poliester resin question

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pablo
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poliester resin question

Post by pablo » Sat Oct 18, 2003 12:28 am

hi
I've a problem
I have to finish a board, I have the resin but unfortonately not one of the catalists (there's a violet and a transparent one, I lost the last one(a spark of the welder))

so, I thought I might be able to start the reaction by using only heat, since I have successfully accelerated the reaction using this method (but with the catalists), once it gets hot enough, the reaction becomes exothermic.
would the heat be enough to complete the reaction?
thanks
Pablo
PS: the new forum is cool

Viv
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Post by Viv » Sat Oct 18, 2003 2:45 am

Sorry that wont work, it is a binary reaction so heat wont make up for the lack of the hardener component.

The heat is just a byproduct of the reaction as you pointed out.

Viv
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Mike Kirney
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That Clear Stuff

Post by Mike Kirney » Sat Oct 18, 2003 2:49 am

That transparent substance is methyl ethyl ketone, isn't it? I'm pretty sure that the violet stuff is styrene but maybe its the other way around. MEK is quite a common solvent in aircraft maintenance shops, and might be in other mechanical maintenance places too.

pablo
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Post by pablo » Sat Oct 18, 2003 3:03 am

once the violet one evaporated and a solid was left in the bottom of the little bottle.
I added common paint solvent(aguarras in spanish) and it worked just fine.

its a shame it wont work, I guess I'll have to go to the shop and buy more catalist (the prob is the minimum quantity they sell is enough for 1 kg of resin, this is why I didnt want to buy it)

well, thanks both for your help
Pablo

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Re: That Clear Stuff

Post by Viv » Sat Oct 18, 2003 3:11 am

Mike Kirney wrote:That transparent substance is methyl ethyl ketone, isn't it? I'm pretty sure that the violet stuff is styrene but maybe its the other way around. MEK is quite a common solvent in aircraft maintenance shops, and might be in other mechanical maintenance places too.
Evil nasty stuff that MEK mike, it is now banned over here in the UK, we used to use it by the gallon in heated tanks for degreasing stuff.

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Tom
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Post by Tom » Sat Oct 18, 2003 8:14 am

the stuff i use that is quite common in halfords (an auto parts store in the uk) is Dibenzol Peroxide. it is cheap too, bout 20g for 2 GBP.
just saying.

T.
Experience speaks more then hypothesizing ever can. More-so in chemistry.

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Heated Tanks?

Post by Mike Kirney » Sat Oct 18, 2003 2:27 pm

You used to heat your MEK in tanks? I can only imagine what the room must have smelled like. I used to use it with paper towels to wipe the brake dust off of jumbo jet wheels. I remember it evapourating almost instantly after it was applied and the fumes gave me a nasty headache and they made my nose itch, although like most hydrocarbon fumes, they smelled great. What sort of shop did you use it in, Viv? Were you working on aircraft? What type?

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The Violet One Is Styrene

Post by Mike Kirney » Sat Oct 18, 2003 2:35 pm

From reading your last post, Pablo, I can tell you the violet substance is dissolved styrene, and the clear stuff is MEK. The styrene is added to the resin to promote molecular cross-linking and the MEK is the catalyst that causes the cross-linking reaction. The more MEK you add, the faster your resin will cure, and the hotter it will get while it is curing. Even just a few extra drops will cut curing time in half.

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Re: Heated Tanks?

Post by Viv » Sat Oct 18, 2003 7:11 pm

Mike Kirney wrote:You used to heat your MEK in tanks? I can only imagine what the room must have smelled like. I used to use it with paper towels to wipe the brake dust off of jumbo jet wheels. I remember it evapourating almost instantly after it was applied and the fumes gave me a nasty headache and they made my nose itch, although like most hydrocarbon fumes, they smelled great. What sort of shop did you use it in, Viv? Were you working on aircraft? What type?
Mike, this was for Oxford instruments who made vacuum chambers for the semiconductor process industry.

The tanks had economiser coils half way up the (cooled) the MEK vaipor just condensed on them and driped back in to the bottom of the tank then got boiled up again.

You just had to hang a part in the vaipor cloud to get it degreased, you could not smell anything as it was in the traped in the tank.

Viv
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marksteamnz
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Re: poliester resin question

Post by marksteamnz » Sat Oct 18, 2003 9:14 pm

OK Pablo. You have lost the clear stuff? If so I was most probably MEKP Methyl Ethyl Ketone Peroxide. The P Peroxide is the important bit and is what catalyses the resin. MEK is just a solvent and completely useless for polyester resin.
The purple / violet stuff is most probably a promoter such a cobalt napthanate. If the instuctions say NEVER add the purple stuff to the clear stuff ALWAYS mix the purple stuff with the resin first that is probably what it is.
OK back to your question The MEKP starts the resin (which has styrene in it) reacting with itself. You will not be able to kick the reaction off with heat unless you get to very high temperatures. At these temperatures the styrene in the resin will start to boil and make a mess unlees you have something like a closed mould.
If you want to try use a small sample and don't breath the fumes. Styrene is not a good chemical to get hot.
There is a lot more involved with promoters vs catalyst vs heat etc. Email me direct if you want more information
Cheeras
Mark Stacey
www.cncprototyping.co.nz
pablo wrote:hi
I've a problem
I have to finish a board, I have the resin but unfortonately not one of the catalists (there's a violet and a transparent one, I lost the last one(a spark of the welder))

so, I thought I might be able to start the reaction by using only heat, since I have successfully accelerated the reaction using this method (but with the catalists), once it gets hot enough, the reaction becomes exothermic.
would the heat be enough to complete the reaction?
thanks
Pablo
PS: the new forum is cool
Cheers
Mark Stacey
www.cncprototyping.co.nz

pablo
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Post by pablo » Tue Oct 21, 2003 11:37 pm

right, thats what the guy at the shop.
in fact, he told me that I can mix the resin with the purple stuff and use it days later.

I have tried to start the reaction using one of those paint removers
I made the resin boil for a couple of second, but with no luck
I guess I'll have to but the MEKP

thanks for your help

Pablo

alain
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polyester resins

Post by alain » Wed Oct 29, 2003 6:57 am

Hi,
To be a little more precise:

- the clear product is methyl ethyl ketone PEROXYDE (not the solvent MEK)
- violet product is cobalt salt (naphtenate)

Both mixed one after the other in the resin induce decomposition of the peroxyde, which induce starting of polymerisation, which hardens resin, ....

Both mixed together gives light and heat (boum).

May I strongly suggest use of epoxy resin instead of polystyren:
- easier to handle, harmless except if you are strongly allergic
- not flamable
- stronger whan PS if used with glass, but 10 to 50 times more stronger if used with carbon or kevlar (missiles noses).

Good luck (et bon courage)

Alain

alain
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polyester resins

Post by alain » Wed Oct 29, 2003 7:04 am

Hi,
To be a little more precise:

- the clear product is methyl ethyl ketone PEROXYDE (not the solvent MEK)
- violet product is cobalt salt (naphtenate)

Both mixed one after the other in the resin induce decomposition of the peroxyde, which induce starting of polymerisation, which hardens resin, ....

Both mixed together gives light and heat (boum).

May I strongly suggest use of epoxy resin instead of polystyren:
- easier to handle, harmless except if you are strongly allergic
- not flamable
- stronger whan PS if used with glass, but 10 to 50 times more stronger if used with carbon or kevlar (missiles noses).

Good luck (et bon courage)

Alain

bobdickgus
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Re: polyester resins

Post by bobdickgus » Wed Oct 29, 2003 9:12 pm

alain wrote:Hi,
To be a little more precise:

- the clear product is methyl ethyl ketone PEROXYDE (not the solvent MEK)
- violet product is cobalt salt (naphtenate)

Both mixed one after the other in the resin induce decomposition of the peroxyde, which induce starting of polymerisation, which hardens resin, ....

Both mixed together gives light and heat (boum).

May I strongly suggest use of epoxy resin instead of polystyren:
- easier to handle, harmless except if you are strongly allergic
- not flamable
- stronger whan PS if used with glass, but 10 to 50 times more stronger if used with carbon or kevlar (missiles noses).

Good luck (et bon courage)

Alain
You don't have to be strongly allergic to become sensitised to the amine hardeners used in epoxies. try to avoid skin contact as much as possible.
But i agree epoxy is much better than polyester.
Proper mix ratios are essential with epoxy excess harderner or resin can effect the cured product properties markedly.
Blah Blah Yackarty Smackarty

cudabean
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Post by cudabean » Wed Oct 29, 2003 9:18 pm

You don't have to be strongly allergic to become sensitised to the amine hardeners used in epoxies. try to avoid skin contact as much as possible.
But i agree epoxy is much better than polyester.
Proper mix ratios are essential with epoxy excess harderner or resin can effect the cured product properties markedly.
Note too that with epoxy resins, latex may not do it. Always do some testing first on your safety equipment! I heard where one Cozy builder thought he was adequately protecting himself by wearing latex gloves, but it turns out that for whatever reason, they weren't providing an effective barrier to the resin.

cudabean

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