Alternative to xylene

Smadar Gabrieli <smadar.gabrieli [at] uwa__edu__au> writes

>Raymond A. Spiteri <raymond.a.spiteri [at] gov__mt> writews
>
>>We are seeking a less hazardous alternative to xylene to be used in
>>solvent mixtures and for dissolving acrylic resins like Paraloid B72
>>for eventual use in conservation treatments. Can anyone suggest, or
>>has used, a viable alternative. Has anyone used 'Clarify' as an
>>alternative to xylene, and if so, is it a viable alternative.
>
>I don't know of a substitute to xylene for all applications, but
>since you specify B72, it is miscible in Acetone and in Ethanol, or
>a mixture of the two. So is B67. Change the proportion according to
>the necessary working time. When making decision about which one to
>use, check also for change of colour - in different situations one
>or the other may cause change, while the other doesn't.

It is important to note that the glass transition temperature (Tg)
of solvent cast B-72 films depends heavily on the solvent used.  The
recent suggestion to switch to ethanol or acetone from xylene could
lead to large changes in the dry film Tg and hence mechanical
properties like strength, toughness, and elasticity.  The Tg
reported by Hansen et al. for B-72 in acetone is 42C while toluene
gave a film with Tg at 31C. Measurements in my lab for young films
(150 days old and less than 1.5% retained solvent) of 4% w/v B-72
have given Tg values at 46C for acetone, 33C for toluene, and 18C
for xylene.  We are waiting to see if the xylene film, which
currently has retained solvent identical to the toluene film,
eventually achieves a similar Tg value over time as one would expect
from such similar solvents.  The current discrepancy may have to do
with the larger radius of xylene and hence greater plasticization
for equal amounts of solvent.  In our experience ethanol (at least
pure, undenatured ethanol) is a very poor solvent for B72 (at least
the old formulation of B-72) forming a thick mucus at even 4% w/v
concentration that could only be dispersed in the solvent with
vigorous shaking.

Gregory Dale Smith, Ph.D.
Otto N. Frenzel III Senior Conservation Scientist
Indianapolis Museum of Art
4000 Michigan Road
Indianapolis, IN  46208-3326
317-923-1331 x154
Fax: 317-931-1978


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                  Conservation DistList Instance 25:38
                 Distributed: Monday, February 20, 2012
                       Message Id: cdl-25-38-004
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