The plastic manufacturing process refers to the series of steps required to turn raw oil and natural gas into plastic products, such as cups, hoses, pipes, and straws. It is a very complicated process that first begins with transforming oil and natural gas into hydrocarbon monomers that are then linked together into long chains known as polymer plastics. Based on the type of monomers linked together, the process can produce a variety of different types of polymer plastics, such as polyethylene terephthalate (PET), high density polyethylene (HDPE), and polyvinyl chloride (PVC).
Once these plastic polymers have been created, the next step in the process is to transform these simple polymers into complex consumer products. The four sub-processes that may be used to do this are injection molding, extrusion molding, blow molding, and rotational molding. Each process produces a different type of plastic product.
Injection molding is a plastic manufacturing process wherein plastic polymers that have been compressed into plastic pellets are fed into an injection molding machine. These machines mold the pellets into the correct shape and add additives to give them the correct color and texture. This process produces plastic products such as butter tubs, yogurt containers, closures, and fittings.
Extrusion molding is practically the same as injection molding, in that it molds plastic pellets into shapes. The difference is that this process also uses a shaped die to give the plastic mold a tube like shape. As such, this plastic manufacturing process is used to create pipes, tubes, and wire insulation.
Blow molding is a more complicated process that is used to create hollow plastic products with an opening or neck. The two types of blow molding are injection blow molding and extrusion blow molding. Both processes involving turning plastic pellets into molds and then injecting air into the molds to make them hollow. The difference is that injection blow molding can only produce small containers, whereas extrusion blow molding isn’t limited by size.
The fourth plastic manufacturing process, rotational molding, is the most complicated and expensive. Like the other processes, it turns plastic pellets into a mold. The difference is that the mold is then rotated to create complex hollow shapes. Where rotational molding differs from blow molding is that the hollow products it produces are entirely closed, and they do not have an opening. Such products include plastic toys and furniture.