Containers made of gas-filled or foaming materials (polystyrene, polystyrene) are a special and very convenient type of packaging. Foam plastics have a low, so-called apparent density, only from 150 to 600 kg / m3 (the density of conventional thermoplastics is 900-1400 kg / m3). The foamed structure is obtained by introducing special additives into the polymer melt - gas generators (solid or liquid substances capable of releasing a significant amount of gaseous substances at high temperatures, which foam the polymer).

The mechanical properties of foams depend on the value of the "apparent" density, the peculiarities of the cellular structure and the chemical nature of the polymer itself. It can be polyolefins, polystyrene, polyvinylchloride, polyurethane. Foam plastics make trays for packing juicy products (fresh meat, fish), as well as inserts for absorbing moisture.

Packaging made of foam plastic is capable of withstanding significant loads, it protects products from shock, mechanical damage, moisture, temperature fluctuations, and the action of microorganisms. Foam plastics are durable and inexpensive to manufacture, have high buoyancy (which is sometimes not superfluous) and low thermal conductivity.