Proper thinning of epoxy

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Onebadhawk

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You guy's r probably going to say this is nuts...
I used to try to thin epoxy...
I used Aeropoxy 6209 structural,,
was injecting internal fillets,,
was using a flashlight behind the glass so I could see where the injection was flowing to and how it was flowing...
For sure it wasn't flowing freely enough so I tried adding a little alcohol and really whipping it in to get it to mix...
It worked,, I didn't feel good about this though, as I thought I must be making it harden differently / not correctly / there must be a loss of strength...

My next foray into thinning 6209 was better...
I'd mix up a batch and put it in the microwave for an extremely short time,, 2 or 3 seconds...
This worked better,, but the more time, the thinner, and the more time the warmer,, and the warmer the faster it would set up...
I like long work times because in my minds eye the longer it is fluid and the thinner the better it is absorbed and the better the bond will be...

That's as far as I got,, this worked though...

Here comes the nuts part...

I wanted to find a broken microwave being thrown out,, bad carousel or something...
I'd take the microwave emitter out of the unit,, sit it on my bench so that I could
point it at the airframe where I was injecting,, run a switch outside of my garage,,
do the injection,, step outside and turn it on for 2 or 3 seconds.........

OK,, go ahead,,,
Are you nut's,,, lol....

Teddy
 
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tfish

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I thin epoxies a lot...over mach 2+ and 30K no issues. I don't use West Systems. I don't care for it and would probably think twice about thinning it.

Tony
 

Winston

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Pretty clear West Systems doesn't think Thinnng is a good idea. I heartly agree. use epoxy (whoevers brand) at the viscosity provided. As stated in the research deep penetration into glass is not required.
Heat is the only way they recommend. It greatly lowers viscosity, doesn't reduce strength like solvents, but lowers working time.

They say in this reference not over 115F, but I've read a reference elsewhere that I'm almost positive was from them that specified the maximum recommended temp in C which converted to 95F. If you look at their graph on the page I linked to, there is virtually nothing to gain in viscosity reduction after 95F, so I'd definitely go with 95F as the max temp for supplemental heating for thinning.

Perhaps their 115F figure is meant more as a max ambient temp figure to be using the stuff since I could see some unpleasant work environments possibly reaching that.
 

Onebadhawk

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I thin epoxies a lot...over mach 2+ and 30K no issues. I don't use West Systems. I don't care for it and would probably think twice about thinning it.

Tony
Tony,,
Which epoxy do you thin ??
And how do you thin it ??
Is there a way to thin epoxy without adversely affecting
it's strength / bond properties or shortening it's pot life ???

Teddy
 

tfish

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Tony,,
Which epoxy do you thin ??
And how do you thin it ??
Is there a way to thin epoxy without adversely affecting
it's strength / bond properties or shortening it's pot life ???

Teddy
Ted, Not sure I'll be able to the answer some of your questions. I use de-natured alcohol to thin my epoxies as needed. The epoxies that I've thinned are System Three T-88, Raka 900 Medium/631 Fast, an unknown "Chevron High Temperature" stuff ( 5 gallon can off ebay) and some Proline 4100 after if began to thicken after a couple of months.
The amount of thinning veries depending on the epoxy and what I'm using it for. The system Three is very thick compared to the Proline 4100. I like it a tad thinner when I'm laying up body tubes compared to doing tip to tip layups. I did a build thread in 2011 to prove hand layed FG and cheap boat epoxy could be used for some extreme flights https://www.rocketryforum.com/showthread.php?19534-My-next-project&highlight=tuff (i'll agree 4 years later, that there are more extreme flights these days. But for 95% of fliers will never go above mach 2) That rocket went to 37K @ mach 2.2
To thin I just add a very small amount...I'm guessing 1ml in 6 oz of epoxy..again a guess, I never actually measured the amount of alcohol. When you first start mixing it's sort of like milky them in mixes in nicely. you can always add more. I've noticed no difference in working time with thinned epoxy. It does take a couple days for the alcohol smell to go away.

Tony
 

Onebadhawk

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Ted, Not sure I'll be able to the answer some of your questions. I use de-natured alcohol to thin my epoxies as needed. The epoxies that I've thinned are System Three T-88, Raka 900 Medium/631 Fast, an unknown "Chevron High Temperature" stuff ( 5 gallon can off ebay) and some Proline 4100 after if began to thicken after a couple of months.
The amount of thinning veries depending on the epoxy and what I'm using it for. The system Three is very thick compared to the Proline 4100. I like it a tad thinner when I'm laying up body tubes compared to doing tip to tip layups. I did a build thread in 2011 to prove hand layed FG and cheap boat epoxy could be used for some extreme flights https://www.rocketryforum.com/showthread.php?19534-My-next-project&highlight=tuff (i'll agree 4 years later, that there are more extreme flights these days. But for 95% of fliers will never go above mach 2) That rocket went to 37K @ mach 2.2
To thin I just add a very small amount...I'm guessing 1ml in 6 oz of epoxy..again a guess, I never actually measured the amount of alcohol. When you first start mixing it's sort of like milky them in mixes in nicely. you can always add more. I've noticed no difference in working time with thinned epoxy. It does take a couple days for the alcohol smell to go away.

Tony
Wow,, me too,,
That's what I did with the 6209 Aeropoxy...
A bit milky at first but after whipping it really well it smoothed out quite nicely...
I was just concerned that I was detrimentally affecting it's adhesion and strength qualities...
But there was no notable difference in pot life...
And I don't remember an alcohol smell after cure / 24 hours...

Teddy
 

CORZERO

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Here comes the nuts part...

I wanted to find a broken microwave being thrown out,, bad carousel or something...
I'd take the microwave emitter out of the unit,, sit it on my bench so that I could
point it at the airframe where I was injecting,, run a switch outside of my garage,,
do the injection,, step outside and turn it on for 2 or 3 seconds.........

OK,, go ahead,,,
Are you nut's,,, lol....

Teddy
That is actually not a bad idea. In terms of general radiation exposure, time, distance and shielding are the three factors radiologic technologists and any others in the field of radiology are taught which minimize exposure. Specifically, less time, greater distance and greater shielding are the principles which mitigate the harmful effects of radiation. That said, microwaves fall into the category of non-ionizing radiation. So you're genetically safe, however you may feel a slight burn on your skin if over-exposed :)

You could, theoretically, remove the magnetron from a scrap microwave and use it for your experiment. As long as you keep enough distance (not far actually) your skin will not be burned and you will not be at risk to the harmful effects of ionizing radiation as mentioned.

This could be an interesting project. I would create an enclosure of sorts, something to fit your purpose, (rectangular with a way to tune magnetron position?) with conductive material, similar to a Faraday cage. As long as the enclosure material is conductive. Even cardboard and foil or something. Insulating it wouldn't hurt either. And make sure your cat isn't stuck inside it when you throw the switch outside the garage.
 

G_T

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The microwave radiation does rather increase the risk of cataracts IIRC.

IMHO, if you want thinner epoxy, get thinner epoxy. When I want thin, I use MGS for instance, for laminating.

Gerald
 

dhbarr

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You will also disrupt every wifi signal around.
 

RocketFeller

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I have thinned BSI epoxy (15 and 30 minute) with alcohol and it worked well, but I don't know how much loss of strength there could have been.

I have used a heat gun on low power with Aeropoxy structural adhesive and it worked great - it flowed nicely with a glassy finish and none of the tackiness you sometimes get.
 

Onebadhawk

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Tackyness is from not hardening correctly. ..
I have a 4 ft roll of 1/8" lead...
It's from when they were building the x ray rooms in Lenox Hill hospital. ...
I could make a great shield out of that,, and plywood. ...
This isn't nessasary for me now though. ..
When I get around to it my next build will need a tip to tip lamination. ..

Teddy
 

RocketFeller

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Tackyness is from not hardening correctly. ..
I have a 4 ft roll of 1/8" lead...
It's from when they were building the x ray rooms in Lenox Hill hospital. ...
I could make a great shield out of that,, and plywood. ...
This isn't nessasary for me now though. ..
When I get around to it my next build will need a tip to tip lamination. ..

Teddy
I've heard that sometimes the surface won't harden properly in low temperature/high humidity conditions. Not sure if that is necessarily it, but I've noticed that if I warm the epoxy with a heat gun it never happens.

From Aeropoxy FAQ: https://www.ptm-w.com/aeropoxy/aeropoxy-faq.html#4

Why is the Back of the Laminate Tacky the Next Day?

There are several reasons why this can occur. First, the mix ratio could be off. Under or over catalyzed epoxy resins can have the same net effect – rubbery and/or tacky laminate. Second, if the temperature is below 65°F, chances are the laminate has not fully cured, leaving a tacky finish. Third, in extremely humid conditions, moisture can react with the uncured surface forming a tacky compound, called carbamate. This carbamate will not affect the cured properties of the laminate, but will affect adhesion of subsequent layers of epoxy if not removed prior to laminating. The easiest way to prevent this potential problem is to peel ply the final layer of your laminate, protecting the epoxy from the moisture.

It should be noted; laminating in high humidity conditions will not affect the cured properties of the laminate. The tacky condition described above will only occur while the laminate is gelling or curing.
 
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Onebadhawk

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Yes,, and yes Dan..
Low temp and high humidity are the top reasons
I've experienced for not hardening correctly or delaying the hardening...

Teddy
 

CzTeacherMan

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You guy's r probably going to say this is nuts...
I used to try to thin epoxy...
I used Aeropoxy 6209 structural,,
was injecting internal fillets,,
was using a flashlight behind the glass so I could see where the injection was flowing to and how it was flowing...
For sure it wasn't flowing freely enough so I tried adding a little alcohol and really whipping it in to get it to mix...
It worked,, I didn't feel good about this though, as I thought I must be making it harden differently / not correctly / there must be a loss of strength...

My next foray into thinning 6209 was better...
I'd mix up a batch and put it in the microwave for an extremely short time,, 2 or 3 seconds...
This worked better,, but the more time, the thinner, and the more time the warmer,, and the warmer the faster it would set up...
I like long work times because in my minds eye the longer it is fluid and the thinner the better it is absorbed and the better the bond will be...

That's as far as I got,, this worked though...

Here comes the nuts part...

I wanted to find a broken microwave being thrown out,, bad carousel or something...
I'd take the microwave emitter out of the unit,, sit it on my bench so that I could
point it at the airframe where I was injecting,, run a switch outside of my garage,,
do the injection,, step outside and turn it on for 2 or 3 seconds.........

OK,, go ahead,,,
Are you nut's,,, lol....

Teddy
This explains a lot, Teddy... ... ...
I'm not asking if you're nuts, I know you are.
 

watermelonman

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I thinned West with acetone.

It seemed fine at the time, but knowing what I know now I would not do it again.
 

mpitfield

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This explains a lot, Teddy... ... ...
I'm not asking if you're nuts, I know you are.
Yeah but that is part of Teddy's charm, that and the fact that Teddy needs to get that period key fixed as it is clearly sticky..
 

CORZERO

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Tackyness is from not hardening correctly. ..
I have a 4 ft roll of 1/8" lead...
It's from when they were building the x ray rooms in Lenox Hill hospital. ...
I could make a great shield out of that,, and plywood. ...
This isn't nessasary for me now though. ..
When I get around to it my next build will need a tip to tip lamination. ..

Teddy
The seed is planted! 1/8 inch lead? Now you're cooking with... microwaves!

You could use something like this to monitor temps at different points on the structure. You could get this down to a science!

https://www.amazon.com/dp/B00SH4F0LK/?tag=skimlinks_replacement-20
 
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Onebadhawk

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I have the lead sheet and a melting pot ( I used to make fishing sinkers )
but I won't be needing to thin epoxy anytime soon...
I've been leaning toward minimum D and my next build will require a tip to tip lay up
that I am planning on kidnapping Michael Pit for.................

Teddy
 

markkoelsch

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You guy's r probably going to say this is nuts...
I used to try to thin epoxy...
I used Aeropoxy 6209 structural,,
was injecting internal fillets,,
was using a flashlight behind the glass so I could see where the injection was flowing to and how it was flowing...
For sure it wasn't flowing freely enough so I tried adding a little alcohol and really whipping it in to get it to mix...
It worked,, I didn't feel good about this though, as I thought I must be making it harden differently / not correctly / there must be a loss of strength...

My next foray into thinning 6209 was better...
I'd mix up a batch and put it in the microwave for an extremely short time,, 2 or 3 seconds...
This worked better,, but the more time, the thinner, and the more time the warmer,, and the warmer the faster it would set up...
I like long work times because in my minds eye the longer it is fluid and the thinner the better it is absorbed and the better the bond will be...

That's as far as I got,, this worked though...

Here comes the nuts part...

I wanted to find a broken microwave being thrown out,, bad carousel or something...
I'd take the microwave emitter out of the unit,, sit it on my bench so that I could
point it at the airframe where I was injecting,, run a switch outside of my garage,,
do the injection,, step outside and turn it on for 2 or 3 seconds.........

OK,, go ahead,,,
Are you nut's,,, lol....

Teddy
Teddy, I am not liking the idea of the microwave very much. Have you thought about building a composite oven. Heck, even a space heater in the vicinity of the rocket should warm things up adequately.
 

Onebadhawk

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Teddy, I am not liking the idea of the microwave very much. Have you thought about building a composite oven. Heck, even a space heater in the vicinity of the rocket should warm things up adequately.
OK,, OK,, I give,, no microwave,, lol...
I have no build to inject now anyway...
I thought it'd work really well for injections though....

Teddy
 

G_T

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Going by memory here, but if one were to thin epoxy, the proper thinner is isobutyl alcohol. It does the least damage to the resulting structural properties. Lighter alcohols even in rather small percentages can cost up around 50% of ultimate structural properties (I think 50% was with 3% isopropyl alcohol by weight; it doesn't take much of the wrong solvent to really mess up epoxy). Now for your application it may well be that you can afford to lose that much and still be fine. A suitable application might be to wick into soft wood to essentially resin impregnate it near the surface. But as I've said before, for most uses don't thin, but instead change to an appropriate epoxy. They are available with quite a wide range of properties to suit specific needs.

Gerald
 
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