Weeping polyurethane elastomer sculpture

This posting seeks information about the deterioration and treatment
of cast elastomeric polyurethane sculptures.

I am investigating a cast elastomeric polyurethane sculpture.  A
portion of the sculpture is converting from an elastic solid to a
viscous liquid.  The viscous liquid flows at "glacial" speed,
dissolving the underlying elastic solid and dripping from the
sculpture.  The sculpture was fabricated in the 1970s, but attempts
to reach the fabricator for information about fabrication materials
and process have been unsuccessful.

Light microscopy of samples of the viscous liquid reveals clear
birefringent particles (filler)--Chemical analysis of the clear
birefringent particles using Raman microspectroscopy showed bands
consistent with quartz, which was confirmed using FTIR
microspectroscopy--and fine black particles (pigment) dispersed in a
clear liquid.  Light microscopy also reveals that a specimen of the
elastic solid softens and slowly dissolves on prolonged immersion in
the viscous liquid.

Chemical analyses of the viscous liquid and elastic solid using FTIR
microspectroscopy give nearly identical mid-infrared spectra, which
show features consistent with reference spectra for polypropylene
glycol and diisocyanate-type ether urethane, and features that
suggest the presence of aromatic plasticizer. I am corresponding
with Thea Van Oosten, who has investigated deterioration of a series
of elastomeric polyurethane chairs by Pesce, and would be grateful
to hear from conservators and scientists who have observed weeping
or similar deterioration on cast elastomeric polyurethane objects,
in an effort to determine the cause of deterioration and whether the
deterioration can be arrested.

James Martin


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                  Conservation DistList Instance 22:59
                 Distributed: Wednesday, April 15, 2009
                       Message Id: cdl-22-59-008
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