Where do plastic bottles come from?
The majority of plastic drink bottles that you use every day are made of polyethylene terephthalate or PET. The PET material undergoes a four-step process to become the bottle you know:
1) The preform
A preform looks like a test tube, but it is actually a miniature bottle. The neck is the only part in its final form. The preform is made by heating plastic pellets to 270°C (recycled pellets can be used). These pellets will be mixed to create a homogenous paste that will be injected into a mold to become the preform.
2) Reheating
The preform regains its plasticity when reheated to about 100°C by infrared lamps. The intensity and distribution of the heat is very important to set the material and create a finished product with excellent visual and mechanical properties.
3) Stretching and blow molding
The preform is inserted into the final mold. It is stretched and blow molded under high pressure to create the bottle’s final shape:
- A stretching rod elongates the preform while blowing air into it to inflate the preform like a balloon,
- Compressed air presses the material against the mold walls to give the bottle its volume and final shape,
- A degassing process allows the bottle to retain its shape when it returns to atmospheric pressure.
4) Product packaging
The bottle is filled, capped, labeled, grouped in packs, and placed on a pallet so that it can be shipped to stores and stocked on shelves.
Except for preform manufacturing, all of these steps occur on the same production line.
