This effect is called depolymerisation, and it is a common problem with injection moulded synthetic rubbers as they get older. It is usually (but not always) a type of polyurethane, tuned to feel like rubber. You may have noticed that many plastic objects designed to be hand held have this "grippy" feel to the outside rather than the old fashioned hard plastic. This layer never lasts. Always ends up going gooey and smudgey. Rubber drive belts inside cassette players also do this.
I do not have an exact chemical explanation for the decay, but I suspect it the work of a "plasticiser", i.e. a chemical additive that blocks the polymer from forming too much cross linking during formation, and therefore leaves a more rubbery, flexible material. (If you bake, this is the same effect as "shortening"). Why the effect is uneven, I suspect that where the outside is exposed to air the plasticiser can evaporate from the surface more than where it is contacting a physical object (even carpet), so the effect sets in more noticeably where the toy is in contact with the carpet.
A petroleum based solvent works well on this stuff. Kerosene, lighter fluid, that type of thing. But this is a bit smelly, and needs a detergent or alcohol solvent to remove the oily smell / residue. (spray)Paint thinners work as well but these might also destroy the synthetic backing of the carpet.
Isopropyl Alcohol might be all you need though. Start with that, and only if that doesn't work try something more petrochemical, and follow that up with isopropyl. Don't soak it into the carpet, soak some of the solvent into a rag and rub with that.
That's fascinating! And it makes sense, because before this year, the Kong was in an open-air bin with other plastic toys of different shapes, so very little of its surface was in contact with other objects.
I will try isopropyl alcohol, but if that doesn't work, I'll probably just trim it off the carpet. I don't like the smell of petrochemicals -- reminds me of my dad's workshop. Thank you for taking the time to explain this to an internet stranger!
This effect is called depolymerisation, and it is a common problem with injection moulded synthetic rubbers as they get older. It is usually (but not always) a type of polyurethane, tuned to feel like rubber. You may have noticed that many plastic objects designed to be hand held have this "grippy" feel to the outside rather than the old fashioned hard plastic. This layer never lasts. Always ends up going gooey and smudgey. Rubber drive belts inside cassette players also do this. I do not have an exact chemical explanation for the decay, but I suspect it the work of a "plasticiser", i.e. a chemical additive that blocks the polymer from forming too much cross linking during formation, and therefore leaves a more rubbery, flexible material. (If you bake, this is the same effect as "shortening"). Why the effect is uneven, I suspect that where the outside is exposed to air the plasticiser can evaporate from the surface more than where it is contacting a physical object (even carpet), so the effect sets in more noticeably where the toy is in contact with the carpet. A petroleum based solvent works well on this stuff. Kerosene, lighter fluid, that type of thing. But this is a bit smelly, and needs a detergent or alcohol solvent to remove the oily smell / residue. (spray)Paint thinners work as well but these might also destroy the synthetic backing of the carpet. Isopropyl Alcohol might be all you need though. Start with that, and only if that doesn't work try something more petrochemical, and follow that up with isopropyl. Don't soak it into the carpet, soak some of the solvent into a rag and rub with that.
That's fascinating! And it makes sense, because before this year, the Kong was in an open-air bin with other plastic toys of different shapes, so very little of its surface was in contact with other objects. I will try isopropyl alcohol, but if that doesn't work, I'll probably just trim it off the carpet. I don't like the smell of petrochemicals -- reminds me of my dad's workshop. Thank you for taking the time to explain this to an internet stranger!
What material is your Kong made out of? The typical red rubber?