Compressive strength, measured in kilopascals (kPa) or pounds per square inch (psi), is the foam’s resistance to being squeezed. It is determined by:
- Material Density: The single most important factor. Higher density (kg/m³) directly equals higher compressive strength.
- Cell Structure: The uniformity, size, and wall thickness of the closed cells. The extrusion process creates a very uniform structure.
- Polymer Composition: The grade and formulation of the polystyrene resin used.
- Manufacturing Process: Precise control of temperature, pressure, and cooling during extrusion ensures optimal cell formation and strength.
Manufacturers test this per standards like ASTM C165 or D1621 and report values at 10% deformation (the stress required to compress the sample by 10% of its original thickness), which is the industry standard for design loading.
