Peeling Direction and Adhesive Force: Explained

[jangheej]

peeling direction...?

when I tried to peel a tape off the surface, I realized that it requires much larger force to pull in the direction shown in the left picture. Why is that?

if we think about it, the adhesive force is caused by the adhesive filament that stretches and breaks as we apply force. But if the angle of pulling is the same, it seems there should be no particular reason why the left case would be harder to peel the tape off.

And also, why does the elastic deformation become more evident in the left case?

 

[JaredJames]

Interesting, something I've never really thought about.

If I had to put an initial guess without really thinking too deeply about it, I'd say it's to do with the concentration of force.

On the right, the force is applied directly to the edge only. Equal force on each tape, but the pressure resulting from the angle of pull is greater in the right hand diagram.

 

[Molydood]

What about if we were to consider the extreme case of zero degrees pulling angle - with left hand diagram we would be attempting to pull all the tape off the table in one go whereas with right hand we would still be doing it sequentially. So it's the vertical force component which is constant in both cases but as I think this extreme case shows us, it is also he horizontal component that helps remove the tape, which is only effective when we pull it in the correct direction

Just my 2c :-)

 

[pallidin]

On the right hand pic, one is only pulling away from the surface a very small amount of total adhesive at a time, and the remaining tape does not resist this.
On the left hand pic, the remaining tape does resist. This resistance can be substantial.