Typically the production of plastic bottles has a number of stages to it. Bottles that are used to hold drinking water are generally made from Polyethylene Terephthalate or PET as it’s commonly known as. PET is a brilliant material to manufacture bottles from because it’s strong, durable and light.
What is PET?
PET belongs to a group called thermoplastic polymers, also known as thermo softening plastics which are a group of plastics which when heated to a certain temperature become moldable and then solidify upon cooling. Because of this, PET can be moulded into any shape and can be transparent or opaque if needed. Thermoplastics, however typically have a high molecular weight making them heavy for their size.
How is PET produced?
PET is produced from petroleum hydrocarbons, terephthalic acid and ethylene glycol. All of these are combined at high temperatures, typically 250 Degrees Celsius where the product goes through a polymerization process. This process includes removing excess ethylene glycol and removing water from the product, after this the polymer is cooled, forming pellets of PET. These pellets can be stored for long periods of time and when needed can be heated to a molten state that can be moulded and extruded into almost any shape.
How are plastic bottles manufactured?
Once the PET is in a molten state it is placed into a mould, it is then formed into a tube through a process called injection moulding. This tube of PET is then moved into a bottle-shaped mould where pressurized air is blown into the hot PET, causing it to take the shape of the mould. To ensure that the PET retains it is cooled, usually with cold water or carbon dioxide.
What liquids can PET bottles not appropriate for?
PET bottles are not suitable for pesticides, agricultural chemicals, household and industrial cleaners, solvents, flavourings, additives, waxes, petrol, gasoline, kerosene and acetones. This is due to their corrosive nature which can deteriorate PET bottles. For these applications, Fluorine-treated HDPE bottles are generally used. These bottles are exposed to Fluorine gas during the manufacturing process.