PEEK polymer is obtained through stepwise polymerization of bisphenol A and difluorobenzophenone or 1,4-bis(4-fluorobenzoyl)benzene with hydroquinone in the presence of alkali metal carbonates. The polymer is then separated by removing alkali metal fluoride and polymerization solvent. Due to its relatively hard aromatic polymer backbone, the polymer exhibits some of the highest thermal transitions among several commercial polymers and can be used at temperatures up to 240℃.
Polyetheretherketone can be processed by conventional methods such as injection molding, extrusion molding, and compression molding. However, processing conditions for molding polyetheretherketone can affect the crystallinity and thus mechanical properties. As a linear thermoplastic, PEEK polymer can be melt-processed in the temperature range of 370 to 420℃. No corrosive gas is produced during processing polyetheretherketone. Prior to processing polyetheretherketone, it is recommended to dry it for 3 hours at 150℃ or 2 hours at 180℃ to avoid any molding defects. Polyetheretherketone can be processed by injection molding and extrusion. The processes and their handling guidelines are described below:
Injection Molding: Mold temperature of 160-190℃ is recommended to achieve good crystallization and minimize warpage. Post-crystallization can be carried out at 200℃, but is not recommended for applications requiring high dimensional stability. PEEK polymer is suitable for injection molding of very small parts with strict dimensional tolerances. Injection pressure: 70-140Mpa; molding shrinkage: unfilled-1.2%-2.4%, filled-0.1%-1.1%.
Extrusion: Cooling temperature has a significant impact on crystallinity and thus performance. For thin film and sheet extrusion, a cooling barrel of 50℃ will produce a transparent amorphous material. A cooling barrel at 170℃ will result in an opaque and highly crystalline material. Oriented or biaxial films can also be produced by extrusion methods.
3D Printing: Due to its unique properties, 3D printing of polyetheretherketone allows for the construction of almost any complex design geometry, which cannot be manufactured using other techniques. The fused deposition modeling-FDM (or fused filament fabrication-FFF) method is used for 3D printing using PEEK filament. Nozzle temperature: 360—400°C; heated bed: 120°C.
Compared to other common FFF materials such as acrylonitrile butadiene styrene (ABS), polyetheretherketone has low hygroscopicity, making it an excellent candidate material for FFF.