Currently, polyurethane rigid foam remains a key material in thermal insulation due to its extremely low thermal conductivity and ease of molding. However, as a reaction-molded polymer, it naturally experiences mold shrinkage — the final foam volume is often smaller than the maximum volume achieved during the molding process. This shrinkage is one of its most significant drawbacks.
Mold shrinkage can lead to several issues, such as the final foam volume being smaller than the cavity size, resulting in separation between the foam and the outer shell. This not only affects the product’s appearance but also compromises its thermal insulation performance and overall durability. To address this, many applications use high-density foaming or molding techniques to minimize the impact of shrinkage.
However, in the case of Changsha and Hunan solar water heaters, traditional molding methods are not feasible due to their unique structure — including thin shells, inner liners, and complex nozzle designs. High-density filling, while effective in reducing shrinkage, significantly increases production costs. As a result, these products often rely on high-free foam filling, which introduces new problems such as foam separation from the outer casing, deformation of the tank, and even damage to the heat collection nozzles. These defects lead to a high rate of process failures and poor quality control.
Through extensive research and analysis, it has become clear that the key to solving these issues lies in reducing the shrinkage during the foam molding process without increasing the foam density. To achieve this, we have developed a tailored formulation and material selection strategy specifically for solar water heaters. Pilot tests on some production lines have shown promising results — the degree of foam-shell separation has been significantly reduced, and the risk of casing deformation has decreased dramatically, making the product much safer and more reliable.
Mini piston vacuum pumps are small-sized pumps that are designed to create a vacuum in various applications. These pumps are typically used in laboratory experiments, medical devices, and other industrial applications that require a small amount of vacuum. They are also commonly used in vacuum packaging machines, vacuum conveyors, and vacuum elevators. There are different types of mini piston vacuum pumps available in the market, including diaphragm, rotary vane, and piston pumps. Piston pumps are the most common type of Mini Vacuum Pump and are known for their high pumping speed and vacuum level. They are also highly reliable and durable, making them a popular choice for many applications. Electric mini piston vacuum pumps are the most common and are powered by an electric motor. In addition, mini piston vacuum pumps can be classified based on their flow rate, vacuum level, and pressure range. The flow rate refers to the amount of air that the pump can move per unit of time, while the vacuum level refers to the degree of vacuum that the pump can create. The pressure range refers to the range of pressures that the pump can handle, from atmospheric pressure to high vacuum. Overall, mini piston vacuum pumps are versatile and widely used in various applications due to their compact size, high pumping speed and reliability.
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