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 material used in this process begins as a continuous sheet of acrylic, polypropylene, polyvinyl chloride, or other similar polymer. That thin layer is carefully heated to the point that it becomes pliable, but not liquid. Using one of three methods, it is then applied to a specifically designed mold, allowed to cool, and trimmed. The result is a smooth, finished piece or component.
The heat is provided by radiant electrical units positioned approximately five inches from the sheet. Different polymers require specific warming periods, but once the correct temperature has been reached, they are ready to be molded into the requested shape. The most common method is called vacuum forming, which employs negative pressure similar to a home vacuum device.
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.
Many products require two-sided molds. The unformed plastic is heated, forced between the parts under pressure, and assumes the texture and shape of the space in between. This gives manufacturers much better control over important product details, but is costlier. Regardless of the method being used, only thermoplastics can survive reheating without breaking down.
Thicker gauges are used to make vehicle parts, medical industry accessories, electronic component housings, and are even important in some bathroom fixtures. Thinner gauges are perfect for packaging foods, cosmetic products, and numerous other small items such as screws or paper clips. While most are not biodegradable, methods of disposal and recycling are 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 material used in this process begins as a continuous sheet of acrylic, polypropylene, polyvinyl chloride, or other similar polymer. That thin layer is carefully heated to the point that it becomes pliable, but not liquid. Using one of three methods, it is then applied to a specifically designed mold, allowed to cool, and trimmed. The result is a smooth, finished piece or component.
The heat is provided by radiant electrical units positioned approximately five inches from the sheet. Different polymers require specific warming periods, but once the correct temperature has been reached, they are ready to be molded into the requested shape. The most common method is called vacuum forming, which employs negative pressure similar to a home vacuum device.
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.
Many products require two-sided molds. The unformed plastic is heated, forced between the parts under pressure, and assumes the texture and shape of the space in between. This gives manufacturers much better control over important product details, but is costlier. Regardless of the method being used, only thermoplastics can survive reheating without breaking down.
Thicker gauges are used to make vehicle parts, medical industry accessories, electronic component housings, and are even important in some bathroom fixtures. Thinner gauges are perfect for packaging foods, cosmetic products, and numerous other small items such as screws or paper clips. While most are not biodegradable, methods of disposal and recycling are 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 innovative plastic solutions then he recommends you visit his friends at PTM: Plastic Injection Molding Services.
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