TopTechnical DictionaryPET

PET

PET, i.e. polyethylene terephthalate is a linear polyester synthesized by the polycondensation reaction between terephthalic acid and ethylene glycol.
The main process medium is an atmospheric nitrogen. PET is a semi-crystalline, high-strength and high ductility engineering thermoplastic material with excellent machinability and very good sound attenuation properties. It has a wide range of applications: i.e. bottles for liquids, camera cases, tamper-proof products and textiles.

 

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PET was developed in 1941 by British Calico Printers for use in manufacturing of synthetic fibres. It was later used in photographic films, video cassettes, x-ray films, packaging etc. In the 70s, a new bottle production technology was developed using biaxial orientation blow molding, which currently is the largest field of PET application.

 

Properties:

  • high mechanical strength,
  • UV resistance - PET shows good UV resistance and low moisture absorption and can be used in outdoor applications (reduced surface treatment costs compared to metals),
  • very high wear resistance (comparable or higher than polyamides),
  • resistance to diluted acids, cleaning agents and many solvents,
  • rigidity and hardness,
  • very good electrical insulation properties,
  • high strength at high temperatures,
  • good ductility,
  • good gluability and weldability,
  • very high creep resistance,
  • low and constant friction coefficient,
  • very good dimensional stability (compared to polyacetal),
  • excellent soiling resistance,
  • improved acid resistance compared to PA and POM,
  • neutrality (approved for food contact),
  • very high resistance to high-energy radiation (gamma and X),
  • low impact resistance and crack resistance at dynamic loads (lower compared to polyamide and polyacetal),
  • good machinability and polishing properties,
  • glass transition temperature: 70°C to 115°C,
  • softening point: 265°C,
  • density: approx. 1.39 g/cm³.

     

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    Machining

    Good machinability and thermal shape stability, PET is suitable for manufacturing parts with narrow tolerance limits.

     

    Slip and abrasive properties

    Perfect for slip and abrasive applications showing low slip coefficient and high dynamic load. PET reduces the power required to drive different devices, prevents friction-induced vibrations and extends device life. It is used for manufacturing slats and slide bearings, guides and gears. Specific properties of pure PET make it a perfect material for precision mechanical components resistant to high loads and/or wear.

     

    How to identify PET?

    Polyethylene terephthalate burns with a smoky flame without a characteristic hyacinth fragrance. It does not dissolve in standard solvents, however it dissolves in hot tetrachloroethylene.

     

    PET may be relatively easily recycled using common polymer recycling methods. No by-products or waste are emitted to the environment in the PET manufacturing process.