At first glance similar to expanded polystyrene (EPS), XPS conceals a completely different production DNA. Identifiable by its bright colours (blue, pink, yellow or green), it is the material that supports the foundations of modern buildings without fearing water.
While EPS is obtained by expanding beads that join together leaving interstitial micro-voids, XPS is produced by continuous extrusion. The molten resin, mixed with a blowing gas, is forced through a die creating a structure made 100% of closed cells, externally sealed by a compact skin. This architecture physically prevents capillarity: water, even under strong hydrostatic pressure, cannot penetrate the panel.
The structural density gives XPS an exceptional compressive strength (up to 700 kPa), making it suitable beneath reinforced-concrete foundation slabs. Its closed-cell structure, however, makes it a strong vapour retarder (mu > 150): for this reason it is not recommended on breathable facades.
Standards
European and international references applicable.
Physical properties
Usage environment
XPS dissolves instantly on contact with organic solvents (acetone, paint thinners) or cold bituminous waterproofing containing solvents. Only cement mortars or specific polyurethane adhesive foams must be used for bonding.