Posts
Many beautiful objects have been created by breathing air into a mass of colored, melted glass to form a hollow shape. The process dates back centuries, and in modern times has been transformed into an industrial application for producing plastic products, including containers, toys, medical devices and auto parts. That transition was made possible by the emergence of blow molding.
The process begins with a heated raw plastic tube called a parison, a word that originally referred to a mass of unformed, melted glass. Once the parison is sealed carefully inside a mold, air is forced through under pressures that range from 25 to 150 psi, evenly forcing the material onto the inner shape. The plastic is spread throughout the mold at a precise thickness, and cools quickly.
The tubes of unformed plastic consist mainly of polypropylene, polyvinyl chloride, and various forms of polyethylene. These materials are thermoplastics, meaning that they melt at a rate and consistency ideal for industrial production, unlike those which become liquid when heated. They can be custom made, and are designed to be inserted mechanically.
Once inside, the parison can be shaped in several ways. Extrusion methods employ a screw-shaped device that evenly forces the soft mass into a mold. Inside that space, pressurized air fills the cavity from the center of the plastic outward, forming the soft material into an exact duplication of the interior walls, and exactly reproducing the originally engineered shape.
Extrusion can be intermittent or continuous, depending on the style and quantity of the product. Large milk or juice containers are commonly made using variations of this method, but others are produced most effectively using injection molding. Injection forces the polymer into a core pin, which is inflated with air, allowed to cool, and then ejected.
Individual serving containers and other small items can also be manufactured using injection stretch molding. A nozzle injects melted plastic, it is allowed to cool, and then is reheated and extended. Metal exterior molds are used, and high-pressure air helps complete the process. All of these methods work well using base plastics that can be reused, often more than once.
Plastics are derived from hydrocarbons, and there is no way to ignore their environmental impact. Less than five percent of total oil production goes to plastic production, however, and intensified recycling efforts help to balance the equation. Plastics are an integral part of modern life, and he cost benefits of using these production methods are proven.
The process begins with a heated raw plastic tube called a parison, a word that originally referred to a mass of unformed, melted glass. Once the parison is sealed carefully inside a mold, air is forced through under pressures that range from 25 to 150 psi, evenly forcing the material onto the inner shape. The plastic is spread throughout the mold at a precise thickness, and cools quickly.
The tubes of unformed plastic consist mainly of polypropylene, polyvinyl chloride, and various forms of polyethylene. These materials are thermoplastics, meaning that they melt at a rate and consistency ideal for industrial production, unlike those which become liquid when heated. They can be custom made, and are designed to be inserted mechanically.
Once inside, the parison can be shaped in several ways. Extrusion methods employ a screw-shaped device that evenly forces the soft mass into a mold. Inside that space, pressurized air fills the cavity from the center of the plastic outward, forming the soft material into an exact duplication of the interior walls, and exactly reproducing the originally engineered shape.
Extrusion can be intermittent or continuous, depending on the style and quantity of the product. Large milk or juice containers are commonly made using variations of this method, but others are produced most effectively using injection molding. Injection forces the polymer into a core pin, which is inflated with air, allowed to cool, and then ejected.
Individual serving containers and other small items can also be manufactured using injection stretch molding. A nozzle injects melted plastic, it is allowed to cool, and then is reheated and extended. Metal exterior molds are used, and high-pressure air helps complete the process. All of these methods work well using base plastics that can be reused, often more than once.
Plastics are derived from hydrocarbons, and there is no way to ignore their environmental impact. Less than five percent of total oil production goes to plastic production, however, and intensified recycling efforts help to balance the equation. Plastics are an integral part of modern life, and he cost benefits of using these production methods are proven.
About the Author:
Genevive B. Mata has over 20 years of professional sales experience, 10 of them directly in the plastic pallets and materials handling industry. On her spare time she works on applied-sustainability projects. If you are interested in recycle plastic pallets, she suggests you check out her friends www.ptm.com/global.
No comments:
Post a Comment