What is the full form of PET?
PET: Polyethylene Terephthalate
PET stands for Polyethylene Terephthalate. It is a type of plastic that is clear, tough and shatterproof and is widely used in the manufacturing of plastic bottles, film packaging, fabrics, moulded parts of automotive, etc. In its natural state, it is very flexible and colourless. However, depending on the processing method, it can be rigid or semi-rigid. PET resembles very much to Polybutylene Terephthalate chemically.
We can say that it is a general-purpose thermoplastic polymer from the polyester family of polymers. Polyester resins have a wide range of properties such as thermal resistance, chemical resistance, mechanical and dimensional stability. These properties make it one of the most recycled thermoplastics. Its recycling symbol is ‘1’.
Key Properties of PET Resin:
- Its strength and stiffness are higher than PBT.
- It is light-weight and strong so can be transported easily without any damage.
- It has gas and moisture barrier properties.
- It is a good electrical insulator.
- It can be used over a wide range of temperature, from minus 60 to 130 degree centigrade.
- It has a higher heat distortion temperature (HDT) than PBT.
- It is a better alternative for glass in some applications as it is shatter-resistant.
- It is approved by the FDA as a safe material for contact with food items and beverages.
Chemical Properties:
It is resistant to alcohols, oils, greases, and diluted acids. However, it is less resistant to aromatic hydrocarbons, and diluted alkalis.
Besides so many advantages, there are also some limitations of Polyethylene Terephthalate:
- The impact strength is less than PBT.
- Its crystallization rate is slow than PBT, so its moldability is less than PBT.
- It is affected by boiling water.
- It is sensitive to strong bases and alkalis.
- It has poor burning behaviour.
PET can be blended with other thermoplastics and thermosets to improve its performance and to use it for different purposes. The purpose of producing its blends is to improve cost-effectiveness and its properties such as mechanical strength, flame retardancy, processability, etc.
Major Uses of PET products:
- For manufacturing water bottles and carbonated soft drinks bottles like coca cola, Pepsi bottles, etc.
- To create packaging trays
- To produce PET film to use in tape application
- To make the cosmetic jars, microwave containers, and other such packaging items
- To make mesh fabrics required in printing, filter oil, filter cloth, woven belt, etc.
- To make wiper arm, gear housing, engine cover, etc.
- To make polyester fabrics that are flexible, firm and resistant to shrinkage as compared to cotton
- Besides this, the recycled PET can be used for various other purposes such as to make carpets, tote bag, comforter fill, film sheet, strapping, etc.
How is PET made?
It is made by the polycondensation reaction of the monomers obtained by the esterification reaction between terephthalic acid and ethylene glycol or by the trans-esterification reaction between dimethyl terephthalate and ethylene glycol. In this reaction, the PET is produced in a molten form which can be spun to fibres or moulded into different shapes.