PTFE Can Not Be Bonded Without Etching

In order to bond a PTFE product with another material, the surface needs to be chemically modified. This process, known as etching, is done with sodium/ammonia based solutions and produces a bondable surface quickly and efficiently.

The etching process defluorinates the surface of a PTFE polymer by stripping away fluorine molecules from the carbon-fluorine backbone of the polymer, leaving a surface containing mainly electron-deficient carbon atoms. This increases the concentration of carbon-carbon covalent bonds and facilitates covalent bonding with the subsequent bonding material.

When etched ptfe is exposed to moisture, it can become soft and brittle and will be more susceptible to breakage or failure. This can cause problems for applications where the PTFE is to be joined to other materials, including metals and tubing.

During storage, etching PTFE should be stored in a dark place and kept away from moisture. Depending on the application, the PTFE may require a UV-blocking bag.

A PTFE with an etched surface will usually have a brown or tan tint. This is due to the etching process altering the PTFE’s surface properties such as water contact angle. This color variation does not correlate to the quality of the etch, but it can be used to help determine how good the surface is for adhesion.

When using etched ptfe, it is important to test the water contact angle after the etching process before applying any adhesive. This will ensure that the etching process created a surface that is suitable for adhesion with your specific adhesive. It is also a good idea to get a baseline cleanliness assessment of the PTFE prior to your etch. This will allow you to know exactly how much of an etching is needed to reach your water contact angle requirements.