators should comply with the requirements of JC/T998-2006 “Spray Polyurethane Rigid Foam Insulation Materials”. During on-site spraying operations, the ambient temperature should not be lower than 10°C, the wind force should not be greater than 5m/s (level 3 wind), the relative humidity should be less than 80%, and no construction is allowed on rainy days.
If the foam appears abnormally during spraying, the blast holes are large, and the black material is excessively foamy Too much black or white material will turn white and soft. You can refer to the reasons:
The mixing is not good, there is an interlayer in the middle of the foam, and it shrinks locally;
Out of proportion, organized and shrunk;
The temperature is not suitable, the foaming is too small or the fire is too high;
Solution: When manually foaming, control the mixing effect of the mixing head and keep the diameter to 2/3 of the mixing container. When foaming by machine, pay attention to managing abnormal changes in pressure. Check whether the piping system and mixing head are blocked and clean them.
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