The expandable polystyrene is a translucent bead composed of polystyrene and a 

foaming agent. The blowing agent is n-butane, pentane, heptane, petroleum ether or 

dichlorodifluoromethane. The most common ones are pentane and petroleum ether. 

Commercially available expandable polystyrene having a blowing agent content of ab-

out 6%, an apparent density of 680 g/l, and a bead diameter of 0.25-2 mm.

   The process of producing foamed plastic parts using expandable polystyrene pellets 

is as follows:

1.Pre-expansion

    The expandable polystyrene beads are heated to heat-vaporize the blowing agent, 

thereby expanding the volume of the beads to ensure that the molded product reaches 

a prescribed density and uniformity.

2. Ripening

  The pre-expanded beads need to be stored for a period of time, and the air is absorbed 

for aging to prevent shrinkage after molding. Usually done in large silos or open contain-

ers.

3. Forming

Commonly used molding methods are steam heating molding and extrusion.

(1) Steam heating molding method is divided into steaming cylinder foaming and hydraulic 

machine direct steaming foaming according to the heating method.

①Steam foaming method is suitable for producing small, thin-walled and complex shaped 

plastic parts

② The hydraulic press directly through the steam foaming method is suitable for producing 

foam sheets with a large thickness.

(2) Extrusion foam molding

Extrusion foam molding is suitable for the production of sheets and films.