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Why does stretch blow molding increase the strength of PET bottles?
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Plastic soft-drink bottles are commonly made of polyethylene terephthalate (PET).
Stretch blow molding increases the strength of polyethylene terephthalate (PET) bottles through the process of biaxial orientation.1
During the expansion of the parison in both diameter and length, the polymer chains are physically stretched and aligned with one another in an orderly arrangement. This alignment significantly enhances the material's strength and, specifically for PET, increases its crystallinity. By organizing the molecular structure in this way, the resulting container achieves high rigidity and durability, which are essential for its use in beverage packaging.12