Fire performance is one of the most critical engineering considerations when selecting a foam core material for sandwich panels, especially in transportation, marine, architectural, and industrial applications. Different foam cores exhibit fundamentally different behaviors under heat exposure due to their polymer chemistry and cell structure.
XPS (Extruded Polystyrene) is highly flammable unless treated with flame retardants. Under fire conditions, XPS tends to soften rapidly, shrink, and release combustible gases. Although it offers excellent insulation performance, its fire rating is generally limited, making it unsuitable for strict fire-code environments without additional protective layers.
PU (Polyurethane) foam provides excellent thermal insulation but also presents combustion risks. Standard PU can produce dense smoke and toxic gases during combustion. Modified PIR (Polyisocyanurate) versions improve fire resistance significantly, but conventional PU still requires careful fire engineering design.
PVC foam core performs much better in fire resistance because PVC contains chlorine, which contributes to self-extinguishing behavior. High-grade structural PVC foams used in marine and rail applications often comply with international fire standards such as:
- IMO FTP Code
- EN45545
- ASTM E84
PET foam has emerged as a strong environmentally friendly option with relatively balanced fire performance. Some flame-retardant PET grades achieve low smoke emission and reduced toxicity compared to traditional foams.
From an engineering perspective, fire resistance is not determined solely by the core itself. The total sandwich structure—including face sheets, adhesives, laminates, and coatings—must be evaluated as a complete fire system.
