The Methods Used to Manufacture Thermoplastics
Thermoplastics serve a variety of different functions, typically fulfilling commercial plastic needs. They most often are used for car parts, product packaging and for any other molded plastic needs. Characterized by their ability to become malleable at high temperatures, thermoplastics are shaped and hardened as their temperature cools. Thermoplastics are capable of being reheated and reshaped over and over again, making them highly recyclable.
The most basic component of a thermoplastic is the chemical mixture that is combined to create a thermoplastic granule, which is later used in the manufacturing process. The most common chemicals used to create granules are polypropylene, polyester, acrylics, nylons, spandex-type polyurethanes, cellulosics, polyethylene and polystyrene. All these elements are developed in either combination or used singularly, depending on what thermoplastic is being produced. Manufactures tend to vary the mix within their thermoplastics; however they all maintain the basic properties of a thermoplastic--malleability and recyclable. Combined in a large mixing pot, the mixture is heated; dye is added for color and then cooled. While the mixture is cooling, it is separated, drying into small granules.
Thermoplastics are almost all sold in packages of plastic granules. The small granules are shipped in the granule shape for transportation and convenience when separating quantities for processing. The granule form factor makes it easy for manufacturers to measure how much plastic needs to be melted down for use. The next step for manufacturing thermoplastics is adding the granules to a large container, where they are melted down slowly, sometimes using hot water. The result is a viscous plastic liquid. When the granules have been completely melted, they are ready to be set in a mold.
Injection molding is one way to manufacture and shape thermoplastics. Because thermoplastics are viscous in nature when heated, they need to be set in a mold, where they are provided a shape and allowed time to cool. Injection molds are constructed from steel or a hardened alloy and constructed to shape thermoplastics as they cool. As the name implies, the thermoplastic liquid is injected into the molding, where it may remain for a couple of hours as it cools. After cooling, thermoplastics are hard and ready for commercial purposes.