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Old 05-09-2018, 22:40   #1
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Adhesive recommendations for sticking ptfe sheet to fibreglass

The original plastic slider strips at the fore and aft edges of our daggerboard cases are worn down and no longer protect the cases nor help the daggerboards to slide. Iím considering taking 60mm wide x 900mm long strips of 2mm thick 100% ptfe sheet and bending each strip lengthwise to fit the front curve (a sharp U) and aft curve (a shallow V) of each daggerboard case.

Each strip will overlap the fully lowered daggerboard by about 150mm and there is enough room in the cases for the 2mm thick strips at the front and aft ends of the cases. The lowest part of the strip will be about 300mm above waterline.

What adhesive can I use with the ptfe? I originally though 5200, as that will give me some working time to get each strip into position, but Iíve been told the ptfe is too slippery. Thereís a Loctite high strength contact adhesive that works with ptfe, but it wouldnít give me any working time.

Any suggestions? Thanks.
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Old 06-09-2018, 07:34   #2
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Re: Adhesive recommendations for sticking ptfe sheet to fibreglass

I'd consider using a different material. Ptfe does have a very low coefficient of friction, so is very slippery, but it is very difficult to bond, and is not particularly strong or tough. So it may take damage or wear out prematurely.
Vinyl sheet, while not as slippery as ptfe, is still pretty slippery, especially when wet. And it bonds well, and has superior mechanical properties

Just my 10c worth. Hope it helps
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Old 06-09-2018, 07:44   #3
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Re: Adhesive recommendations for sticking ptfe sheet to fibreglass

McMaster does sell various sizes of off a tape.
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Old 06-09-2018, 07:52   #4
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Re: Adhesive recommendations for sticking ptfe sheet to fibreglass

I'm not sure you will find anything really suitable. I have looked into this in the past and only found 3 really acceptable options available to mortals.

1. PERMABOND TA4605
2. PERMABOND TA4610
3. Special primer and cyanoacrylate (superglue)

However, none of them are "super strong" and will fail under moderate stress. There are a couple of other option that works better, but are really intended for specialist companies.

Unfortunately I think you would be better off coming up with another material, or figuring out how to "phsyically" attach them. I have seen deep countersunk screws used often on PTFE wear plates. Might be a better option for you.
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Old 06-09-2018, 08:02   #5
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Re: Adhesive recommendations for sticking ptfe sheet to fibreglass

How about a couple of kevlar/aramid layers laid up with epoxy.If you add some graphite powder to the mix that could work....
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Old 06-09-2018, 08:10   #6
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Re: Adhesive recommendations for sticking ptfe sheet to fibreglass

Another slippery material is HDPE, the that stuff plastic milk cartons are made. You can get in thin sheets and easy to form with a heat gun, unlike teflon. I would look at using 3M VHB tape for bonding, depending on the surface smoothness. If it's not real smooth you will need to use the foam backed version. If it's smooth they make transfer tape version of just adhesive and no foam.

If you head down that path, clean the surfaces with alcohol wipes and when mounting follow the direction and pressure/time/temperature. Especially the bond and cure times before use.

The 100W solar panels on our airstream are mounted with 4 L-brackets that are mounted with VHB tape with each bracket having mounting surface area of approximately 1.5x2.5". After curing, those brackets are not coming off without nasty solvents and a heat gun, plus no holes for leaks. And it's been 8 years in the elements without a waver.
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Old 06-09-2018, 08:56   #7
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Re: Adhesive recommendations for sticking ptfe sheet to fibreglass

I cannot remember the name of it but there is an etch that needs to be done first. I worked at a company in the early 80's where we attached, with epoxy, PTFE to aluminum and stainless.

I remember it being an acid-base and it turned the Teflon brown.

Sorry I can't remember the name.

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Old 06-09-2018, 09:12   #8
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Re: Adhesive recommendations for sticking ptfe sheet to fibreglass

Just a note:
HDPE is another plastic that is very difficult to bond. It's got excellent mechanical properties, & is used in industry for pipelines carrying abrasive mixtures. But the only way it can be joined is by melting & fusing it.

I suggest talking to a local plastic supplier, and getting their advice
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Old 06-09-2018, 09:21   #9
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Re: Adhesive recommendations for sticking ptfe sheet to fibreglass

You need to use a very powerful base as opposed to an acid to remove the Fluorine atoms from the surface of the Teflon. It is a blue liquid containing Sodium ions. Not easy to get I would think. Using it turns the white surface brown, Carbon. To it you can glue. But probably not well.

But like the others I would not do it. Teflon is soft and high density polyethylene is almost as slippery although also not easy to glue well.

So I would echo the mechanical attachment of HDPE or ronstory's suggestion.

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Old 06-09-2018, 09:34   #10
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Re: Adhesive recommendations for sticking ptfe sheet to fibreglass

Jim, thanks for the clarification. I thought it was an acid.

HDPE is a high-density polyethylene, Starboard is about the same and can be found at most chandlers.

Another option, if you don't want to use Teflon, is UHMW (ultra high molecular weight). It is also a polyethylene.

I use this on my boat where there is wear. Also, we make anchor rollers out of it.
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Old 06-09-2018, 09:41   #11
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Re: Adhesive recommendations for sticking ptfe sheet to fibreglass

Good luck bonding PTFE, we had it all over an aircraft, and were constantly replacing parts cause it had disbonded.
Mechanically fastening strips of Starboard will work if you can mechanically fasten then.
Also 3M UHB tape is particularly tenacious, it holds trim on cars for decades
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Old 06-09-2018, 10:25   #12
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Re: Adhesive recommendations for sticking ptfe sheet to fibreglass

I just did some testing for Practical Sailor related to PE tank repair.
  • You MUST flame treat the PE first. Google it. Vital.
  • Not 3M5200. Skia 291, Locktite PL S40, and surprisingly, G-Flex is quite good (epoxy in general sucks).
  • Back it up with mechanical fasteners. They can work well together.
  • I'd use HDPE, not PTFE. That's just asking too much. I have used HDPE for similar strips, no problems.
The article also covers welding and some other things.
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Old 06-09-2018, 11:08   #13
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Re: Adhesive recommendations for sticking ptfe sheet to fibreglass

[QUOTE=a64pilot;2714594]Good luck bonding PTFE, we had it all over an aircraft, and were constantly replacing parts cause it had disbonded.


Almost nothing sticks to an AG plane, and nothing sticks behind a turbine engine either. I use 3M #5451 on control surface areas. It holds up well unless it gets hot turbine oil on it. It's a PTFE tape with silicone glue.
There are all kinds of aviation tapes, some are crazy $$. The one above is $35 per roll, some are $350!
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Old 06-09-2018, 11:18   #14
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Re: Adhesive recommendations for sticking ptfe sheet to fibreglass

fx-
There are some specialty adhesives and double-sided tapes, but I think you are better off looking for PTFE tape which comes with the adhesive film pre-applied on the back of it. Just peel and stick, job all done. Sometimes hard to find sources, and usually sold in rolls of 25' and longer, but in a variety of widths and thicknesses.
Sometimes a good hardware store will carry it as well, intended for draws that no longer slide easily.
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Old 06-09-2018, 11:42   #15
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Re: Adhesive recommendations for sticking ptfe sheet to fibreglass

I don't remember 3M having a UHB version anymore, I thought they standardize on VHB nomenclature.
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