In the field of high-end manufacturing, PEEK (Polyetheretherketone) has become the material of choice for industries such as aerospace, medical devices, and automotive electronics due to its exceptional high-temperature resistance, chemical resistance, and mechanical properties. However, the injection molding process for PEEK demands extremely high standards for equipment, technology, and process management. Even minor oversights can lead to product defects or substandard performance. This article provides a systematic analysis of the core considerations for PEEK injection molding, helping you avoid risks and achieve high-quality molding.
1. Material Characteristics and Drying Process: The Foundation for Avoiding Hydrolysis
PEEK is highly sensitive to moisture and prone to hydrolysis during the injection molding process, which can cause molecular chain breakage and degrade mechanical properties.
- Strict Drying: Dry at 150-160℃ in a hot air circulating oven for 4-6 hours to ensure moisture content is below 0.02%.
- Use Immediately After Drying: Dried PEEK should be used within 2 hours to prevent re-absorption of moisture.
- Material Batch Management: Different batches of PEEK may vary in flowability due to differences in molecular weight distribution, requiring prior testing and adjustment of process parameters.
2. Mold Design and Temperature Control System: The Guarantee for Precision Molding
PEEK’s high melting point (343℃) and low thermal conductivity necessitate efficient thermal management in the mold.
- Hot Runner Design: Adopt a needle valve hot runner system to reduce sprue residue and prevent contamination of the mold cavity by carbonized materials from PEEK decomposition.
- Mold Temperature Control: Maintain mold temperature at 170-200℃. It is recommended to use a mold temperature controller for zoned temperature control, ensuring cavity temperature uniformity within ±3℃.
- Ventilation Optimization: PEEK has high melt viscosity and is prone to air entrapment. Design vent slots with a depth of 0.02-0.05mm at the parting line and insert gaps, and consider adding vacuum extraction devices if necessary.
3. Injection Molding Process Parameters: The Key to Balancing Flow and Degradation
PEEK injection molding requires rapid forming under high temperature and pressure, but thermal-mechanical history must be strictly controlled.
- Three-Stage Temperature Control:
- Barrel Temperature: 380-420℃ (decreasing from front to rear);
- Nozzle Temperature: 400-410℃ (to prevent drooling);
- Mold Temperature: 180-200℃ (to avoid excessive cooling and internal stress).
- Injection Speed and Pressure: Use high-speed and high-pressure injection (speed ≥100mm/s, pressure ≥150MPa) to shorten the melt’s residence time in the barrel and reduce the risk of degradation.
- Holding Pressure and Cooling: Maintain holding pressure at over 80% of the injection pressure, with a cooling time of 30-60 seconds to prevent warpage from premature mold opening.
4. Equipment and Environment: Hard Requirements for Clean Manufacturing
PEEK injection molding imposes stringent requirements on equipment cleanliness and environmental stability.
- Screw Assembly Optimization: Use a bimetallic screw (with a wear-resistant alloy coating) and a compression ratio of 2.5:1-3:1 to reduce shear heat.
- Clean Production Environment: The injection molding workshop should meet Class 10,000 cleanliness standards (ISO Class 7) to prevent dust particles from embedding in the product surface.
- Equipment Maintenance: Regularly inspect the barrel inner wall for wear to prevent black spot defects in the product caused by PEEK carbonization.
5. Post-Processing and Inspection: The Final Step in Performance Verification
The performance of PEEK products is highly dependent on the post-processing process.
- Annealing Treatment: For precision products, anneal at 200℃ for 4 hours to eliminate internal stress and improve dimensional stability.
- Performance Testing:
- Tensile Strength ≥95MPa (ASTM D638);
- Flexural Modulus ≥3.5GPa (ASTM D790);
- Weld line strength must be verified through CT scanning and mechanical testing.
- Batch Traceability: Establish a complete quality archive from raw materials to finished products to meet traceability requirements in medical, aerospace, and other fields.
Conclusion: Technical Barriers and Breakthrough Directions
The challenges in PEEK injection molding lie in the synergistic optimization of material characteristics, process parameters, and equipment capabilities. Companies need to predict defects through digital simulation (such as Moldflow) and optimize the process window using Design of Experiments (DOE). In the future, with the application of AI temperature control systems and supercritical CO₂-assisted molding technologies, the yield and efficiency of PEEK injection molding are expected to improve further.
Dongguan Yize Mold Co., Ltd. has been deeply involved in the PEEK injection molding field for 17 years, successfully delivering over 300 PEEK mold projects for medical and aerospace applications. We possess a Class 10,000 clean workshop and a full-process testing laboratory. For custom PEEK mold or injection molding problem-solving needs, please contact us at +86 13302615729 (WeChat, Whatsapp same number) for professional solutions!
