Polyethylene terephthalate (PET) was developed in 1941 in the course of polyester production by John Rex Whinfield and J. T. Dixon.
The further development was then continued by the British chemical company ICI and the American company Du Pont. This led to the production of the first PET fibres, which spread worldwide, especially from 1970 onwards. The polyester fibres were used for textile production and are still used in various fields.
PET is obtained in polyester production and can be further modified with different molecules to obtain different properties. The PETG used in 3D printing is a PET extended by a glycol. This gives the material special properties and can also be melted down more often without the material losing transparency or becoming brittle.
PET is obtained by polycondensation, in which monomers are fed into polymers by condensation reactions. The reaction produces, among other things, intermediates, such as oligomers, which react themselves and form macromolecules.
For example, in the reaction of terephthalic acid (C8H6O4) with ethandiol (C2H6O2) occurs under separation of a polyester from a water molecule. If this reaction is multi-stage, it is called polycondensation.
In 3D printing, the PETG is known for its special optical properties and ease of use, along with the good print results. In addition, it has a high mechanical resistance, which is why it can also be used for large printed pieces. The high chemical resistance and 100% reusability as well as the odourless printing make the material attractive for a wide range of applications.
Special properties of the PET are resistance to inorganic acids (mineral acids), and the high breaking strength. For these reasons, THE PET is used in many ways. PET also has special recycling properties. In Europe, 48.5% of PET bottles are now recycled.
The material is colourless and transparent when undyed and can be used for special applications.
In addition to the production of plastic bottles, PET applications can also be found in the processing into textile fibres – used in sports clothing – or as the main material of plastic prostheses. The material is also used for foils, vases and textile fibres. Other applications are generally where a high level of transparency is required.
Thanks to its low warping and ease of printing, the filament is easy to access. To get the most out of the print object, it can either be sanded or coated with clear varnish to get a smooth surface.