engineerguy

Bill explains how the two-liter plastic soda bottle begins as a plastic tube, called a preform, which is heated and inflated with air in a bottle-shaped mold. He explains how the stretching of the preform creates a crystalline regions in the bottle's plastic (polyethylene terephthalate) that create a bottle with great strength, low permeability to carbon dioxide, but which is also lightweight—some 35 times lighter than a glass bottle of the same size. Bill explains key features of the bottles design, including: why the bottle looks like it does, why the neck has gaps in its threads, and how the tamper-proof ring works. He also discusses "hot-fill bottles" used for sports drinks and plastic juice bottles, noting the panels molded into the bottles to accommodate temperature changes. Lastly, he discusses briefly the recycling of PET bottles, although noting that about 75% of the 500 billion PET bottles manufactured annually end up in landfills or are incinerated.