LEXAN and sealants

[rbrentp]

First i tried searching several different ways and got nada.

I have lexan windows that need resealing. Have been on forums from construction to aircraft to here.

For relatively easy solutions I have found two that no one has cussed: Lexel and 3M vhb 5952. I have mechanical fasteners so I need a sealant more than an adhesive.
I used GE silicon before and have fond a fair silicon remover (Mechanica). So with 3 of 8 windows starting to leak I thought I would dip into the pool of knowledge and see if anyone has found a straightforward sealant that does not call for primer (VHB asks for primer), is fairly easy to use and clean up.

and of course impervious to UV, chemicals, waxes, etc. (Lexel is the only claimant so far).

Thanks
Brent

[SVTatia]

Dow 795 is your product.
Search here and you'll find lots of info on it.

[Cotemar]

Maybe this will help.

1) Dow Automotive BETAMATE7120 Single-component, high-viscosity, atmospheric humidity-curing polyurethane bonding/sealing compound for high-strength, permanently elastic adhesive joints. Apply ½ thick and squeezed out to 3/8 when window is installed

2) Dow Automotive Betaprime 5404 Pinchweld and encapsulation Primer. Used only on the plastic window sheet. Lightly scotbright 2” around bounding edge and apply this primer onto the sanded 2” area around the outer edge

http://www.cruisersforum.com/forums/...tml#post511878
.
.

[hellosailor]

3M's 4000 UV or the West Marine clone of it should work on Lexan, right out of a caulking gun. But 3M also doesn't mention any need for primer on their main product page for that VHB tape. I've seen it hold lexan for five+ years, no primer, no signs of failure to come.

Primer is usually there to enhance a bond, and if you are just trying to make a seal, should not be needed. Plastics are often expected to move over a seal and not really be bonded to it, since then the seal itself would have to expand and contract with the plastic.

You might consider calling 3M, if you're in the US that's one toll-free number and they'll find you an actual engineer with specific answers and recommendations.

[rbrentp]

Called 3M and they recommended VHB 5952 with Primer 94 on the lexan. They said the Lexan was the culprit. Some of the issue with the VHB was concern about leakage around the mechanical fasteners. Seems easiy enough to deal with but hat is what they said.

Dow had no help as the lexan to paint was not in the products intended use design. Really, the materials are common enough, but they would not offer advice.

I am going to check out the tape and the Lexal.

Have any of you used Mechanica as a silicon remover?

Thanks for help
Brent

[HopCar]

Life Seal by Boat Life
LifeSeal Sealant Cartridges - BoatLIFE

Sudbury Sealant
Elastomeric Sealant 10 oz - Sudbury Boat Care
I've used this on other plastics including Starboard. It should stick to Lexan.

[puffcard]

Originally Posted by SVTatia

Dow 795 is your product.
Search here and you'll find lots of info on it.

This is a great product for sealing Lexan.

[sparrowhawk1]

If only for sealing and not bonding I would think butyl tape would be your best bet. Very easy to apply and clean up. Never gets hard.

[UNCIVILIZED]

Whatever you use, first research it in depth. As some sealants & adhesives can alter polycarbonate (Lexan), or acrylic (Plexiglass) on the molecular level, making them brittle. It's a chemistry thing.

You also need to consider the UV resistive properties of the sealant, as well as that of the Lexan. Particularly along any exposed edges, where there may be no factory applied anti-UV coating.