Polyurethane foam material molding method
Hard The foam forming methods mainly include pouring and spraying
Plate production technology and precautions
Rigid polyurethane foam plastic sheets are light in weight, high in strength and have good thermal insulation effect. They are ideal building materials , used for roof insulation, cold storage, etc. Most of this kind of board is covered with a surface layer, so it is a sandwich board or composite board with hard foam as the core material. The surface layer can be made of soft or hard materials. Soft materials include kraft paper, polyethylene-coated kraft paper, asphalt paper, fiberglass fabric, asphalt fiberglass fabric, aluminum foil, etc. Hard surface materials include steel plates (flat plates and profiles, scrap wood plywood, chipboard, mortar boards, reinforced cement boards, mineral wool boards, perlite boards, gypsum boards, etc.
Composite plate processing methods can be roughly divided into continuous composite molding method, discontinuous composite molding method, hard foam block cutting method, etc. p>
The continuous method has low labor cost and energy saving, and is a relativelyGoodmethod.
The production of PU rigid foam sandwich panels is mainly divided into two methods:
1. Intermittent production
2、 Continuous production
Intermittent production Most processes use single-hole injection molding ,Suitable for processing plates that do not require a high production rate, or that are thicker, larger in size, or have a more complex structure.
Production process: pre-assembly→The template enters the laminating machine→ Template locking → pouring → mold heating and maturing → mold opening → picking up and cleaning → transfer to the next cycle.
Spray rigid polyurethane foam
The sprayed foam is directly bonded to the substrate to form a continuous seamless coating
Foam quality
When the mixture leaves the nozzle of the spray gun, a fan-shaped atomization effect should be formed. The humidity and temperature of the air and The temperature of the substrate itself has a significant impact on the final quality of the foam.
Temperature
Spray foam on the frozen substrate (i.e. below about 10℃), the cold surface may act as a heat dissipator and absorb Part of the heat energy required to completely evaporate the blowing agent and slow down the polymerization reaction rate. As a result, a thick crisp foam skin is formed on the surface, resulting in poor adhesion and the later formation of foam bubbles.
If the foam is sprayed on a hot substrate, the density of the foam will increase due to the loss of the foaming agent. What is called a needle eye will form. Therefore, for substrates with temperatures as high as50°C, a special system with a longer milky white period must be selected, and the amount of foaming agent must be increased if necessary.
Moisture/humidity
The most important thing is to spray the polyurethane foam on a dry surface. The water will react with the isocyanate component, resulting in low adhesion between the foam and the substrate and a brittle skin. .
Spraying conditions
If it happens Outdoor spraying should not be carried out under the following circumstances: It rains、Dense fog、Windy、Visible water droplets, Humidity exceeds80%、The surface moisture content exceeds10% ( Measured with a moisture meter), 风（If the wind speed exceeds25 kilometers/hour, it will be difficult to spray evenly of foam layer. The cooling effect of the wind reduces the surface quality of the foam because the surface layer does not mature properly. ）This can be a problem when constructing in cold climates.
Operator skills
To be able to produce qualified foam surface texture, that is, smooth surface and uniform thickness. Operators must be fully trained. These two characteristics have a significant impact on costs and therefore profits.
Device adjustment
if If the temperature is slightly lower than the recommended temperature, the pressure of each component can be adjusted. If there is an excess of isocyanate, a crisp or brittle foam will form, which is characterized by a dark black color and a smooth, hard structure.
If the polyol is excessive, a soft or spongy foam will form, which is light in color and has a “rough orange” color. Leather” texture and needle holes.
n>,The surface moisture content exceeds10% (measured with a moisture meter)、风（If the wind speed exceeds It is difficult to spray a uniform layer of foam at 25 km/h. The cooling effect of the wind will reduce the surface quality of the foam because the surface layer cannot be properly cured. )<font face This can be a problem when constructing in cold climates.
Operator skills
To be able to produce qualified foam surface texture, that is, smooth surface and uniform thickness. Operators must be fully trained. These two characteristics have a significant impact on costs and therefore profits.
Device adjustment
if If the temperature is slightly lower than the recommended temperature, the pressure of each component can be adjusted. If there is an excess of isocyanate, a crisp or brittle foam will form, which is characterized by a dark black color and a smooth, hard structure.
If the polyol is excessive, a soft or spongy foam will form, which is light in color and has a “rough orange” color. Leather” texture and needle holes.
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