epoxy +polyester resin

[viago]

does anyone know if it is possible to mix epoxy resin with hardener and mix polyester resin with harder and then combine the two mixes in order to provide a strong adhesive layer between the two products?

obviously it is better to use polyester to repair with from a financial perspective but better to use epoxy from a strength based perspective and i was wondering if the adhesive issues between the two products could be addressed in this way.

just an early morning thought.

 

[TradewindSailor]

does anyone know if it is possible to mix epoxy resin with hardener and mix polyester resin with harder and then combine the two mixes in order to provide a strong adhesive layer between the two products?

obviously it is better to use polyester to repair with from a financial perspective but better to use epoxy from a strength based perspective and i was wondering if the adhesive issues between the two products could be addressed in this way.

just an early morning thought.

Simple answer : NO ..... they are completely incompatible. Un-cured polyester will prevent the epoxy from curing .... and polyester takes months to cure thoroughly under room temperature.

 

[coopec]

This guy seems to be expert.

Quote All of this leads to this: Can polyester or vinyl ester resin be mixed with epoxy resin?"
Absolutely not! Polyester and vinyl ester use MEKP to initiate a reaction between the monomers. Using more MEKP will cause the reaction to happen faster. Using less with slow the reaction. Epoxies cure via poly-addition. Meaning that the molecules within the hardener link with molecules within the resin. Adding too much hardener will result in too many molecules of one kind. These molecules won't be able to find a mating connection. They will actually then get in the way and further block the linking. Typically the resin will end up being more flexible due to the lower level of cross-linking and the increased space between the polymer chains. If not enough hardener is used then the resin molecular connections will go unfulfilled. No one wants unfulfilled epoxide groups. They then feel very lonely and live out their lives with unfulfilled potential. If you listen closely you can hear them cry.UNQUOTE

http://www.rcgroups.com/forums/showthread.php?t=1478702

 

[viago]

thanks guys.
well that's that idea well and truly out of the window. i wouldn't want to make the epoxy molecules cry even though they make me cry when i see the rip off prices.

 

[Tranona]

thanks guys.
well that's that idea well and truly out of the window. i wouldn't want to make the epoxy molecules cry even though they make me cry when i see the rip off prices.

Not all epoxy is the same price as there are different types depending on the application. Useful article in this month's PBO on the subject.

 

[macd]

Not all epoxy is the same price as there are different types depending on the application. Useful article in this month's PBO on the subject.

+1
I haven't seen the article but epoxy resin (which covers literally thousands of compounds) is not specifically a marine product. So why buy it from a specifically marine supplier unless you specifically delight in marine mark-ups? On the other hand a specialist epoxy supplier will be happy and able to advise on the right one for your use, at half the cost of something beginning with 'W' (for 'Wonga'?)

 

[single]

Well i was after some epoxy this morning so did research and headed out.I came back with 5lts epoxy for £20.When i asked, he said its the same stuff they supply to the boat manufacturers.

 

[SteveSarabande]

Well i was after some epoxy this morning so did research and headed out.I came back with 5lts epoxy for £20.When i asked, he said its the same stuff they supply to the boat manufacturers.

Was that in the Cardiff area?

 

[skipper681]

Absolutely not poly and epoxy are two different beasts, contact http://www.mbfg.co.uk/ that's where i buy my fibreglass and they will tell you the chemistry behind it.

 

[single]

Was that in the Cardiff area?

Trade at Atlantic in Splott.

 

[William_H]

Simple answer : NO ..... they are completely incompatible. Un-cured polyester will prevent the epoxy from curing .... and polyester takes months to cure thoroughly under room temperature.

Polyester resin as said cures when the hardener reeacts with the catalyst (usually) already in the resin. More hardener (MEKP) gives faster hardening the time also depending on temp. There is no reason to say Polyester takes months to cure. Certainly not long to harden. "cure " is another concept which perhaps does not matter much to most of us.

Interesting I had occasion to cut an inspection port in the tank of a little dinghy. It had been built about 10 years before and was totally sealed. The inside of the polyester resin was still tacky from wax or perhaps resin. But the GRP itself was fine. good luck olewill

 

[TradewindSailor]

It generally takes polyester resin several weeks to post cure at normal room temperature. I understand that styrene is liberated during this process and hence it is likely to prevent the curing of the epoxy.

This is my understanding. I may be wrong, or I may only be partially right ..... perhaps someone will correct me with some suitable references so I and other readers may learn more.

 

[coopec]

I think you are correct as I was instructed by the designer of the yacht it was best not to leave f/g more than two weeks before laying up further. If you leave it longer than that you won't get a chemical bond. You can lay-up further if you sand the f/g before laying up.

 

[BruceDanforth]

You need to add wax to the final coat if using laminating resin or the surface never cures due to air contact otherwise - same as using wax to make flowcoat from gelcoat. Some resin already contains a wax - this is known as finishing resin.

Polyester resin as said cures when the hardener reeacts with the catalyst (usually) already in the resin. More hardener (MEKP) gives faster hardening the time also depending on temp. There is no reason to say Polyester takes months to cure. Certainly not long to harden. "cure " is another concept which perhaps does not matter much to most of us.

Interesting I had occasion to cut an inspection port in the tank of a little dinghy. It had been built about 10 years before and was totally sealed. The inside of the polyester resin was still tacky from wax or perhaps resin. But the GRP itself was fine. good luck olewill