Borax and Glue Slime

name         Nicole
status       other
location     IL

Question -   When I make borax and glue slime with students, I 
explain that the sodium borate from the borax acts as a 
crosslinker to link the chains of polyvinyl alcohol together, 
resulting in a big gooey mass of slime. I recently read the 
Elmer's glue contains 2 polymers - polyvinyl alcohol and 
polyvinyl acetate. When I make slime with borax and Elmer's, am I 
linking the polyvinyl alcohol strands or the polyvinyl acetate 
strands - or both? Help! I want to make sure I'm presenting an 
accurate explanation to my students.
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The crosslinking with Elmer's Glue is primarily with the polyvinyl 
alcohol. However, it may be a bit more complicated in its details. 
The polymers is Elmer's Glue may be a copolymer of polyvinyl alcohol 
and polyvinyl acetate, in which case the co-monomer polyvinyl 
alcohol can participate in the crosslinking with borax. In addition, 
polyvinyl acetate reacts with water (slowly) producing acetic acid 
and a hydroxyl group remaining in the polymer backbone, especially 
if the Elmer's Glue is old. In this case  the hydroxyl group could 
also crosslink with the borax. The fundamental reaction is between 
the hydroxyl group and the boric acid from the borax, whatever the 
source of the hydroxyl group. Elmer's Glue is a much more clever 
product than most people think, so you are wise to want to be 
accurate in your explanation.

Vince Calder
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