PET chemical called ethanol terephthalate, also known as polyester.
Now is the most used GF - in the customers
PET, mainly playing bottle embryo.
The rheological properties of PET in the molten state, stress on the influence of the viscosity is bigger than the temperature, therefore, mainly from the pressure to change the melt flow rate.
1, plastic processing because of PET macromolecular contains aliphatic, has certain hydrophilicity, aggregate at high temperature is more sensitive to water, when the moisture content is more than the limit, in the processing of PET molecular weight drops, products with color, crisp.
Trapped here, in front of the processing must be carried out on the material drying, the drying temperature is 150 ℃, more than 4 hours, generally is 170 ℃, 3 -
Air-launched available to test whether the material completely dry.
Generally not more than 25% recycled material and recycled material to dry thoroughly.
2, selection of injection molding machine
PET since the stable time is short, after melting point and melting point is high, so need more temperature control section and plasticizing the friction heat generating less injection system, and the products (
Water cut materials)
Actual weight can not less than two-thirds of injection machine.
Based on these requirements, the injection molding machine in recent years, developed a series of PET special molding machine.
3, mould and PET bottle embryo gate design mold hot runner mould is commonly used in molding, between the mold and injection molding machine template must have the best insulation board, its thickness is about 12 mm, and heat insulation board must be able to bear high pressure.
Exhaust must be sufficient to avoid local overheating or fracture, but its vent depth generally not more than 0.
3 mm, otherwise prone to flash.
4, melt temperature available air-launched measure method.
GF - 295 ℃, enhance the level
PET can be set to 290 -
315 ℃, etc.
5, generally faster injection, injection speed can prevent premature solidification injection.
But too fast, high shear rate makes material brittle.
Shot is usually done in 4 seconds.
6, the lower the back pressure, the better to avoid wear and tear.
Is generally not more than 100 bar.
Usually do not need to use.
7, residence time, do not use the long residence time, in order to prevent the molecular weight decreased.
As far as possible avoid temperature above 300 ℃.
If the downtime is less than 15 minutes.
Just make air-launched processing;
If more than 15 minutes, then use PE clean, viscosity and the barrel temperature drop to PE, until it is.
8, note (1) recycling materials can't be too big, otherwise easy to produce the material & quot;
Bridge & quot;
2 if the mold temperature control is not good or improper material temperature control, easy to produce & quot;
White mist & quot;
And not transparent.
Die temperature low and uniform, cooling speed, transparent crystal is less products.
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