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Question about epoxy resin chemistry..



 
 
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  #1  
Old April 8th 04, 11:53 AM
Chris
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Default Question about epoxy resin chemistry..

Hello everyone.

I am attempting to find a suitable epoxy resin in SE Asia (Thailand
specifically) for building a composite airplane.

It doesn't appear that any recognized brands are sold here, however
there are factories that produce epoxy of all kinds.

However, in order to get the correct epoxy I need to know what to ask
for. Specifically, my research on the web has led me to conclude that
most aviation/aerospace epoxies are Bisphenol-A based resins with an
amine based hardener? Is this correct or have I interpreted the data
incorrectly?

What I am looking for is a very high strength hardner that performs
well in humid climates and is oven cured at about 120C/250F. I also
need good viscosity for long periods at room temperature.

Additionally, I need a room temperature curing epoxy that can cure
much quicker but gives me similar strength.

As I understand the technology, the resin really isn't that important
in the overall equation. Any bisphenol-A resin will generally work.
But the choice of hardner is crucial. Can someone help me understand
the chemistry here? Should I be looking at an amine based hardner, and
if so, which type?

Aromatic Amines
Aliphatic Amines
Cycloaliphatic Amines
Boron-Hydride Amines
etc.

Then there are "modified" versions of each of these, and they also
make and sell blends.

There are other types of hardners as well, and I don't understand
those either.

Can anyone tell me what a "normal" aviation grade expoxy resin
consists of? What about resources that will help me to understand this
so I can make an informed choice.

Thanks for any information.

Chris
Ads
  #3  
Old April 8th 04, 08:11 PM
Ernest Christley
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Posts: n/a
Default

Chris wrote:
Hello everyone.

I am attempting to find a suitable epoxy resin in SE Asia (Thailand
specifically) for building a composite airplane.

It doesn't appear that any recognized brands are sold here, however
there are factories that produce epoxy of all kinds.

However, in order to get the correct epoxy I need to know what to ask
for. Specifically, my research on the web has led me to conclude that
most aviation/aerospace epoxies are Bisphenol-A based resins with an
amine based hardener? Is this correct or have I interpreted the data
incorrectly?
Chris


I'm at the same stage, Chris, except that I'm in the states and still
can't sort through all the muss.

There are multiple brands that I can choose from. They all say they are
the best, and list 100 properties that seem to be important. The
newsgroups are full of people saying, "I used brand X, and I liked it!"
When questioned, they had never used anything else, and had basically
done the inny-minny-mienni-moe roututine out of aircraft spruce.

There were some interesting postings in this newsgroup around 1994,
which discussed the importance of some strength properties of different
formulations, but I don't have any idea how that applies to what's on
the market today.

To make matters worse, I've started looking at premade panels. FR4 and
G-10. One of the other builders just gave me a lead. IL/Norplex
manufactures a variety of premade panels, and publishes data sheets on
the web. Now there is a load of confusion.

I guess the point of this post is the hope that someone out there who
has some real information on the different properties and how that
interrelate will help both of us.

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber
  #4  
Old April 9th 04, 12:54 PM
Corky Scott
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Posts: n/a
Default

On Thu, 08 Apr 2004 19:11:05 GMT, Ernest Christley
wrote:

Chris wrote:
Hello everyone.

I am attempting to find a suitable epoxy resin in SE Asia (Thailand
specifically) for building a composite airplane.

It doesn't appear that any recognized brands are sold here, however
there are factories that produce epoxy of all kinds.

However, in order to get the correct epoxy I need to know what to ask
for. Specifically, my research on the web has led me to conclude that
most aviation/aerospace epoxies are Bisphenol-A based resins with an
amine based hardener? Is this correct or have I interpreted the data
incorrectly?
Chris


I'm at the same stage, Chris, except that I'm in the states and still
can't sort through all the muss.

There are multiple brands that I can choose from. They all say they are
the best, and list 100 properties that seem to be important. The
newsgroups are full of people saying, "I used brand X, and I liked it!"
When questioned, they had never used anything else, and had basically
done the inny-minny-mienni-moe roututine out of aircraft spruce.

There were some interesting postings in this newsgroup around 1994,
which discussed the importance of some strength properties of different
formulations, but I don't have any idea how that applies to what's on
the market today.

To make matters worse, I've started looking at premade panels. FR4 and
G-10. One of the other builders just gave me a lead. IL/Norplex
manufactures a variety of premade panels, and publishes data sheets on
the web. Now there is a load of confusion.

I guess the point of this post is the hope that someone out there who
has some real information on the different properties and how that
interrelate will help both of us.

Ernest, I'm not sure I understand the problem. Most kits that require
fiberglass supply the recommended type of resin. If you are doing
something other than buiding a kit, you could just look at what the
kits supply and use that, couldn't you?

Why is this so difficult? Are you designing your own airplane?

Thanks, Corky Scott


  #5  
Old April 9th 04, 02:29 PM
Stealth Pilot
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Posts: n/a
Default

On Thu, 08 Apr 2004 19:11:05 GMT, Ernest Christley
wrote:

Chris wrote:
Hello everyone.

I am attempting to find a suitable epoxy resin in SE Asia (Thailand
specifically) for building a composite airplane.


the major strength reducing contaminant for epoxy is moisture.
make sure you take humidity into account when doing a layup.
ie the lower the humidity the better.

btw got a ciba geigy dealer nearby? they have aircraft stuff.
Stealth Pilot
  #6  
Old April 9th 04, 04:37 PM
Ernest Christley
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Posts: n/a
Default

Corky Scott wrote:

Ernest, I'm not sure I understand the problem. Most kits that require
fiberglass supply the recommended type of resin. If you are doing
something other than buiding a kit, you could just look at what the
kits supply and use that, couldn't you?

Why is this so difficult? Are you designing your own airplane?

Thanks, Corky Scott



Hey, Corky! I believe you were involved in the most informative thread
I found as I was searching the archives of this group.

Let me see if I can convey a least part of my confusion. The Dyke Delta
JD-2 is a plans built craft...ie, no kit. The plans specify that the
composite wing skins be laid up on a flat table and then wrapped and
riveted to the stainless steel ribs before it is fully cured.

I'm at work, so don't have the plans in front of me, but the instruction
read something like:

The prototype uses polyester vinyl resin. Other types of resins are
available. Follow resin manufacturer's instructions.

May not be the exact wording, but that is the gist of it. John Dyke has
had a lot of problems over the years with the resin continuing to
shrink, exposing the weave, etc. So I want to avoid those problems.
That's the start of the confusion.

Larry LaBeau just completed his Delta a year ago, and had a lot of
success using premade panels. Hmmm...get a stronger, pin-hole free skin
without all the work, smell, or exposure to hazardous chemicals. Great
idea in my book. He bought his panels 6yrs ago. If you look at a
manufactures web site, you'll be inundated with choices, all only
slightly different.

The thread I read here occured in 1994, and it discussed how brittle
resins were and that some 'new' developments were making resins tougher
vs just harder. It discussed how West Systems was not a good laminating
epoxy, even though Aircraft Spruce sells it as a laminating epoxy.

In fact, every place you look that sells epoxy says that every
formulation is the perfect solution for everything. Just a lot of noise
and practically no signal. I go to the EAA meeting and mention "resin
system" and really get noise. If you try this, be ready to duck the
flak from those supporting epoxy vs vinyl ester vs polyester vinyl vs
chicken soup soaked paper napkins. I get the impression that very few
know anything other than what their kit specified, and are arguing from
the 'my choice must be the best, else I'm an idiot' perspective.

I'd like to make these skins once, and not have a lot of regrets in
5yrs. I want to pick the BEST sytem, not just a good system. But as
far as I can tell, the stuff that Lowe's has on its shelf is no
different than the 'aircraft' epoxies, except in the lower price. I
find VERY little difference in the mechanical properties of the
different resins, but a LOT of difference in prices. Either I'm missing
out on something, or a lot of people are getting taken for a ride. At
this point, I'm assuming the former.

Where can I find recent information other than sales brochures? More
importantly, does it really matter? Is the stuff at Lowe's so much
stronger than what's required that it just doesn't make sense to spend more?

I forget who said it, but answers are easy. It's asking the right
questions that's hard. Right now, I'm at the point of not even knowing
if there is a good question to ask.

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber
  #7  
Old April 9th 04, 06:55 PM
Corky Scott
external usenet poster
 
Posts: n/a
Default

On Fri, 09 Apr 2004 15:37:51 GMT, Ernest Christley
wrote:

Corky Scott wrote:

Ernest, I'm not sure I understand the problem. Most kits that require
fiberglass supply the recommended type of resin. If you are doing
something other than buiding a kit, you could just look at what the
kits supply and use that, couldn't you?

Why is this so difficult? Are you designing your own airplane?

Thanks, Corky Scott



Hey, Corky! I believe you were involved in the most informative thread
I found as I was searching the archives of this group.

Let me see if I can convey a least part of my confusion. The Dyke Delta
JD-2 is a plans built craft...ie, no kit. The plans specify that the
composite wing skins be laid up on a flat table and then wrapped and
riveted to the stainless steel ribs before it is fully cured.

I'm at work, so don't have the plans in front of me, but the instruction
read something like:

The prototype uses polyester vinyl resin. Other types of resins are
available. Follow resin manufacturer's instructions.

May not be the exact wording, but that is the gist of it. John Dyke has
had a lot of problems over the years with the resin continuing to
shrink, exposing the weave, etc. So I want to avoid those problems.
That's the start of the confusion.


Ah, got it. The only suggestion I can make would be to speak to the
folks who supply the plans materials and see what type of resin they
are now offering. Perhaps it's different from the one originally
called for by John Dyke.

If that doesn't give you satisfaction, I think I'd speak to the
manufacturers of the various resin systems and ask the opinion of the
experts there. Explain what it is you are trying to do and why you
are asking for their opinion.

The covering process sounds complex: you have to allow the cloth to
semi cure, and then lay it one such that it bonds in place. Man, that
sounds like a narrow window.

Saw one of those things zipping by at a Waco fly-in in Ohio back in
'93 or so. It was FAST.

Corky Scott
  #8  
Old April 9th 04, 11:28 PM
Richard Lamb
external usenet poster
 
Posts: n/a
Default

Corky Scott wrote:

On Fri, 09 Apr 2004 15:37:51 GMT, Ernest Christley
wrote:

Corky Scott wrote:

Ernest, I'm not sure I understand the problem. Most kits that require
fiberglass supply the recommended type of resin. If you are doing
something other than buiding a kit, you could just look at what the
kits supply and use that, couldn't you?

Why is this so difficult? Are you designing your own airplane?

Thanks, Corky Scott



Hey, Corky! I believe you were involved in the most informative thread
I found as I was searching the archives of this group.

Let me see if I can convey a least part of my confusion. The Dyke Delta
JD-2 is a plans built craft...ie, no kit. The plans specify that the
composite wing skins be laid up on a flat table and then wrapped and
riveted to the stainless steel ribs before it is fully cured.

I'm at work, so don't have the plans in front of me, but the instruction
read something like:

The prototype uses polyester vinyl resin. Other types of resins are
available. Follow resin manufacturer's instructions.

May not be the exact wording, but that is the gist of it. John Dyke has
had a lot of problems over the years with the resin continuing to
shrink, exposing the weave, etc. So I want to avoid those problems.
That's the start of the confusion.


Ah, got it. The only suggestion I can make would be to speak to the
folks who supply the plans materials and see what type of resin they
are now offering. Perhaps it's different from the one originally
called for by John Dyke.

If that doesn't give you satisfaction, I think I'd speak to the
manufacturers of the various resin systems and ask the opinion of the
experts there. Explain what it is you are trying to do and why you
are asking for their opinion.

The covering process sounds complex: you have to allow the cloth to
semi cure, and then lay it one such that it bonds in place. Man, that
sounds like a narrow window.

Saw one of those things zipping by at a Waco fly-in in Ohio back in
'93 or so. It was FAST.

Corky Scott


Back in "the old days", polyester resin was all that was really
available.
Not wanting to start the resin wars again, I'll only point out that
JD used polyester resin for the Delta skins.

But if he were designing this plane today?

It would use epoxy resin. And foam cored composite structure -
(instead of the welded/brazed steel structure)

just the way he originally envisioned it.


John was _way_ ahead of his time...

Richard
  #9  
Old April 10th 04, 01:15 AM
Richard Riley
external usenet poster
 
Posts: n/a
Default

On Fri, 09 Apr 2004 15:37:51 GMT, Ernest Christley
wrote:

:In fact, every place you look that sells epoxy says that every
:formulation is the perfect solution for everything. Just a lot of noise
:and practically no signal. I go to the EAA meeting and mention "resin
:system" and really get noise. If you try this, be ready to duck the
:flak from those supporting epoxy vs vinyl ester vs polyester vinyl vs
:chicken soup soaked paper napkins. I get the impression that very few
:know anything other than what their kit specified, and are arguing from
:the 'my choice must be the best, else I'm an idiot' perspective.

Talk to Gary Hunter, of Gary Hunter Composites in Houston, Texas. The
last email I have for him is gluegaru (at) earth (dot) net. Another
one I have is gary (dot) hunter (at) resins (dot) com but that one is
older and my not be good anymore. Do the obvious replacements to
despamify.

"Gary is an Epoxy Resin Chemist for Shell Chemical Company, with over
26 years experience formulating and using epoxies in various end uses
throughout the industry."
  #10  
Old April 10th 04, 02:58 AM
Blueskies
external usenet poster
 
Posts: n/a
Default

Me thinks the 'panels' are riveted on semi-cured because in the good ol' days when resins cured they were brittle. These
are simply skins on the wing and they are not adhered via the resin; the resin is supposed to be slightly green to allow
it to conform to the airfoil without cracking.

Lay out the panels on a big piece of glass and it will be pin hole free when you pull it off. The panel can be trimmed
to size while still on the glass. How many layers of what kind of glass are used in the lay-up? How sharp is the
tightest bend?

--
Dan D.



..
"Corky Scott" wrote in message ...
On Fri, 09 Apr 2004 15:37:51 GMT, Ernest Christley
wrote:

Corky Scott wrote:

Ernest, I'm not sure I understand the problem. Most kits that require
fiberglass supply the recommended type of resin. If you are doing
something other than buiding a kit, you could just look at what the
kits supply and use that, couldn't you?

Why is this so difficult? Are you designing your own airplane?

Thanks, Corky Scott



Hey, Corky! I believe you were involved in the most informative thread
I found as I was searching the archives of this group.

Let me see if I can convey a least part of my confusion. The Dyke Delta
JD-2 is a plans built craft...ie, no kit. The plans specify that the
composite wing skins be laid up on a flat table and then wrapped and
riveted to the stainless steel ribs before it is fully cured.

I'm at work, so don't have the plans in front of me, but the instruction
read something like:

The prototype uses polyester vinyl resin. Other types of resins are
available. Follow resin manufacturer's instructions.

May not be the exact wording, but that is the gist of it. John Dyke has
had a lot of problems over the years with the resin continuing to
shrink, exposing the weave, etc. So I want to avoid those problems.
That's the start of the confusion.


Ah, got it. The only suggestion I can make would be to speak to the
folks who supply the plans materials and see what type of resin they
are now offering. Perhaps it's different from the one originally
called for by John Dyke.

If that doesn't give you satisfaction, I think I'd speak to the
manufacturers of the various resin systems and ask the opinion of the
experts there. Explain what it is you are trying to do and why you
are asking for their opinion.

The covering process sounds complex: you have to allow the cloth to
semi cure, and then lay it one such that it bonds in place. Man, that
sounds like a narrow window.

Saw one of those things zipping by at a Waco fly-in in Ohio back in
'93 or so. It was FAST.

Corky Scott



 




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