Principle of rotational molding
Rotational Molding of Industrial Parts with Polymer Materials

The process can be described as follows : a mold loaded with the thermoplastic material rotates in two vertical directions of space, at a low rotational speed (2 to 40 rpm). The rotating mold is transferred to an oven whose temperature cycle is piloted by a thermal regulator. The heat is transferred by conduction from the wall of the mold to the mixture “powder/melted material/air”. While the mold is rotating, as soon as the temperature of its internal wall reaches the melting temperature of the polymer, the 1 ^st  molten polymer layer is formed on this wall under the combined effects of surface tension, shear between molten layer and internal surface of the mold and gravity. The balance of these...