Yesterday I embarked on what turned out to be a rather long “bit” on textiles, covering at that point polyester and various different fibres of biological origin. Today I plan to finish that off by returning to synthetic fibres and also talking about inorganic versions, among other things.
The illustration above shows a monomer of Nylon-66. There are a number of different types of nylon, hence the, er, numbers, but before going there I should explain what a monomer is, and also a polymer. A polymer is a potentially infinitely long molecule, sometimes branched and sometimes a single chain, whose links consist of repeating units of a smaller molecule, called a monomer. There can also be alternating units, in which case the substance is called a copolymer. One of the simplest polymers is polyethylene, which we generally call polythene, which can be branched but each sequence of molecules has the following structural formula:
Among the fibres I’ve already mentioned, cellulose is very like a classic synthetic polymer as it consists of repeating units of glucose, but protein-based textiles are not generally like this, since they are sometimes composites, as with silk, and also have more complex structures consisting of repeating units of larger molecules. However, it is possible to make simple polymers of amino acids, as has been done using a repeating chain of uracils in an RNA molecule, which would in turn produce polyphenylalanine. The other possibilities here without actual genetic engineering would be polyproline, polylysine and polyglycine, the last of which is also the simplest and is not chiral (left- or right-handed). However, these are not the way synthetic fibres are usually prepared.
Back to nylon. In the interwar period demand for silken hosiery climbed in the West as diplomatic relations with Japan went into decline, so there was economic pressure to develop a better substitute for silk. In the 1930s, the Du Pont scientist Wallace Carothers was attempting to make molecules with large rings to use in perfumery, but instead found that they formed chains. The monomers he used were hexamethylenediamine and adipic acid. That twenty-letter word probably looks intimidating to a non-chemist, but in general systematic names for compounds are simply verbal versions of their structural formulæ organised along carefully defined lines. Hence there is methanol, ethanol, propanol, butanol, metanoic, ethanoic, propanoic and butanoic acids, methane, ethane, propane and butane, and so forth, all of which refer to the number of carbon atoms linked together in the molecules. Hexamethylenediamine has six (`εχ) carbons next to each other in a single chain with an amine (NH2) group at either end, so it might be expected to behave like an amino acid, which has an amine group at one end, hence the name. Adipic acid, by contrast, formally known as hexanedioic acid, is similar except for having a carboxyl (COOH) group at either end, and amino acids again have a carboxyl group at one end, which is why they’re acidic. Joining these two compounds together is very similar to two amino acids joining together in a protein, and part of what the chemists had in mind was mimicking silk by creating chains of acids which were each rather similar to amino acids except that they alternated, with one molecule of hexamethylenediamine joined to another of hexanedioic acid, itself joined to another hexamethylenediamine and so on all the way along the chain. This is nylon-66. In order for this reaction to happen efficiently, water has to be removed, so it was carried out under low pressure to evaporate the water. This substance was then melted, squirted through holes and stretched, forming fibres. In 1939 this was first marketed as nylon.
The name “nylon” is quite interesting. There’s an urban myth that it stands for “New York – LONdon” but in fact it’s the winner of about four hundred suggestions, including “norun”, “Delawear”, “Rayamide”, “Silkex”, “Wacara” after Wallace Carothers, and “Duparoo” for “Du Pont Pulls A Rabbit Out Of its hat”, which was a joke. “Norun” was one of the front runners with the R replaced by an L and the U by an O, and less significantly the O by a Y. This makes the name difficult for Japanese first language speakers to pronounce, so in that sense the word is actually racist. It tends to be called some variation of “polyamide” in other languages. It also represents something of a linguistic landmark in English because of the use of the “-lon” ending as a morpheme in its own right suggesting a synthetic fibre, found as “-on” in “rayon”, which was in fact just the French for “ray” because of how it was extruded, and also “orlon”, with the L, which was used for acrylic fibre.
Nylon is a thermoplastic. There are two types of plastic: thermoplastics and thermosetting resins. Thermoplastics simply melt when they’re heated and solidify again on cooling. Thermosetting resins have the unfortunate property of breaking up into different compounds when heated, and are therefore generally hazardous. Nylon doesn’t suffer from this drawback. There are also a number of different types of nylon. Nylon-6 is produced by breaking the ring-shaped caprolactam molecules open and joining them together at the ends, and was invented to avoid violating Du Pont’s patent on Nylon-66. It tends to form longer chains than its predecessor, making it stronger, and can be biodegraded by certain bacteria and fungi provided the chains have broken up to some extent. Nylon-6 and other plastics have in common with Vinalon their symbolism for countries portraying themselves as socialist. In East Germany, Nylon-6 was called Dederon, i.e. Deutsche Demokratische Republik + “-on”. Its durability was seen as a counterpoint to the wasteful practices of Western capitalism and the ability to reshape “nature” paralleled the ability to reshape “human nature” and the power humans could have over the fundamental building blocks of physical reality. The DDR presented Nylon-6 as a durable rather than disposable material, as opposed to the popular Western image of plastic as used for temporary disposable items which would then have to be replaced. It also acts as a metaphor for progress, and brings to mind the 2003 film ‘Good Bye Lenin‘, which focusses on Ostalgie, the yearning some people in the DDR feel for the old régime, and in fact I’d agree that it isn’t as simple as the good just replacing the bad, and in fact suggests more positive uses of plastics than the way they’re generally constructed in the West.
Nylon-510 is different again. It was patented at the same time as Nylon-66, but involves a more expensive process, but significantly is the basis for the extremely strong Kevlar, used in tyres, shoes and bullet-proof clothing. Finally, although there are still others, there’s Nylon-1,6. Unlike other Nylons, it can absorb its own weight in water because it contains a large number of amide groups (not to be confused with amines). However, also unlike other nylons, it’s a thermosetting resin.
Acrylic is another synthetic fibre which is also familiar in bulk forms such as perspex (plexiglass) and in paints. I have to be honest here and confess that up until today I thought acrylic was just another name for polyester, but a few moments’ thought would’ve made it obvious they aren’t. Perspex is clearly not what polyester bottles are made of, for example. It’s a polymer of acrylonitrile, also known as vinyl cyanide, and the fact that that group, cyanide, turns up in its name suggests that you wouldn’t want to be anywhere near it if it caught fire but I don’t honestly know if that makes it dangerous or even whether it’s flammable. It was invented in 1950 and is often used to give clothing a wool-like feel. This led to some concern on my part back in the early 1990s when I became aware that some vegans used it as a substitute for wool, because I wasn’t clear about its environmental impact. It actually releases more than half as many again microplastic fibres as polyester during washing, which again doesn’t sound good. Five-sixths of the plastic found on beaches is acrylic, polyester or Nylon from textiles. It tends to fuzz or pill easily. There is a modified form known as modacrylic which also contains bromine-based flame retardants and is used to make wigs and fake fur, which makes sense as it’s clearly physically similar to keratin. Acrylic is also used like wool in knitting. It can be dyed easily, I think in the production process rather than afterwards although I could be wrong. All of these uses puts acrylic in a special and difficult position morally speaking. Its use means that mammals are not killed or otherwise exploited directly for its production. Moreover, and here I’m straying onto Transwaffle territory somewhat, its use in wigs makes it significant in drag and some trans women, along with hiding the loss of hair caused by chemotherapy or various hair-related conditions which particularly affect womyn due to gender norms. In these uses it also lends itself to being brightly coloured in unusual ways, and is therefore a spur to creativity in image, but there is also a major problem in that it is quite environmentally harmful. Nylon can be made from wheat husks and therefore does not depend on fossil fuels to the same extent as some other synthetic fabrics, although the will to do that has to be there. Acrylic has a kind of “arty” life outside its use as a textile, cropping up prominently in artistic paints for example. This is an emulsion of acrylic in which pigment is suspended, and it was in fact the first use of the substance in the 1930s. It combines properties of watercolour and oil paint, since it’s water-based but dries to become water-resistant.
Although I don’t know this for sure, I suspect that Lycra as a name is a reference to the word “acrylic”, since it’s “Acryl” written backwards. Lycra, also known as Spandex, is never used on its own, which I’m guessing means that it can never be worn by observant Orthodox Jews who practice Chumra, but I also imagine this issue would never arise because it isn’t exactly modest when worn as outerwear. It’s an elastane, and as such we start to get into the realms of potentially fetishisable fabrics, although its history is rather different. To me it brings to mind the huge black wobbly mounds of tights, leggings and the like which I have a bad habit of producing due to my rather untidy nature. It’s another example of a fibre which was under a dubious moral cloud for quite some time, particularly in the ’80s, because under that name it was almost exclusively produced by Du Pont, also the main manufacturer of CFCs and became the target of a boycotting campaign. There was a time when I couldn’t put on a pair of leggings without feeling guilty because they were so prominently branded as including a fabric manufactured by Du Pont, and had a Du Pont label to that effect. This probably also meant people got judged for wearing it in certain circles in a similar way to how someone among animal liberationists might be judged for wearing leather. It’s also quite a judgy fabric anyway, as you can’t easily hide away your “sins” in the stuff, such as poor muscle tone, fat or in some cases genitals. Depending on how it’s used, it tends to be rather unforgiving and also carries with it a weight of guilt for other reasons. The whole “leggings are underwear”/”leggings are trousers” debate, for example, which I can’t escape feeling is partly about body-shaming and was notably completely absent, at least in my social circles, in the ’80s and early ’90s.
But what is it? Well, for a long time nobody was allowed to know, but it is in fact a polyurea-polyether copolymer. It was first used on underwear, in particular for girdles where it replaced the less convenient rubber. It was perfected in 1958, so it’s a little later than some of the others, and it took a long time for it to be used on outerwear. Due to the rise of feminism, the use of girdles declined and Du Pont started to branch out into its use in ærobic wear. This spilled over into street fashion in the 1980s. Its marketing is also unusual as it has tended to be marketed directly in advertising, which also applies to wool. Because it’s usually (or always?) in the form of a blend, it’s difficult to recycle. Four-fifths of garments purchased in the US in 2010 contained it, so this is a significant problem. Materials which used to be, for example, 100% now often include it to make them easier to get into and more flexible. As such, it’s one of those insidious things which it’s very difficult to address using consumer pressure, and this emphasises the difficulty in addressing capitalism through the likes of boycotts. In reality, much of the time consumer activism is only something to keep us busy while the megacorps continue their everyday business of mucking up the environment and destroying our future, and can also be used to guilt-trip people when the actual impact any of us can make is rather minute. That said, it’s still important not to be part of the problem and the same could be said of veganism for different reasons, but I’m still vegan. Lycra is also a little like acrylic in the sense that you can’t necessarily help what you end up getting imprinted on sexually, but as far as I know whereas there are attempts to produce sustainable rubber and latex fetish garments and also replacements for leather, there don’t seem to be any similar moves with elastane. Similarly, if you have an allergy to latex what are you supposed to do if you can’t replace it with Lycra?
Then there’s triacetate. This seems to have been discontinued as a textile fibre due to health hazards in its production, and as such can be used as a way to date vintage clothing. This also means that it’s no longer practical to reproduce certain clothing in exactly the same form as it used to exist back in the day. Its full name is cellulose triacetate, and you may be looking at it right now as it’s used as a polarising filter for LCDs, and it’s also used for film stock. Although I’m aware that it isn’t considered safe to manufacture, to me the process actually sounds quite innocent. Cellulose is treated with acetic acid to replace the hydroxyl groups on the glucose monomers with acetyls. This is then dissolved in methanol and dichloromethane (that last may be the problem in fact), then extruded into warm air, evaporating the solvent. Although this last bit does sound hazardous, and in fact may be more so because of the larger surface area fibres have as opposed to sheets of the stuff, I dunno, it just seems a bit out of place for this to have happened. It is also sometimes treated with caustic soda to remove the acetyl groups, making it almost a soap and rendering it less “staticky”. In photographic film, it tends to break down in a process known as “vinegar syndrome”, although it’s safer and more durable than its predecessor celluloid, which is flammable and breaks down faster. I presume this also happens to the fabric when it hasn’t been saponified. Triacetate strikes me as the quintessential ’80s fabric, unlike elastane which is still with us today.
There is a whole book, or maybe a library, to be written on allied materials and techniques here, including methods of weaving and knitting, dyeing (which is allied, incidentally, to both herbalism and pharmacology depending on the dyes used) and associated substances such as leather, latex, polyurethane and PVC, but if I went into that this post would never end, so at this point I’m going to turn to inorganic fibres. The most notorious of these is probably asbestos. The problem with asbestos is quite similar to that of microplastics, because it’s caused by small bits of the fibre breaking off and getting inhaled. As a child, I and apparently the general public were unaware of the risk posed by the mineral, but while discourse is dominated by its status as a health hazard, it’s actually an interesting substance in itself, and I’ll concentrate on that. It’s a silicate, more specifically an amphibole, which is a double chain of silicate molecules, which are tetrahedral, linked at their corners, so it’s arranged like a series of overlapping six-pointed stars. There are also sheet silicate asbestoi, and in fact most commercial use of asbestos has been of the sheet silicate rather than the amphibole. These are again overlapping six-pointed stars but this time they tessellate in planes rather than lines. It was traditionally used as a textile for fire-fighting suits and as thermal insulation in buildings, which is all rather horrifying today, but it is even so notably similar to two types of organic fibre, and also graphite and graphene, namely the α- and β-sheets mentioned yesterday regarding silk and wool (or hair in general). This should not be surprising as silicon is immediately beneath carbon in the periodic table, and the two elements have a lot in common.
Glass or quartz wool present similar health hazards to asbestos, though not to the same extent. They have the same uses, and are generally found in attics and walls. Although there is a glass fibre textile, it isn’t used for clothing. However, the Stanford Torus project, which attempted to come up with a detailed plan for a space habitat, included the idea that glass fibre could be used as a clothing fabric somewhat like denim, since synthetics aren’t really an option for a self-sustaining community in space. I’m not sure how this would work because in general glass fibres seem to embed themselves nicely in one’s flesh in a particularly nasty way, but maybe they had an answer to that. Another option there would seem to be metal fibres. There is in fact such a thing as platinum fibre, which is really a felt rather than woven – fibres of platinum matted together and heated to melt them together. I seem to recall this was once used to make the world’s most expensive dress. There’s also the famous Cloth of Gold, which has a biological fibre core, and was subject to sumptuary laws banning it from being worn by the lower classes.
Then there’s the question of the Space Elevator.
Again, I think this is widely known but I’ll talk about it anyway. Satellites can and are placed in orbit around the Equator at a height where their orbit takes exactly one solar day. They’re used, of course, for telecommunications, and in theory a fibre could be hung down from, or extended up to, such a satellite and used as a cable for a lift, although the vehicle involved couldn’t literally be a lift in the sense of those things which go up or down inside buildings. The problem is that that fibre would have to be 35786 kilometres high, measured from sea level at the Equator, so the fibre, or tower, would need to be thousands of times higher than the highest human structure ever built, and even the highest possible mountain. A few suggestions have been made, and they could prove relevant to textiles if they’re ever done.
Two of the ideas involve carbon, unsurprisingly since carbon fibre is well-known as a strengthening material and diamond is one of the hardest materials known. Metals can only support their own weight up to about thirty kilometres in height. More sophisticated organic materials such as Kevlar do somewhat better and can manage up to about four hundred kilometres, because they’re lightweight as well as strong. Carbon nanotubes and graphene ribbons can manage about six thousand kilometres, which is getting there but still not enough.
A carbon nanotube is a thin tube of carbon atoms linked together in a hexagonal pattern around its sides. They form spontaneously quite easily, such as in a candle flame, but to be strong enough to extend over that length they would also need to be long while consisting of a single molecule, since then atomic electrical forces would hold the structure together. They would have no weaker points. Clearly there would be a bundle of multiple such tubes rather than just one. The longest carbon nanotube grown so far is only half a metre, so it isn’t quite there yet. Furthermore, the growth is under special laboratory conditions and these would have to be replicated in situ to construct the cable. And it still wouldn’t be high enough. Carbon nanotubes are the stiffest known materials, meaning that they wouldn’t be suitable for clothing in the form of a woven or knitted fibre. One of their pluses as far as space elevators are concerned is that they conduct electricity, so they could be used, for example, to bring solar-generated electricity safely down to Earth without using what would basically amount to a death ray.
Graphene is a sheet of carbon atoms rather similar to the sheet silicate which some asbestos consists of. Graphene is the strongest known material made of ordinary matter, and the strongest ever tested. Since it’s only one atom thick, it has a density around a hundred thousandth that of paper, and clearly since paper is cellulose this means it only weighs a hundred thousandth as much as cotton or linen. It does seem to be a suitable material to make the cable, probably in many layers, but again it would need to be formed as a single crystal on-site, or rather, each sheet would. They’d also need to be kept separate as the alternative is for them simply to become graphite, which would be useless. You can’t make a pencil lead long enough to reach space.
There is a final substance to be considered which has made progress in this area: boron nitride. Time for another look at a bit of the periodic table:
Boron is top left, next to carbon. Because it’s an odd-numbered element, it’s less common in the Universe than its neighbours carbon and beryllium, but more common in Earth’s crust than beryllium. It’s subject to the diagonal relationship, which is where elements separated diagonally tend to be similar to each other, and in this case that’s silicon. Something else which may just be nothing here is that gallium arsenide used to be considered a candidate for replacing silicon in microprocessors and was able to work something like eight times faster, and it consists of two elements either side of germanium, from which transistors can also be made, so I sometimes wonder if I’m missing something and the properties of one element can be achieved by compounds consisting of its neighbours on either side, or maybe I’m making patterns out of nothing. In any case, boron, being next to carbon, i.e. diamond, in the periodic table, is unsurprisingly able to make extremely hard, strong crystals. Then there’s nitrogen, very common in explosives and good at suffocating people and other organisms and therefore also good at preserving food, because it does practically nothing. This is because it forms extremely strong bonds with itself, and these bonds also explain its reactivity, since it wants to react very strongly and then gets “stuck” on things. Combine the two and you get boron nitride, of which there are various different varieties, just as there are of carbon – graphite and diamond being two, but also the fullerenes, graphene and carbon nanotubes. The thing about boron nitride is that it averages out the bonds between nitrogen and boron, leading to the formation of a hexagonal crystal lattice. Since boron is lighter than carbon, boron nitride is less dense than diamond and this means that boron nitride nanotubes can be formed which are both strong and lighter than diamond, so they can support their own weight over a longer distance. Boron nitride nanotubes can be made by heating boron in nitrogen, similarly to how carbon nanotubes are made in candle flames, and they look white and fluffy:
It’s possible to spin yarns from these:
Boron nitride nanotubes, hereinafter referred to as BNNT and in the singular, doesn’t burn and is a good insulator. Boron and nitrogen are small atoms, meaning that their nuclei are relatively large and they can therefore absorb neutrons well, so they protect from certain forms of radiation, as does BNNT. Its strength, radiation, lightness and heat resistance makes it an excellent material for space travel, and it could be used to make spacesuits for wearing on Mars. It could replace asbestos for fire-fighters. Since they absorb neutrons, they can be used to target radiotherapy for cancer. It’s notable that it tends to form longer tubes more easily than carbon nanotubes do, and therefore once again in needs to be made where the elevator will be situated but could do so more easily. Once again, it would need to be in single crystals. It has several advantages over carbon nanotubes in this application, for instance resistance to radiation and lack of flammability. They’re also stickier than carbon nanotubes, making it easier to construct composites with polymers. This has been tested with acrylics, and it’s down to the fact that boron nitride is a compound rather than a pure element, which leads to electrons bunching in some places and being deficient in others, which pulls other materials more strongly.
Although this bit has mainly been about the space elevator, it also illustrates well how research into space science and technology has positive consequences for everyday life. If the space elevator was ever built, it’s possible the material it was made from would be a very useful textile. In fact, boron nitride sounds remarkably similar to the material in ‘The Man In The White Suit’, even down to its colour. It’s tough, light, flame-resistant, radiation resistant and extremely durable, and probably just as difficult to cut.
That, then, is where I’m going to end this for now. As I said, there are bound to be obvious bloopers in this because I’m out of my comfort zone here and don’t know much about textiles, but I thought I’d give it a go and I’d like to thank Steve again for the inspiration. Here’s to a future where, to paraphrase Donald Fagen, there’ll be boron nitride jackets, one for everyone.
A Box Of Chocolates 