I’ve had several objects over the years that are sticky on purpose (game pieces for travel games, Cricut cutting mats, jelly window clings, etc), and usually instructions will say if they begin to lose their stickiness, wash with soap and water and leave out to dry. I understand that debris can cover up a sticky surface, but why does the soap not remove or otherwise create a film that would prevent the sticky from sticking? What properties of the soap and the sticky item are at play? And if the item is entirely sticky, does it count as an adhesive, and why does soap not just remove the adhesive?
In: Chemistry
The sticky object gathers dust over time. Cleaning it removes the dust exposing the adhesive surface.
The objects are made of materials that are inherently sticky. Over time, the surface area of the object comes into contact with dust, lint, or other fine particles, that cling to the object. When enough of the surface is covered in particulates, it inhibits the material from sticking to other surfaces. Washing the object removes the particulates from the surface clearing it to be inherently sticky again.
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soap is an emulsifier. soap molecules are little chains where one end likes water and the other likes oil. most home messes have a significant oil component, which is why it’s such a ubiquitous cleaning agent.
the sticky objects you describe simply don’t bond with the soap. since the creators know how soap works, they simply engineer their product to not react chemically with it.
how they do this varies quite a bit, but they’re usually plastics or rubbers with a compound that prevents them from fully solidifying.
It’s all about molecular/atomic bonds. Sticky things have an electron structure that make them bind well to most other molecules/atoms. Things like oils have the opposite effect: they don’t bind well to most other molecules/atoms. So what happens is that when the oils coat the sticky things, they form a barrier between the sticky material and whatever other materials, so eliminating the stickiness.
Soap + water binds to oils very strongly and pulls them away from other materials. When done to a sticky material, it removes the layer of oil, exposing the sticky surface again, and thus restoring stickiness.
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