Closed-cell PVC foamboard

Closed-cell PVC foamboard is a light-weight rigid material used primarily in the manufacture of signs and displays. It is considered robust for outdoor use, being immune to rain and resistant to wind and sunlight.

PVC foamboard is distinct from the extra-lightweight foamcore board, laminated of foam and card surfaces, used for indoor signage and modelling.

Its material properties have also made it extremely popular among makers of models and props, and builders of yachts and composite experimental aircraft. Like PVC, closed-cell PVC foamboard is solid and has a very rigid structure. Where it differs is in its closed-cell foam structure, which makes it very light (as little as half the weight of solid PVC), highly resistant to moisture and some chemicals, and very easy to cut and shape. It also has thermoplastic properties, and begins to soften at around 65°C. Typically, closed-cell PVC foamboard can be cut as easily as wood, softened and shaped by immersing in boiling water or with a standard heat gun, and painted with standard automobile paints.

One drawback to PVC materials is that hot working them produces noxious fumes containing hydrochloric acid and potentially even dioxins. These are a respiratory hazard in a workshop and the acid fumes are so serious that they may damage equipment. Some heat-based processes, notably laser cutting, are generally considered impossible owing to the equipment risk. Where PVC materials are cut by laser, this is a highly specialist process requiring adapted machines and acid-specific fume extraction and filtering.

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Foam board for different projects