How does “Fix-a-Flat” work?

Can of fix-a-flat blesses needy tire with its contents

If your tire pops and you aren’t able to change it, having a can of Fix-a-Flat can come in awfully handy. This intriguing substance comes in a 16 oz. can and, by following some basic instructions, allows users to (seemingly) magically bring their tire back to life for just long enough to hobble to the nearest mechanic.

It doesn’t take much more than one experience with Fix-a-Flat to wonder: how the heck does this thing work?

The Science Behind Fix-a-Flat

Fix-a-Flat contains both a liquid tire sealant and a small amount of air. When you hook the can up to your tire and push the button, the air inside forces the sealant out and into the tire. Once inside, a latex emulsion foam plugs any leaks, and the propellant expands to inflate the tire. The tire continues to fill with enough gas to get the rim off the ground.

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How does the liquid inside a can of Fix-a-Flat inflate the tire?

The propellant used in Fix-a-Flat is a gas at room temperature, but becomes a liquid when compressed into the can. When the button is pressed and air forces the liquid out of the can, the propellant turns back into a gas. In this way, the amount of propellant that’s packed in a 16 oz. can is able to expand and fill the whole tire.

This particular capability is why this specific gas is chosen; other gasses such as nitrogen and oxygen don’t compress as easily to fit into a small can.

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How does Fix-a-Flat plug the holes in a popped tire?

Of course, if your tire is flat, there’s another problem other than just needing to get it inflated again: the tire has been punctured. To deal with this, the propellant also carries polymer latex with it. When blasted from the can, the latex foams and fills the tire, which is what successfully plugs any minor holes (again, this solution is just enough to get you to the nearest mechanic).

To prevent rust formation and other damage to the wheel, corrosion-inhibitors are also included in the Fix-a-Flat mixture.

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