From PEEK to HAVER AdPEEK®
A new compound exceeds all expectations
It is one of the most popular and frequently used high-performance plastics: Polyetheretherketone (PEEK for short) is resistant to almost all organic and inorganic chemicals and radiation and is suitable for all industries. For the overmoulding of a wire mesh hybrid component as a resistance heating element, however, the process technology reached its limits when processing this plastic.
This resistance heating element is made of a very fine wire mesh strip with a width of 5.4 mm, which - pressed with tin foil - is very thinly over-moulded with plastic. The wall thickness of 0.6 mm specified here does not allow any over-moulding, especially on the inside of the component, as only the wire mesh, but not the plastic, may have contact with the heating zone. In addition to material strength, surface integrity is also one of the customer's requirements, supplemented by Haver & Boecker's own expectations of an economical and safe manufacturing process.
Initial test runs with the plastic PEEK revealed far-reaching negative effects of the high temperatures, starting with the evaporation and deposits of the plastic in the mould. High product rejects due to the need for excessive demoulding forces, superficial plastic defects and melted tin foil were the results. Longer cooling times and increased cleaning and maintenance costs also made it difficult to achieve the target from the perspective of a continuous series process.
Long tool life, low output rates, and defective components were the consequences of the above grievances. Unfortunately, neither plastics manufacturers nor renowned institutes of plastics engineering were able to contribute to a solution. In the past, Haver & Boecker has often distinguished itself by developing solutions to problems, and this innovative spirit also led to success in this project. A team of employees from the company's toolmaking department, the R&D department, the engineering department, and experts from the plastics engineering department provided advice on new tool and system concepts right through to the optimisation of the plastic.
After several successful test series, the plastic PEEK delivered promising results early on with the addition of a silicone-based additive. This compound, later named and registered as HAVER AdPEEK®, exhibits improved flowability even when the melting temperature is lowered.
The positive effects on the complete production process also began with the evaporation and deposits in the mould, which - unlike before - are kept to a minimum.
In the end, all previously diagnosed disadvantages could be turned into advantages:
- More energy-efficient and resource-saving plant utilisation.
- Low demoulding forces not only avoid deformation of the components, but also protect equipment and tools in the long term.
- No weld lines while achieving the required structural strength.
To ensure risk-free use of the Haver AdPEEK® in all industries, including medicine, chemical, and toxin analyses had to be carried out during the heating of the hybrid element.
In the end, after iterative changes to the mould and balancing of the individual cavities, the results exceeded the client's expectations and our own.