What causes this odd office accessory chemical reaction

I was cleaning out a file cabinet in my office and found this unusual
chemical reaction had occured.
I use a Fellowes monitor riser like this one:
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The supporting legs are stackable cylinders of various lenghts that
you can combine for different monitor heights. I had a few extra
cylinders in the file cabinet sitting on a piece of ruled yellow
paper.
Stuffed inside one of the legs, I had a nylon-wrapped silicon "stress
ball".
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The kind you get a trade shows, that are made of the same materials
as many keyboard hand-rests. Not really a gel, but rubbery. The ball
and the leg it was stuffed into were likely in this closed file drawer
for 1-2 years, and not exposed to light or liquids.
The plastic leg where it comes in contact with the stress ball is
breaking down, and liquifying and has pooled on the sheet of paper it
was sitting on. The silicon stress-ball seems intact and the blue
fabric is taut. The plastic leg is softened and has growing stress
fractures as the ball trys to expand.
There is an adjacent plastic leg that was just sitting in contact with
the other on, not interlocked and now they are welded together with
ooze leaking out from between them.
Reply to
Tim.Conama
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It looks like there is plasticiser coming out of the stress ball and into the plastic leg. Are you sure the stress ball is silicone and not plasticised PVC?
Reply to
Colin Cook
I believe it is silica gel. Isn't plasticised PVC rigid, used for signs and stuff like that? This is a ball, rubber-like. Like the wrist rests, and covered in blue lycra.
Reply to
Tim.Conama
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Wrist rests are often made of styrenic block copolymers (such as Kraton) swollen with mineral oil. Mineral oil is a "nice" alternative to plasticizers in that they are regularly used for human contact.
Regardless of the exact chemical details of the gel in the ball, Colin is correct in his assessment: something is coming out of the balls and plasticizing the legs. We can argue about the what the base polymer is and what the plasticizer is, and even about the polymer of the legs, but the reaction is still the same in the end. You could send the materials out for analysis (probably not worth the cost) or try a few of the simple "at-home polymer identification tests" to narrow the options.
By the way of being picky, this would be considered a physical reaction and not a chemical reaction as there are no chemical bonds being formed or broken. Since it is a physical reaction, we can still reach a conclusion on what is occuring without knowing the exact chemistry of the materials.
John Aspen Research, -
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"Turning Questions into Answers"
Opinions expressed herein are my own and may not represent those of my employer.
Reply to
john.spevacek

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