Wednesday, July 5, 2017

Definitions: Dyneema

Dyneema is a material invented in 1963 and now produced by the Dutch company DSM ("Koninklijke DSM Naamloze vennootschap". To this day we continue to use the English translation of the company's original name, the Nederlandse Staatsmijnen, Dutch State Mines, signifying both our heritage and how far we've come in just over a century.). It is made from ultra high molecular weight polyethylene.


Ethylene is a simple organic chemical (C2H4). Cram it together with water in the right way and you have ethanol, or drinking alcohol (unless you're an ultralighter, in which case you don't drink it but only burn it in your stove to heat noodles for lunch.)

Polyethylene is a chain of ethylene molecules, a polymer. (Poly, get it? "Many, much, multi, more", poly. Polymer.)

So there we have it. Dyneema exists as superlong polyethylene chains all in a bunch. Super super super long polyethylene chains. Very tough too. This helps make Dyneema resistant to most chemicals, to UV radiation, and to micro-critters that might try munching it. In other words, Dyneema is hard to kill just like ordinary old polyethylene, the stuff clear plastic bags are made of, but tweaked, of course.

Officially, Dyneema is known as "High Modulus Polyethylene" or "HMPE", which, if you look that up, takes you back to "ultra high molecular weight polyethylene", which is about where we started with this definition. Big help there, right?

You might also see "HDPE", which stands for "High Density Polyethylene". But you don't need to care, really. Though now you know, in case you are ever asked. Welcome to the club.

OK, so back to the real world. This stuff doesn't absorb water or even easily get wet. Likewise, it feels slippery. It's so slippery that a Dyneema cord won't hardly hold a knot even if you put one there. So what's it good for then? Well Dyneema is used in webbing, specialized rope and cordage like ship's hawsers, body armor, and in making a ripstop fabric called Dyneema Gridstop, something that is used in packs and is loved by backpackers, who are always on the lookout for the next unicorn of fabrics, so maybe you've heard of it already.

That Gridstop, as used in packs, isn't all Dyneema though, just some of it is. You can easily see the Dyneema part — it's the reinforcing threads, which show up white. They show up white because Dyneema, like Spectra (another miracle material), is impervious to dyeing. (Dyneema and Spectra are actually just two brand names for what is almost exactly the same thing.)

Dyneema is gnarly, seriously gnarly, and currently holds the world record as the strongest synthetic fiber in existence, at eight to 15 times the strength of old-fashioned steel. It's also 40 percent stronger than aramids, also known as ye olde "aromatic polyamides" (Kevlar for example), and has twice their cut resistance.

Spectra, to get back to that for a moment, is also less strong somehow than Dyneema, at up to only 10 times the strength of steel, max, or so they say. Dyneema, in case you were wondering, and definitely unlike steel, is light enough to float, while exhibiting a resistance to many chemicals (like water) that is way beyond steel's as well.

Elsewhere in the commercial world, Dyneema has been sneaked into climbing equipment, shoes, and luggage, among other ordinary things.

Though all of the High Modulus Polyethylenes have a lot of strength for little weight, no matter what they're called, they do have a seriously weak spot — they melt at relatively low temperatures. What's low? Somewhere between 266° to 277° F (130° to 136°C), for Dyneema, which hardly rates a woot, so we won't give a woot. Not here, not now, and probably not ever.

So anyway, what else?

Well, while all these HDPE variants could easily be made into a much wider range of fabrics because humans are clever and capable of such achievements, their chemical makeup of extremely long molecules of almost inert substances produces a slippery feel that gives people creepy feelings if it's used in clothes, for example, so it isn't, although HMPE could make your underwear bullet proof.

Something to think about.

We few, we grumpy few, we rumply-hat geezers say to you Effort or Eff it. No sniveling.

Source: How to talk in the woods.


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