... era of plastics began with the appearance of plastic foams This period might be called the Plastic Foam Age.” Plastic foams can be called expanded plastics, cellular plastics or foamed plastics,... Spraying of foams Extrusion of foams using expandable beads or pellets Injection molding of expandable beads or pellets Rotational casting of foams Frothing of foams, either by introduction of air... preparation of thermoset foams (e.g polyurethane foams) 8 Handbook of Plastic Foams of The “electrical double layer” effect, i.e the orientation electrical charge on each film surface due to the use of