PET blank
PET blank (also PETling or PET preform ) is the injection-molded preform of the well-known PET bottle , with a finished PCO 28 mm screw thread.
The path from a PET blank to a PET bottle goes through the following steps, which are collectively referred to as stretch blow molding :
- The blank is heated (conditioned), that is, a temperature profile corresponding to the desired wall thickness distribution is introduced into the blank. Infrared heat emitters, for example, can be used for this purpose .
- The blank is clamped in a mostly three-part mold
- A mandrel goes into the blank and stretches it to the final length of the bottle
- Compressed air blows the resulting hose into its final shape
- The temperature of the bottle is brought below the glass transition temperature by cooling the tool
- The forming tool opens
- The finished bottle is ejected
A closer look at a PET bottle reveals two long vertical lines and one all-round line in the bottom area, which are typical of a three-part mold. Because of the bottle bottom geometry, the tool usually has to be moved downwards while the side parts open outwards.
If the blank is heated too much, the crystalline C-PET is formed from the amorphous A-PET at a temperature of around 140 ° C , which looks cloudy, whitish and hard and is therefore not desired for PET bottles.
Alternative use
In addition to the obvious use as a blank for PET bottles, PET blanks can also be used as a waterproof container for small objects in the open air, such as for geocaching .
literature
- Bleisch, Goldhahn, Schricker, Vogt: Lexicon packaging technology. Behr's Verlag, Hamburg 2003, ISBN 3-86022-974-5 .