Consistency in appearance and performance is a key concern in PEEK injection moulding.
Note: The applications illustrated are general applications of PEEK and do not imply that ZYPEEK materials have entered every application shown.
In production, some parts may exhibit colour variation, surface defects, dimensional instability or mechanical properties below the required level. These issues are often closely related to processing control.
Jilin Joinature Polymer Co., Ltd. (ZYPEEK; stock code 688716) has focused on PEEK research and industrial applications for nearly 20 years, building systematic injection-moulding experience through its work with downstream suppliers.
This article reviews five key areas of PEEK injection moulding: equipment configuration, material drying, equipment cleaning, temperature control and gate design.
01 Equipment Configuration for High-Temperature Processing
PEEK requires high melt-processing temperatures. For ZYPEEK materials, the recommended processing range is 360-400 degrees C, with a maximum of 420 degrees C. Equipment selection should address the following points:
Heating system: heater bands and thermocouples must be suitable for high-temperature operation. Ceramic heater bands can help improve heating uniformity.
Barrel insulation: insulating the barrel is recommended to reduce heat loss.
Screw and components: general-purpose screw designs meet most processing needs. Metal components in contact with the melt should be polished to reduce material accumulation. Surface hardening may be considered for mould-cavity areas that contact the part directly to improve surface durability.
Mould temperature: the actual mould temperature should generally be maintained at 175-205 degrees C. This refers to the measured mould temperature, rather than the temperature controller setting. Use a mould temperature controller and measure cavity temperature with a contact thermometer.
02 Material Drying and Moisture Control
PEEK absorbs some moisture. The moisture content of ZYPEEK FD-PEEK is typically below 0.3 wt% when it leaves the factory, but it may absorb approximately 0.5 wt% atmospheric moisture during storage.
Moisture target: reduce material moisture to below 0.02 wt% before processing.
Drying conditions: dry at 150-160 degrees C for 2-3 hours. For film processing, extend drying to more than 4 hours.
Drying equipment: use a dry-air or vacuum drying oven. The dryer dew point should be no higher than -30 degrees C. PU tubing is recommended for pellet conveying.
03 Equipment Cleaning to Prevent Cross-Contamination
Many polymers can thermally degrade at PEEK processing temperatures. If they are not completely removed, residues can appear as black specks in the finished part and affect appearance and performance.
PEEK can retain good melt stability when held at 400 degrees C for 1 hour. However, prolonged exposure to high temperatures may affect its properties.
If an unexpected shutdown occurs and the material remains in the equipment for no more than 1 hour, changes in material properties at 360 degrees C are relatively limited.
For a residence time of 1-3 hours, reduce the barrel temperature to 340 degrees C.
For a residence time exceeding 3 hours, clean the barrel. When production resumes, segregate the initial parts produced.
04 Temperature Control, Crystallisation and Part Quality
PEEK is a semi-crystalline material. Mould temperature directly affects crystallisation behaviour and final part performance.
Mould temperature too low: rapid cooling restricts the orderly arrangement of molecular chains. Parts tend towards an amorphous state, with insufficient flow and a darker colour.
Suitable mould temperature of 175-205 degrees C: molecular chains have sufficient time to arrange into a crystalline structure, supporting more consistent colour and overall performance.
Possible effects of poor mould-temperature control: sticking, uneven colour, ejection deformation, warpage and reduced wear resistance.
Measurement: the displayed controller temperature may differ from the actual cavity temperature. Measure the inner cavity wall using a contact-type K thermocouple and use the measured result as the processing reference.
For related practical analysis, see how mould temperature affects PEEK injection-moulded part quality.
05 Gate Design to Compensate for Shrinkage
As a semi-crystalline material, PEEK undergoes relatively substantial dimensional shrinkage after injection moulding and cooling. Its shrinkage is greater than that of amorphous materials.
Gate size: a larger gate can improve shrinkage compensation. A general reference is two-thirds of the part wall thickness. The final dimensions should account for wall-thickness distribution, cavity count and part geometry.
Shrinkage data: refer to the property data for the relevant ZYPEEK grade.
Bringing the Process Together
PEEK injection moulding requires systematic processing control. Equipment temperature capability, material dryness, equipment cleanliness, accurate mould temperature and appropriate gate design all have a substantial effect on finished-part quality.
ZYPEEK develops and produces PEEK materials and supports downstream customers with material selection, process optimisation and technical consultation. For further discussion, contact the company through its official channels.
Service hotline: 400-186-1177
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