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