Silly Putty as body armor

Silly putty is wierd stuff. Push slowly and it deforms, whack it with a hammer and it shatters.

There’s probably a good technical term for this but in general, it’s fun, wierd, stuff.

A cop friend has a body armor vest with steel plates in it, it’s bulky and doesn’t move well. (They make him buy it himself, too - it’s not issued. Cheap bastards!) I was thinking that there should be some cool silly-putty-like material that a vest could be made with- under normal movement it should flex and move but hit quickly it should be stiff.

Anything out there like this?

You bet there’s stuff like that out there!

Liquid Armor

Video: Liquid armor


Yep. I don’t know if it’s of practical use yet.

Actually, I think Non-Newtonian fluid is a better descriptor.

Thixotropy is the term you’re looking for.

That’s the opposite of what Silly Putty does, though. A thixotropic material is stiff when let to stand, but thins out when agitated or stirred. Silly putty is semi-solid, normally, but gets stiffer when struck.

Non-Newtonian fluid describes a wide range of materials with properties ranging from viscoelastic to thixotropic.

Not true. Silly putty is stiff when it stands – it flows slowly with time to fill that egg container, but it’s a slow flow. When worked slowly silly putty thins out (it’s only when struck rapidly that it shatters). A lot of paints are thixotropic – they spread when you work them slowly with a brush, but gel when standing. The refeerences in Jearl Walker’s Flying Circyus of Physics call Silly Putty thixotropic.

It’s a Dilatant material.

It’s a practical application for oobleck!

Well, if Cal is right about the material thinning out when worked slowly, and I’ve no reason to doubt that he is, then that’s not quite right, either. It seems to have properties of several different classes of materials, and not really belonging to any one of them. In that case, Gabe’s “Non-Newtonian fluid” is probably about the most accurate classification, after all.

Could be. Silly Putty is weird stuff, any way you look at it.

I’m so dense that it was years before I realized that “Silly” Putty was probably inspired by "sili-"cone putty.

I’m not sure it’s correct to say it “thins out” when worked slowly. It flows/deforms slowly, like an extremely thick liquid. If you attempt to deform it too quickly, it breaks sharply. I have a hunk of it right here if you want me to perform any experiments. :smiley:


…and I never made the connection until right now! (not that I really *made *a connection as had it made *for *me.)

Wow, more Larry Niven stuff come to life. This sounds exactly like the “impact armor” he had Louis Wu wearing in the Ringworld sequels – ordinarily it was pretty soft and flexible, but if something like a bullet hit it, it would go instantly rigid and protect the user.

so it’s a Viscoelastic, non-newtonian, thixotropic, dilatantic, oobleckian substance, right?

What properties does it possessed when placed on a treadmill?

ducks and flees

But seriously, does anybody have a sizable quantity of silly putty and a gun that we could use for experimenting? Even if it doesn’t work, it should be entertaining.

E-mail Mythbusters. Now.


No, it’s a soquid.

My thought exactly. Q.E.D., paging Q.E.D!

Squink’s cite:
"but when agitated or hit with an impact it stiffens and behaves like a solid. This temporary stiffening occurs less than a millisecond after impact, "

How far does a pistol bullet travel in a millisecond?