Heat Stabilized PET

In broad terms there are two methods for producing heat stabilized bottles, the 
Single Blow and the Double Blow systems :

Single Blow

The Single  Blow  technique can be applied on a conventional   One-Step   ASB 
machine. The PET  container  is  blown inside  a heated blow mold. This  raises
the level of crystallinity of the PET, and  also  relaxes  some  of   the  stresses
induced in the PET by the stretching process so that the amount by which the 
bottles shrink when hot filled is reduced.

The  temperature  of  the  mold  is  limited by the need to ensure that  bottles 
on leaving the blow mold are rigid & will not be subject  to   deformation. Even
using special in-mold cooling systems, "single blow" methods   can  only   raise 
service temperatures to about 83°C (after storage).