What is PU Sandwich Panel?

July 13, 2020by Fineagles

sandwich panel is a structure made of three layers:

  • Core
  • Two side skin

Sandwich panels are used in applications where a combination of high structural rigidity and low weight is required. The following is the list of the applications whereby sandwich panel is used:

  • Cold Storage
  • Pack Houses
  • CA Chambers
  • Ripening Chambers
  • Freezer Rooms
  • Clean Rooms
  • Control Rooms
  • Insulated Roofs
  • Wall Claddings
  • Partition
  • Prefabricated Houses and shelters
  • Portable Cabins
  • Health Centers and Schools, Stadiums, Warehouses
  • Communication Shelters
  • Insulated Sheds
  • Sub Zero Temperature Areas

PU Sandwich Panel:

Polyurethane rigid foam is the core in these kinds of panels. A special feature of polyurethanes is their method of production. Generally, metering and mixing four or more streams of liquid components containing polyurethane precursors at the processing stage produce polyurethanes. Thus, the final, high molecular weight polymer is normally manufactured by the manufacture of Sandwich Panel who has a PU sandwich panel production line. In the production line of sandwich panel, one section is dedicated to performing this process, called “PU Foaming Machine” or “Metering Machine”.

Polyurethane has been used as a considerably suitable thermal insulator since 1950. Holding very high insulator properties, Polyurethanes result in energy-saving and consequently related charges up to %60. Since the use of fossil fuels gives birth to about %80 of the world’s carbon dioxide (CO2), therefore, use of polyurethane can be a suitable method for reducing energy consumption and, as a result, reduced CO2 gas as one of the most principal causes of global warming. Moreover, polyurethane insulator while holding higher efficiency in thermal insulation, it is considered lightweight and cost-effective compared to other thermal and cold insulators.

There might be questions about resistibility against fire; which is explained by the fire resistance rate. The fire-resistance rating means the duration for which a passive fire protection system can withstand a standard fire resistance test.

Tests according to DIN 4102-1, fire behavior of building materials and building components. Classification of building materials according to EN 13501-1:

  • A Classnon-combustible materials – Test according to DIN EN ISO 1182 (non-inflammable classes)

– A1 Class: without organic content,

– A2 Class: with organic content

  • B Class: combustible materials (such as textiles, furniture, and other interiors)

– B1 Class : Flame Retardant

– B2 Class: Normal Flammability (selfextinguishing)

– B3 Class: Easily Flammable (not usable in Industrial Buildings)

In most countries, the PU of the Sandwich panel must pass the classification of B2. The purpose of the test according to DIN 4102-1: 1998-05 section 6.1 is the classification of building materials (except floor coverings) on the basis of their fire behavior. The classification of polyurethane foam in a polyurethane sandwich panel is determined by the raw material used in the foaming machine when manufacturing rigid PU foam.

A sandwich panel with polyurethane typically consists of two sheets. The sheets could be PPGI (pre-painted galvanized iron, also known as pre-coated steel, coil coated steel, color coated steel coated by a hot dip zinc substrate), PPGL (pre-painted Galvalume iron, coated by a hot dip zinc substrate),  Aluminum sheets, and paper foils. The sheets are formed or in other words grooved as required by The Roll Forming Machine.

There are two production lines for manufacturing PU sandwich panels:

Manufacturing sandwich panel methods are mentioned above whereby machinery for manufacturing sandwich panels has significant differences.

In the continuous PU Sandwich Panel Line, the speed of production is almost 10 times more than the discontinuous PU Sandwich Panel Line. Furthermore, manpower required would be significantly reduced when using continuous PU Sandwich Panel machinery. In the Continuous Sandwich Panel, Line Rock wool sandwich panel can also be manufactured by extending the equipment.

PU Sandwich Panel Sizes and Types:

There are different types of PU sandwich which can be manufactured with both continuous and discontinues sandwich panel line:

  • PU Wall Panel for Cold Rooms
    Typical Size of Cold Room Sandwich Panel: 120, 150, 170, 200 mm
  • PU Roof Panels
    The number of Grooves can be selected / Typical Size of Roof Sandwich Panel: 40, 50, 60, 70, 80, 90, 100, 120 mm
  • PU Wall Panels
    Typical Size of Wall Sandwich Panel: 40, 50, 60, 70, 80, 90, 100, 120, 150, 170, 200 mm
  • Secret Fix Panels (hidden screw sandwich panel, boltless sandwich panel, and hidden joint sandwich panel)
    Typical Size of Secret Fix Sandwich Panel: 40, 50, 60, 70, 80, 90, 100, 120, 150, 170, 200 mm
  • Solar Roof Panels
    Typical Size of Roof Sandwich Panel: 40, 50, 60, 70, 80, 90, 100, 120 mm
  • Duct Panel
    Typical Size of Duct Panel Sandwich Panel: 20, 30 mm
  • Board Panel
    Typical Size of Board Panel Sandwich Panel: 20, 30, 40, 50, 70, 100, 120, 150, 200 mm

Weight And Length Of PU Sandwich Panel

The two factors which determine the sandwich panel weight are:

  1. The thickness of skin, previously mentioned that the sheets could be PPGI (pre-painted Galvanized iron, also known as pre-coated steel, coil coated steel, color coated steel coated by a hot dip zinc substrate), PPGL (pre-painted Galvalume iron, coated by a hot dip zinc substrate),  Aluminum sheets and paper foils.
  2. The density of PU foam produced by metering or foam machine in the sandwich panel production line.

The length of the sandwich panel produced by continuous sandwich panel production depends on the usage requirements which could be a minimum of 0.5 meters to 22-meter long. Yet, sandwich panels are normally produced less than 12 meters for easier transportation and avoiding over-length cargo.

How Much Does It Cost?

The two main factors which determine the sandwich panel prices:

  • The thickness of the sandwich panel
  • The type and thickness of the skin

Therefore, the price of the sandwich panel will be different with every single specification and request. There is of course one more factor in sandwich panel prices; the country in which sandwich panel is produced. The raw material of sandwich panel could be available in some countries, so sandwich panel manufacturer can easily access the raw material, and sandwich panel might be lower in those countries whereas in some countries raw material for sandwich panel production might be imported (associated import cost to be added) and locally not available. As a result, the sandwich panel price will be higher.

Thermal Insulation of PU Sandwich Panel: 

Thermal Transmittance or K-value is the rate of transfer of heat through a structure (which can be a single material or a composite), divided by the difference in temperature across that structure. The units of measurement are W/m²K. The K-value is determined by the thickness of the sandwich panel.

The below chart shows an example of approx. weight and K-value of the sandwich panel where 40 ± 2 (kg/m³) density of sandwich panel is considered consistent and PPGI for both sides of PU foam is 0.5 mm.

The thickness of the Sandwich panel line (mm) 40 50 60 80 100 120 150 200
Weight of Sandwich Panel  (kg/m2) 10.1 10.6 11 11.9 12.8 13,4 14.7 16,8
Thermal Transmission K-Value of Sandwich Panel (w/m2 K) 0.52 0.43 0.35 0.27 0.21 0.18 0.14 0.11

Comparing 30 mm PU Sandwich Panel with Other Materials in Equivalent:


Following is the List of Advantages of Sandwich Panels:

  • Lightweight (resulting to save and use less material in buildings and reduced total costs)
  • Low heat transfer coefficient
  • Fire resistance class of B1 and B2 Low
  • Installation cost
  • Moisture insulator
  • Sound insulator
  • Appropriate mechanical features (against shear, tensile, and pressure forces)
  • Low energy consumption (cooling and heating cost-effectiveness)
  • High resistance against microbial and biologic contamination
  • Product appearance and various color options


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