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Polyethylene Bulletproof Vests Better Than Kevlar
teflonscout writes "When I think of bulletproof vests, the first word that comes to mind is Kevlar. Wired is running a story on Dynema SB61, a bulletproof material that is made of polyethylene. It is a higher grade of the plastic found in Tupperware. The story also mentions the recall of Second Chance bulletproof vests that were made from Zylon, a material that degraded slowly when exposed to moisture. At least one police officer was injured when a bullet penetrated his Zylon vest. Polyethylene is impervious to moisture. The first vests made from this new material are 5mm thick and can stop a 9mm bullet traveling at 1777 feet per second, which is slightly better than other top of the line vests."
Dynema SB61, a bulletproof material that is made of polyethylene. It is a higher grade of the plastic found in Tupperware.
There goes my idea for a zip-tie & Tupperware bulletproof vest. It also explains why the prototypes failed in the field.
Trolling is a art,
Can't wait to see The Box O' Truth give it a try.
Do they burp when they're hit?
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I think maybe they should rethink the name of the material ("Dynema SB61")when/if it goes into production.
I, for one, would rather not have my bulletproof vest sound like it's a cross of high explosives and bowel cleansing kits.
"Trolls they were, but filled with the evil will of their master: a fell race..." -- J.R.R. Tolkien on Olog-hai
"especially in hot/wet conditions"
And it really brings a whole new dimension to crotchpot cooking.
Like the stuff that's good enough that we already have, that to my knowledge, still isn't being used in Iraq?
Maybe it's a few months out of date, but last I heard, the only troops who have bullet resistant body armor over there are the ones who's families bought/shipped it, or got it from an NPO that is buying them and shipping them to the troops.
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If you haven't heard about the history of "second chance" one of the very first commercial vest manufacturers, that is basically how they sold it. Walk into a police station, pull a gun, shoot oneself at point blank. Put the gun, vest, and business card on the front desk and walk out. As I understand they arrested the founder (Richard Davis) for firing a pistol within city limits, and placed a huge order. He eventually had to quit doing it because all the bruises from the gunshots were starting to give him heart problems.
Read the whole article.
Exerpts:
"Ask not what your country can do for you." --John F. Kennedy
If it's basically like wearing a big plastic slab, isn't that going to get super hot?
That's why you lacquer the chestplates in white to dissipate heat, and give them a black spandex bodysuit underneath...add a scary looking helmet and most of your vitals are covered. In theory it should deflect blaster bolts. Where I'm stationed we wear them all the time (I work in law enforcement).
In practice, they don't stop crap. Like last week this scruffy-looking nutjob with a walking carpet for a sidekick breaks in to rescue his girlfriend. Next thing we know there's a weapons malfunction down in the cell block, and four of my buddies find out the chestplates don't quite work as advertised.
I hate this posting...maybe I can get transferred before something else goes wrong.
- TK421
Study everything, you'll find something you can use - Jason Bourne
Because if you carry less weight in body armor, you carry more weight in ammunition, med supplies, whatever. The protection they have today is generally sufficient for small arms rounds, so they don't usually need more protection. Reducing the weight of current equipment, however, goes a long way toward making your troops more mobile, responsive, and better prepared to face an enemy. Not to mention, it makes them feel better to not lift a 35 pound vest over their head.
I've worn the modern vests, and while they aren't nearly as bad as they were 10 years ago, they still aren't good. If I could get the same protection from something even a quarter less weight, I'd make the switch without a second thought. That two or three extra pounds can mean the difference of being able to march my ass another couple of kilometers to safety or have a few extra rounds of ammunition when I really need it. That's a huge mental advantage, and despite all we say about war, it's the mental aspects (on the soldier) that make it difficult in the long run.
"Growing old is inevitable; growing up is optional."
This is one of those cases where allegory is truly misleading. The article makes the comparison to shopping bags and tupperware in order to emphasize the "everyday" nature of the material. The truth is that they have similar basic components, but the exact composition and processing differences cause one material to be good at resisting bullets and another at storing food (or selling at parties.) Unlike Tupperware, Dyneema vests are composed of woven and laminated fabric.
Dyneema is actually a trade name for a thread derived from Ultra High Molecular Weight polyethylene. The intrinsic strength of the material comes from the ability to increase the length of the polyethylene chain to extreme lengths. Since the structure of UHMW derives its strength mostly from the intermolecular Van-der Waals forces, the longer the polythethylene chains get, the stronger the forces holding the material together become. When the processing of the polythylene allows the length of the chains to become uniform, then you can engineer it into useful forms, such as a fiber which eventually be formed into fabric, then laminated and put on your chest.
Of course, being UHMW, Dyneema has a weakness: Its melting point is about 300 degrees Fahrenheit, or about the temperature of a hot light bulb. Which means that while your body heat might not harm the vest, carelessness in storage might.
Independent tests do not support the army's conclusions. Since there is already some question about the validity of the army's tests (e.g. the designer of the vest that "won" in the army's test says that dragon skin is actually better, the person who conducted the army tests left to work for a dragon skin competitor, etc.) I don't think just repeating the army's conclusions (or quoting the Washington Compost as doing so) really proves anything.
--MarkusQ
The low melting point is also not good in combat situations.
Its highly recommended to wear *cotton* and not nylon clothes, for example, because cotton won't melt to your skin if you survive an IED attack.
-- My Sig is a P228.
My Ph.D. project happens to be on super-fibre materials, nice coincidence.
As it happens, dyneema is highly stretched polyethylene. As such, it melts at a fairly low temperature (and performs less well before reaching such temeratures. Temperatures around 80 degrees centigrade would do...). Twaron and Kevlar are aramids. They decompose at around 400 degrees, and hardly any change in performance is seen.
Now, 80 degrees C is a quite high temperature, but with a (desert) sun baking on a vest, I would rather wear the slightly heavier aramid vest.
B.
Every experiment which ends in a big bang is a good experiment.
I'm from the small town in Michigan in which second chance was founded, and I know the entire history of the "incident"
The officer in that shooting was shot 6 or 7 times. *ONE* bullet penetrated the Zylon, and it was on the periphery of the vest. The edges of *ANY* vest are vulnerable and not as strong as center-mass.
Second chance has 960+ confirmed saves with their body armor.
What they've done to the second chance business as a result is, on the whole, a travesty. They were/are one of the few american manufacturers, and they did nothing wrong at all.
The idea that FMJ bullets tend to zip straight through people leaving a relatively simple wound developed in the late 19th century when ammunition was commonly loaded with flat-based, round-nosed bullets. These bullets were inherently pretty stable due to their center of gravity being forward of the middle of the bullet.
When the spitzer (pointed) bullet was developed in an effort to improve the bullet's aerodynamics and increase range, a secondary effect was discovered. The longer point of the spitzer bullets caused the center of gravity to be pushed more toward the rear of the bullet. This resulted in bullets that were inherently inclined to travel backwards. The gun's rifling was adequate to stabilize these bullets in a point forward orientation through the air, but when they encountered a denser medium (such as a human body) the bullets would tumble as it tried to reorient it's self. The tumbling bullet caused much more sever wounding than the 'icepick' type wounds seen with the older round-nose bullets. Often the combination of tumbling and centrifugal forces (bullets commonly spin in excess of 100,000 rpm) causes the bullet to break into fragments and cause even more nasty wounds (often far worse than what would be seen with soft-point or hollow-point expanding bullets).
Bullet fragmentation is a critical factor in the wounding characteristics of modern military rifle bullets.
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