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Molding Technology for PLASTRON® PP-GF Grades


Long Fiber Reinforced Thermoplastics

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Molding Technology for PLASTRON® PP-GF Grades


• Drying the material

Material drying is not necessary in typical usage situations, but glass fibers have some moisture absorbency, so we recommend predrying for around one to two hours at 80℃.


• Resin temperature

Cylinder temperature setting range is from 200 to 250℃. 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 40 to 80℃ (actual measured temperatures). Set the mold surface temperature higher when better appearance is desired.

Surface appearance worsens 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

PP-GF30-01

2

80

220

220

210

200

220

60

PP-GF40-02

2

80

230

230

220

210

230

60

PP-GF50-02

2

80

240

240

230

210

240

60


• 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

Taking breakage of the fibers into consideration, medium 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 270℃ for 20 minutes or longer.


• Other considerations

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.