Epoxy / Polyester Resins Question

[Wotname]

Originally Posted by ramblinrod

What source are you using for UV that does not include radiant heat and raise the ambient temp?

While I have zero experience with dental epoxy, I have the sneaking suspicion that it is different than marine epoxy.

Anyway, I have to go fix boats.

If you are interested in an FRP primer that covers polyester, epoxy, and the differences between them, I conduct regular seminars in the off-season at marine retailers and yacht clubs in South Central Ontario. Come and take one in, if you are in the area. (Every years sells out quickly, and last year, the first date booked up so fast, a popular marine retailer in Toronto requested a second date, that immediately sold out from folks on the waiting list for the first.)

I'll certainly consider this subject for a future article in a Canadian sailing magazine where I write a regular DIY feature.

BLB coded fluorescent tubes, UV LEDs and some "sun" lamps produce are fair mount of UV without much heat / IR.

But I not an authority on epoxy, just a long term epoxy DIYer and an observer of what I notice . I have never carried out tests of UV on different marine epoxies but for quite some time my "off the shelf goto epoxy" was Bote Cote (Aussie made) and this did seem to cure faster in the presence of UV. Combined with this observation was some info I picked up at one of their sales seminars. Someone asked the question "was there any way of increasing the curing speed without adding heat"? Their answer was to expose it to UV but of course, to protect it from UV as soon as the cure was "green".

Maybe it is particular to their formula, I dunno...
Which is why I asked if UV made any difference to the curing of the average poly and the answer seems to be "no".

Thanks for the invite to your seminars but it is unlikely I will ever be in your part of the world so perhaps you could point me to some half decent on-line resources covering "poly 101 & 210"

FWIW, I bought some poly filler for the first time in decades yesterday to compare it to epoxy fillers regarding ease of use etc.

First step in converting from epoxy to poly is to admit you have a problem

[Three Sisters]

Cobalt based compounds are used to accelerate the cure in polyester resins.

Cobalt naphthenate is one such accelerator, with strict mixing guidelines.

[lateral]

Originally Posted by Three Sisters

Cobalt based compounds are used to accelerate the cure in polyester resins.

Cobalt naphthenate is one such accelerator, with strict mixing guidelines.

Plus DMA Dimethyl aniline which we used for 5min PE "glue" for tacking.
(pretty nasty stuff) Clearer than cobalt.

[minaret]

Gotta remember both cobalt and DMA will cause the laminate to read wet to a meter thereafter. Only one of the reasons not to use (DMA is potentially explosive, just mix it with MEKP to find out the hard way).

I've generally found accelerating cure is not an issue (just use more catalyst, cure times are already much faster than epoxy). However, slowing cure time for big layups can be a problem. To facilitate this, remember that the average manufacturer uses an accelerant (usually cobalt) in the winter without asking you. Therefore you have "summer" and "winter" resin under the exact same label. "Winter" resin will usually be blue and "summer" resin pink. Both turn amber when catalyzed. Do not use "winter" resin for a huge layup, even in the winter! Also there is more than one type of catalyst to consider. Most manufacturers stock catalyst is around 40% MEKP with a proprietary blend of other accelerants and promoters in it. Many make different types of catalyst. Hi Point 90 is generally considered the industry standard but there are many options, some of which dramatically reduce gel time, cure time, or some combination of both. So by a combination of a couple of different catalysts on your shelf, different mix ratios, and some trial and error, you can achieve a wide variety of pot life, gel time, and cure times as well as final Barcol readings.

For instance:


https://blog-fgci.com/2016/08/23/nor...atalyst-guide/


"We have talked about catalyst long and hard on this blog, a post you can read HERE. But now we are going to look a little more closely at the different Norox products offered in gallon size and up. There are some differences, which most people aren’t aware of, so, let’s highlight those differences here so you can be sure you are getting the perfect product for the job.

These products are offered in both red and clear. The red catalyst is preferred for resin applications so you can easily see if the resin and catalyst is properly mixed. The red color isn’t used for gelcoat as it will affect the color.

Norox MEK-P 9 – The standard catalyst for Noroc, the MEK-P 9 gives consistent room temperature performance with both resins and gelcoats. A reliable product of high purity assures quality in every system.

Norox MEK-P 925 – High dimer content gives excellent performance in most Vinylester resins. 925 also performs well when used with General Purpose and Isophtallic resins. This product is what is used for the 1 oz, 2 oz, 8 oz, pint and quart bottles. This is what is used when a customer wants “high-point 90.”

Norox MEK-P 9H – This product features a reduced level of hydrogen peroxide. 9H is particularly useful in critical gelcoat applications. Another application is in heated, continuous mixing systems for polymer concrete.

Noxox MEK-P 30 – A reduced strength version of the 9, the 30 provides the fabricator more accurate metering control in hot weather or with a highly reactive resin. This is a favorite during the hot summer months."

[excess_risk]

Want to thank all who participated in this thread--particularly those with professional experience even when the conversation strayed.

As a DIYer with only a dinghy, it is a luxury to have access to pros through this forum. I'm sure I will refer back to this thread in the future.

Sincere thanks!

[lateral]

I remember doing some odd things with PE years ago, that worked out really well. Repairs to sewer pipes, insitu sill flashings for windows (with bond breaker), repairs to a roof the owner couldn't afford to re-roof at the time.
Really cost & time effective.

I got asked to make some life sized elephant tusks that held up tables in an indian restaurant.
We made female molds but getting the MEKP ratio right was a chore. Of course
we had to water bath them, but the heat generation cracked the first two until
we got it right.I don't think the Ca CO3 helped. Looked like the genuine article. In fact we got flack back then from the conservation people & they wouldn't believe they were fake. We had to show them the mold. I think the ratio was std Norox 0.43% with casting resin.

Something that I've tried , a less brittle epoxy using west 105, is to increase the ratio of resin to up to 6.25:1 . Elongation before failing improved a lot. Of course other attributes suffered, but worked for intended purpose.

[minaret]

Originally Posted by Wotname

BLB coded fluorescent tubes, UV LEDs and some "sun" lamps produce are fair mount of UV without much heat / IR.

But I not an authority on epoxy, just a long term epoxy DIYer and an observer of what I notice . I have never carried out tests of UV on different marine epoxies but for quite some time my "off the shelf goto epoxy" was Bote Cote (Aussie made) and this did seem to cure faster in the presence of UV. Combined with this observation was some info I picked up at one of their sales seminars. Someone asked the question "was there any way of increasing the curing speed without adding heat"? Their answer was to expose it to UV but of course, to protect it from UV as soon as the cure was "green".

Maybe it is particular to their formula, I dunno...
Which is why I asked if UV made any difference to the curing of the average poly and the answer seems to be "no".

Thanks for the invite to your seminars but it is unlikely I will ever be in your part of the world so perhaps you could point me to some half decent on-line resources covering "poly 101 & 210"

FWIW, I bought some poly filler for the first time in decades yesterday to compare it to epoxy fillers regarding ease of use etc.

First step in converting from epoxy to poly is to admit you have a problem

For the record, UV curing resin systems have been around for decades. They are just now really taking off for some purposes. UV will most certainly accelerate the cure cycle of most resin systems, but this stuff cures under a UV lamp with no hardener added. Cure time can be as short as seconds once the cure lamp is flipped on.


UV Curable Epoxies – Illumabond UV Curable Epoxy Systems


https://www.masterbond.com/products/uv-curable-systems

https://www.youtube.com/watch?v=9XjSchhX7Q4

[minaret]

Never ceases to amaze me how once the petty arguments cease and we settle down to posting actual usable factual information, all interest in a thread immediately stops. Guess it just goes to show how far the epoxy guys marketing has gone, very little interest out there in learning to do it like the pro's do instead of using stuff designed for the DIYer. You can bring a horse to water (sometimes), but you can't make him drink...

[smj]

Originally Posted by minaret

Never ceases to amaze me how once the petty arguments cease and we settle down to posting actual usable factual information, all interest in a thread immediately stops. Guess it just goes to show how far the epoxy guys marketing has gone, very little interest out there in learning to do it like the pro's do instead of using stuff designed for the DIYer. You can bring a horse to water (sometimes), but you can't make him drink...

Guess you want to start the petty arguments? You have your opinions and I have mine. I agree and appreciate many of your opinions and disagree with a few. That's life and no your not god, live with it.

[NevisDog]

Not so Minaret - we're still reading and learning, just don't have any more questions now that our misunderstandings have been aired and answered. Never assume that, because no one is arguing any more, no one is listening.

You realise of course that if none of us had voiced our disagreement, none of us would have been any the wiser now - voicing disagreement is a good thing as those few patient, polite posters out there will take pity on us and put us right; only the angry, impatient and rude ones will put us off and we'll learn nothing, which kinda defeats the purpose of these forums.

[minaret]

Originally Posted by NevisDog

Not so Minaret - we're still reading and learning, just don't have any more questions now that our misunderstandings have been aired and answered. Never assume that, because no one is arguing any more, no one is listening.

You realise of course that if none of us had voiced our disagreement, none of us would have been any the wiser now - voicing disagreement is a good thing as those few patient, polite posters out there will take pity on us and put us right; only the angry, impatient and rude ones will put us off and we'll learn nothing, which kinda defeats the purpose of these forums.

Yes, I'm certainly not averse to reasoned debate. And there has been some of that here, leavened with the usual dose of-what to call it? The Internet, I guess.


I'll go out of my way to continue posting relevant information here, always happy to answer questions on resin systems to the best of my ability. Glad to hear someone feels they learned something from it. Stay sticky out there!

[Wotname]

Originally Posted by minaret

Yes, I'm certainly not averse to reasoned debate. And there has been some of that here, leavened with the usual dose of-what to call it? The Internet, I guess.


I'll go out of my way to continue posting relevant information here, always happy to answer questions on resin systems to the best of my ability. Glad to hear someone feels they learned something from it. Stay sticky out there!

FWIW, as the OP, I have learnt quite a lot from this thread - and some of it was even about resins .

A picture tells a thousand words so

[minaret]

Originally Posted by Wotname

FWIW, as the OP, I have learnt quite a lot from this thread - and some of it was even about resins .

A picture tells a thousand words so

to you too!




On UV resin systems-


Recently ran into a guy at Fisco who had developed a UV epoxy resin system for marine use. Fascinating stuff. They carried it for a bit but interest is so low I'm guessing they've already dropped it.

Some of these systems are designed to cure in sunlight, others need a specific wavelength of UV which isn't in sunlight (much), therefore they require a curing lamp. Benefits and drawbacks to both approaches. Neat stuff.