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Do you know the basic process of polyurethane foaming in refrigerators?

2022-03-26

The foaming material is mixed and injected into the insulation cavity or shell interlayer through a polyurethane high-pressure foaming machine. Before it is cured, it must flow for a long distance to be filled. After filling, the density, pore structure, strength and thermal conductivity of the entire foam are distributed. There is a significant difference, there is a clear gradient. Fluidity is to characterize the ability of the foaming system to overcome the resistance and evenly fill various complex thermal insulation cavities or shell interlayers during the foaming process. Essentially, polyurethane foaming is a complex physical and chemical process, and three basic reactions of chain growth, foaming and cross-linking occur almost simultaneously. The initial stage of the reaction (milk white stage) is mainly the chain growth of linear molecules, the reaction heat is small, and a small amount of foaming gas is generated or vaporized. It exhibits a certain degree of fluidity, but it is not very significant; as the reaction continues, the exothermic heat further increases, and the vaporization of a large amount of blowing agent causes the rapid expansion of the foam (foaming period), which is caused by the expansion of the foam at this time. The flow fills most of the cavity; when the gel appears, that is, the macromolecules begin to cross-link (the curing period), the sudden increase in the viscosity of the foaming system increases the friction between the foam and the cavity wall, although the internal pressure acts as a chain (the curing period). ), the sudden increase in the viscosity of the foaming system increases the friction between the foam and the cavity wall. Although it expands slightly under the action of internal pressure, the boundary effect makes the cells of the foam stretch and deform, showing strong anisotropy. A section of the foam is therefore also very susceptible to shrinkage and deformation.

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Guangdong Foret Electromechanical Technology Co., Ltd. is located in Shenghui North Industrial Zone, Nantou Town, Zhongshan City, Guangdong Province. It is a polyurethane machinery automation production enterprise integrating R&D, production, sales and after-sales service. Our company develops and manufactures various polyurethane casting machines, polyurethane foaming machines, automatic foaming production lines (hanging foaming lines/ground rail foaming lines/turntable lines, etc.), automatic foaming mold mold bases, robotic arms and other polyurethane complete sets of foaming equipment, helping thousands of polyurethane product manufacturers to achieve "high product quality rate and low equipment failure rate".

 


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