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Materials Processes



Rotational Casting

The process of forming hollow articles from fluid materials by rotating a mold containing a charge of the material about one or more axes at relatively low speeds until the charge is distributed on the inner mold walls by gravitational forces and hardened by heating, cooling or curing.  Rotation about one axis is suitable for cylindrical objects. Rotation about two axes and/or rocking motions are employed for completely closed articles.  The process dates back to 1855, when a British patent was granted for the rotational casting of hollow articles from molten metals.  Vinyl plastisols were first used in the process in 1947 by Claude Delacoste, a French toy manufacturer.  The process of rotational casting of plastisols comprises placing a measured charge of plastisol in the bottom half of an open mold, closing the mold, rotating the mold about one or more axes in the presence of heat until the charge has been distributed and fused against the mold walls, cooling the mold until the deposit is of sufficient strength, opening the mold and removing the article. [LW]


Rotational Molding

A process that is a variation fo the rotational casting process utilizing dry, finely divided sinterable powders, such as polyethylene rather than fluid materials.  The powders are first sintered, then fused against the mold walls.  This variation of the process dates back to 1947, when a British patent issued to I.C.I. ltd. for the rotational molding of powders such as polyethylene and PVC. [LW]