Importance

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Abstract

A method and apparatus are disclosed for developing a strain crystallized morphology in blowbottles of thermoplastic material by a heat treatment process subsequent to a blow molding operation. In a first embodiment, the blow mold itself includes means for differentially heating the blown article along its length so that only those portions which have been significantly molecularly oriented are heat treated. In a second embodiment, separate mold-shaped members are mounted adjacent the blow mold to receive the blown articles to apply the desired heat treatment process. In the method, an essentially amorphous thermoplastic parison is expanded in a blow molding operation at a temperature conducive to molecular orientation and strain induced crystallization. Then, the highly molecularly oriented bottle portions are heat treated to develop crystalline growth, while other non-molecularly oriented bottle portions may be simultaneously cooled.

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First Claim