Epoxy / Poly compatibility

[i386]

It's discussed a lot here about how well one bonds to the other. I read an interesting article about it (sorry I don't have a link) the other day.

In a nutshell it went something like this...

Within a certain window of time poly binds to poly or epoxy binds to epoxy at the molecular level. However, after either resin has cured the, bond is only mechanical.

So for example if you're making repairs on an old boat your first layer is a mechanical bond so abrading the surface is important. Epoxy should have a stronger mechanical right?

 

[klos]

Re: Epoxy / Poly compatibility

I just got out an old fiberglass book by Jack Wiley. There is a section in there that explains this.
According to him you can bond poly to epoxy.
The example is when using plywood as a core material use epoxy for the first layer because of the superior bonding qualities and then after fully cured follow with poly.
Yesterday I checked out a local sailboat builders shop. They use vinylester for the skin and the rest poly.

Kind of funny I was just sitting at my desk to post the same topic when I read your post.

 

[andy6374]

Re: Epoxy / Poly compatibility

Yesterday I checked out a local sailboat builders shop. They use vinylester for the skin and the rest poly.

The are both ester resins and will bond well together.

 

[KRS]

Re: Epoxy / Poly compatibility

I just got out an old fiberglass book by Jack Wiley. There is a section in there that explains this.
According to him you can bond poly to epoxy.
The example is when using plywood as a core material use epoxy for the first layer because of the superior bonding qualities and then after fully cured follow with poly.

I have to disagree. I believe that you can bond poly to poly, epoxy to epoxy, and epoxy to poly,... but not poly to epoxy. As the saying goes... once you switch to epoxy you can't go back.

 

[klos]

Re: Epoxy / Poly compatibility

I thought the same, I've never heard of using poly over epoxy. I thought I was missing something.
I read that part in the book again and sure enough it says you can bond poly to epoxy, not saying its right though.

 

[dhatcher]

Re: Epoxy / Poly compatibility

i know this is off topic but i386, i think i saw that you got fishing on the apalchecola for mullet, is this correct?

 

[i386]

Re: Epoxy / Poly compatibility

i know this is off topic but i386, i think i saw that you got fishing on the apalchecola for mullet, is this correct?

Yea when I was a kid...

My Grandad had a mullet boat. The outboard was in a "well" up towards the bow of the boat leaving the stern free to store the gill net. It's got a cork line and a lead line with mesh in between. It sorta makes a fence under water. Anyway you have several hundred yards of net piled up on the stern. When you see the mullet striking you throw out a weight that's attached to the net and drive the boat in a circle as the net pays out. Well that's the fun part. Then it's time to work. Two men stand on the stern. One takes the cork line and the other takes the lead line. You pull the net in and take out the mullet and everything else that gets caught in there. It's no fun to get a garr in there for sure.

We made a whole family thing out of it. It took the whole family to clean those mullet. We'd be eating fried/smoked mullet and row for weeks. Good times.

 

[General0]

Re: Epoxy / Poly compatibility

So what's the take can you really use poly over epoxy? the reason I ask is I have ran out of epoxy and I still need to do a lot of gluing.
Could I go get the poly stuff which is way cheaper and local or do I have to get epoxy to finish it?

 

[ondarvr]

Re: Epoxy / Poly compatibility

You need to finish it with epoxy, poly "WILL NOT" bond well to epoxy, plus if you're glueing stuff you need to use epoxy, because poly is a poor glue.

 

[Tail_Gunner]

Re: Epoxy / Poly compatibility

:'( ok so i used West systems to both glue and lay in my stringer's taped them with it, sealed up my floor and used it in very thick form to glue my floor to the hull. Ondarvr am i ok here?

 

[ondarvr]

Re: Epoxy / Poly compatibility

TG

If it was West Systems epoxy and that's all you used, then there's no problem. If you glassed over the epoxy with a polyester resin, then it's possible that the bond between the two may fail if stressed.

 

[sbklf]

Re: Epoxy / Poly compatibility

I researched epoxy for my repairs and found West to be high priced. I went with RAKA but there are cheaper still. Any epoxy should bond to another no problem. I would not trust a poly to epoxy bond for anything structural.

 

[Tail_Gunner]

Re: Epoxy / Poly compatibility

TG

If it was West Systems epoxy and that's all you used, then there's no problem. If you glassed over the epoxy with a polyester resin, then it's possible that the bond between the two may fail if stressed.

8) Thank you no other resin was used