Identification of plastic object

Mark Ritchie asked about the identification of clear rigid plastics
strips, 3mm thick, from 1974. The most likely materials are pvc or
pmma (acrylic), with a possibility of one of the cellulose esters.
The smell of rancid butter does suggest cellulose acetate butyrate,
a sheeting material that was made in 3mm thick. PMMA (Plexiglass,
Perspex, etc.) would have been commonly used at the time, but would
be unlikely to degrade with this smell. PVC would probably yellow as
an early sign of degradation. and presumably this would have been
mentioned if it had occurred, the smell would normally be described
as acidic. It could be a semi-plasticised pvc, with a plasticiser
migration. CAB is not a common sheet material but on balance, the
degradation smell is probably the most important clue.



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                  Conservation DistList Instance 15:51
                Distributed: Wednesday, January 23, 2002
                       Message Id: cdl-15-51-001
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