Most plastics are derived from oil, natural gas, and some plant materials. Although plastic products have been called the ultimate symbol of a throwaway consumer society, everyone uses them. Even the most ardent critics express their concerns via plastic computer keyboards. Thermoforming is a manufacturing process that shapes this raw material into finished products.
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.
Vacuum processes are limited to a relatively low maximum force, but pressure forming can achieve consistently stronger levels, and is more versatile. Before heating, the sheets are pre-stretched to eliminate thin spots over uneven surfaces. Once inserted into a mold under pressure, the air trapped inside is released, and any remaining excess can be trimmed away.
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 manufacture electronics housings, medical equipment for daily care needs, external car components, and even in some bathroom accessories and fixtures. Thinner sizes are used to package cosmetics, many processed and fresh foods, and small, loose items like screws. While not biodegradable, methods of recycling and disposal are constantly improving.
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.
Vacuum processes are limited to a relatively low maximum force, but pressure forming can achieve consistently stronger levels, and is more versatile. Before heating, the sheets are pre-stretched to eliminate thin spots over uneven surfaces. Once inserted into a mold under pressure, the air trapped inside is released, and any remaining excess can be trimmed away.
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 manufacture electronics housings, medical equipment for daily care needs, external car components, and even in some bathroom accessories and fixtures. Thinner sizes are used to package cosmetics, many processed and fresh foods, and small, loose items like screws. While not biodegradable, methods of recycling and disposal are constantly improving.
About the Author:
Genevive B. Mata has taught plastics molding techniques for over 15 years. He specializes in injection molding and thermoforming. If you are interested in learning more about plastic recycling solutions then he recommends you visit his friends at PTM: Custom Plastics Injection Molding Company.
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