? ? PET application in the field of beverage packaging to promote the rapid development of the beverage packaging industry. At the same time, the development of the beverage packaging industry has provided the development space for the application of PET.
? ?Strict control of PET injection and blowing process is the key to ensure the appearance of PET bottle and its economy.
PET characteristics: PET is a product of ethylene glycol and ethylene glycol terephthalate, and is saturated with thermoplastic polymers. PET molecules have a linear and semi crystalline state.
? ?The most simple process of producing PET is the reaction of ethylene and ethylene glycol (esterification), and then the polymer pET. Degree of polymerization varies with temperature and pressure. PET, like many plastic, has three state changes during the process, i.e., the glass state, the high elastic state, and the viscous flow regime. Which involves three temperature changes: glass temperature Tg, crystallization temperature Tc melting point Tf.
? ?Change from glassy to rubbery type called glass transition, it said the long chain segment movement. External heating can increase the degree of freedom (molecular chain), moving at the molecular glass solidification can now. Glass transition depends on the morphology of PET. When the intrinsic viscosity (IV) was higher, the degree of crystallinity was more obvious, and the degree of freedom of the molecular chain was restricted, and the Tg was higher. With the increase of temperature gradually produce local spherulite, resulting in local molecular chain due to intermolecular force and rearrangement, namely crystallization. For PET, the maximum crystallinity is about 55%, which is caused by the slow rearrangement of the aromatic ring, so that the formation of the aromatic ring hinders the formation of the crystal region.

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