Tearing Tape: Understanding the Differences in Fracture Behavior

[JTC]

(If this is posted in the wrong area, please feel free to move it.)

If I take Scotch tape (using the product name), pull out a long strand and then, beginning at the free end, tear it down along its length (to get two strips of the same length, but thinner), the "fracture" (if I may call it that in excess) continues to tear along the length.

But if I take the kind of tape used in packing boxes (I forget the name), the tear deviates to the side.

Why is this?

Is it something about the molecular structure?

 

[A.T.]

Is it something about the molecular structure?

Usually there is a predominant fiber or long molecule orientation. This happens with normal paper too.

 

[JTC]

Usually there it a predominant fiber or long molecule orientation. This happens with normal paper too.

I have been told by a friend -- and I am not a material scientist -- that in this case, there are no mascroscopic fibers. It has something to do with the molecular structure that redirects the tear (at least as far as TAPE is concerned, not paper).

 

[A.T.]

I have been told by a friend -- and I am not a material scientist -- that in this case, there are no mascroscopic fibers. It has something to do with the molecular structure that redirects the tear (at least as far as TAPE is concerned, not paper).

That's why I said fibers or long molecules. There is paper tape too, but the transparent type is made of long molecules (PVC or PP). The orientation depends on whether you want the tape to be very strong along its length, or easy to tear by hand.

 

[JTC]

That's why I said fibers or long molecules. There is paper tape too, but the transparent type is made of long molecules (PVC or PP). The orientation depends on whether you want the tape to be very strong along its length, or easy to tear by hand.

Ah... thank you!