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What are the precautions for PET bottle preform molding
Oct 14,2022
PET bottles have strong applicability and are widely used in daily necessities, daily chemical packaging and other fields. Pharmaceutical plastic bottle preforms are used as intermediate semi-finished products for subsequent biaxial stretch blow molding. Some factors of PET bottle preforms affect the quality of injection molded products , Under a certain temperature and pressure, the raw materials are filled into the mold, and processed by an injection molding machine to form a preform with a certain thickness and height corresponding to the mold. PET preforms are reprocessed into plastic bottles by blow molding, including bottles for packaging cosmetics, medicines, beverages, mineral water, reagents, etc. This method of bottle making is called a two-step method, in which the preform is injection-molded. A method of blow molding PET plastic bottles.
1. Plastic processing
Since the PET macromolecules contain aliphatic groups and are somewhat hydrophilic, the particles are more sensitive to water at high temperatures. When the water content exceeds the limit, the molecular weight of PET decreases during processing, and the product becomes discolored and brittle. Therefore, the material must be dried before processing, and the drying temperature is 150°C for more than 4 hours; generally 170°C for 3-4 hours. Check whether the material is completely dry by air jet method. Generally, the proportion of recycled PET preforms should not exceed 25%, and the recycled materials should be dry.
2. Selection of preform injection mould machine
Due to the short stabilization time after the melting point of PET and the high melting point, it is necessary to choose an injection system with more temperature control sections and less self-friction heat generation during plasticization, and the actual weight of the product (water content)) should not be less than 2 of the injection volume of the machine. /3.
