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Kenplas Forum ==> Injection Molding (Machine) ==> PET preforms standards
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Normally for PET preform:
1. radial stretch ratio <=3.5~4.2;
2. axial stretch ratio <=2.8~3.1;
3. wall thickness <=4.5mm.
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Higher stretch ratio leads to higher crystalline level, higher physical strength and more excellent clarity, but more heating time and difficulty.
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The relationship between preform weight and bottle depends mainly on application; and the size of the preform depends on the stretch ratio. Ideally speaking the stretch ratio should be about 12. (Stretch ratio = Vertical Stretch ratio x Horizontal stretch ratio). Besides the wall thickness of the bottle would also define the weight of the preform. For example, for CSD applicatoins wall thickness is about 0.3mm while that for water applications it is about 0.2mm.
Based on the above factors a bottle is decided for a given preform or viceversa.
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This forum published since July 03, 2002.
Renewed on June 22, 2005. |
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