Glueing Lexan Windows UV Protection outside material recommendations?

[Franziska]

Hi,


we need to reglue some windows, so far I had it done a couple of years ago following Sika's guide, the only thing we missed unfortunately is that their black primer is not enough as UV protection for the joint.
They ask for screen print or paint or a UV protection tape.
As we have our windows already and are on a budget screen print is a no go.


Here is what we did back than:

Joint thicknesses according to guide.

Base Materal: Fully cured epoxy
Sika used is for joints: 295UV Black
Primer on underside of Lexan window as glueing surface: 209D Black
Primer on window support as glueing surface: 209D Black
Glueing surfaces lightly sanded before primer applied
2hr timeframe between Primer application and glueing adhered to


Now we want to add UV protection on the outside of the windows too.
Either tape or paint. The windows are made of Lexan.

Sika offers an overpriced 50m roll of adhesive tape for 100€ and we look for an alternative.

Has anyone used sucessfully black aluminum tape?
https://www.amazon.de/-/en/Aluminium...0353778&sr=8-6

Can anyone recommend a suitable paint which does not harm the Lexan but offers robust UV protection on the Lexan Window outside over the glue joint?

Screen print paint might work though. Experiences? Can it be applied without special tools?

This is primarely on the issue of UV protection of the glue joints!

Thanks for comments.



Franziska

[JPA Cate]

Franziska,

We used black spray paint, after masking carefully. However, it was on acrylic, so don't know if it would work for lexan. Plus, our "windows" were also anchored by screws into the hard dodger. However, fwiw, the paint seemed to prevent UV damage.

Ann

[wholybee]

Maybe something like this? From my model airplane days(something similar must be available in Europe):
https://www.towerhobbies.com/search?...=&lang=default

Cut whatever size shape you need, peel and stick. It's meant for fancy designs, but would also work for "trim" to cover the glue.

Or maybe pinstriping tape from an auto parts store.

[Franziska]

Thanks to both of you.
Ann confirms that it's the right way to go about it.

The reason we like to hear about specific materials is that many tapes do not last well in sunlight/outside and paints are always critical when it comes to plexi/perspex or polycarbonate/lexan due to their solvents.

[Chotu]

If you want paint, use this.

https://www.tamiyausa.com/blog/ps-pa...polycarbonate/


Sorry about the USA specific link. I think it auto detects my location and serves up the appropriate site version.

I’ve used this paint on the BONDING side before I switched to frames to hold my windows and it held up. The Dow adhesive/sealant peeled off the boat before this spray paint would peel off the polycarbonate. It’s very good stuff.

With my new frame-held Windows, I still used Tamiya paint to cover everything just for looks.

The black around the edges of these windows? Tamiya.

[Franziska]

Originally Posted by Chotu

If you want paint, use this.



https://www.tamiyausa.com/blog/ps-pa...polycarbonate/





Sorry about the USA specific link. I think it auto detects my location and serves up the appropriate site version.



I’ve used this paint on the BONDING side before I switched to frames to hold my windows and it held up. The Dow adhesive/sealant peeled off the boat before this spray paint would peel off the polycarbonate. It’s very good stuff.



With my new frame-held Windows, I still used Tamiya paint to cover everything just for looks.



The black around the edges of these windows? Tamiya.

Thanks Chotu, interesting you used this on the inside bonding surface.
We use the Sika supplied Black Primer there.
Did you not use that?
As Sika asks for additional shading of the joint outside, do you think that the Tamiya paint will last there?
Did you sand lightly before applying the paint?

As our windows have a number of big radiuses I think I prefer paint over tape...

Regarding the window panes, we will split the two front windows into four panels instead of two to reduce expansion issues (I know that you have experience concerning this issue! Glad you solved it!)

[Chotu]

Originally Posted by Franziska

Thanks Chotu, interesting you used this on the inside bonding surface.
We use the Sika supplied Black Primer there.
Did you not use that?
As Sika asks for additional shading of the joint outside, do you think that the Tamiya paint will last there?
Did you sand lightly before applying the paint?

As our windows have a number of big radiuses I think I prefer paint over tape...

Regarding the window panes, we will split the two front windows into four panels instead of two to reduce expansion issues (I know that you have experience concerning this issue! Glad you solved it!)

I didn’t use Sitka brand products at all. I used Dow 795 and a slew of others with all the window failures.

So given I was not suggested what primer to use on the windows, I had to find my own. Tamiya is one of the very few paints formulated just for bonding to polycarbonate.

I didn’t sand at all. I think Tamiya bonds chemically with the polycarbonate.

My paint has been good now for years in tropical sun without any evidence of degradation so yes, I think it should last.

[stewy]

Try using a product called PERF on the outside of your hatches and port holes. Its a film, used for store front windows or the back windows of pickup trucks. You can see out but not in. Offers some UV protection. Designed for sign shops to paint logos, designs etc. Available at very affordable prices. Slightly sticky on one side.

[Dsanduril]

Originally Posted by Franziska

...Has anyone used sucessfully black aluminum tape?
https://www.amazon.de/-/en/Aluminium...0353778&sr=8-6

...

Franziska,

we have not used black aluminum tape (didn't even know it it existed - now I want some). We do use silver aluminum tape (link to something like it below - it is readily available at the hardware stores in the US) on most of our hatches and it has become my go-to for outdoor tape on the boat. We had problems with sealant degradation where the hatch "glass" was attached to the frame, we've had aluminum tape on them for 5 years without problems. The Al does eventually begin to pit a little (which is why I would like to look at your black tape) but otherwise it looks decent and stays in place since the Al is pretty much impervious to UV unlike plastic tapes. One caution, at least with the stuff we use, it is nearly impossible to remove, and the glue takes solvent for removal once you pull the tape.

You do have to work slowly and carefully to avoid wrinkles, once wrinkled it stays that way. For rounded corners we either create a corner piece by cutting while the backing is still on, or trim a rounded corner into the tape with a sharp Exacto knife once the tape is in place. Sorry, don't have any photos of the hatches.


https://www.amazon.de/-/en/Aluminium...78WSSMTN&psc=1

[kapnd]

Krylon paint sticks like the devil to very well cleaned lexan!
I used VHB double sticky tape to mount the windows, and black sikaflex to seal around the edges. Five years now, no leaks or signs of degradation in heavy ocean use in the tropics.

[Franziska]

Originally Posted by kapnd

Krylon paint sticks like the devil to very well cleaned lexan!
I used VHB double sticky tape to mount the windows, and black sikaflex to seal around the edges. Five years now, no leaks or signs of degradation in heavy ocean use in the tropics.

Hey, that sounds great. Thanks.
It would also reduce the Sika mess :-)

We would prefer to use paint over a shielding tape due to the window shape (see photo, we will split those two windows into 4 panels).

You did cover the bonding outside with the Kryolan, correct?
No need to sand the Lexan?

Regarding the VHB tape, does it have some thickness to it?
Will it work on those radiuses?
Do you think it will work on our slightly wavy epoxy treated plywood frame?
Do you recall which of the many VHB tapes exactly you used?

Sorry about all those questions.

Thanks also to all the others. Shielding tape is definitely option number two.

[Franziska]

Originally Posted by Franziska

Hey, that sounds great. Thanks.
It would also reduce the Sika mess :-)

We would prefer to use paint over a shielding tape due to the window shape (see photo, we will split those two windows into 4 panels).

You did cover the bonding outside with the Kryolan, correct?
No need to sand the Lexan?

Regarding the VHB tape, does it have some thickness to it?
Will it work on those radiuses?
Do you think it will work on our slightly wavy epoxy treated plywood frame?
Do you recall which of the many VHB tapes exactly you used?

Sorry about all those questions.

Thanks also to all the others. Shielding tape is definitely option number two.

Attachment 244584

Uups Krylon and not Kryolan, the latter is make-up :-)

[Nicholson58]

Note there is another active thread on this. The automotive guys, glass shops, apply a glass etch followed by a bond enhancing UV barrier before the window adhesive urethane rubber. Maybe they have a black out suitable for Lexan.

[Chotu]

VHB on a wavy surface means you’ll need to double and triple up the tape to get the thickness required to fill the gaps.

It’s very thin stuff. Even in the thickest variety they make.

It’ll definitely fall right off if you don’t have a perfect mating surface.

[Franziska]

Originally Posted by Chotu

VHB on a wavy surface means you’ll need to double and triple up the tape to get the thickness required to fill the gaps.

It’s very thin stuff. Even in the thickest variety they make.

It’ll definitely fall right off if you don’t have a perfect mating surface.

Thanks. So we might end up with Sika altogether, but this time with paint outside on top...