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Molding Technology for PLASTRON® PAX-GF(CF) Grades


Long Fiber Reinforced Thermoplastics

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Molding Technology for PLASTRON® PAX-GF(CF) Grades


• Drying the material

PLASTRON® PAX-GF(CF) grades use a form of packaging that prevents moisture absorption. If the package has just been opened, there is no particular need to dry them.

However, if the pellets are left out after the package has been opened, they will need drying.

Dry for around three hours at 120℃ using a vacuum dryer.

Natural materials will change color due to oxidation at temperatures of 90℃ or higher, so please be careful. This is not a problem with black-colored materials or CF grades.


• Resin temperature

Cylinder temperature setting range is from 240 to 290℃.

Grades with high fiber content have poor flowability, so we recommend setting a temperature in the higher end of the above setting range for these grades.

Flowability, appearance of the product surface, formation of burrs and occurrence of gas burns differ depending on the screw structure of the molding machine and the structure of the metal mold, so the optimal temperature should be set while observing these conditions.


• Mold temperature

Molding temperature range is around 120 to 150℃ (actual measured temperatures). Do not set a temperature below this temperature range, as mold temperature significantly alters the properties of the resin.

Surface appearance worsens and fibers are more likely to float to the surface of the products if mold temperature is low.


Molding temperature setting examples

Grade

Preliminary drying*

Temperature (℃)

Time
(hrs)

Temp
(℃)

Nozzle

Front section

Center section

Rear section

Resin

Mold

PAX-GF50-02

3

120

255

260

260

250

260

130

PAX-GF60-02

3

120

260

270

270

260

270

130

PAX-CF40-02

3

120

260

270

270

260

270

130

*These are the time and temperature under using a vacuum dryer.


• Screw back pressure and rotation speed

Normally when molding PLASTRON® LFT, hardly any back pressure is set (1 to 5 MPa) in order to utilize the physical properties of the long fiber length, but high back pressure is applied during plasticization when desiring balance with the outer appearance of the product.

Considering potential breakage of the fibers, screw rotation speed should be slow at around 50 rpm.


• Injection speed

PLASTRON® PA resin solidifies much faster than unreinforced PA resin, so medium to high filling speed should normally be set.

Raise the filling speed until fibers do not float to the surface, up to around 90% of the cavity volume.

In the advanced stages of filling, fill at low speed to prevent gas burns and formation of burrs.

Fiber breakage often tends to occur due to the effect of shear if the filling speed is too high.


• Holding pressure

Set high holding pressure in a range that prevents formation of burrs and other imperfections in order to improve appearance issues such as sink marks and warpage deformation. Set holding time about one to two seconds longer than gate sealing time.


• Retention in the cylinder

As a basic handling precaution, please avoid retaining PLASTRON® LFT in the cylinder for long periods of time.

The cylinder should be emptied when it has been at 290℃ for 15 minutes or longer.


• Other considerations

While performing repeated molding using normal cold runner molds, once injection and metering are complete retract the injection unit and separate it from the mold to keep the nozzle temperature from dropping.

If the nozzle is left touching the mold for an extended period of time, the temperature in the tip of the nozzle will drop and it will become obstructed . Resin drooling from the nozzle can occur in repeated molding. Please use sufficient decompression (suck back) in these cases.

For disposal of materials that are purged, when these materials are left as-is, the heat on the inside of clumps could cause carbonization or combustion. Make sure to keep a water tank next to the molding machine and cool these down with water immediately after purging.