We typically use polyurethane foam sandwiched with double-sided color steel panels for cold storage insulation, or apply polyurethane wall coating directly to the walls for insulation. In southeastern regions of our country, double-sided color steel panels with polyurethane foam cores are more prevalent; while in the northwestern regions, polyurethane wall coatings are more commonly used. What are the advantages and disadvantages of using polyurethane wall coatings for insulation?
Insulation and Energy Conservation: Polyurethane rigid foam boasts an exceptionally low thermal conductivity, unparalleled by other materials, offering a cost-effective and high-quality solution.
2. High performance and broad application. Due to the diversity of various engineering projects, there are different mechanical and thermal conductivity requirements for thermal insulation materials. Rigid foam plastics possess the characteristics of light weight and high strength, and by adjusting the formula according to the specific requirements of the project, we achieve the mechanical properties suitable for the project, thereby meeting the quality standards of the product.
3. Advanced technology, easy construction. Polyurethane rigid foam processing is simple, allowing both pre-fabrication and on-site foam shaping. It can be poured or sprayed, adapting processing techniques to meet project requirements. Especially for on-site spraying, it not only saves labor and materials but also can apply to 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 of polyurethane rigid foam is a complex process that occurs under the presence of catalysts, foam stabilizers, blowing agents, and other auxiliaries. It is formed through a combination of complex chemical reactions (exothermic) and physical changes involving polyether and isocyanate. The main reactions include chain growth, gas formation, and cross-linking reactions.
5. Raw Materials for Producing Polyurethane Rigid Foam: The raw materials for producing polyurethane rigid foam include isocyanates, polyethers, catalysts, foam stabilizers, flame retardants, and more. Currently, the production of rigid foam 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 composite polyether.
2), (Black Material): MDI Aggregate
6. Life Span: Over the past 30-40 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 improve 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 large cold storage composite sandwich panels is convenient and quick. The facades are made of steel and other metal materials, offering high strength and resistance to deformation upon impact. The core is polyurethane rigid foam. Composite sandwich panels are produced using either continuous or discontinuous methods. The width of the panels is generally 60-120 cm, and the thickness ranges from 6 to 20 cm, varying according to the freezing temperature. The edges of the composite panels feature tongue-and-groove structures for easy assembly. They are secured using elastic sealant or by injecting polyurethane foam liquid into the gaps, resulting in a full foam filling. Proper sealing of gaps is essential 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 spray molding method for producing cold storage foam insulation. The storage body and outer walls are first constructed, and then the interior is sprayed with foam before the inner walls are made. Special attention must be paid to safety during the spray foam construction of cold storage, as it is a sealed structure with no external ventilation windows except for the loading/unloading doors. The heat generated during the foaming reaction is difficult to dissipate, and excessive heat accumulation can lead to spontaneous combustion of the foam. Therefore, the spray rate and thickness of each layer of foam should be controlled to prevent accidents. Additionally, during the spray process inside the cold storage, hazardous isocyanate sprays are not easily dispersed, so adequate labor protection for the operators should be ensured. Cold storage facilities vary in size, with smaller ones often being a低温 refrigeration room within a building. These small cold storage units can be conveniently assembled using rigid foam panels or transformed from existing buildings through spray modification. Polyurethane rigid foam is also widely used in refrigerated trains, cars, trucks, refrigerated containers, and ship refrigeration compartments.
