xylene will probably damage PC. The best sealant is probably water based silicone sealant. Use the greatstuff behind that and perhaps over any bridging metal frames (to keep the metal protected and reduce the conduction losses).

I would use GE silicone 2, its used for aquariums and food prep areas in resturants.

Dap-Tex & Alex plus stay somewhat soft and aren't very strong.

GE Silicone II is, as already stated, the ulitimate- safe to use. Aquarists have been using it for years to seal, or re-seal fish tanks.

I suppose other mfg. make the same stuff, but once I knew the GE II was safe, I stayed with it. The price difference is also not that great. For a few dollars more per tube, I got what works best and won't damage my polycarb or kill my fish.

Hi
As a side note there are some types of acrylic materials
that silicone adheres very poorly.Acrylic comes to mind.
Will stick for a long time and then pop off. It does adhere to vinyl in spite of what I was told. I had to use a hammer to get old vinyl boards apart over ten years old!!
During the hurricane , material failed before the silicone!! and it pulled out screws.!!
Does anyone know of a chemical that will remove silicone.?? A lot more labor to take it off then put it on.
Please save me from scraping the entire roof!!lol
gary

I believe that there are no safe chemicals to dissolve silicone, especially that are safe on other plastics. Time to sharpen your scraper...

Hi
Don't really have to worry about other plastics as the frame is aluminum. I'm not using the silicone on the new roof just breakaway screws. Have been told the only way to go for hurricanes though I had no structural damage with the silicone.
The scraping will be a real chore especially from the gasket grooves. Actually a dull scraper seems to work better sharp ones tend to slice rather than get under.
gary

According to the info on the polycarbonate label, "do not use ammonia based products" Vinegar, use to clean the polycarbonate ,does not cause any problems. Although not a direct answer to your question, the warnings may help in your evaluation of of sealants.

Kitty

"The previous thread talked about "Great Stuff". IÂve used a lot of this in a project before with PVC pipe, it really is great stuff, and it had no significant odor nor did it damage the PVC."

Even though it has no odor, you should use Great Stuff with adequate ventilation. There are several Great Stuff products, and there are some health hazards associated with using it, as you can see from the links on this Household Products Database webpage.

MM

Great Stuff sets up faster and is much stronger than the latex-based foams. The latex-based foams clean up much easier (Great Stuff is messy and hard to remove even from skin, but it adheres really well). As with many things in life, there are tradeoffs involved. Over the years, I've only used one can of latex foam vs. dozens of Great Stuff and similar products.

You know that your supposed to use the corrugated foam strips to enclose the top and bottom of your roof. Also the panels are 51" so they overlap. You use neoprene washered Hex screws to fasten. I have never heard of anyone using a sealant(except on the ovelaps)
GE Silicone II is recommeded by GE (who make Lexan polycarbonate).

Here is a link that might be useful: important G.E.Lexan info

Yes, I used the corrugated foam strips so far. I haven't used any sealant, as I'm not yet sure I'll need to. I'm going to wait and see. Sides and roof are all done now. I've put in a storm door. On many normal winter days I may just leave the storm door window open for ventilation.