chemistry question

[wseyller]

Basically I am trying to apply a teflon coating which is based with isoproply alcohol solvent.
I am applying it to a polyurethane material, actually it is a wiper blade that is in an HP laser toner cartridge if any of you see them before. The blade is not an oem HP, which are mostly silicone blades, but a new aftermarket polyurethane.

Problem is that when applying the lubricant with a swap across the blade it tends to separate, bead up as if it had a wax surface, so therefore it does not apply correctly. I tried to clean the blade with isoproply, ethanol, Isopar C, Acetone, and none helps. I believe it is just these blades themselves. It there any workaround for this or fix, or some means of preparation can could be done to keep it from doing that. My friend a chemist that made the liquid lives in belguim but he is on vacation so I can't get a hold of him. Anyone that has an idea.

 

[Born2bwire]

So it begs the question then, if teflon is nonstick, then who do they get the teflon to stick to the pan?

 

[wseyller]

The coating seems to stick well to silicone blades. The teflon is for lubrication between the blade and the drum to reduce friction.


I took a picture and uploaded it to my web server.

Top blade coated correctly

The bottom blade is the new polyurethane with the problem.

High Res - about 1/2 meg

http://nrscoatings.com/temp/wiper_blades.jpg

 

[Engraver]

I make stencils out of polyurethane because many substances won't stick to it, and are easy to clean off. Seems like it would be the blades themselves.

 

[wseyller]

Yeah I may have to try and persuade a company that buys 200,000 blades a month to switch to a silicone blade. This will be fun.

 

[rezinn]

Maybe you can spray it on with an airbrush.

 

[wseyller]

Well air spraying would be wasteful of the coating which is expensive for the customer. About $65 per 40ml. We have designed a coating unit which will applied the lubricant very presise, but it does not help in this situation. This poly blade even after being cleaned very well feels very oily and slick. This blade manufacturer is not very consistant with their product. They used to be not much of a problem.

Here is the coating unit pics

http://nrscoatings.com/temp/IHWBCUNIT(1).jpg

http://nrscoatings.com/temp/IHWBCUNIT(2).jpg

 

[Nathelion]

Just a quick though... have you tried varying the temperature at which you do this?

 

[Nathelion]

Looking at wikipedia, the general formula for polyurethane seems to indicate that it's basically a monopole, while isopropyl alcohol is a dipole. This would cause them to repell. You can test this theory with a drop of water. Let some water drop onto your polyurethane blade. Does it clump up like if it were on wax? In that case, the problem is your solvent. If you produce a teflon mixture with a monopole solvent (typically some form of oil or other) then your problem should go away. You'd probably have to use a different mixture for the silicon blades if you're doing both, though. Umm... This might ruin the teflon mixture, but what happens if you put a tiny bit of dishwashing detergent in? Does it distribute itself better then? A professional chemist should be able to come up with a way to either change the teflon solution formula or to add a room-temperature volatile detergent without too much trouble. I'm afraid I'm at the limit of my high school chemistry skills, however

 

[Nathelion]

Thinking about it some more, ethyl acetate should suit your needs nicely. It is a moderately bipolar solvent that should dissolve in the teflon mix while still not being repelled too much by the polyurethane blade. It is also volatile, and will dissipate fairly quickly after application. It is certainly worth a try.

 

[DrPizza]

If all else fails, how about an intermediate coat - something that will bond with the polyurethane, and later, allow the teflon to bond to it?

 

[CycloWizard]

The problem you're having is that the cohesive forces within the coating layer are stronger than the adhesive forces between the coating and the PU blade. This gives rise to surface tension. So, if you want to get a somewhat even coating, you somehow need to overcome these surface tension forces. An intermediate coating is probably your best bet, as DrPizza mentioned. Essentially, you need to modify the PU blade's surcace with something that will be IPA-philic. Or, you could change solvents. You might even be able to get something done by changing the concentration of teflon, but I doubt this would have any major effects.

 

[wseyller]

I was thinking about some kind of intermediate coat myself. I talked to the chemist and he said that for these types of blades he has a special cleaning solution that must be use before application of the coating. He is going to send me a sample next week for me to try.

 

[wseyller]

I just found out that the manufacturer of these blades are putting a mineral oil on them which is causing the problem. A detergent and water seem to help remove the mineral oil but I can't seem to get it all off. I am still waiting on the cleaning solution from the chemist. Anyone know of something that will very easily remove mineral oil?

 

[Nathelion]

"Mineral oil is a petroleum product. In the simplest of terms, it could be described as highly refined and edible lubricating oil. As such, it does not dry when it is applied to the wood. Mineral oil is soluble in all petroleum based thinners and turpentine, and any finish that uses these same solvents can be put over it. Lacquer, shellac, varnish, and drying oils will absorb any mineral oil that is already in the wood into the new finish, and there will be no adhesion problems."

A quick google search turned up this. The part you would be interested in is the "petroleum based thinners and turpentine". Until someone gives you a more professional answer, it might be worth a try? Acetone might also work.