Polyurethane sandwich panels are composite panels produced in a continuous process. The panel consists of a rigid polyurethane foam core bonded between two metal facings. Facing materials include color-coated steel, galvanized steel, Al-Zn coated steel, or stainless steel. After the metal sheets are roll-formed, a polyurethane foaming agent is injected between them. High-temperature foaming and curing create a strong bond between the core and the facings. Production takes place on fully computer-controlled continuous lines, which helps maintain uniform core density and consistent adhesion.
Color-coated steel facings typically range from 0.4 mm to 0.8 mm in thickness. Available surface coatings include polyester (PE) and PVDF fluorocarbon. The rigid polyurethane core has a density of 30 kg/m³ to 80 kg/m³ and a closed-cell content above 95% to 97%. The core contains a large number of independent sealed cells that restrict air movement and reduce convective heat transfer. The thermal conductivity of the core ranges from 0.017 W/(m·K) to 0.024 W/(m·K). Under the same energy-saving requirements, a 20 mm thick polyurethane sandwich panel provides thermal insulation comparable to a 50 mm thick polystyrene panel.
The standard effective panel width is 1,000 mm. Common thicknesses are 50 mm, 75 mm, 100 mm, 150 mm, and 200 mm, with customization available. Panel profiles include flat, micro-ribbed, water-wave, and triangular patterns, allowing architects to match different facade design requirements.
| Performance Indicator | Parameter / Specification | Basis or Remarks |
|---|---|---|
| Executive Standard | GB/T 23932-2009 | Metal-faced thermal insulation sandwich panels for building applications |
| Facing Material | Color-coated steel / Galvanized steel / Stainless steel / Aluminum | Thickness 0.4–0.8 mm |
| Core Material | Rigid polyurethane (PU/PIR) | Density 30–80 kg/m³ |
| Thermal Conductivity | 0.017–0.024 W/(m·K) | Low-conductivity products can reach 0.017–0.019 W/(m·K) |
| Bond Strength | ≥0.09 MPa | Between facing and core |
| Flexural Load Capacity | ≥0.5 kN/m² at deflection L₀/200 | Standard minimum requirement |
| Closed-cell Content | ≥95% | Up to 100% in self-skinning areas |
| Fire Performance | Class B1 (Flame-retardant) | Oxygen index ≥30% |
| Effective Width | 1000 mm | Standard |
| Common Thicknesses | 50 / 75 / 100 / 150 / 200 mm | Customizable |
Polyurethane sandwich panels offer low thermal conductivity values compared with many other insulation materials. Next-generation low-conductivity polyurethane systems can achieve thermal conductivity values from 0.017 W/(m·K) to 0.019 W/(m·K), which is about 20% better than traditional polyurethane formulations. For a given building area and panel thickness, using low-conductivity panels may reduce annual energy consumption by approximately 13.6%. Polyurethane sandwich panels produced by Xinjiang Gangzhisheng have shown measured thermal conductivity as low as 0.024 W/(m·K). These panels have been used in more than one hundred projects, including the Korla Guoxin Power Plant and Xinjiang Tianshan Aluminum.
The combustion performance of these polyurethane sandwich panels meets the Class B1 flame-retardant standard, with an oxygen index of 30% or higher. Polyurethane is a thermosetting material. When exposed to fire, the surface forms a carbonized layer and does not melt or produce burning droplets, which helps delay flame spread. The Shanxi Xinhui Food cold storage project, with an area of nearly 30,000 m², uses polyurethane sandwich panels with BASF Elastopir® SBI B1 core material. This material provides high flame retardancy and meets the fire safety requirements for large-scale cold storage facilities.
The bond strength between the facing sheets and the polyurethane core is not less than 0.09 MPa. The flexural load capacity is at least 0.5 kN/m² at a deflection of L₀/200. The continuous production process helps ensure a secure bond, which reduces the risk of delamination or blistering during long-term use.
The closed-cell content of the rigid polyurethane foam exceeds 95% and can reach 100% in self-skinning areas. This results in very low water absorption and helps prevent rainwater and condensation from penetrating the panel. The material shows dimensional stability with variation below 1% under temperature fluctuations of ±30°C, reducing the risk of cracking caused by thermal expansion or contraction. It is suitable for environments with operating temperatures from -170°C to +100°C.
In 2025, the Shanxi Xinhui Food project became the first in China to use low-thermal-conductivity polyurethane sandwich panels in a cold storage facility. The project was a collaboration between BASF and Master Cold Chain. It includes more than 50 individual spaces, such as a 22.7-meter fully automated high-bay warehouse, blast-freezing and standard freezing chambers, and processing workshops. Nearly 30,000 m² of panels were used, with facing options including single-sided stainless steel, double-sided stainless steel, and double-sided color-coated steel. This project provides practical validation of the thermal insulation and fire safety performance of polyurethane sandwich panels in ultra-low-temperature cold chain environments.
Both PU (polyurethane) and PIR (polyisocyanurate) are rigid foam cores. PIR has a modified chemical structure that provides improved fire performance and higher temperature resistance compared with standard PU. For applications with stricter fire safety requirements, PIR cores are often recommended.
Polyurethane sandwich panels with a B1 fire rating can be used in many building types, but local building codes and fire regulations must be checked first. For high-rise buildings or areas with specific fire safety requirements, a project-specific evaluation is necessary.
Panel thickness depends on the required internal temperature, ambient conditions, and energy efficiency targets. A thermal calculation should be performed for the specific project. Common thicknesses for cold storage range from 100 mm to 200 mm.
Regular visual inspection is recommended to check for surface damage, joint sealant failure, or fastener corrosion. Minor scratches on coated steel facings should be touched up with compatible paint to prevent corrosion. Keep drainage paths clear to avoid water accumulation.
Incoming raw materials are inspected for each batch, including metal facing thickness, coating type, and polyurethane raw material quality. During production, core density, panel thickness, and bond strength are monitored. Finished panels are checked for dimensional accuracy, surface quality, and packaging before shipment. Factory inspection reports in accordance with GB/T 23932-2009 are available, and third-party type test reports can be provided upon project request.
Some polyurethane sandwich panels are available with biomass-balanced raw materials. For example, BASF and Master have collaborated on Biomass Balance (BMB) polyurethane sandwich panels that have received ISCC PLUS certification. This approach helps reduce the carbon footprint of the panel production process while maintaining the same product performance. Panels can also be designed for disassembly and recycling at the end of their service life, depending on the facing and core material combination.
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