Peek molding is the process of injection-molding a high-performance plastic known as polyether ether ketone (PEEK). This engineering thermoplastic offers excellent thermal and mechanical properties. It resists corrosion, can be sterilized, and offers good wear resistance.
However, the material is not without its challenges. Injection molding PEEK requires special considerations that may not be present in other types of plastics. If these are not addressed properly, the resulting molded parts will have sub-optimal performance.
The material can degrade at high temperatures, causing dark specks to appear on the surface of the final part. To avoid this, the injection machine should be cleaned thoroughly before running with PEEK. This includes dismantling and cleaning the screw and barrel, particularly since they are the hottest parts of the machine. It is also recommended to clean other ancillary processing machines like the nozzle, runners and molds. This reduces the chance of contamination by residues of lower melting materials.
PEEK is a semi-crystalline material, with some molecules being more ordered than others. This is important because crystalline structure influences the mechanical properties of the material. It can be pigmented black to improve its visual appearance, but this degrades the mechanical properties.
While it is possible to injection mold other plastics using standard equipment, the process for PEEK can be more complicated than with most other polymers. This is due to the high temperature of the material, which can cause problems with dimensional stability and crystallization. PEEK is a high-performance polymer, and it is important to keep these factors in mind to ensure that the resulting molded products will perform well.
Most polymers shrink a little as they cool from their molten state to their hard, solid-state. This is generally accounted for in the design of the molds, but PEEK is different. This polymer is anisotropic, which means that it shrinks in a different way in each direction. It is important to understand this before designing the mold for PEEK injection molding Ohio.
The rate of cooling can influence the crystallinity of the molded product, so it is vital to have good control over the injection molding machine temperature for peek injection. This will prevent the material from cooling too quickly, resulting in a mixture of amorphous and crystalline regions in the finished molded product, as shown by the amorphous and crystalline areas in the image below. The ideal temperature is around 170-2000C, which is achievable with electrical heaters or oil-heated injection molders. If the temperature is not properly controlled, it can cause a number of other issues with the molding process.