Another question that came through recently:

“I’m looking for assistance bonding a Teflon^® wire jacket to a PEEK housing. Do you have an adhesive recommendation?”

Response:

Teflon^® or polytetrafluoroethylene (PTFE) is a low-surface energy plastic used in a variety of different industries from non-stick cookware to wire jacketing. Its accidental development led to the unique characteristics we have come to associate with Teflon, such as its use as a low-friction coating or non-stick surface. Because of these unique properties, Teflon presents many challenges to adhesive manufacturers whose customers wish to bond to it.

PEEK or PolyEtherEtherKetone is a high-performance polymer ideal for high heat-resistant applications where dimensional stability is needed. Its excellent chemical resistance makes it an ideal choice for many automotive, medical, and food processing applications. PEEK also presents many adhesive-bonding challenges.

While the question asked seems pretty straightforward, it is far from it. Before any adhesive manufacturer can answer a question like this, additional information is needed to identify a solution.

• The adhesive manufacturer needs to know what industry or market the finished part will be used in. For example, if it will be used in the medical industry, the customer may require a USP Class VI or ISO 10993 approved adhesive.
• Information on how the adhesive will be qualified, such as any temperature, chemical, or strength testing, will help an adhesive manufacturer narrow down their potential list of suitable products.
• Also, understanding the environment in which the final product will operate will provide additional information needed for the adhesive manufacturer to make a qualified adhesive recommendation.

While both substrates are difficult to bond, Teflon is considered to be the more challenging of the two. In this question, bonding the Teflon wire to PEEK may not be feasible. It may make more sense to encapsulate over the Teflon wire to the PEEK using a UV light-curable adhesive instead of bonding the two substrates together. In this case, you would bond to the PEEK by encapsulating the Teflon jacketed wire in place. Provided there are minimal external forces or stresses on the wire, this solution could pass a manufacturer’s qualification testing. In many cases, adhesion to PEEK can be improved by surface treating (i.e. corona, plasma, etc) the plastic before bonding. This will improve the overall performance of the adhesive bond and the quality of the finished assembly.

Any recommendation made by an adhesive manufacturer should be treated as such. The adhesive company will provide a manufacturer with their best candidate for the application based on the information provided to them during discussions with the company’s technical staff. Every company is responsible for determining the success of the adhesive recommendation by testing the performance of the assembly to see if it meets their established test criteria.

Adhesives, Medical PEEK, Teflon

Another question that came in recently:

“I am investigating insert molding potential of PC/ABS or PC over PEEK tubing. With the significant melt temperature differential I am uncertain that I can achieve a secure bond. Can you suggest an adhesive that can be applied to the PEEK outer diameter prior to molding that will act as a bond layer?”

Answer:

I would recommend investigating a silane primer, sometimes called an adhesion promoter. These thin materials can be applied to the outer surface of the PEEK tubing, allowing it to dry (most contain some type of solvent), and then overmold as normal. The silane groups usually have two different reactive chemistries attached to them - one that will be attractive to the PEEK, and one that will be attractive to the PC. There are a number of different primers available from different companies. You might have to try a few different ones to determine which primer will work best for your combination. The primers can be applied with a brush, foam wipe, spray, or even a simple dip application (only coat the outside, not the inside). Apply the primer just short of the length of the overmold, and this will hide the primer under the PC.

Structural PEEK, Plastic Bonding, Plastics, Primer