Polyvinyl acetate

I have read with interest Leslie Beck and Barbara Appelbaum's
comments about poly(vinyl acetate) adhesives.  Here are my thoughts
on the subject.

First, about terminology:  According to the ASTM Annual Book of
Standards (vol. 8.04, Standard D 1600 "Standard Terminology Relating
to Abbreviations, Acronyms and Codes for Terms Relating to
Plastics"),  the "designation that has come into established use"
for poly(vinyl acetate) is PVAC.  The one for poly(vinyl alcohol) is
PVAL not PVA.  By the way, the generally accepted way to write these
chemical names in full is "poly(vinyl acetate)" and not "polyvinyl
acetate".  In our adhesive research at the Canadian Conservation
Institute (CCI), we use the abbreviations PVAC and PVAL and not PVA.

Second, about using dispersions versus resins:  In 1990, I was asked
by the Library Binding Institute in the US to review W.J. Barrow's
research which was done in 1965 that stated that "an emulsion
copolymer of internally plasticized PVAC that is flexible and that
will not crosslink on long term aging at normal room temperature"
should be used for bookbinding adhesives. I reviewed Barrows
research and came to the conclusion that his recommendations were
still valid.  The PVAC resins from solutions that Barbara Appelbaum
talks about, I believe, are homopolymers.  The homopolymer PVAC
resins in solution that we tested at CCI were very brittle and not
flexible as Barrows suggests they should be.

Third, about additives for PVAC adhesives:  To my knowledge, not
much is known about what might make films made from PVAC dispersions
hard to remove or redissolve with time.  We are currently doing
research in this area on a vinyl acetate/ethylene copolymer emulsion
adhesive.  I should have much more to say about additives and what
their effect is on PVAC emulsions in the near future.  Anyone
interested, could write to me at the address below.

I hope this is helpful to your readers.

Jane 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 11:45
                 Distributed: Monday, November 17, 1997
                       Message Id: cdl-11-45-003
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