This is the material used in aircraft wings and control surfaces, as well as surfboards. It was chosen because its strength properties are well matched to the need of these particular structures, and because it can be hot-wire contoured without generating poisonous gases. It has the strong disadvantage of being soluble in Styrene monomer, which is a major part of polyester and vinyl ester resins, and it is softened badly by exposure to petrol and several other solvents. It is processed by expansion or extrusion.
In addition to an unpredictable strength level, the pattern of expanded beads usually leaves an inter-connecting web of tiny spaces which makes the finished material permeable to most liquids and gases.
We do not supply polystyrene foam but can inform of reputable companies that you can contact.