polysulfide sealant interaction with plastics

[kb1ooo]

Hi,

I've used polysulfide sealants with great success on my boat and they seem like a good fit for another application. A friend has built a skateboard ramp with the top surface made of a material called "ramp armor" or "skatelite." I'd like to recommend trying a polysulfide sealant for filling the gaps between sheets of this material, to prevent water penetration into the underlying base plywood surface. I'd like to know if polysulfide sealants are safe to use for this material because I know that it attacks certain plastics. The material is made from phenolic resin. My contact at the company that makes the product thinks that it should be ok because phenolic resin is a thermoset plastic resin similar to polyester resins used in fiberglass. Any thoughts?

Sorry for the off topic post.

Thanks,
Marc

[sailingdog]

Your contact at the company is an idiot... because polysulfide sealants don't bother the resins used in fiberglass... they attack other plastics quite well though...including plexiglass, abs, lexan, etc.

[kb1ooo]

Originally Posted by sailingdog

Your contact at the company is an idiot... because polysulfide sealants don't bother the resins used in fiberglass... they attack other plastics quite well though...including plexiglass, abs, lexan, etc.

My contact did *not* say that polysulfide attacks the resins in fiberglass. He simply said that the resins used in the ramp material are similar to the resins used in fiberglass, so if polysulfide is safe with fiberglass then it is also likely safe with the material. I was trying to determine if others concur.

Thanks,
Marc

[sailingdog]

Ahh, my bad, I must have mis-read what you wrote. I don't think that polysulfide will be a problem with phenolic resin, but I would question why you're not protecting the plywood with something like a penetrating epoxy first...then apply the sealant over the penetrating epoxy.

Applying the sealant by itself would leave the wood vulnerable any where it was damaged, and being on the working surface of a skateboard ramp seems to pretty much ensure that it will be damaged in some way at some point in time. The penetrating epoxy would protect the wood and the sealant would protect the epoxy from UV.

BTW, is the plywood pressure treated or regular plywood?

[kb1ooo]

Originally Posted by sailingdog

Ahh, my bad, I must have mis-read what you wrote. I don't think that polysulfide will be a problem with phenolic resin, but I would question why you're not protecting the plywood with something like a penetrating epoxy first...then apply the sealant over the penetrating epoxy.

Applying the sealant by itself would leave the wood vulnerable any where it was damaged, and being on the working surface of a skateboard ramp seems to pretty much ensure that it will be damaged in some way at some point in time. The penetrating epoxy would protect the wood and the sealant would protect the epoxy from UV.

BTW, is the plywood pressure treated or regular plywood?

Hi,

Thanks for your response. The working (top) surface is not plywood, it is this highly durable 1/4" thick material in question. The under layers are plywood and are not directly exposed. We are trying to prevent seepage of water between adjacent sheets of the top surface material, into the plywood under layers. So, the sealant is just for the gaps where the adjacent sheets of the top layer meet.

Thanks,
Marc

[sailingdog]

If the skatelite is 1/4" thick... then using a polysulfide sealant to seal the gaps between them should be fine. If it was thinner, I'd worry about the impact of the skateboard wheels damaging it...but since it is 1/4" thick, you can put a decent bead of it in-between the plates and still allow it to be recessed a bit from the working surface.

[hellosailor]

Instead of guessing, contact the product makers. One or the other may know for sure, and if not, they may be able to run a test if you send them some material.

[kb1ooo]

Thanks guys. Indeed I may check with 3M about compatibility with this material.

Marc

[hellosailor]

3M? You're in luck, they have multiple "adhesive" divisions, they probably have one that works very well with the decking and can tell you just what kind it is.