I mean on a molecular level, what about the surface of tape makes it adhesive?
In: Chemistry
It depends on the kind of tape, but AFAIK the adhesives used in tape – like most other adhesives such as glue or even just sticky things like paint – have to do two main things. The first thing they have to do is “wet” (or spread out all over) the substrate to which you’re trying to adhere, sort of like water, but more like a thin layer of play-doh or silly putty. It needs to get into all the nooks and crannies, and almost every material (even smooth glass!) has these at both macroscopic and microscopic levels.
The second thing adhesive has to do is resist getting pulled back out (water is only just OK at that), and the third thing it to do is resist getting broken apart from itself or separating from the tape strip. These two jobs are what make tape “stick,” and are sort of at odds with each other. There are different ways to make adhesive not want to separate from the substrate, including some crazy molecular-level interactions that are kind of like static electricity or magnets. That is a question for your next ELI5 though.
Ok since the existing posts are a little over 5yo level here’s my attempt.
Most surfaces (even extremely smooth ones) are actually very complex / textured at a microscopic level.
Tape uses pressure adhesives that are normally solid, but temporarily become a very thick liquid when pressure is applied.
So when you press tape against a surface the adhesive becomes this thick liquid goo, which is able to make its way into the nooks and crannies of the surface. When the pressure is removed, it becomes solid again and it’s physically locked into place.
The fascinating thing here is that you would think it’s a chemical / molecular bond but in reality it’s physical.
That’s also why you can use tape over and over again. There’s no chemical reaction that is ‘spent’ when it’s adhered. The only thing limiting its stickiness over time is when the surface gets dirty.
Tape was only invented about one hundred years ago. The “sticky” on the tape makes it adhere to another surface with pressure. The sticky is made out of long chain polymers plus resin. Essentially, the polymers act like they are wet. They’re almost liquid, with weak bonds that interact with what you stick it to via wetting. Some adhesives get stuck harder over time; they dry out. Adhesive also doesn’t stick well on already wet surfaces and stick very poorly with oils.
The molecules in the polymers also have and make a weak electrical bond with what it sticks to, though Van der Waal’s forces. Electrons help largely with cohesiveness of the tape – stuff sticking to itself.
Different adhesives have different properties, some stick hard and some stick less, some stay sticky and some can bond permanently. This comes down to what polymers and resins are used.
Tape has microscopic claws that latch onto the surface, think of them as the claws on the end of a spiders legg. 🙂
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