|Plastics ProjectsPET Preform/Bottle Project|
PET Preform Injection Molding
|PET Preform Processing:|
|Drying and Dehumidifying of PET|
PET is a kind of moisture absorption plastics, usually its water
content is about 0.05%. To get perfect PET preform (transparency and
physical performance), also to enhance molding efficiency, the water
content of PET resin should be <=0.005%. Therefore necessary drying
of PET is required.
The common drying methods:
Drying target is to get moisture level <=0.005% (at the same time, AA level should be strictly controlledto avoid peculiar smell in the drink)
The best drying temperature and time are decided by IV value of PET resin. But generally speaking, it should be 150~ 1700C for about 4 hours.
If dried PET contact air with relative humidity 35~40% for 12 minutes, it's moisture content will reach 0.005%. Long-time drying will reduce its IV value. So it is better to shorten drying time. Drying time should not exceed 7~8 hours.
|Cooling of Preform Mold|
|Cooling of preform mold is also very important. It affects preform's quality directly. The temperature of cooling water should be 15~200C, and the pressure of cooling water should be around 5Bar. Water chiller is suggested.|
For injection machine, temperature of nozzle and front zone should
be about 2800C, and middle zone around 2820C,
rear zone around 2750C. The temperature of hot runner in
preform mold should be around 2700C.
These temperature vary a little bit with IMM, preform's design and weight, mold's structure and cooling, etc.
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