Plastic tanks made by rotational
molding are made in a single seamless piece without stress.
These tanks are ideal for storing chemicals. Matching a
tank with the liquid to be stored is just a matter of 1)
matching the chemical compatibility of the liquid, 2) matching
the specific gravity rating of the tank with the density of the
liquid and, 3) checking to be sure that the plastic is able to
handle the maximum and minimum temperatures involved in storing
Rotational molding is a form of plastic
molding that produces hollow parts. Specific amounts of
plastic resin powder are put in metal molds that are then
rotated in an over on two axis. As the plastic melts, it
coasts the inner surface of the mold in an even thickness.
Once all the plastic is melted and distributed on the inside of
the mold, the mold is removed from the oven to cool. While
cooling, it continues to rotate on two axis. The resulting
part, after cooling, is formed as a single piece of hollow
plastic. It is formed without the stress that is often
built into plastic parts made from other types of molding.
This is ideal for plastic storage tanks.
Several types of plastic can be
rotationally molded. These types of plastic include
Polyethylene (usually HDPE), Polypropylene, Nylon and PVDF.
The best known brand name of PVDF is Kynar. Each kind of
plastic has different chemical resistance and temperature
tolerances. Those factors and the difference in price of
the various plastics are the reasons why you might choose a
plastic tank made from one resin instead of another.