Question about epoxy resin chemistry..

Stealth Pilot wrote in message . ..
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


Actually, CIBA Geigy sold their entire Araldite product line to
Vantico. (Yes, already talked with them.

Vantico does have a small office here in Thailand, but no word from
them yet on whether their recommended aircraft epoxies are available
in SE Asia, and here in Thailand specifically.

I'll definitely be following up on this though. Thanks for the help.

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.

Try Bruce Pfund, he's the composites editor for Professional
Boatbuilder, http://www.bpspecialprojects.com/

Or try Andy Marshall, he's another composites consultant, an EAA
member.
Marshall Consulting
720 Apploosa Dr.
Walnut Creek, CA USA 94596

Phone: (925) 945-6051
Fax: (925) 945-1461

Dow epoxy resins and hardeners seem to be widely available throughout
SE Asia, and their properties are well known. You're looking for a
system with low to medium viscosity, high glass transition
temperature, room temperature cure. Dow talks a lot about their
resins, but not much about their cured properties. But here's some
suggestions: resins DER 331 or 332. Hardeners DEH 29 or 39. They
appear to have about the right properties.

Chris wrote:
Hello everyone.

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

More about possible Dow resins, I found this on the web from an
ANCIENT KR newsletter that has been machine scanned:

"A search for a local economical source of the Epon 813 and Uersamid
125 resins currently supplied by R/R has produced good prospects of an
alternate type and source. After describing our epoxy application and
the specified Shell Epon 813 to a marketing chemist of the Allied
Resins Corp., he recommended a Dow epoxy D.E.R. 324 with the Uersamid
140 hardener to give better all around performance and safety. The
dilutent used in the D.E.R. 324, an aliphatic glycidyl ether is much
less toxic or allergenic than the BGE or CGE dilutents used in other
epoxie.s, including tha Epon 813, and should be much safer to use,
even for those who have already developed an allergenic reasfcioni
Once a person has become sensitized, it may be difficult to avoid
increased sensitivity from further contact but it turns out that the
dilutent is the most toxic of the epoxy formulation and perhaps a
sensitivity will not react to the D.E.R. 324.

Other characteristics of the 324 such as specific gravity, epoxy
equivalent weight, viscosity, and various strengths and flexibilities
are equivalent to the Epon 813 with the exception that it is almost
odorless which is another plus.

The recommended Uersamid 140 is half as viscous as the Versamid 125
and makes wetting fabrics and fillers such as microballons easier.
The pot life or set time of the 1 to 1 mixture is several hours for
small quantities, down to approx. 1 hour for large batches due to
exothermic heat build up. My experience has been that after a 12 hour
65 F cure it is still flexible and takes about 48 hours for a hard
cure that can be sanded. maximum strength doss not develops for 7
days. The proportion of the Vsrsarnid 140 to the f- resin can range
all the way from 33 PHR (parts per hundred resin) to 400 PHR and still
( have a complete cure. It is unusual that the greater the
proportion of the Uersamid, the greater the flexibility but the less
strength. The 100 PHR (l to 1 mix) would have the beat comprise of
adhesive qualities and elasticity comparable to the Dynel fabric, but
you can see that the ratio is not critical. I believe that a ratio of
65 PHR of Uersamid 140 would be better that 1 to 1 when fiberglass
fabrics were used for a better flexibility match and provide greater
strength.

Now for the price...as of January 1981 the D.E.R. 324 is 821/gal up to
3 gallons and 120/gal in 4 to 19 gallon lots. The Uersamid 140 is
$25/gal., dropping to $24,50 in 4 to 19 gallon lots. Five gallon
pails are Sl9.50/gal. and |24/gal respectively. Prices will probably
go up in April. Allied Resins address is Weymouth Industrial Park,
East Weymouth, WA 02189. They have a nice products catalog that
includes 2 Ib. density liquid urethane foam and lots of other goodies
and have assured me that there is no problem shipping anywhere. If
anyone would like additional info or has had some other experience
with this resin, drop a line to ED COOK.,, 80 J.B. Drive, Warstons
Will, fflA 02648=

A few weeks after I received the first letter this second letter
followed!

Ernie, I received this letter from Paul Semco of Providence, R.I.
after I sent him a sample of the epoxy I wrote you about. He was so
sensitized to the Epon 815 that he couldn't even pick up a sealed
container without breaking out, and as you can see, he had no
reaction at all to the D.E.R. 324.

Ed, I glued up a half dozen wood samples, with the Dows D.E.R. 324,
last week and tested them yesterday. Not one of the samples parted at
the glue Joints. I purposely allowed some the glue to smear on the
most sensitive parts of..my hand for test purpose, Ed, the glue is
great! Absolutely jig reaction at all. I'm amazed, I couldn't touch
the Epon 815 without breaking into a rash....Paul Semca

O.K. you allergic types now have an alternative. Looks like the rest
of us could benefit by the lower price."

It looks like 324 is still available. And I think the hardner is
VERSAMID 140, which is also still available. This MAY have been an
ADHESIVE however, although they talk about using it with Dynel, which
was the wing laminate fabric on the first KRs.

More slush about hardeners, source
http://www.miller-stephenson.com/aero_014.htm:

"Cycloaliphatic Amines

An effective alternative to aromatic amines in composites, adhesives,
tooling, and casting applications. Provide superior
chemical resistance, low viscosity, high gloss and low color films
that are non-blushing and non-yellowing."

It looks like DER 330 has also been used in composite airplanes. To
recap, DER 324, 330, 331 and 332 look likely.
==================================
Now, the other resin question, on the Dyke Delta.

Standard polyester resin, the stuff John Dyke used on the prototype,
continues to cross-link, and therfore shrink/print through, FOREVER.
You have two choices for the thin skin laminate used on this plane.
Use a low shrinkage polyester, such as that used in "cultured marble"
countertops, or ANY epoxy. Epoxies have a different cure mechanism,
and they stop shrinking. Here is one source for the low shrink
polyester: http://www.glen-l.com/supplies/cflex.html

Still more on epoxy resins....

I downloaded the Canard Pusher text files, and started searching for
"Epoxy", this patch in particular caught my attention:

MATERIALS SUBSTITUTION - Those of you who receive "Sport Aviation" may
have noticed an article in the January issue by Hans Neubert inferring
that VariEzes could be built from commercial weave 181 and 143
fiberglass and any one of a number of commercial epoxy systems.
Particularly disturbing was the author's inference that our
distributors were merely pouring the low-cost, highly-toxic 815 resin
into containers with a different label. We are not concerned that
VariEze builders are being misled, as they have been kept aware of the
reasons we had to resort to special formulations and cloth weaves.
"CP" 10 (Oct '76) describes the problems we encountered trying to use
181/143 cloth and attempting to use Shell 815 resin systems. It also
describes our fight to reduce the materials' cost. As we discussed in
"CP" 12, development of the resin/hardener system after the first
vendor went out of business, was a difficult, time-consuming task.
This required five months of testing over 20 different formulations
from three different vendors to develop a system that would meet our
requested specifications of (1) min SPI of II, (2) heat distortion,
(3) odor, (4) room temperature physicals, (5) fuel and foam
compatibility (6) moisture absorption (7) cure time at 65 degrees and
95 degrees (8) exotherm with micro mix, in insulated foam core, (9)
mix ratio, (10) viscosity, and (11) shelf life. It is of interest to
note that one of the larger formulators in the Los Angeles area was
unable to develop a system to simultaneously meet the requirements,
and Applied Plastics required over a dozen different system variants
to arrive at the solution. I have asked Applied Plastics, the RAE
formulator, to respond to the Neubert article. Their comments follow:
"I believe it to be fairly well known that in early 77 the R A resin
system was changed from the "Lambert Blend" to epoxy resin and
hardeners manufactured by Applied Plastics Co. Inc, 612 E. Franklin,
El Segundo, Calif. Applied Plastics is a resin manufacturer supplying
the aircraft and aerospace industry world-wide and have been
manufacturing chemical intermediates for more than twenty-five years.
Explaining the varied technical capabilities, unique abilities of our
chemists and our extensive quality control department would be time
consuming and may indicate an attitude of DEFENSE while to the
contrary we are offensively incensed by this article which in our
opinion does not take sufficient regard for the personal safety of
fellow EAA builders and of others who might follow these suggestions.
The statement that R A resins after March are the familiar Shell Epon
815, only further substantiates our feeling that substituting resin
systems without laboratory evaluation by QUALIFIED INDIVIDUALS can be
extremely dangerous. Our laboratory testing showed the use of B.G.E.
resins in this construction to cause extensive foam damage. Let me
state here that Applied Plastics does not now, and never has, supplied
Shell 815 or Shell 828 as R A resin. The cost comparison example
which suggests you buy 828 by the drum is an extremely hazardous
recommendation, in our opinion. The pages that address themselves to
epoxy hardener substitutions are equally as potentially hazardous.
The suggestion that would encourage a homebuilder to handle materials
such as DETA and TETA are in our opinion reckless and unnecessary.
The following hardeners were not usable because of the safety problems
they represent; also our knowledge of working with these materials
showed them to be too exothermic when used in foam cores with
microballoons: AEP, TETA, SHELL U, SHELL T. Shell A was never
considered as it is a system that requires heat curing and not too
many have autoclaves or walk-in ovens, not to mention the added
responsibilities heat-curing systems require to make good laminates.
Shell T has been discontinued for well over a year. The chart which
showed the above curing agents along with Versamid 140, which is a
high viscosity material, and then suggested that you thin with toluene
or alcohol can again produce a hazardous situation, hazardous when
working with them as well as hazardous from the standpoint that you
change the physical properties of the hardeners when you cut them with
solvents. When solvents are trapped in laminates you will also get
long term degradation of the laminate, and foam core damage. The
development of the RAE slow hardener to meet the requirement of
adequate cure and yet not result in exotherm damage deep in a foam
core, required several months testing. More than a dozen different
systems were tested, not merely to optimize the pot life but in fact
to achieve a system that provided the homebuilder with a safe
structure. Both the fast hardener and the slow hardener required
numerous tests to meet the specifications. Often we would find
material that would be excellent in all properties but then would fail
to meet the all important heat resistance test. This requirement
alone excluded most of the common base hardeners referred to in the
article by Hans Neubert. Let me add that Applied Plastics sells most
of its materials in drum quantities and would be most pleased to pass
on savings through the distributors to builders who have the resources
and the equipment necessary to handle five-hundred-pound drums.
Finally, let me reiterate that from the beginning our intention was to
provide safety and safety at a moderate cost; in our opinion the R A
resin systems are sold at a very low cost for formulated systems."
I have invited Mr. Neubert to our shop for a first-hand demonstration
of what happens when the VariEze layups are attempted with 181 and 143
cloth. While they perform nicely when used in vacuum bag operations
they present unacceptable problems when used in most of the Eze
hand-layups. We made many measurements of this when we originally
attempted to use them. They can more than double some lay up times
due to the frustration of chasing wrinkles and bubbles, they cannot be
flagged for spar caps, they hide air making inspection more difficult
and less reliable, they draw in air after a moderate pass with the
squeegee, their ability to conform to compound curves is less than BID
and UND, the difficulty in determining major fiber orientation leads
to errors, and they require more resin to wet out for the
inexperienced laminator, resulting in a weight increase.
Summarizing, we have spent a considerable amount of effort developing
methods and materials to make it possible for the homebuilder to do
what the aviation industry cannot yet do - that is, build a safe
all-composite airplane. To allow the average individual to be capable
of this task did require other than the commercially available
materials. A VariEze with engine and radio will cost from $5000 to
$10,000. Saving 3% of that by substituting unsafe structural
materials is foolish."

So, you can forget what I suggested about using Versamid 140 for a
hardener, it appears as if it will make the mixed resin too viscous
for hand layups. And don't use Epon 815.

This pitch about RAE epoxy (no longer available) is also interesting
(it's actually the portion of CP 10 referred to above):

"Next, we ran into several problems with the epoxy. Its toxicity was
quite high (SPI-4), mix ratio at 12 percent was very critical and we
were certain we would need two pot lives due to the exotherm damage we
found on our high temperature insulated tests. Thus, due to the high
ventilation and skin protection requirements and uncertainty of local
availability of the required hardener systems, the viability of the
project was in doubt. About that time we met with several composite
engineers working in the advanced composite development department of
a large aerospace corporation. We had a meeting at their facility and
described the entire VariEze structure to them and discussed with them
the epoxy problems we were experiencing. They were anxious to not
only solve our problems but also to suggest that recent developments
of elastomeric - modified epoxy systems would greatly add to the
fatigue life and peel strengths in our structure. We initially tried
a commercially available system but found the work-ability poor due to
higher viscosity and the pot life still not optimum. What followed
was a long series of testing numerous variations, attempting to
optimize the formulation of the epoxy system. Building components for
N4EZ (the homebuilt prototype), samples for strength, environmental
and exotherm tests, gave us a good basis to evaluate the system for
not only physical properties but also for work-ability. The result
was a system that was not only less toxic (SPI - 2) but also had
considerably better fatigue and peel strengths (data are shown in an
article in the July issue of "Sport Aviation")."

This looks like it would be the July 1976, or perhaps 1975 issue. So,
at least THIS epoxy is NOT a STRAIGHT Bisphenol-A resin.

Going back to your original posting, I noticed you were looking for
TWO hardeners, and you wanted the same strength properties in both a
room temperature cure and an elevated temperature cure. I think I've
demonstrated I'm a dangerous amateur in this field, but what little I
DO know suggests that this is impossible. You might be able to
approach the properties of the high temperaure cure hardener by
post-curing the room temperature layups.

Good luck, and I hope I've been of SOME help.

Blueskies wrote:
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?


Wow. Big piece of glass. The skins will be a triangle with 8ft sides.
The plans specify two layers of 7.5 or 10oz glass. They extend up to
the 1" radius of the leading edge, but don't actually go around it.

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

On 10 Apr 2004 17:54:48 -0700, (Ryan Young) wrote:

Still more on epoxy resins....

hedge trimming
Going back to your original posting, I noticed you were looking for
TWO hardeners, and you wanted the same strength properties in both a
room temperature cure and an elevated temperature cure. I think I've
demonstrated I'm a dangerous amateur in this field, but what little I
DO know suggests that this is impossible. You might be able to
approach the properties of the high temperaure cure hardener by
post-curing the room temperature layups.

Good luck, and I hope I've been of SOME help.

Chris and Ryan.
It may be worth noting that you arent limited to epoxy resin for
layups. The production three winged Eagle-X used vinyl ester with
kevlar, glass, honeycomb and carbon fiber.
a tour through the factory was amazing for the total lack of resin
smells.
I recall also that composite nosebowls which are required to be flame
retardant use vinyl ester for that reason.
may be worth an additional search.
Stealth Pilot
Australia

Stealth Pilot wrote in message

It may be worth noting that you arent limited to epoxy resin for
layups. The production three winged Eagle-X used vinyl ester with
kevlar, glass, honeycomb and carbon fiber.
a tour through the factory was amazing for the total lack of resin
smells.
I recall also that composite nosebowls which are required to be flame
retardant use vinyl ester for that reason.
may be worth an additional search.
Stealth Pilot
Australia

Cured Vinyl Esters are no more flame retardant than normal polyesters.
Flame retardant resins have various things (antimony, silica) added
to them to make them so, which usually degrade strength properties.

Vinyl Esters MAY be a better choice for this SE Asia/Direct from the
source application for no other reason than there are not as many
choices to make!

Vinyl Esters need to be promoted to cure, and once they are promoted,
the shelf life is short, about 2 months. Do it yourself promoting is
not a good idea, toxic, reactive stuff ( cobalt naphthenate) is
involved.

The lack of resin smells may have been due to vacuum bagging, which
keeps the styrene fumes in the part! Open molding vinyl ester is just
as smelly as Polyester or Epoxy.

Vinyl Esters have mechanical properties midway between polyesters and
epoxies.

On 11 Apr 2004 21:43:28 -0700, (Ryan Young) wrote:



Cured Vinyl Esters are no more flame retardant than normal polyesters.
Flame retardant resins have various things (antimony, silica) added
to them to make them so, which usually degrade strength properties.

Vinyl Esters MAY be a better choice for this SE Asia/Direct from the
source application for no other reason than there are not as many
choices to make!

Vinyl Esters need to be promoted to cure, and once they are promoted,
the shelf life is short, about 2 months. Do it yourself promoting is
not a good idea, toxic, reactive stuff ( cobalt naphthenate) is
involved.

The lack of resin smells may have been due to vacuum bagging, which
keeps the styrene fumes in the part! Open molding vinyl ester is just
as smelly as Polyester or Epoxy.

Vinyl Esters have mechanical properties midway between polyesters and
epoxies.

thanks.
Stealth Pilot

Yes, I guess that would be a big piece of glass (don't take anything out of context here!). Do the plans/instructions
have any other suggested way to lay up the panels?

As far as bending the finished panels, a two layer lay-up will be quite flexible, even fully cured, and as long as you
don't have to wrap around the LE I'm sure you will not have any problems with cracking. Have you looked at the
http://www.westsystem.com/ site? Good stuff...

--
Dan D.



..
"Ernest Christley" wrote in message om...
Blueskies wrote:
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?


Wow. Big piece of glass. The skins will be a triangle with 8ft sides.
The plans specify two layers of 7.5 or 10oz glass. They extend up to
the 1" radius of the leading edge, but don't actually go around it.

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

Blueskies wrote:

Yes, I guess that would be a big piece of glass (don't take anything out of context here!). Do the plans/instructions
have any other suggested way to lay up the panels?

As far as bending the finished panels, a two layer lay-up will be quite flexible, even fully cured, and as long as you
don't have to wrap around the LE I'm sure you will not have any problems with cracking. Have you looked at the
http://www.westsystem.com/ site? Good stuff...

--
Dan D.

.

I've been told that West does indeed make a laminating resin,
but this isn't it.

West 105/205 is absolute best stuff I've ever used - on wood.

It will probably be great on wood/foam structures.

But it's not what I ever use (again) for laminating glass fabrics.

I used to use Dow 330 / 147(?) but my source quit carrying it
(because I was the only one buying it?)

My impression is that resins like 330 that don't use MDA (Methyl
Diethel Amines???) share a common "problem". At low temperatures
they tend to "separate out". The resin has an odd lumpy look on
the surface and there will be a lump of soft rock candy in the center.

It is real simple to correct by immersing the resin container in hot
water for a while. When the soup is clear again, it's ready to use.

But if the resin is at all "crystallized", it won't completely set -
ever.

It even says so in the directions!
For those who read such things...

Got AeroPoxy(?) last resupply to make a new cowling for Leo's
Super Zodiac. I've used it before, no complaints (other than the
MDA toxicity?).


So, what is it that you are building?

Richard