Tom @ Mon Oct 23, 2006 12:45 pm wrote:Haze in the preforms could indicate that the PET is beginning to crystallize. That might also produce excessive shrinkage and release problems. Crytalization could be due to slow cooling and might also be related to the grade of PET.
Often I find that the melt temperature from the plasticating unit is too hot because the screw is run too fast and the bottle grades are very viscous. The hot melt temperature will keep the preform too hot for too long in the mold, especially the thicker parts. If you see haze in the thicker parts this is your issue. If haze occurs throughout the part then contamination is likely the issue. If on the surface, then it is a release issue.
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