Adhesives

In response to Peter N. Krantz's inquiry about adhesives:

If I understand this query properly, I think there is some
confusion.  I assume that the adhesives being referred to are
emulsions, not resins.  If this is the case, then the additives, not
the resins, are the source of aging problems.  (For example, some
aging problems in polyvinyl acetate emulsions have been linked to
polyvinyl alcohol.  This is additionally confusing because, to
chemists, PVA is polyvinyl alcohol, not polyvinyl acetate.) In
addition, since the point of emulsion adhesives is to deliver a
non-aqueous adhesive within an aqueous carrier, the dry product is
not generally water-soluble.  Of course many emulsions soften in
water when dry, but I have never seen one that can actually be
removed with, for example, a damp swab.

It is my personal opinion that the best way to produce an adhesive
that can be delivered in water (that is, other than ones actually
water-soluble, like some of the cellulose ethers), is to make it
yourself.  PVA resins if dissolved in ethanol will stay in solution
if water is added to the solution;  I have no idea how far this can
be taken, that is, what dilutions will work, or how viscous a liquid
can be produced.  Emulsions can also be made out of common
conservation resins, like B-72, just with the addition of a wetting
agent.  Although I am sure that library conservators do not want to
"make their own," this minimalist approach should be pursued, as the
job of adhesive chemists usually is to use a large number of
additives to produce a product with desirable handling properties,
and that does not suit conservators' needs for being able to predict
the long-term behavior of materials.

There are quite a few articles in the conservation literature that
give some clue as to the complexity of the behavior of commercial
emulsion adhesives--there are several in the IIC adhesives
conference papers.

B. Appelbaum


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                  Conservation DistList Instance 15:16
                 Distributed: Thursday, August 9, 2001
                       Message Id: cdl-15-16-005
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