Causes and solutions for yellowing and bubbles in PET bottle embryo.
During the production process, PET bottle embryos occasionally turn yellow and have bubbles, which not only affects the appearance of the product, but may also affect its physical properties. These problems are usually caused by raw materials, process control and equipment factors.
Causes of yellowing and bubbles
1.Raw material factors:
The impurity content in PET raw materials is high, especially heavy metal ions and ash. These impurities will decompose and oxidize at high temperatures, causing the product to turn yellow.
The moisture content in PET raw materials is too high. At high temperatures, moisture will cause PET to decompose and produce by-products such as acetaldehyde, causing the product to turn yellow and bubbles to appear.
2.Process control:
Injection temperature that is too high or too low will cause the product to turn yellow and produce bubbles. Too high a temperature will accelerate the decomposition of PET, while too low a temperature will cause poor material fluidity and difficulty in removing bubbles.
Improper injection pressure and speed control. If the injection pressure is too high or the speed is too fast, it is easy to entrain air in the material and form bubbles.
3.Equipment factors:
The screw and barrel of the injection molding machine are seriously worn, resulting in uneven mixing and easy generation of bubbles.
The drying equipment has poor performance and cannot effectively remove moisture from the PET raw materials.
Solution
1.Raw material control:
Select high-quality PET raw materials to ensure that their impurity content and moisture content are within the control range.
Carry out strict inspection of raw materials entering the factory, especially the detection of moisture content and impurity content.
2.Process optimization:
Adjust the injection molding temperature to keep it within the appropriate range, usually 270-290°C.
Optimize the injection molding pressure and speed to ensure that the material is evenly filled in the mold and the air is excluded.
Regularly maintain and check the screw and barrel of the injection molding machine to ensure that they are in good working condition.
3.Equipment upgrade:
Introduce a dehumidifier dryer. The drying of PET raw materials is the key. It is recommended to use an efficient dehumidifier dryer to ensure that the raw materials are fully dried before entering the injection molding machine. The dehumidifier dryer can effectively reduce yellowing and the generation of bubbles by reducing the humidity in the air and preventing the PET raw materials from absorbing moisture.
Focus: Application of dehumidifier dryer
Principle and advantages of dehumidifier dryer:
Dehumidifier dryer continuously removes moisture from dry air through a combination of dehumidifier wheel and regeneration heater.
More efficient than traditional hot air dryer, it can reduce air humidity to extremely low level, ensuring that PET raw materials are completely dried before entering the injection molding machine.
Simple operation, high degree of automation, can continuously and stably provide dry air, and improve production efficiency.
Specific steps for using dehumidifier dryer:
Installation and commissioning: Select the appropriate type of dehumidifier dryer according to the needs of the production line to ensure that it can meet production requirements.
Set drying parameters: According to the characteristics of PET raw materials, set the temperature and time of the dehumidifier dryer, generally drying at 160-180°C for 4-6 hours.
Regular maintenance: Regularly clean the dehumidifier wheel and replace the filter to ensure the stable operation of the dehumidifier dryer.
Conclusion
By optimizing raw material selection, process control and equipment upgrades, especially the introduction of efficient dehumidifier dryers, the quality of PET bottle embryos can be significantly improved, yellowing and bubble problems can be avoided, and production efficiency and product qualification rate can be improved. This will not only enhance the competitiveness of enterprises, but also meet the market demand for high-quality PET bottle embryos.
