Expanded polystyrene, manufactured from styrene, is a thermal plastic material supplied to moulders in the form of a polystyrene bead. The beads, which contain a blowing agent, are processed and moulded into low-density foam articles, such as protective packaging, foam insulation and building and construction.

Refers to a lightweight cellular plastic material available in block form and in various tile sizes.

A roof insulation board formed from expanded beads of a plastic polVmer molded into blocks and then cut to size.