Importance

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Abstract

Spherulites are grown in such sections as neck, neck end, bottom center and/or bottom periphery of a hollow bottle-shaped container of biaxially oriented-blow molded polyethylene terephthalate (PET) resin where the resin is not substantially subjected to orientation, thereby to improve the thermal resistance, stiffness and content resistance of such sections to almost the same extent as the biaxially oriented sections of the container such as the shoulder and cylindrical sections thereof. The aforesaid non-oriented sections of the preformed piece before being blow-molded or of the blow-molded container are first heated at or above the glass transition temperature of the resin for about 2-8 minutes and are then annealed at room temperature, with the result that such sections have a spherulite texture of an increased density and are rendered opaque.

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First Claim