Polyurethane sandwich panels are produced using fully automatic lines (Continius).
This type of sandwich panel is produced with two types of polyurethane foam, which differ from each other in terms of fire resistance:

The first type is slow-burning polyurethane with flammability grade B2 and the second type is fireproof polyurethane made in Germany with grade B1. It is known as PIR and it is completely resistant to fire.
Due to the integrated injection of foam throughout the panel, all points of the panel, including the grooves and ridges of the crotch and tongue (Nero material), are filled with foam, and this makes the panel more thermally resistant and minimizes energy transfer.

The density of the polyurethane foam used in the panel is 40 kilograms per cubic meter, which is the highest possible. The sheet used in the panels is pre-painted galvanized, which is mainly procured from reputable domestic companies, such as Isfahan Mobarake Steel.

Polyurethane sandwich panel is produced in two ceiling and wall types:
Ceiling sandwich panels with a width of 107 cm and a useful performance of 100 cm are produced in five steps in sizes of 2 to 6 cm.

Polyurethane sandwich panel production methods
In general, two methods are used to produce polyurethane sandwich panels:
continues method
In the continuous or mechanized method, devices and mechanical ligaments turn the raw materials into the final sandwich panel, in other words, the raw materials are the galvanized sheet roll, the raw materials of polyurethane foam or polystyrene foam sheet and glue on one side of the machine. They come in and on the other hand, the completed sandwich panel is cut into desired pieces and ready for packing.
Continuous polyurethane device
This model of devices is the first samples imported to the country that started the production of sandwich panels in Iran, and it can be said that the first sandwich panels produced in Iran are polyurethane sandwich panels, in this type of devices at the beginning of the production line. There are two or four, or more than four roll catchers in advanced models, which increase the work speed, and there is one row of roll catchers for the top of the panel and one row for the bottom of the panel. After the unroller opens the roll of galvanized sheet, the sheet enters the roll forming machine and after passing through several gates, it is transformed into the desired form, the sheet on the panel enters a series of special rollers and the bottom sheet enters another series of The rollers are made, usually these two designs are different, then the formed sheets are brought together from the top and bottom and are placed at the desired distance of the order, and then polyol and isocyanate are mixed between them by a special machine with The special dose is injected together, then this material – which is polyurethane insulation foam – begins to expand and releases significant heat, at this stage the panel should be quickly placed under the press and heat to more The allowed limit does not swell, then the panel is placed in the cooking pot under high heat to stabilize in the same state. Finally, the panel is cut to desired dimensions by the movable cutting blade and arranged in rows next to each other to cool and be ready for packing.

Discontinuance method
In the discontinuous or non-continuous method, the production line is separated from each other and each operation is performed in one station and then transferred to the next station.
Polyurethane discontinuous production line
In this method, each part of the polyurethane panel production is done in one station, so that the sheet should be cut by the roll forming machine, and the sheet below and on top of the panel are placed under the press in special molds, and between these two with the machine The injection moldings are filled with polyurethane foam and at the end, the foam dries by heating and cooling, and the panel is removed from the mold and the next panel is made.

Advantages of polyurethane foam insulation
The highest density among core insulations is related to this foam: a number of 40 ± 2 kg/m3
For the first time in Iran, this foam was used to produce sandwich panels.
It is produced in two forms, continuous and discontinuous.
Due to the heating process of isocyanate and polyol during the composition, it has a high molecular bond.
Due to the heating process, it has good adhesion to the galvanized sheet or the outer layers of the panel.
Due to the increase in volume of ISO and poly after mixing, all the holes are filled by foam.
Compared to polystyrene insulation, it has a lower thermal conductivity coefficient. (that is, it has a higher thermal resistance R)
Disadvantages of polyurethane foam insulation
Compared to other insulators, it has a higher price, so it significantly increases the finished price of the product.

During a fire, it produces cyanide gas, which causes instant death, and this is the reason why the use of this foam is prohibited in the building safety directive.

One of the biggest problems of cold storage manufacturers with this foam is the absorption of water above the polyurethane insulation, which reduces the efficiency of the cold storage and the conductivity of the foam and transfers heat easily.
Due to the high price, it is not suitable for places where coldness and insulation are not important and it is not recommended.
It has many limitations for production in different thicknesses.
In some cases, it has been seen that due to defects in the combination of poly and ISO materials, the volume increase was incomplete, and as a result, the panel was produced in a hollow form, and it is difficult to detect such defects.
The raw materials of polyurethane insulation foam are completely imported and unfortunately, in this regard, our producers have faced many problems such as sanctions.

During the production of this insulation, it creates greenhouse gases, which are very destructive and harmful to the environment and the ozone layer, and for this reason, it is becoming obsolete in countries committed to protecting the environment.