Nearly all forms of plastic are made from natural gas, oil, and some types of vegetation. Plastics have been demonized as a symbol of all that is wrong with society, but nearly everyone still uses them. Even the most vocal opponents express their disapproval using a plastic computer keyboard. The manufacturing method that makes these finished products possible is called thermoforming.
The environmental impact of hydrocarbon use is difficult to ignore. Surprisingly, production of plastics uses less than 3% of all the oil and gas burned each year in the United States by vehicles. That is still a huge number, but illustrates how halting all production of plastic would do very little to end reliance on oil as a primary fuel, and would force consumer prices upward.
The process begins by transforming refined oil into a continuous sheet of polyvinyl chloride, polypropylene, acrylic, or similar related polymers. They are fed into a production line where they are heat-treated enough to become pliable, but not completely liquid. Using one of three common methods, the plastic is forced into or over a mold, cooled, and the excess removed.
During production, radiant electric devices five inches from the sheet produce heat. The amount of time plastic takes to become malleable is determined by the variety of polymer, and there are three methods that are most commonly used during molding. Vacuum forming uses principles similar to an everyday vacuum cleaner, sucking the warm plastic into a mold with carefully measured force.
When a positive force is used, it is called pressure forming. Because vacuum processes are naturally limited, positive pressure can reach higher levels, making the process more versatile. The raw plastic is usually pre-stretched in order to avoid an uneven thickness over corners. After being applied, trapped air is released from the mold, and the product is cleaned up.
Some thermoplastic processes require molds with both positive and negative sides. The warm plastic is positioned between the two, and after appropriate pressure has been applied, the material assumes the size, shape, and detailing of the interior space. While this affords greater control, costs are higher. Regardless of the process chosen, only thermoplastics can be reheated safely.
Thicker sheets are used to make different vehicle components, are molded into health care accessories, and even make an appearance in the bathroom. Thinner gauge plastic sheeting is used to package cosmetics, small individual products like screws, and fresh and processed foods. While not yet biodegradable, recycling and disposal methods have been greatly improved.
