We typically use polyurethane foam sandwiched with double-sided color steel panels for cold storage insulation, or directly apply polyurethane facade spray insulation to the walls. In southeastern China, double-sided color steel cold storage panels with polyurethane foam cores are more common, while in the northwestern regions, polyurethane facade spray insulation is more prevalent. What are the advantages and disadvantages of polyurethane facade spray insulation for insulation?

1. Insulation and Energy Conservation: Polyurethane rigid foam boasts an exceptionally low thermal conductivity, unparalleled by other materials. It offers a cost-effective and high-quality solution.

2. Excellent performance and wide application. Due to the varied nature of different engineering projects, there are various mechanical and thermal conductivity requirements for thermal insulation materials. Rigid foam plastics have the characteristics of lightweight and high strength, and by adjusting the formula according to the specific requirements of each project, we achieve the necessary mechanical properties to meet the quality standards of the product.

3. Advanced technology and convenient construction. Polyurethane rigid foam processing is simple, allowing both pre-fabrication and on-site foaming, which can be cast or sprayed. The processing technology can be adjusted according to project requirements, catering to various construction needs. Particularly, on-site spraying not only saves labor and materials but also enables the application of complex shapes without any additional processing. It has the characteristic of self-adhering to metals, wood, concrete, and other non-metallic materials. The bonding strength is generally equal to or exceeds the fracture strength of the foam itself.

The Chemical Mechanism of Polyurethane Rigid Foam Formation: The formation process of polyurethane rigid foam is complex, involving the reaction of polyether and isocyanate through complex chemical reactions (exothermic) and physical changes in the presence of catalysts, foam stabilizers, and blowing agents. The main reactions include chain growth, gas formation, and cross-linking reactions.

5. Raw Materials for Polyurethane Rigid Foam Production: The raw materials for producing polyurethane rigid foam include isocyanates, polyethers, catalysts, foam stabilizers, flame retardants, and more. Currently, rigid foam production often involves two main groups:

1) (White Material): Comprised of pre-mixed polyether, catalyst, foam stabilizer, flame retardant, etc., the white material is commonly referred to as compounded polyether.

2), (Black Material): Polyether MDI

6. Lifespan: Over the past 30 to 40 years since the inception of rigid foam industry, it has been proven that rigid foam withstands the test of time with minimal performance changes. With the development of marine fisheries, meat processing, and other food industries, these products are often processed, flash-frozen, and stored locally to reduce spoilage and enhance resource utilization. Traditional foods from various regions are exported to distant countries. Cold storage, freezing, and refrigeration rooms have become indispensable facilities in economic development, bringing significant economic benefits.

7. Cold Storage Construction Methods: The assembly of composite sandwich panels for large cold storage facilities is convenient and quick. The facings are made of steel and other metal materials, which are highly durable and resist deformation upon impact, with the core being polyurethane foam. These panels can be produced using either continuous or discontinuous methods. The width of the panels is generally 60-120 cm, with thickness ranging from 6 to 20 cm, depending on the freezing temperature. The edges of the composite panels feature tongue-and-groove structures for easy assembly. They are secured with elastic sealant or by injecting polyurethane foam material into the gaps, which then fills the space. Proper sealing is crucial to minimize heat loss. Practical evidence shows that, with reasonable application, the insulating effect of the foam will not significantly degrade within 25-30 years. There is also the method of spray forming for creating the cold storage foam insulation layer. This involves constructing the building shell first, then applying the foam to the exterior walls before constructing the interior walls. Spray foam construction in cold storage requires heightened safety precautions as the sealed structure has no external ventilation or air exchange windows except for the entrance and exit doors. The heat released during the foaming reaction is not easily dissipated, and excessive heat accumulation can lead to spontaneous combustion. Therefore, the spray application should control the speed and thickness of each layer of foam to prevent accidents. Additionally, during the spray process within the cold storage, harmful isocyanate mists are not easily dispersed, so adequate labor protection for the operators is essential. Cold storage facilities vary in size, with smaller ones often being a small low-temperature refrigeration room within a building. These small cold storages can be conveniently assembled using sandwich panels and can also be converted from existing buildings through spray foam modifications. Polyurethane foam is also widely used in refrigerated trains, cars, trucks, refrigerated containers, and ship refrigeration compartments.