At times it is necessary to negate the effect of the non-stick properties of fluoropolymers – most commonly to enable adhesives to be used to adhere the product to a substrate. There are three methods used to treat the fluoropolymer surface.
This involves treating the surface of the fluoropolymer using an electrical discharge. This can only be used on thin gauge FEP film – not exceeding 50 microns.
Sodium Naphthalene Etching
The etchant is made using sodium in a naphthalene suspension. The etching solution is applied to the surface of the fluoropolymer in an inert atmosphere. The surface composition of the fluoroplastic sees a reduction is the fluorine and/or chlorine content and an increase in the carbon content and oxygen content. The etched surface is composed virtually entirely of carbon and oxygen and a small amount of fluorine. The change in the surface of the etched fluoropolymer is also reflected in the contact angle. This can be tested by the use of a Sessile Tester.
The Sodium Naphthalene etching process is used by Holscot on FEP and PFA and is the most commonly used treatment. The resultant product has a light brown hue.
Sodium Ammonia Etching
Also comprised of sodium in a solution but this time it is ammonia. With a limited shelf life, this has to be used instantly after it is formed. Holscot use this process only for PFA in tube form. The resultant tubes have a much darker brown finish than those etched using the sodium naphthalene process and are sometimes splashy in appearance.
Holscot will be happy to carry out the etching process for customers’ own fluoropolymer products.