Why is packing tape nearly impossible to tear when intact, but easily shreds if you cut the slightest nick into it?
In: 6079
All these answers are wrong.
It is the same as trying to pull apart a closed zipper and properly undoing a zipper by pulling down on the slider.
If you pull on two sides of a zipper, you are trying to unmesh all the teeth at once. When you slide the slider through it, it’s only unmeshing 2 opposing teeth.
It is the same with the tape, except instead of mechanically interlocked zipper teeth, it is the electrostatic forces between the polymer chains holding them together. A nick/cut allows you to separate chains a few at a time.
This is not unique to packing tape, all material behave this way.
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