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Epoxy question

Old 01-23-2007, 02:00 PM
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Gargoyle
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Default Epoxy question

Does thinning epoxy with a drop or two of alcohol affect its adheasion properties ?

Thank you

George
Old 01-23-2007, 02:12 PM
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RCKen
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Default RE: Epoxy question

It depends on how much epoxy and alcohol you have. The alcohol changes the chemical makeup of the epoxy when you thin it that way. If you have a lot of epoxy a couple of drops probably won't hurt. But if you only have a small bit of epoxy the alcohol will definitely make a big change. I prefer to thin epoxy by heating it if I can. Apply a small amount of epoxy to the area you are working in and use a heat gun to thin it out. Since heating shortens the curing time of the epoxy make sure you use 30 minute (or higher) epoxy

Hope this helps

Ken
Old 01-23-2007, 02:22 PM
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Dr1Driver
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Default RE: Epoxy question

RCKen is right on with his recommendations concerning epoxy. One reason alcohol will not work well is the alcohol we buy in the drugstore as "isopropyl" contains a LOT of water. Water is NOT the base for epoxy amd will weaken it and/or even prevent it from drying properly. Acetone will work only slightly better in SMALL quantities.

Dr.1
Old 01-23-2007, 03:58 PM
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Charlie P.
 
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Default RE: Epoxy question

Yep. Rubbing alcohol is 30% or more water.

Isporopyl 91% is . . . 9% water.

Solvent alcohol and stove alcohol are similar; in the 90% range.

"A drop or two" won't make much difference. I use about 30% solvent alcohol with 30 minute epoxy when fuelproofing firewalls. That's just to fill the wood and NOT as a fastener cement.

Always mix the epoxy first and let it set to cross-link, then add whatever - fillers, thinners, thixotropic additives, etc. You can thin epoxy with acetone, also. It adheres, but you're tempting the fates as far as the final overall strength. If you need it thinner you can warm it up in a bath of dishwater temp. hot water. But, the cure time will be much shorter.
Old 01-23-2007, 04:23 PM
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Default RE: Epoxy question

If you use alcohol to thin epoxy, go to the hardware store and get denatured alcohol. As stated, isopropyl has too much water. I use up to about a 1:4 mix it to thin epoxy with no apparent problems. I've read where others use Acetone to thin their epoxy. I have not tried Acetone.

Scott
Old 01-23-2007, 08:44 PM
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da Rock
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Default RE: Epoxy question

Denatured alcohol has no water in it. A can of it is not much more than a quart of rubbing alcohol.
Acetone is sold as a thinner for epoxy. It says it right on the front of the can, "FOR THINNING EPOXY". It is about the same price as Denatured Alcohol, maybe a bit more.

Acetone also wipes CA off Monokote and Ultracote. Nothing else sees to do that as well. It's cheap. It thins epoxy great. Heat often shortens the pot life. The acetone doesn't shorten the pot life. What's not to like about it?
Old 01-23-2007, 09:29 PM
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Default RE: Epoxy question

What's not to like is that testing has shown that thinning epoxy with any solvent makes it:
1. Pourous
2. Weaker
3. Potentially not cure correctly
4. Prone to cracking

If one doesn't want the above, the simple solution is to thin it with heat or buy a thinner type of epoxy. A side benefit of thinning with heat it that it's been shown to improve how well the epoxy wicks into the wood.
Old 01-24-2007, 06:54 AM
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Dr1Driver
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Default RE: Epoxy question

What's not to like about it?

From the MSDS for Acetone:

3. Hazards Identification
Emergency Overview
DANGER! EXTREMELY FLAMMABLE LIQUID AND VAPOR. VAPOR MAY CAUSE
FLASH FIRE. HARMFUL IF SWALLOWED OR INHALED. CAUSES IRRITATION
TO SKIN, EYES AND RESPIRATORY TRACT. AFFECTS CENTRAL NERVOUS
SYSTEM.

J.T. Baker SAF-T-DATA(tm) Ratings (Provided here for your convenience)
---------------
Health Rating: 1 - Slight
Flammability Rating: 4 - Extreme (Flammable)
Reactivity Rating: 2 - Moderate
Contact Rating: 1 - Slight
Lab Protective Equip: GOGGLES; LAB COAT; VENT HOOD; PROPER GLOVES; CLASS B
EXTINGUISHER
Storage Color Code: Red (Flammable)
---------------
Inhalation:
Inhalation of vapors irritates the respiratory tract. May cause coughing, dizziness, dullness, and headache. Higher concentrations can produce central nervous system depression, narcosis, and unconsciousness.

Ingestion:
Swallowing small amounts is not likely to produce harmful effects. Ingestion of larger amounts may produce abdominal pain, nausea and vomiting. Aspiration into lungs can produce severe lung damage and is a medical emergency. Other symptoms are expected to parallel inhalation.

Skin Contact:
Irritating due to defatting action on skin. Causes redness, pain, drying and cracking of the skin.

Eye Contact:
Vapors are irritating to the eyes. Splashes may cause severe irritation, with stinging, tearing, redness and pain.

Chronic Exposure:
Prolonged or repeated skin contact may produce severe irritation or dermatitis.

Aggravation of Pre-existing Conditions:
Use of alcoholic beverages enhances toxic effects. Exposure may increase the toxic potential of chlorinated hydrocarbons, such as chloroform, trichloroethane.
---------------

Do a Google for "MSDS acetone". Pull one up and read it and you'll find a LOT to not like about it.

Dr.1
Old 01-24-2007, 06:24 PM
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da Rock
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Default RE: Epoxy question

Thinning with alcohol does all of the above.
Thinning with acetone (the product developed to thin epoxy) doesn't.

But there is an excellent suggestion just made...................

If you wish for thinner epoxy, then try the ones that're labeled as surfacing resins. I use the stuff all the time for fuelproofing and strengthening the insides of fuselages from inside the firewall back. Works great. Brushes on excellently. And it can also be used structurally (understanding that it's not going to give the same results as regular resins) with fiberglass cloth, and can be layered as long as the layers are done at the same time. Great stuff.

Just modified a P-47 to have a round tunnel through the firewall into the next bulkhead. I wanted to completely enclose the muffler within that big old nose. I used a mailing tube that was about the right size. Cut the holes in the firewall and bulkhead to match the tube. Cut the tube to match the length from hole to hole. CA's the tube into the hole, then painted it and all the raw wood with surfacing resin. It's as solid as anyone would wish. And was dead simple to do. The resin was especially simple and easy to do. If fuelproofs perfectly and turned the tube into a structural piece. There actually wasn't much support fore and aft in that area for the front of the wing's attachment to the fuselage. Now there's more.
Old 02-10-2007, 08:43 PM
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John Sohm
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Default RE: Epoxy question

I've used both denatured alcohol and acetone for thinning epoxy and I keep both in store for just that purpose. I never use more than a couple drops to thin it, we're not talking 1 part hardener to 1 part resin to 1 part alcohol/acetone mix. We're talking just a few drops. As for heating epoxy? Not only does it shorten the pot life but the additional fumes emitted from heated epoxy are worse than the acetone even in a reasonably ventilated area.

The best idea here is the one using the finishing resins. John Greer and associates sells a 1.5 quart finishing resin kit for $24 plus $8 shipping. That's twice as much finishing epoxy as you get with the ZAP brand. It's thinner, cures to a clear hard finish and doesn't "blush" so it's suitable for finishing table tops if you want. It works great.

Check it out at www.jgreer.com

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