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Name: Jhon
Status: Student
Grade: 9-12
Location: CO
Country: United States
Date: January 2007


Question:
Stickiness and friction: how does friction apply to tape or any adhesive, or does it?



Replies:
John,

Remember that friction is just a term for the force that has to be overcome in order for something to slide or come away from another object. In that sense, it does not matter what is causing an object to adhere to another, there is a frictional force associated with it.

On the other hand, if you want to look at how different substances can increase or decrease adhesion (and therefore friction), then you would have to look into what different ways adhesion can be achieved. There are many ways to do this. Off the top of my head I can think of: intermolecular attractive forces, permeation, chemisorption, adsorption, entanglement of long chain molecules and so on. Adhesive in sticky tape uses many of these different principles.

Greg (Roberto Gregorius)


The two properties are related, but only with a lot of conditions. Normally, one thinks of friction as the resistance to movement of an object in the direction of the applied force. But the same setup could be thought of as pulling a piece of tape horizontally with respect to a flat object to which it is attached. If the force is vertical with respect to the flat surface, one thinks of that as measuring the adhesive properties of the joint connecting the two objects. There is a similar contrast in a curved object rolling across a flat surface (for example a tire on a car rolling across the flat roadbed) versus a ball bearing rolling across a "sticky" surface of a piece of tape. The "model" one applies to a particular condition depends upon what is useful or conventional, but on a molecular scale the same sorts of forces are involved.

Vince Calder



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