Vinamul 3252

On behalf of Colin Johnson, Glennda Marsh-Letts
<g_marshletts [at] hotmail__com> writes

>    Vinamul3252 poly vinyl acetate/polyethylene copolymer stock
>    solution is soluble in water and acetone. It is a 57% solids
>    suspension in water: for practical purposes I regard this as
>    100% or 'full strength'. Once set it is partially soluble in
>    acetone.
>...
>    I am informed by friends at the BM (British Museum) that recent
>    batches show browning of the stock solution and a tendency to
>    stain original material (a great sin!). It is suspected that the
>    formulation has been changed. Anyway, a substitute is required!

This is in answer to the query on Vinamul 3252. Unfortunately, we
did not include Vinamul 3252 in our full scale testing of PVAC
adhesives but it is a vinyl acetate/ethylene copolymer (VAE)
adhesive with a poly(vinyl alcohol) (PVOH) stabilizing system much
like Jade No. 403 and some of the Elvace products but with different
additives. We have studied Dur-O-Set E-150, another VAE adhesive
with PVOH stabilizing system containing no additives, in some
detail. We have added modifiers to the base adhesive and tested the
dry films of the resulting products as they age for pH, yellowing,
gloss, cohesive strength, flexibility, and removability (swelling in
toluene only). Although rather acidic, which Vinamul 3252 is also,
and has a tendency to become less removable with age (depending on
the additive), Dur-O-Set E-150 generally retained its other
properties after 4 years of aging. We will be testing the films
again next year after nearly 10 years of aging.

I think it will be very interesting to see what the British Museum
find in their review of Vinamul and other emulsions. I would be
interested to know more about this browning of stock solutions. If
they can pin down the cause: expired shelf-life, bad batch or what?
I also agree with Susan Bradley that good practice for these
adhesives should be observed for application and storage. There are
situations where these adhesives should not be used and they should
not be stored and used for years on end. We try to encourage
conservators to find non-adhesive solutions wherever possible, to
use as little as possible (less is best--enough to do the job but no
more), and to use fresh products (observe manufacturer's recommended
shelf life). I usually store these adhesives in the refrigerator and
warm to room temperature before opening).

Concerning Sara Moy's suggestion of Rhoplex AC-33, I would like to
bring to the DistList's attention that this product should probably
not be used on anything that is pH sensitive. It was included in our
testing program and originally the wet emulsion was quite alkaline
(pH 9). Once a film was laid and dried for 1 month the film was in
the neutral region (pH 6ish). As the films aged they became quite
acidic--as low as pH 3.6 on light aging. We caution people that
changes in pH of this magnitude might be damaging to pH sensitive
artifacts.

I hope this is helpful. If anyone would like more information,
please do not hesitate to contact me at any time.

Jane L. Down
Senior Conservation Scientist
Canadian Conservation Institute
1030 Innes Road, Ottawa, Ontario K1A 0M5 Canada
613-998-3721
Fax: 613-998-4721


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                  Conservation DistList Instance 16:71
                   Distributed: Tuesday, May 13, 2003
                       Message Id: cdl-16-71-002
                                  ***