Blue barrels are constructed from plastic materials, the color typically signifying that the barrels are capable of FDA-approved transport or storage. The most common type of plastic used in manufacturing blue barrels is high density polyethylene (HDPE), which is used for its many advantageous characteristics such as high tensile strength and chemical resistance as well as its recyclability.
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There are many industries that utilize blue barrels for material handling applications including: food and beverage, for FDA-approved liquid and low viscosity food transport and storage; chemical processing, for safe transport and storage of a wide range of chemicals such as ammonium carbonate, barium chloride and carbonic acid; wastewater, for safe handling of potentially hazardous materials; automotive and aerospace, for handling and storage of lubricating oils; and industrial manufacturing, for the handling and storage of various chemicals and oils required in various manufacturing processes. An additional popular commercial and residential-based application of blue barrels is for use as rain barrels, meaning that they are used to collect precipitation during rain storms. Blue barrels are most often stocked as 55 gallon barrels, but can also be stocked as 30 gallon and even 40 gallon barrels.
Blue barrels are most commonly manufactured through an injection blow molding process. Since this process is a combination of injection molding and blow molding, it involves many more steps than either single process. As a result, injection blow molded barrels are typically made in very high volumes, in order to negate the increased cost of setting up two different molds for one process. To begin injection blow molding, a parisan made of plastic is formed when a thermoplastic preform is heated to a molten state and then injected around a hollow mandrel, which is referred to as a blow stem. Once semi-cured, the newly formed parison is soft and formable and still around the stem, from which it is placed into the blow molding chamber. The steel blow stem then extends, forcing elongation of the plastic to the desired product size, which will also enhance the tensile strength of the barrel. Next, the hollow blow stem is used to inject compressed air into the parisan. The compressed air causes the almost-molten plastic to inflate much like a balloon, resulting in compression against the walls of the mold cavity, and forces the plastic to take its shape. After cooling and hardening, the newly formed blue barrel is ejected from the mold. The blue barrel immediately exhibits a seamless design and does not need further trimming. As injection blow molding machines use multiple mandrels, they may be used to form up to 12 blue barrels at a time.
