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Introduction to the production process of pet plastic bottles

TIME:2021-03-21 Share

The pet plastic bottle has better rheology in the molten state, and the pressure has a greater influence on the viscosity than the temperature. Therefore, the pressure is mainly used to change the mobility of the melt. Plastic bottles have different usage conditions in different environments, so the rheology and viscosity of the plastic bottles are effectively controlled in the molten state.

1. Plastic processing. Because pet plastic bottle macromolecule contains fat base, which has certain hydrophilicity, pellets are more sensitive to water at high temperature. When the moisture content exceeds the limit, the molecular weight of pet plastic bottle will decrease during processing. The product is colored and brittle. Because of this, the materials must be dried before processing. The drying temperature is 150°C for more than 4 hours, generally 170°C for 3-4 hours. The air shot method can be used to check whether the material is completely dry. When using materials, the raw materials should be dried to a certain extent, and different drying temperatures and time limits should be paid attention to to ensure that the plastic bottles produced have good product functions.
2. The injection molding machine uses pet plastic bottles because the time after the melting point is short and the melting point is higher. Therefore, it is necessary to select an injection system with more temperature control sections and less self-friction heat generation during plasticization. Material) The actual weight cannot be less than 2/3 of the injection volume of the machine.

pet plastic bottle / cap
3. Retention time Do not use too long retention time to prevent molecular weight drop. Try to avoid temperatures above 300°C. If the downtime is less than 15 minutes. Only need to do air injection treatment; if it exceeds 15 minutes, clean with viscosity pe, and reduce the barrel temperature to pe temperature until it is turned on again. Strict control should be carried out on the residence time of plastic bottles. Different temperatures need to be processed differently, so the time limit should be strictly controlled.
4. Matters needing attention: The recycled material should not be too large, otherwise it is easy to cause "bridging" at the unloading place and affect the plasticization. When recycling plastics, strictly control the number of recycled materials to ensure the plasticization quality of the plastic. If the mold temperature is not well controlled or the material temperature is not properly controlled, it is easy to produce "white fog" and opacity. The mold temperature must be strictly controlled, otherwise there will be undesirable events. The mold temperature is low and average, the cooling rate is fast, and the product is transparent with less crystallization.
5. Mold and gate design. Pet plastic preforms are generally formed by hot runner molds. It is better to have a heat insulation board between the mold and the injection molding machine template, the thickness of which is about 12mm, and the heat insulation board must be able to withstand high pressure. The exhaust must be sufficient to avoid local overheating or chipping, but the depth of the exhaust port should generally not exceed 0.03mm, otherwise flash will easily occur. The production process of pet plastic bottles requires strict quality system maintenance to ensure that the produced plastic bottles have good product quality and guarantee. The production process is complicated, and different production processes need to be strictly controlled to ensure that each process is carried out in strict accordance with the standards.

Lisong Machinery focuses on customized plastic container injection molding machine manufacturers, professional HDPE bottles, PP bottles, PET bottles, PS bottles, acrylic bottles and plastic bottle caps, which are widely used in health care products, food, cosmetics, pharmaceutical packaging, etc.

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