Expanded Polystyrene is used in packaging extensively,
Polystyrene Food Packaging: Being an insulator, the food stays fresh, and warm or cold, as it is packed. Since the material does not react, the food is also safe and does not undergo any reaction and remains fresh!
Polystyrene is expandable and thus can be of various densities. It can thus be used in protecting layer for CD DVD cases, and other items.