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Precautions For Injection Molding Of Pet Bottle Embryo
Apr 14, 2017

1. Treatment of plastics As the pet macromolecule contains lipid-based, has a certain hydrophilic, granular materials at high temperatures are sensitive to water, when the moisture content exceeds the limit, in the processing of pet molecular weight drops, products with color, brittle. Trapped this, in the processing before the material must be dried, its drying temperature for 150 ℃, more than 4 hours, generally 170 ℃, 3-4 hours. The available air-jet method is used to verify that the material is completely dry. The recycling ratio generally does not exceed 25%, and the recycling material is thoroughly dried. 2, injection molding machine selection Pet because after the melting point of the stable time is short, and the melting point is higher, so need to choose the temperature control section more, when plasticizing from the friction heat less injection system, and products (water content) actual weight can not be less than 2/3 of the amount of machine injection. Based on these requirements, Huamei has developed a small series of pet-specific plasticizing systems in recent years. Clamping force is greater than 6300t/m2 selection. 3, Mould and gate design Pet bottle embryo commonly used hot runner mold molding, mold and injection molding machine template between the best to have the insulation board, its thickness of about 12mm, and the insulation board must withstand high pressure. Exhaust must be sufficient to avoid local overheating or fragmentation, but the depth of the exhaust nozzle generally do not exceed 0.03mm, otherwise prone to fly edge. 4, Melt adhesive temperature Available air-jet measurements. 270-295 ℃ Unequal, enhanced level GF-PET can be set to 290-315 ℃ and so on. 5, injection speed The general injection speed is fast, can prevent premature solidification during injection. But too fast, high shear rate makes the material fragile. The ejection is usually completed within 4 seconds. 6, back pressure The lower the better, lest wear. Generally not exceeding 100bar. usually no use. 7. Retention time Do not use excessive retention time to prevent a decrease in molecular weight. Try to avoid temperatures above 300 ℃. If downtime is less than 15 minutes. Should only be used for air shooting, if more than 15 minutes, then use the viscosity of PE clean, and the barrel temperature to the PE temperature, until then power up. 8. Matters needing attention (1) Recycling material can not be too large, otherwise prone to produce at the bottom of the "bridging" and affect the plasticizing. (2) If the mold temperature control is not good or the material temperature control improper, easy to produce "white fog" and not transparent. The mould temperature is low and uniform, the cooling speed is fast, the crystallization is less transparent.

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