Guide to Choosing Polyurethane as Insulation Material for Cold Storage

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　　Polyurethane, as an insulation material for cold storage, plays an important role in cold storage construction in terms of both initial investment costs and long-term benefits； While cheap raw materials can reduce initial investment, high-quality raw materials yield better long-term returns. Faced with highly competitive raw material suppliers, and with raw materials whose quality can only be determined after they are used, making better choices has become a major headache for every investor in cold storage facilities. 　　Regarding the polyurethane spray coatings used for insulation in cold storage facilities, the black components used as well as the spraying techniques are more or less the same across different manufacturers, and the foam produced has a similar appearance. However, differences in the white components used can significantly affect the performance of the final products; in some cases, the use of low-quality white components can even prevent the intended insulating effects from being achieved. To ensure that the products provide good insulation and energy-saving effects, thereby maximizing the long-term benefits for investors in cold storage facilities, the following brief introduction is provided, based on the quality control practices of a company in Shandong: 　　Insulation performance of cold storage materials: 　　The primary requirement for polyurethane materials used in cold storage is their insulation performance. However, it is not possible to determine the quality of this insulation performance visually before the materials are put into use; by the time differences in power consumption become apparent, it is already too late. Through numerous experimental tests, the company exercises strict control over material selection in order to achieve this goal: ① Using structural amine ethers to reduce the thermal conductivity and improve insulation performance ； ②The moisture content in various raw materials and formulations should be reduced as much as possible to prevent water-induced foaming from leading to a decline in insulation performance ； ③The main material, polyether: Products from large manufacturers that have undergone rigorous post-treatment are used (such as Jinling Petrochemical Company, etc.). Compared with polyethers from smaller manufacturers that lack such post-treatment, these materials result in foam cells with greater uniformity and thinner cell walls, offering significantly better insulation properties than ordinary foams with thick walls and large cells ； ④The use of efficient, odorless amine catalysts helps to adjust the balance of the foaming-gelation reaction, resulting in a thinner surface layer between coating layers, which facilitates the optimal performance of insulation materials in cold storage ； ⑤Ordinary polyester polyols are not used. These control measures have yielded quite good results; when comparing several cold storage facilities at a client in Jining, those that used its own refrigerant consumed significantly less electricity compared to those that used refrigerants from other manufacturers. 　　Dimensional stability of polyurethane insulation foam: Polyurethane foam used in cold storage facilities can experience changes in dimension due to drastic temperature fluctuations or prolonged exposure to low temperatures (usually contraction). Such dimensional changes often manifest as cracking or peeling of the foam, which inevitably affects the proper functioning of the cold storage facility. In addition to regularly conducting performance tests using simulations, more emphasis is placed on controlling the selection of high-quality materials: ① The use of special high-functionality polyether compounds enables the foam to form a three-dimensional network structure, **improving the foam’s resistance to low temperatures ； The 4110 polyether commonly used in spray coatings currently contains a large amount of difunctional components, and the numerous linear molecular structures formed as a result of reactions are difficult to remain stable at low temperatures ； ②The use of high-functionality crosslinking agents also **improved the dimensional stability of the foam** ； ③The polyether used in its production is catalyzed by strong alkalis during the manufacturing process, ensuring a complete reaction that allows the polyether to maintain a high reactivity rate (meaning it can react quite completely when in contact with the black material) ； To prevent the foam from deforming in appearance, some manufacturers add pore-forming components to the foaming material, which reduces the foam’s closed-cell density and thus helps maintain a stable shape; however, this comes at the cost of the thermal insulation properties of the polyurethane foam used in cold storage systems. 　　Service life of polyurethane insulation foam for cold storage: In addition to the basic properties of polyurethane foam at the beginning, the degree of degradation of its performance is also an important indicator. When preparing the white material, the use of certain polyester materials gives the foam better toughness and impact resistance on the surface, but after being used in a cold storage for some time it becomes brittle and loses its impact and collision resistance ； Furthermore, the poor hydrolysis resistance of certain polyester-based structural foams can also affect their service life ； It features a polyether structure; although it is slightly brittle at first, this brittleness generally disappears after a few days, after which it maintains stable performance as a refrigeration insulation material over the long term. 　　Recommendation on the amount of polyurethane insulation material to use in cold storage: Investing in a cold storage is a long-term investment with potential returns. While using more of this material can indeed reduce initial costs, it is necessary to keep things within certain limits. Long-term energy consumption must be taken into consideration along with the initial investment, as there is a parabolic relationship between the insulating efficiency of polyurethane insulation materials and their density ； Numerous studies have shown that foam with a bulk density of 33–35 kg/m³ exhibits good thermal insulation properties; therefore, it is generally recommended that the volume per ton for constant-temperature cold storage be around 22–23 cubic meters per ton. 　　Key performance indicators of polyurethane insulation materials for cold storage, such as their insulating capacity, dimensional stability, and service life, are not visible, tangible, or perceptible; the difference between good and poor quality can be very subtle. Therefore, when choosing insulation materials for cold storage, it is necessary to prioritize quality first and only then consider cost – one should not focus solely on price! Quality is what matters!