Materials PET

Some characters have been described in “Types of Plastic Materials“. Here we extend more characters.

PET is used to make bottles. PET bottle has highly transparent just like a glass bottle. There are three main colors for PET bottle including clear (transparent), amber and opaque white. An easy way to discriminate opaque white PET bottle and opaque white HDPE/PP bottle is the PET bottle’s surface is very smooth while the HDPE/PP bottle’s surface is somewhat matt.

PET bottle is made via two steps. The first step is making a preform via plastic injection. The second step is making a finished bottle via stretch blowing. Tranditionally, these two steps are done in separated machines. Currently, a kind of all-in-one machine can complete these two steps in one machine, but the progross still includes two steps. Although all-in-one machine has higher efficient, it can not say the all-in-one machine must be better than machines for separated steps. A good preform requirts enough cooling time, but all-in -one machine doesn’t allow so long time. Using an all-in-one machine depends on the requirements of bottles.

A variant of PET is PETG. The character of PETG relating to the application in pharmaceutical packaging is very similar to PET. The PETG bottle is slightly softer but not much. The main difference is PETG bottle is made via injection blowing or extrusion blowing just like a HDPE bottle, so prodution progress is faster. However, the chemical resistance of PETG is a little lower than PET.