Is Kevlar a mystery?

[Omniscient]

In another thread this link was posted:

The Latest News from the UK and Around the World | Sky News

Within that link it states:

Scientists still do not know fully why Kevlar is so strong but believe it is because of its molecular composition.

Is this true? It sounds like typical news media laziness, and I’m skeptical that Kevlar is really that much of a mystery. With our knowledge of chemistry, molecular structure and inter-molecular forces I find it very hard to believe that a invented material is really just a fluke of good luck.

[ticker]

Link

[Cardinal]

How could it NOT be because of its molecular structure? It IS its molecular structure. It’s like saying, “I think titanium is strong because of its crystaline structure.”

[Mangetout]

I can just imagine those scientists scratching their beards, sighing and saying “I guess we’ll just never know, so let’s not bother trying”

A duck’s quack is made of Kevlar and no one knows why

[panamajack]

Anyone else think the reporter looked at the first page of ticker’s link and didn’t bother to read the rest of it? Two of the factoids in the article seem to be copied from it (including the ‘mystery’).

After seeing this, though, I will be always hearing " monomer, monomer, monomer" when a train rolls by (and wondering why Berkeley bought a freight company).

[Omniscient]

Please tell me that link wasn’t supposed to act as an answer to my question.

[Popup]

*Originally posted by Omniscient *
**Please tell me that link wasn’t supposed to act as an answer to my question. **

It’s not such a bad answer. If you follow the links you get to:

As you have discovered, there are many components that contribute to the strength of Kevlar, including the fact that Kevlar is a polymer containing aromatic and amide molecular groups. When the molten Kevlar is spun into fibers, the polymers have a crystalline arrangement, with the polymer chains oriented parallel to the fiber’s axis. The amide groups are able to form hydrogen bonds between the polymer chains, which act like glue holding the separate polymer chains together. The most recent XANES images confirm that the aromatic components of Kevlar have a radial (spoke-like) orientation, which allows for a high degree of symmetry and order.

While not discussing the strength of the individual molecular bonds, I thik it gives a pretty good explanation, in layman terms, of WHY it’s strong.
Which semed to be your question.

[Boyo_Jim]

Science does not pretend to address the question of why. Science is about answering the question of how.

[Andy]

So if I as a chemist ask why kevlar has such high impact strength, am I breaking the rules?
How is this different from asking how kevlar has such strength?

I’m off to bin my (organic chemistry) PhD thesis as apparently I asked why.
Oh well, all hail Boyo Jim;)

[Andy]

Oh, and in answer to the OP, I’m just wading through some very dull papers…I should have the answer later as to why Kevlar is so strong.
Sorry, how kevlar is so strong.

[diffdam]

I thought Kevlar was a COMPOSITE of polyimide & glass fibre.If its a composite, whoever was talking about “molecular structure” is a bit off beam.Polyimide is itself very strong & chemically inert.

[Andy]

This seems like a pretty good pseudo-chemical explanation

To achieve both the strength and stiffness of Kevlar®, the molecular chains within the organic fiber needed to be fully extended and perfectly aligned to make them strong, stiff and tough. Such a high degree of alignment was not easy to achieve. Kevlar® fibers are based on poly-paraphenylene terephthalamide, a rigid molecule that makes it easier to realize a fully extended, or straight, chain configuration.
Also, these rigid molecules will even arrange in solutions. Such solutions are called liquid crystalline, which underscores their good organization. Poly-paraphenylene terephthalamide molecules behave like uncooked spaghetti, whereas other, less rigid molecules behave more like cooked strands of spaghetti. Thus, the nature of the molecule makes it easier to achieve the desired aligned structure.

[scr4]

This page basically says the same thing, with a few more diagrams.

It’s funny that it says “I suppose one could even make bullet proof bicycle tires from Kevlar if one felt the need.” Don’t they know that kevlar belted bicycle tires are common these days? They do seem to be more puncture-resistant than regular tires.

[Omniscient]

OK, this last link is the kind of thing I ws looking for.

I was critical of the fist cite because it said on it’s first page that Kevlar was a mystery, basically confirming the Sky News story. I read the relatively remedial instruction pages along with it and didn’t see anything in there that explained what about it was a mystery. So the fact that it seemed to contradict itself was a big issue for me, and the fact that it used a train as a descriptive element didn’t help ;).

So, is there any reason after reading the last link to conclude that the claim in the Sky article is simple bullshit?