Talk:Ultra high molecular weight polyethylene

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If I suppose the carbon bonds lengths are ~1 angstrom, then a molecular weight of 5,000,000 would make a molecule ~30 microns long.

I'd think you could actually see that if you looked closely. Do these fibers have any interesting optical effects? 64.164.5.210 09:15, 4 November 2005 (UTC)

Unfortunately, the other dimension (the width of the polymer) is too small to resolve, being only as wide as any other polyethylene molecule. There aren't any optical effects that I know of, since I believe the olefins are electrically insulating; in fact, polaroid filters (with much smaller chain lengths) show strong anisotropy only when they're doped with iodine.--Joel 21:24, 4 November 2005 (UTC)

[edit] Molecular weight and Density correlation

The following appears in the leading paragraphs of the UHMWPE entry:

"The high molecular weight results from a very good packing of the chains into the crystal structure."

However, in the UHMWPE section of the POLYETHYLENE article, the following appears (emphasis is mine):

"UHMWPE is polyethylene with a molecular weight numbering in the millions, usually between 3.1 and 5.67 million. --->>> The high molecular weight results in less efficient packing of the chains into the crystal structure <<<--- as evidenced by densities less than high density polyethylene (e.g. 0.935 - 0.930)"

It is my understanding that higher molecular weight polymers generally exhibit lower "densities" because the molecules are larger. The example I've most often heard is that a bucket of rocks features higher-weight "molecules" but fewer of them than a similar bucket filled with sand.

Polymer chemists - which of the articles correctly states the correlation between molecular weight and packing?

Charlie 19:01, 19 August 2006 (UTC)euHodos

[edit] Spectra vs Dyneema

Can anyone comment on why Kevlar and Dyneema have entries, but not Spectra. Dyneema and Kevlar are corporate brand names. Spectra is made by Honeywell and Dyneema by DSM. Every post to include anything about Spectra gets deleted.

Thanks —The preceding unsigned comment was added by 2006sf (talk • contribs).

From what I understand from the Dyneema article, they're the same material. Is this incorrect? If they aren't the same material, then they should have separate articles. However, if this is correct and they are the same material, then they should be in one article about the material. Unfortunately, there doesn't seem to be a generic name for the material if so, so we have a problem in deciding what to name the article about the material. Can you enlighten us? — Saxifrage ✎ 21:41, 21 September 2006 (UTC)

Hi. Dyneema and Spectra are different, but I do not know the exact technical differences. Spectra (Honeywell) and Dyneema (DSM) are both brand names for UHMWPE technology which has an entry. Kelvar (DuPont) is also a brand name for aramid technology. Other companies also make aramids under other brand names such as Gold Flex (which has an entry, made by Honeywell). Interesting though... any thoughts? I will research this some more.

SBIC - There are hundreds of UHMWPE morphologies other than the elongated fibers such as Dyneema and Spectra. The most common use for UHMWPE is not in the elongated or fiber form. Million and Mipalin (Mitsui chem) are just a couple. These are used for filters and modifiers of other plastics as well as artificial bones (Hip and knee sockets) These forms are random coil in beads or pellets and generally can not be extruded or processed in the same way shorter chain PE can.

[edit] Merge from Dyneema

At Talk:Dyneema, there seems to be rough consensus that Dyneema/Spectra are merely non-notable name-brands of UHMWPE material, albeit with a gel-spinning process that's particular to them. Since Wikipedia doesn't need an article on the brands (them being not especially notable) and since we already have an generically-titled article covering the material here, the Dyneema/Spectra article should be merged into this one. Any comments or objections? — Saxifrage ✎ 02:44, 4 November 2006 (UTC)

Absolutely not! The UHMWPE article doesn't (and shouldn't) cover the applications of Dyneema as a bulletproof material, as well as other uses - merging the articles would be like combining 'paper' and 'wood.' —The preceding unsigned comment was added by 72.24.243.170 (talk • contribs).

Your analogy is broken. Where Dyneema is a kind of UHMWPE, neither paper nor wood are a kind of the other. There's currently no reasons to have a Dyneema article, as the brand itself is insufficiently notable for Wikipedia to have an article. The solution is to move all the material information from that article into this one, if any is missing, and to let the information about the brand die a proper and deserved death. As such, I don't think you have much to worry about. If UHMWPE should discuss applications, then it will. If not, it won't.

Does that answer your objection? — Saxifrage ✎ 03:21, 22 November 2006 (UTC)

I made the merge today, but perhaps I should have waited? Any suggestions?