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Re: [BKARTS] pva vs. elvace



Hi Litani:

PLEASE DON'T USE THE WRONG ADHESIVE!
Some people are suggesting most cold emulsion adhesives are quite alike. My
own tests have shown otherwise. I have done tests which indicate some cold
emulsion adhesives are only 1/6 as strong as others. Some are being sold for
padding pages, and are meant to tear very easily. Two local bookbinders
where I live it seems are happy to use padding glue and don't care to know
the difference.

I hate to preach, but please, please, be careful to use a proper cold
emulsion adhesive if you are using it for any strength applications like
page binding. Even other applications can use the strength. Low strength
adhesives can peel easily. If in doubt you may just have to do some tests. A
good grade of VAE cast in a thin strip should feel strong. It's supposed to
be about 725 psi in strength which is about 1/4 that of 2 part epoxy. A poor
PVA  or PVAC adhesive may only be a fraction of this. I have found that when
I stretch cured VAE adhesive to it's limit it gets stronger while the PVA
padding glue just went snap and felt more like jelly.

VAE IS BEST
Most modern cold emulsion adhesives are not PVA adhesives. If anything they
may be PVAC (C=copolymer) adhesives. But the best are VAE adhesives. Each is
a different family of adhesive. For more details just do a search on the
COOL website for messages between me and Rupert Evans on this about half a
year ago. If you live outside the US, totally different name brands may
apply.

RECENT REPORT
I just took out a book from my local library on cold emulsion adhesives
published by the Canadian Conservation Institute http://www.cci-icc.gc.ca/
in 2000. Here are a few quotes:

"From this study, a few commercial PVAC adhesives, mostly VAE copolymers,
were identified as having suitable properties for conservation, but there
were still problems."

"For example the best PVAC adhesive identified by the testing was Jade
403...but had an irritating odor...Most other PVAC adhesives tested were too
acidic to be considered for use in conservation.

"This illustrated the problems encountered with testing commercial
products-formulators can change adhesive recipes or stop selling them
without notice. Nevertheless, this study did identify VAE copolymers as
potentially excellent adhesives for conservation."

" In July 1994, a new adhesive project was initiated to examine VAE
copolymers in more detail. Initially we investigated synthesizing a VAE
emulsion specifically for conservation use, but this was not viable or
realistic because the process was far too complicated for the typical
conservation laboratory. Instead we began looking at VAE emulsions sold by
manufacturers as opposed to formulators, suppliers, and distributors. There
are many differences between manufacturers and formulators and the products
they sell...formulators add modifiers...long term physical aging effects are
of little importance to most commercial suppliers."

Of course some of the emulsion names may have changed by now but here are
one's that were tested:

   1. Airflex 320...VAE
   2. Airflex 465...VAE
   3. Dur-O-Set E-150...VAE...most tested in study
   4. Elvace 40705...VAE
   5. Elvace 40709...VAE
   6. Elvace 40724...VAE...Too brittle
   7. Jade 403...PVAC...Smells

None of these were found to be suitable for conservation, they need
additional chemicals added. Most of the commercial VAE adhesives are not
formulated for conservation. They are used by the barrel for things like
paperboard manufacturing. It appears that Dur-O-Set E-150 was identified as
a good adhesive and was used the most in tests. It was found that it's
strength was about 5 MPa or 725 psi without any modifiers but certain
additives reduced both it's initial and long term strength down to as little
as 290 psi. The report also mentioned yellowing with age, reduced
flexibility, but did not mention problems with opening books at low
temperatures.

Ben Wiens...applied energy scientist
Ben Wiens Energy Science Inc.
8-1200 Brunette Ave. Coquitlam BC V3K1G3 Canada
E-mail: ben@benwiens.com
Energy Website: http://www.benwiens.com
Read my popular web-booklet "The Future of Fuel Cells"

-----Original Message-----
Elvace is a brand name for a particular PVA adhesive. PVA is the generic
name.  On the other hand various PVA's can be formulated differently but
they are the same family of adhesives.

Steve Hess
www.archivalmethods.com

-----Original Message-----
Does anyone know what the practical differences are between PVA and
Elvace (45675 from Talas). In the catalog it says that they can be used
for the same things. Why might I choose Elvace over PVA; is one better
for certain materials than the other?

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