Explaining the Tensile Strength

The strongest zipper currently on the market is the largest SIZE coil zipper.

Because it is the most CONTINUOUS zipper.
The coils have very small gaps between them unlike the puzzle piece zipper teeth of metal or plastic molded zippers.

This is also why the Zipr Shift zipper is the strongest zipper ever!
There are absolutely zero gaps in the closure’s structure.

Evidence: the ability to make a fully hermetic ring

No other closure in existence can do this.



The trend with current zippers (tooth, coil) is that the larger the interlocking part, the stronger the zipper.
The difference in strength between a size #3 coil zipper and a size #10 coil zipper is pretty large.

This trend of increasing size and shape with increasing zipper strength does NOT hold true with the Zipr Shift zipper.

As far as the trend for zipper strength for the Zipr Shift zipper, it is that the thicker and harder that the metal is, the stronger the closure.
So, whether I make a zipper that’s 20 feet tall or 20 mm tall, the strength won’t increase much if the same exact kind of metal is used.

The strength does not depend on the size of the closure, only on the strength of the metal endoskeleton itself.


What matters is yield strength, hardness, and thickness.
The higher the yield strength, hardness, and thickness, the less the metal is going to want to bend.
And, these strength properties are independent of stiffness (modulus of elasticity) of the metal overall. Metals are pretty constant in stiffness among their type even though there are hundreds of grades of strength of metal type to choose from.

And, it’s important to note that I’m setting the shape of the metal BEFORE tensile testing by putting it into a U-shape.
This means it is already plastically deformed and set in that U-shape.
So, it’s resistance is going to be much greater because the tensile machine is trying to reverse the set deformation.


Making a flat piece of metal into a U-shape = Increase Stiffness, Plastically Deformed (to Yield Strength)
Thicker metal = Increases stiffness
Harder metal = Increased strength


This shape is already set. So, undoing the shape is going to be a huge challenge.
The tensile machine has to undo each bend to get the halves to slip past one another.

…it’s like breaking down a wall. Well, bending it down.


Metal is one stubborn piece of material, especially when super hard and thick.

Yield strength, hardness, and thickness are pretty well correlated with tensile strength.
When you increase any one of those things, tensile strength will increase.



The strongest ZS zipper will be the one with the strongest, stiffest metal.
The size of the overall closure, unlike with the coil zipper, doesn’t matter much.






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5 thoughts on “Explaining the Tensile Strength

        1. No, I’d have to sell a closure with plastic in place of metal for $1500 for that to be the case.
          You can put any rigid material as the endoskeleton. A hard plastic works but it is much less strong than metal especially because it snaps/breaks instead of just bending.

  1. It is actually a great and useful piece of information. I’m satisfied that you just shared this useful info with us. Please keep us informed like this. Thank you for sharing.

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