Plastic covers may be as simple and versatile as tarps, which can be securely tied down in order to protect objects. This type of covering is not, however, easily applied in situations requiring a complete or airtight seal. Plastic covers are found in electronics, manufacturing, food processing, packaging, storage and shipping industrial settings where they may cover items such as bins, keyboards and large equipment. These items reduce contamination and prolong the working life of machinery as well as the shelf-life of certain food items. Domestic covers are also popular for such uses as furniture covers as well as storage and packaging. To suit such varied applications, plastic covers may be rigid or semi-flexible and may be clear, translucent or opaque. Colored covers are also popular as they allow for easy organization and identification. A wide range of sizes and dimensions are also available.
While several manufacturing processes may be used in the production of plastic covers, vacuum forming is ideal as it allows for the inexpensive production of lightweight elements that fit exactly to an object, product, machine or container. This thermoforming technique begins with extruded or rolled plastic sheets of the desired thickness that are fed into a pre-heating machine. Electric, infrared or natural gas heaters warm the materials to the temperature at which they become soft and pliable, but not fluid. Next, the still warm sheets are carefully guided into a form station that holds a pre-made mold. Presses, stamps or air pressure force the material to adhere and conform to the shape of the mold, often the inverse of the intended cover. A vacuum is employed to suction all excess air from the confined space, further pulling the plastic material into the mold. While in place the plastic is cooled until it reaches the desired rigidity. The final cover is ejected with reverse air flow before being trimmed or otherwise finished. Plastics such aspolycarbonate, noryl, PVC, royalite, polyurethane and vinyl are commonly formed into covers, but may require additional protective coatings for special properties such as UV blocking and moisture resistance.