Solvent for Teflon 5

[gciriani]

I have teflon-coated screws (stainless steel, diameter 1 mm) which locked up because of the spring effect of teflon on the threads. The screws are so tight that I need to soften the teflon before untightening. We tried already one and it damages the screw. What solvent do you recommend to this job? The italian subcontractor, who made the teflon film on the screw thread, suggested to try with "nitro" solvent (by that he means an aliphatic solvent used in paint); however, I am not sure he knows much about it. Any further suggestion?

 

[gsxr6]

There are no known solvents for "Teflon" fluorocarbon resins under ordinary conditions. That's why they are so great!!

 

[cub3bead]

Have you considered gently warming the screws? Be cautious as the PTFE coating may thin to much and strip off the screw.

 

[fideliter]

Teflon is one of the most stable materials on Earth, therefore aggressive chemical means must be used to remove it. I have used "Tetra-Etch" by WL Gore successfully, but you must check how it will react towards the stainless steel substrate.

 

[aspearin1]

Vendors who perform teflon coating remove the coating by elevating the temperature to over 1000 deg F. According to my vendor, the Teflon powderizes. Not sure what the effect would be on the screw.

ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee

 

[arto]

Be careful heating teflon!! You can get "Fluoropolymer Fever" with the old "flu-like symptoms" if it goes >~700F
- look on the MSDS's

 

[gciriani]

Thank you for flagging this problem. The MSDS I consulted though, only warned about "powder regarded as a potential carcinogen if inhaled". There are several types of teflon, and perhaps I didn't find the appropriate one. Can you please give me a link where you found about this flu-like symptomes?

 

[arto]

http://www.fluoropolymers.org/news/APFOsafehandlingguide.pdf

The lab guys in Valve land warned about this on high-temp tests. It's also a problem for teflon machinists that smoke & people that burn the frying pan with nothing in it

"Polymer Fume Fever: A type of inhalation fever associated with the inhalation of fluoropolymer decomposition products (exhaust effluents, fumes, and gases). It is characterized by temporary flu-like symptoms, which may include fever, chills, and / or, cough. Symptoms may be delayed approximately 4-24 hours following exposure. The severity of effects depends on the extent of overheating and the quantity inhaled. Decomposition products may produce progressive breathing difficulty and later develop into severe pulmonary edema. Edema may be delayed and unlike polymer fume fever, requires medical intervention."

 

[riewies]

I don't think your problem is with the teflon coating on the screws. If the stainless steel screw had been fitted to a steel substrate, it is the stainless steel that is causing the problem, not the teflon. Teflon does not have a spring effect. With the dia of the screw only being 1mm the coating will probably be very thin, around 50 microns at most. I think that the coating was sraped off the steel surface of the screw and then "bit" onto the female thread. This effect is called "galling".
It's a condition whereby excessive friction between mating parts results in localized welding or the damaging of one or both metallic surfaces by removal of particles from localized areas due to seizure during sliding friction.
I know that in certain elctronic applications some parts are teflon coated because of this problem.