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.
Even though there are environmental concerns regarding hydrocarbon pollution, the production of plastic products uses less than 3% of all the oil and natural gas burned yearly in the United States. That is still a huge number, but calling a complete halt to all production would do virtually nothing to decrease fossil fuel reliance, and would likely increase consumer costs.
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 sheets are commonly processed using radiant electrical heat coming from devices positioned around five inches away. The type of polymer being used determines how long the heat must be applied. Once pliable, there are three primary methods of achieving the final shape. The first is called vacuum forming, which uses negative pressure to draw the warm plastic into a mold.
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 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.
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 injection molding services then he recommends you visit his friends at PTM: Custom Plastics Injection Molding Company.