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Old 12-04-2008, 13:58   #16
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Thumbs up Protective gear when working with chemicals

"all our personel is protected with gloves and covered cloting , eye glasses etc to prevent them from touching epoxy" Excellent, Gideon, I'm glad you are taking good care of your workers!
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Old 12-04-2008, 14:05   #17
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Quote:
Originally Posted by BigCat View Post
"all our personel is protected with gloves and covered cloting , eye glasses etc to prevent them from touching epoxy" Excellent, Gideon, I'm glad you are taking good care of your workers!

My employees are the most important assets to me in my factory
we work like a team and have fun doing it.
I sometimes visit other factorys and am almost always amazed how poorly the working conditions are , unsafe and some times even unhuman
I cannot live with that.
Gideon
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Old 13-04-2008, 02:05   #18
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EVERYONE will eventually develop an allergy to epoxy, given enough exposure. Some folks will get it in a few exposures, others may take years. The amount of exposure you get with each episode has a lot to do with it, as the effects are cumulative.

Management of Allergic Skin Disease by Epoxy’s ...
http://www.saioh.org/ioha2005/Procee...PaperH1web.pdf

"... Epoxies are potent sensitizers. Frequently, skin contact with epoxy resins or their hardeners gives rise to allergic contact dermatitis (eczema). The contact dermatitis generally expressed at the hands or forearms, and sometimes in the face.
Workers that have acquired an epoxy-allergy will be faced with an ever stronger skin reaction after each contact with the products. Avoiding every contact is the only option left. In practice, this means that the worker will have to change his profession.
In the Dutch construction industry it has been estimated that one out of every five
workers that frequently use epoxies (e.g. floor layers) develops an epoxy-allergy at a certain moment in their career ..."

That Gideon's factory has only experienced about 1/10Th the expected allergy rate, is a testament to the care & control they exert in avoiding exposure.
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Old 13-04-2008, 10:48   #19
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Here in Denmark, you need a license to purchase epoxy for proffesional use. You get the license by passing a recognised course in safety procedures.

In fact oil/thinner based paints will be forbidden in the future for buildings, as there have been too many cases of painters developing serious health problems, and they still don't bother with protection.

If you employ someone to fix your roof, and he goes up without the required safety equipment, you as the owner as well as the guy on the roof are liable to a 5000$ fine -each!

Health and safety cost societies large amounts of money when people get hurt/sick.

I think it's good that these threads highlight these issues as well.

Regards

Alan
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Old 13-04-2008, 11:22   #20
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Epoxy is yummy

(note the feet on Jullian in the fore ground, me in the back ground)

This was doing the hulls of my last 30 foot cat.

I dont swim in it quite like that anymore.

Dave
I think the most comical part of this photo is Jullian's glove. One, single rubber/latex glove to protect him, while he swims in the stuff.

Which reminds me a lot of this:

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Old 13-04-2008, 11:27   #21
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It is the same in the Netherlands for all type of resin if any of you has ever experienced a thermal runaway or in laymans terms a load of resin setting of make sure you are not nearby !!!
It heats up to 600 degrees catches fire and can explode.
Gideon
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Old 13-04-2008, 15:06   #22
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Runaway resin

Quote:
Originally Posted by fastcat435 View Post
It is the same in the Netherlands for all type of resin if any of you has ever experienced a thermal runaway or in laymans terms a load of resin setting of make sure you are not nearby !!!
It heats up to 600 degrees catches fire and can explode.
Gideon
I spent 6 months at Skookum boat works in Port Townsend, Washington, USA, in 1974. They taught home boat builders who bought hulls from them a lot about boat building in a kind of informal apprenticeship. It was a fiberglass shop, and they made a lot of fishing boats. The USCG required a very high standard for fishing boats of 50% resin, which is very high for a hand layup, but Skookum regularly attained it.

I bought a hull and deck from them, and finished it out. This was Batwing, which is shown in Practical Junk Rig, by Hasler and McCloud.

I saw one runaway there in which some workers poured about a gallon of resin into a container for use as a filler in something, and it ended up looking like the top of a pizza that was ready to come out of the oven. Obviously, someone had been sloppy with the catalyst and used too much. The moral of the story is, have a thermometer to measure room temperature, and use a chart that tells you how much catalyst to use.
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Old 14-04-2008, 15:52   #23
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Balsa vs. various foams tested to destruction

Here is a head to head test of different cores, where everything is the same besides the cores, so you get a real feel for what the relative strengths are. They even show photos of the tests, so you can see just what the dry technical language is telling us.

http://www.acmanet.org/resources/06p...htinger172.pdf
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Old 14-04-2008, 19:11   #24
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Very Interesting.
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Old 15-04-2008, 12:26   #25
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Correcting more misinfomation about vinylester

I have seen posts which say that vinylester is not used in making airplanes. It is in common use in making small airplanes.

Also, I have seen posts which claim that vinylester is not used in laminating carbon fiber. It is in common use in laminating carbon fiber.

Googling "vinylester airplane" will bring over 50,000 hits, and googling "vinylester carbon fiber" brings over 200,000 hits.

One example:

"Reichhold’s HYDREX 100 vinyl ester was chosen by Velocity in conjunction with carbon fiber and Kevlar reinforcements to provide the forty-one-foot Velocity Super Sport with both the strength and beauty required for a boat capable of speeds over 100 m.p.h."

from:
HYDREX 100 (33350) Vinyl Ester Named
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Old 15-04-2008, 14:16   #26
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Styrene boil in vinylester infusion?

I asked Reichhold, manufacturers of Dion 9300-10 if styrene boil could be an issue when infusing that product, since Gideon (aka fastcat435,) says it is a problem.



My question: 'My research indicates that vinylester resins vary quite a lot in their vacuum tolerance in resin infusion for boat building-at least from 24 to 29" of mercury. What vacuum level will Dion 9300-10 tolerate with 1.5% antimony trioxide? We are contemplating using this product on a 65' catamaran. We are a customer of Composites One, which is a dealer of your products.'


Here is their answer:


"You should be able to run the resin at a high vacuum level. I think there is a bit of a misconception about what I have heard termed as “styrene boil” in the composites industry. I have a suspicion would be difficult, on a large production scale, to lower the pressure in the infusion process below the vapor pressure of styrene at room temperature; not to mention there is a pressure rise in the portion of the laminate that is wet out that progresses toward atmospheric pressure as the laminate becomes fully wet. Lower pressures will allow styrene to come off at a faster rate, but the flow front area is relatively small… As far as backing off once the laminate is wet out… that’s really a processing choice associated with your infusion setup. I recently saw an ACMA paper that implied that another component of the mixed resin (in this case the initiator MEKP) could “boil off” and may be the cause of bubbles in the cured laminate. The paper cites a much higher vapor pressure for MEKP than I have seen in the literature and again doesn’t account for the fact that the wet-out-laminate is no longer at the pressure level of the applied vacuum.

Generally if you see air bubbles, it is from a leak in the system, entrapped air in the resin prior to infusion or using the wrong initiator (i.e. some resins will foam or bubble if you use the wrong initiator).

Steve Brooks"


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Old 15-04-2008, 14:40   #27
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Further reading indicates that small air bubbles (or dissolved air) in the resin become big ones when the vacuum is supplied, which makes perfect sense to me. Many feel that this is the source of bubbles which are (perhaps) mistakenly attributed to syrene boil. This is, of course, what happens when divers get the bends. Some suggest pre-vacuuming the resin to remove entrapped air before mixing in the catalyst to prevent this.
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Old 15-04-2008, 14:47   #28
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That was a "no-answer". You asked a very specific question, and he replied with some general statements.

I suggest you ask him to specify vacuum levels at different temperatures.

How the pressure in the wetted out part rises to atmospheric pressure, while the whole part is under vacuum, is difficult for me to comprehend. Pressure is force per unit area, how that changes with the atmospheric pressure exerting force on the outside must be one of the new wonders of science

If it is the initiator boiling off, then that will surely decrease the quality of the bond?
As far as I can determine, it's not the styrene that boils, but the other components. Styrene boils at 5-10 mm Hg, which is around 98-99% vacuum

Ask their technical department to answer instead of their marketing guy.

Regards

Alan
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Old 15-04-2008, 15:28   #29
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Styrene boiling - AOC speaks

"Ask their technical department to answer instead of their marketing guy." I never ask marketing if I have a tech question. That was their tech answer guy, and I don't think he knows the answer.

Here is my correspondence with AOC, another vinylester manufacturer:

The product can and is used without post curing IE Room temperature lamination.
The tensile strength and % elongation question is best answered by noting that the properties noted on the data sheet are clear cast coupons of neat resin 1/8 inch thick. These are not glass filled laminate values.

In a glass filled laminate; Very likely you are going to get ≈ 80% of the modulus properties that we report without post curing, likely higher elongation and about the same flex and tensile strengths. Attached are three laminate studies of Tensile, Flexure and Compression comparing ambient to elevated temperature. In all cases the K023-AAA-00 is the second column of information

As to your earlier three questions we offer the following:
  • Is this resin suitable for infusion
    • Yes
  • What vacuum will it tolerate without styrene boil
    • Expect styrene boil at 27 in/Hg and above on leading edges of flow
  • Do you need to back off vacuum after initial vacuum
    • A Yes after composite is completely infused reduce vacuum to 12 – 14 in/Hg and maintain until laminate exotherm is passed.
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Old 15-04-2008, 15:34   #30
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Reducing pressure after the resin is completely distributed is what Derek Kelsall does with polyester, too. My somewhat speculative conclusion is that entrapped air is more of a problem than any styrene issues, and that one gets the best results by being very careful not to mix in air when mixing in the catalyst, and / or pre-vacuuming the resin to remove air. Then one should reduce the vacuum to 1/2 once the resin is distributed.

From the panel study above I conclude that, if you try to super-compress your fiber reinforcement, you had better use a thicker core than you would if you didn't, or it will be counterproductive because the decreased thickness does more harm than the good you do by decreasing the resin content.
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