Rigid polyurethane foam molding

日期:2022/6/22 8:58:33 / 阅读: / 来源:本站

Rigid polyurethane foam molding
Rigid polyurethane foam is a kind of foam that does not deform under a certain load and cannot return to its original shape when the load is too large. Lithium battery diaphragm production line www.handern com
Rigid polyurethane foam has the characteristics of good heat insulation effect, high specific strength, electrical performance, chemical resistance and superior sound insulation effect. It is widely used as heat insulation materials, structural materials and "synthetic wood".
Another feature of rigid polyurethane foam is that it can be made into rigid foam with different density, hardness, heat resistance, flame retardancy and electrical properties by changing the formula and adjusting the raw material specification according to different use requirements. It can also be made into synthetic materials to replace wood and cement through reinforcement measures, and used for wing reinforcement to make radar radome and combustion resistant materials for spacecraft. Today, rigid polyurethane foam has penetrated into various industrial sectors such as architecture, petrochemical industry, vehicles, shipbuilding, aviation, machinery, refrigeration, instrumentation, packaging, electrical appliances, space technology, aircraft interior decoration, etc.
1、 Casting lithium battery diaphragm production line www.handern com
Cast rigid polyurethane foam is widely used. More than 50% of rigid polyurethane foam is formed by this method. It is suitable for the hard foam which is poured into the mold by hand and machine. This kind of foam is characterized by being able to fill all kinds of interlayer, pipe or shell.
1. casting principle lithium battery diaphragm production line www.handern com
After general materials are injected into the mold, the materials close to the mold first undergo foaming reaction. This is because the temperature of the mold is higher than the atmospheric boiling point of the foaming agent and the heat of the mold is transferred to the raw materials. With the exothermic reaction, when the temperature of the material near the mold wall is higher than the mold temperature, the heat is transferred back from the foaming material to the mold. When the mold is overfilled, the increase of the average temperature of the foaming material and the continuous evaporation of the foaming agent lead to the increase of the pressure in the mold, thus increasing the condensation temperature of the foaming agent.
The temperature gradient from the foam body to the mold wall (gradually decreasing) and the increase of the foaming agent condensation temperature produce the skin of the foam body. Where the temperature of the foam is lower than the condensation temperature of the foaming agent, the foaming agent will condense into a liquid, and this condensation will continue until the foam solidifies. Therefore, the foaming mechanism of self skinned foam is a dynamic process, which involves that the foaming agent can not vaporize when it increases, and the foaming agent condenses in the foaming materials around the city wall, thus forming a solid layer without foaming. Lithium battery diaphragm production line www.handern com
2. forming characteristics
Compared with other foaming methods, it has the following characteristics.
① The raw material is a mixture of low viscosity. After casting, the viscoelasticity of the raw material gradually increases with the progress of polymer reaction until it is cured.
② The foaming process and the polymerization process go hand in hand. ③ It is mainly used for molding high foaming plastic products.
④ The forming equipment is simple and can be operated on site.
⑤ It can be used for forming large strip and block shaped foamed plastic products and spraying foamed plastic layers. Because of the above characteristics, casting foaming has become the main forming method of foamed plastics, and has occupied an irreplaceable position, especially for thermosetting foamed plastics, most of them are formed by this method. Lithium battery diaphragm production line www.handern com
Generally, all kinds of raw materials are uniformly mixed according to the formula proportion, and then injected into the cavity of the mold or parts (such as between the inner and outer shells of the refrigerator). The mixed materials are foamed and solidified at the same time of chemical reaction to produce rigid polyurethane foam.
3. foaming type
There are two foaming types for casting molding according to the conditions of injection molding.
① It is not necessary to take the foam out of the cavity after mixing, such as the rigid polyurethane foam injected into the refrigerator.
② The raw materials are divided and injected into the mold. After foaming, the foamed plastic needs a lithium battery diaphragm production line www.handern com

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