**3. Polymer foaming**

In parallel with other technologies a fast development in foaming technology of plastic parts is observed, driven primarily by the transportation sector demands. The main reason is that porous components allow to reduce the amount of raw materials and fuel consumption at the same time. Another characteristic of foams is thermal insulation, therefore an important application field is insulation of buildings and industrial constructions. A typical example is polystyrene foam, which is used in the construction industry for over 50 years. Polyurethane and polyethylene foams have been used for insulations of pipelines, air ducts, containers, solar collectors etc. (Fig. 7). Plastic foams are used extensively for thermal insulation of refrigerators and freezers.

Fig. 7. Foam insulation made of synthetic rubber ARMAFLEX HT (www.azflex.pl)

Fig. 6. Principle of gas-assisted injection molding (acc. to www.cinpres.net)

In parallel with other technologies a fast development in foaming technology of plastic parts is observed, driven primarily by the transportation sector demands. The main reason is that porous components allow to reduce the amount of raw materials and fuel consumption at the same time. Another characteristic of foams is thermal insulation, therefore an important application field is insulation of buildings and industrial constructions. A typical example is polystyrene foam, which is used in the construction industry for over 50 years. Polyurethane and polyethylene foams have been used for insulations of pipelines, air ducts, containers, solar collectors etc. (Fig. 7). Plastic foams are used extensively for thermal insulation of

Fig. 7. Foam insulation made of synthetic rubber ARMAFLEX HT (www.azflex.pl)

**3. Polymer foaming** 

refrigerators and freezers.

Cellular structure of foams allows also sound and vibration damping, which has been used in sound insulating panels, upholstery in furniture, car seats, protective pads etc.

Cellular plastics may be manufactured either by the periodic or continuous technology, using chemical or physical foaming agents. The conventional foams have cells of large size (0.1-1 mm) and broad size distribution (Fig. 8), therefore their mechanical properties are inferior to that of bulky polymers. The cell density of conventional foams is in a range of 104 - 106 cells/cm3.

The microfoams contain much higher number of cells (>109/cm3), which size is markedly smaller (ca. 10 μm). Such materials exhibit better performance than the conventional foams, with higher mechanical properties and better thermal insulating characteristics.

Fig. 8. Polystyrene foams – conventional (left) and microfoam (www.trexel.com)
