PEEK polyetheretherketone is a high performance material with excellent properties such as high temperature resistance, self-lubrication, easy processing and high mechanical strength, which can be manufactured and processed into a variety of mechanical parts, such as automotive gears, oil screens, gearshift starter discs; aircraft engine parts, automatic washing machine runners, medical device parts, etc..
What are the special requirements of the PEEK injection molding process?
10 factors to consider when injection molding PEEK as follow
- Screw requirements
It is recommended that the minimum value of the L/D ratio of the screw is 16:1, but the preferred L/D ratio should be between 18:1 and 24:1.
- Injection requirements
Pressure: general injection pressure of 70-140Mpa.
Injection speed: medium to high speed.
Back pressure: recommended back pressure setting of 0-1.0MPa (0-10 kgf/cm2).
- Injection machine
Traditional machines that maintain the melt temperature at 360-400°C can be used.
- Nozzle and blocking system
Install a large enough heater at the nozzle to prevent “injection cold material” from cooling down. If the temperature drops to below 343℃, the melt will be cured quickly.
- Barrel capacity
Due to the high processing temperature of the polymer of PEEK injection molding material, the residence time of the material must be as short as possible. The ideal barrel capacity is 2-5 times the total shot weight.
- Mold temperature
The surface temperature of the mold is 175-205°C, up to 220°C.
- Mold design
The mold is heated by high temperature grease resistant to more than 300℃, the mold steel is made of high temperature resistant grades such as H13 or 8407, the mold is installed with heat insulation plate (>8mm) above 250℃, and heat insulation layer can be added around the mold to reduce heat dissipation;
The guide column is made of high temperature self-lubricating grade; the main runner is larger than 4mm, the taper is recommended 2°, the gate is ≥1mm (pure material), ≥2mm (enhanced material). the runner of the mold should be round or trapezoidal.
- Barrel temperature
The unenhanced level is 360-380℃, the enhanced level is 380-400℃, the best choice for the heating system of injection molding machine is ceramic heating ring. For smooth feeding, there must be water cooling in the barrel feeding area to maintain the temperature at 70-100℃.
- Heat stability
Melting process downtime stay no more than 1 hour, then the material at a temperature of 360 ℃ without significant degradation. If the downtime exceeds 1 hour, the barrel temperature should be reduced to 340℃, at this temperature, the material can remain stable for several hours.
If the downtime is more than 3 hours, the barrel should be cleaned.
You can use some materials that can maintain stable performance at 380℃, such as polyethersulfone or polyetherimide, or you can use low MFI polyethylene for cleaning.
- Drying
PEEK injection molding materials are placed in an air circulation oven and dried for a minimum of 3 hours at 150°C, or 2 hours at 160°C.
Workshop to maintain a certain level of cleanliness, must be strictly prevented from mixing other materials, PEEK processing temperature up to 350-400 ℃, most other plastics mixed in will occur serious degradation, affecting product performance.
