General Situation of Application of Polyurethane Spraying in Cold Storage Insulation

Cold storage insulation we usually use polyurethane sandwich double-sided color steel cold storage insulation board or directly spray polyurethane facade on the wall for insulation. In the southeast of my country, polyurethane sandwich double-sided color steel cold storage insulation boards are mostly used; in the northwest, polyurethane facade spraying is used for insulation. So what are the advantages and disadvantages of polyurethane facade spraying for insulation?

　　 1. Thermal insulation, energy saving. Polyurethane rigid foam has a very low thermal conductivity, which is unmatched by other materials, and it is considered high quality and low price.

　　2. Excellent performance and wide application. Due to the difference in various projects, there are also various mechanical and thermal performance requirements for thermal insulation materials. Rigid foam has the characteristics of light weight and high strength, and according to the different requirements of the project, the formula is adjusted to obtain the machinery that meets the requirements of the project. Performance, and then meet the quality requirements of the product.

　　3. Advanced technology and convenient construction. The polyurethane rigid foam has a simple processing technology, which can be prefabricated, foamed on site, poured and sprayed, and the processing technology can be changed according to the needs of the project to engage in various constructions. Especially on-site spraying, not only can save manpower and material resources, but also can spray complex shapes without any processing, and has the characteristics of self-adhesive to metal, wood, cement and other non-metal materials. The degree of adhesion can generally reach or exceed the crushing strength of the foam itself.

4. The chemical mechanism of the formation of rigid polyurethane foam: The formation process of rigid polyurethane foam is complicated. In the presence of catalysts, foam stabilizers, foaming agents and other additives, polyether and isocyanate undergo complex chemical reactions (exothermic) and physical Formed by changes, there are mainly chain growth reactions, gas reactions and cross-chain reactions.

　　5. Raw materials for the production of rigid polyurethane foam: The raw materials for the production of rigid polyurethane foam include: isocyanate, polyether, catalyst, foam stabilizer, flame retardant, etc. At present, hard foam production is often divided into two groups:

　　1), (white material): pre-combined with polyether, catalyst, foam stabilizer, flame retardant, etc., so white material is usually called combined polyether,

　　2), (black material): polymeric MDI

　　6. Service life: 30-40 years have passed since the beginning of the rigid foam industry. Practice has proved that rigid foam can withstand the test of time, and its performance has almost no change. With the development of marine fisheries, meat and other food processing industries, these foods are often processed, quick-frozen, and refrigerated at the place of production to reduce spoilage and improve resource utilization. Traditional foods from various places are exported to other countries. Cold storage, freezing and cold storage rooms have become indispensable facilities in economic development and can bring extremely considerable economic benefits.

　　7. Cold storage construction method: The composite sandwich panels of large-scale cold storage are more convenient and quick to assemble. The surface material is made of metal materials such as steel plates, which have high strength and are not easily deformed after being impacted. The core plate is made of polyurethane rigid foam. Composite sandwich panels are produced by continuous or discontinuous methods. The board width is generally 60-120cm, and the thickness is 6-20cm. The thickness of the sheet varies depending on the freezing temperature. The edge of the composite board has a tongue and groove structure, which is easy to assemble. The board is fixed with an elastic sealant or a hard foam material liquid is injected into the gap, and the gap is filled with hard bubbles after the reaction. The gap should be sealed well to reduce heat loss. It has been practically proved that if the application is reasonable, the thermal insulation effect of the hard foam will not be significantly reduced within 25-30 years. There is also a spray molding method to make hard foam insulation for cold storage. Build the library body, exterior wall first, spray hard foam on the inner side, and then do the inner wall. It is more important to pay attention to the safety of cold storage spraying hard foam than general spraying construction. Because the cold storage is a sealed structure, there is no external ventilation window except for the entrance and exit of the goods. The exothermic heat of the foaming reaction is not easy to dissipate, and excessive heat accumulation may cause spontaneous combustion of foam. Therefore, during spraying construction, the spraying speed and the thickness of each layer of sprayed hard foam should be controlled to avoid accidents. In addition, during the spraying process in the cold storage, harmful sprays such as isocyanate are not easy to disperse, and the labor protection of the operators should be done. There are large and small cold storages, and a small cold storage is actually a small low-temperature cold storage room in a certain building. This kind of small cold storage is more convenient to assemble with hard foam board, and it can also be reconstructed by spraying the original building. Rigid polyurethane foam is also widely used in refrigerated trains, automobiles, trucks, refrigerated containers and refrigerated cabins of ships.