Discoloured fluted polypropylene

Three years ago the State Library of Victoria undertook a project to
pack their objects collection in preparation for moving.  Because of
the distance that the material was to move and the risks involved in
the transport, fully supporting boxes were made from expanded 8mm
polyethylene foam (cell aire) and fluted polypropylene (virgin with
no UV absorber).  The foam was adhered together using hot melt glue
or 3M double sided tape.  In the past year we have noticed that some
of the insides of the boxes have started to yellow where the foam
meets the polypropylene (only on the cut ends of the foam).  Has
anyone noticed this?  We are starting to do some research and are
looking for ideas.  Thanks for your help in advance.

Johann Alcock
State Library of Victoria
Australia

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                  Conservation DistList Instance 9:76
                   Distributed: Sunday, May 19, 1996
                        Message Id: cdl-9-76-005
                                  ***