Glue Dots

Renita Ryan <ryan.renita [at] dpc__sa__gov__au> writes

>I am wondering if anyone knows what Glue Dots are made from? And is
>this stuff appropriate for use next to collection material? ...

I have not analysed anything with the specific name Glue Dots.  I
have analysed many examples of what is sometimes called Snot Glue or
Credit Card Glue.  This is used as described by Renita to adhere
inserts and ad covers to magazines, and to adhere credit cards to
letters when cards are sent to card holders.  Most of these were
styrene-ethylene/butylene-styrene (SEBS) block copolymers.  Some
were styrene-butadiene copolymer rubbers (SBR) with modified rosin
and hydrocarbon tackifiers.  Several created oily stains on the
paper, probably due to oily plasticizers or tackifiers.  Tacky
adhesives with a "range of tack" quite often (usually) achieve this
by changing plasticizer/tackifier content.  It is possible to do
this by changing molecular weight, but I think it is operationally
much more difficult and expense to change polymerization conditions
during polymer production, than it is to change to amount of
additive.  Also, it is probably a converter who is making the
products with different tack, not the polymer producer.  The
producer supplies a few grades, the converter makes the end-use
product.

Much information about Glue Dots, their properties and their
composition is available at

    <URL:http://www.gluedots.com>

For example, at

    <URL:http://www.gluedots.com/media/k2/attachments/Staining_Discoloration_Statement.pdf>

is the following statement:

   "Staining/Discoloration Statement

    Glue Dots Brand Products are produced using a variety of
    synthetic, rubber-based adhesives. To give these adhesives their
    removable capabilities, varying degrees of oils are used during
    the production process. In the vast majority of cases, these
    oils will not stain or discolor the products being adhered
    together in any way. At the same time, there are no absolutes as
    the effects of the oils are very substrate specific based on the
    absorption properties of the surfaces. In general, as the
    permanence of the adhesive increases the concentration of oil
    decreases. Therefore, our more removable adhesives will have a
    greater chance of staining than will our permanent adhesives.
    Due to these factors, we recommend thoroughly testing the
    performance of the adhesives in actual use whenever
    discoloration is a concern. To speed up the testing time we
    suggest applying the dots to the substrates and heating them to
    150 deg. F for 3 days (72 hours) to simulate results at room
    temperature after 6 months."

MSDS info is given at

    <URL:http://www.gluedots.com/adhesives/technical-information/msds.html>

This states that several products contain "white mineral oil", an
oily liquid that could create stains such as described above (low
tack: 20-30%, medium and high tack: 15-25%), and "severely
hydrotreated heavy naphthenic petroleum oil" (super high tack:
8-15%).  Specific gravity for these is list as 0.95, which is in the
range of hydrocarbon elastomers like SEBS (Kraton: 0.91) and SBR
0.92-0.94).

Because of the risk for staining by mobile components in the Glue
Dots, or oxidation of rosin and hydrocarbon tackifiers (if present)
with subsequent loss of tack, I would not recommend the use of Glue
Dots in direct contact with objects.

R. Scott Williams
Senior Conservation Scientist (Chemist)
Canadian Conservation Institute
1030 Innes Road
Ottawa, Ontario
Canada K1A 0M5
613-998-3721
Fax: 613-998-4721


                                  ***
                  Conservation DistList Instance 26:30
                 Distributed: Monday, December 17, 2012
                       Message Id: cdl-26-30-005
                                  ***