PET injection molding for household products
PET plastic injection molding process full analysis:
PET, full name polyethylene terephthalate, is a popular material widely used in plastic packaging. Although blow molding is a common processing method for PET plastics, injection molding also has its unique advantages. Let's learn about the injection molding process of PET plastics!
PET characteristics: PET's glass transition temperature is about 165℃, while the material crystallization temperature range is between 120~220℃. At high temperatures, PET has strong hygroscopicity, especially for glass fiber reinforced PET materials, high temperatures may also cause bending deformation. By adding crystallization enhancers, the degree of crystallization of the material can be increased, thereby enhancing its performance.
The key to the injection molding process. Injection molding is mainly used to enhance the molding of PET, usually using a screw injection machine. The screw needs to be hardened to prevent wear after long-term use. The length of the injection machine nozzle hole should be as short as possible, and the diameter should be controlled at about 3mm. The melting point of enhanced PET is as high as 260℃, so a high-power heater needs to be installed to prevent nozzle clogging. The tip of the nozzle hole is preferably processed into a reverse cone so that the molten material in the flow channel and nozzle can be easily cut off.
Selection of injection molding machine. PET injection molding usually uses a screw injection molding machine. It is recommended to use a mutant screw with a check ring on the top, which has a high surface hardness and wear resistance. The recommended length-to-diameter ratio is L/D = (15-20): 1, and the compression ratio is about 3: 1. Too large L/D may cause the material to stay in the barrel for too long, and excessive heat may easily cause degradation, affecting the performance of the product. If the compression ratio is too small, there will be less shear heat generation, poor plasticization, and poor product performance. On the contrary, too large a compression ratio may cause more glass fiber fractures and reduced mechanical properties.
Details during processing. When processing glass fiber reinforced PET, the inner wall of the barrel is severely worn. It is recommended to use a barrel made of wear-resistant material or lined with wear-resistant material. It is better to have a short nozzle, the inner wall requires polishing, and the aperture is required to be as large as possible. It is better to use a hydraulic brake valve nozzle. The nozzle must have insulation and temperature control measures to ensure that the nozzle will not freeze and clog. However, the nozzle temperature should not be too high, otherwise it may cause drooling. Before starting molding, you must use low-pressure PP material and clean the barrel.
Through the control of these details, we can better master the injection molding process of PET plastics and produce high-quality PET products. Whether it is packaging bottles or other PET products, this knowledge will provide you with strong technical support!
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