Fluoropolymers such as PTFE, FEP, and PFA (often called Teflon) are very lubricious (slippery). This lubricity reduces bonding ability of the material. Etching alter the surface properties of the polymer allowing it to be bonded.

Etching is performed by the chemical reaction between a sodium solution and the fluorine molecules on the surface of the tubing. Fluorine molecules are stripped from the carbon backbone of the fluoropolymer. This leaves the carbon atoms with a deficiency of electrons. When the etched material is exposed to the air, oxygen molecules, water vapor, and hydrogen allow restoration of the electrons. This restoration process results in a group of organic molecules responsible for adhesion.

Will Etching Change the Properties of My Tubing?

The etching process only penetrates to a depth of a few angstroms so the properties of the tubing will remain mostly unaffected. However the etching process will darken the surface of the material, usually to a brown or tan shade. Surface lubricity is also reduced by the etching process. After the material is etched and dries, a white crust may form on the surface. This crust will impede the bonding process. This residue can be removed by dipping in isopropyl alcohol, acetone, or ethyl alcohol.

How Should I Store Etched Tubing?

Etched fluoropolymers will "grab" molecules from the air to repair their electron deficiency. This results in a weakening of the surface etching. For this reason, all etched materials should be stored in their original sealed bags. Zeus ships all etched tubing orders in sealed black protective bags.

Does a Darker Color Mean a Better Etch?

Not necessarily. In the picture below, both tubes have been etched and have nearly the same contact angle. However, as you can tell from the picture, their colors are quite different. Color is not a reliable indicator of etch quality. For this reason Zeus includes etch certifications with each order shipped.

How is the Etch Tested?

The etched material is tested using the contact angle method. Contact angle measurements of liquid droplets on substrate surfaces are used to characterize surface wettability. As shown in Figure 1 below, the contact angle is defined as the angle between the substrate support surface and the tangent line at the point of contact of the liquid droplet with the substrate. In this picture, example "B" demonstrates a more effective etch than example "A"

Zeus performs contact angle tests on all etched tubing orders and includes a Certificate of Compliance with the material. Test results are available by request.

Capabilities

Click here for more information about  Zeus' custom etching capabilities.