| Demonstration Experiment on Video Objective: Pre-foaming, Drying, Mold Foaming Peter Keusch |
Experimental procedure: Pre-foaming: 100 g Polystyrene ® are boiled for 12 seconds in 750 mL of hot water in a 2 L beaker while stirring. In order to stop the pre-foaming process 1 L of cold water is rapidly poured into the beaker. Afterwardes the water is rapidly poured through the sieve. Drying: The pre-foamed particles placed on a towel are allowed to air dry. In order to absorb air, the particles are to remain on the towel for 10 minutes. The mold used consists of two hemispherical parts that fit together forming an empty ball-shaped cavity. The two dry parts of the mold are filled with the pre-foamed polystyrene beads. One part of the mold covered with a plastic plate is put on the other part. After the plastic plate is removed the two parts of the mold are bolt together. The polystyrene-filled mold is placed for 10 minutes into a beaker containing boiling water. Result: After foaming the mold is cooled down by cold water. Afterwards the mold is opened and carefully the polystyrene ball is taken from the mold. 
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