Quality polyurethane foam molding
DATE：2022/1/12 9:08:08 / READ： / SOURCE：This station
Quality polyurethane foam molding
Rigid polyurethane foam has the characteristics of good thermal insulation effect, high specific strength, electrical properties, chemical resistance and sound insulation effect. It is widely used as thermal insulation material, structural material and "synthetic wood".
Another feature of rigid polyurethane foam is that it can be made into rigid foams with different densities, hardness, heat resistance, flame retardant and different electrical properties by changing the formula and adjusting the raw material specifications according to different use requirements. It can also be made into synthetic materials such as wood, cement, and used for wing reinforcement to make radomes, combustion-resistant materials for space vehicles, etc. Today, rigid polyurethane foam has penetrated into various industrial sectors such as construction, petrochemical, vehicle, shipbuilding, aviation, machinery, refrigeration, instrument packaging, electrical appliances, space technology, and aircraft interior decoration.
Casting
Cast-type rigid polyurethane foam is widely used, and more than 50% of the rigid polyurethane foam is formed by this method. It is suitable for rigid foams that are manually and mechanically mixed and poured into the mold. The characteristic of this foam is that it can be filled in various interlayers, pipes or shells.
Casting principle
After the general material is injected into the mold, the material close to the mold first undergoes a foaming reaction. This is because the temperature of the mold is higher than the normal pressure boiling point of the foaming agent and the heat of the mold is transferred to the raw material. As the exothermic reaction occurs, when the temperature of the material adjacent to the mold wall is higher than the mold temperature, the heat is transferred back from the foamed material to the mold. When the mold is overfilled, the pressure in the mold increases due to the increase in the average temperature of the foamed material and the continuous evaporation of the blowing agent, thereby increasing the condensation temperature of the blowing agent.
The temperature gradient of the foam to the mold wall (gradually decreasing) and the increase in the condensation temperature of the blowing agent create the skin of the foam. Where the foam temperature is lower than the condensation temperature of the blowing agent, the blowing agent will condense into a liquid, and this condensation will continue until the foam solidifies. Therefore, the foaming mechanism of self-skin foam is a dynamic process, which involves the phenomenon of coagulation due to the increase of the foaming agent, which cannot be vaporized. Foamed firm skin.
Author：admin