Haze caused by Oligomers in PET when moulding

I am trying to find out about what causes the haze around features in Hot-Fill PET Bottles when moulding. I have been told that it is caused by Oligomer build up in the molds, which then at regular intervals, needs to be removed from the molds, in this case, by dry ice blasting.

If someone knows of this, and a cure, or method of controlling or reducing this effect.

All of the above is in relation to Blow Molding PET bottles that are filled at 83 deg C.

Thanks Jeff (Moody Blue)

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Moody Blue
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Thought this was due to crystallization of unoriented parts like bottle mouth and is normal. Only hot fill bottle I ever saw was like that. I believe that there is a cyclic dimer in PET which could also be a nucleating agent. Frank

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