SYNTHETIC PLASTICS
In the last chapter I told how Alfred Nobel cut his finger and, daubing it over with collodion, was led to the discovery of high explosive, dynamite. I remarked that the first part of this process—the hurting and the healing of the finger—might happen to anybody but not everybody would be led to discovery thereby. That is true enough, but we must not think that the Swedish chemist was the only observant man in the world. About this same time a young man in Albany, named John Wesley Hyatt, got a sore finger and resorted to the same remedy and was led to as great a discovery. His father was a blacksmith and his education was confined to what he could get at the seminary of Eddytown, New York, before he was sixteen. At that age he set out for the West to make his fortune. He made it, but after a long, hard struggle. His trade of typesetter gave him a living in Illinois, New York or wherever he wanted to go, but he was not content with his wages or his hours. However, he did not strike to reduce his hours or increase his wages. On the contrary, he increased his working time and used it to increase his income. He spent his nights and Sundays in making billiard balls, not at all the sort of thing you would expect of a young man of his Christian name. But working with billiard balls is more profitable than playing with them—though that is not the sort of thing you would expect a man of my surname to say. Hyatt had seen in the papers an offer of a prize of $10,000 for the discovery of a satisfactory substitute for ivory in the making of billiard balls and he set out to get that prize. I don't know whether he ever got it or not, but I have in my hand a newly published circular announcing that Mr. Hyatt has now perfected a process for making billiard balls "better than ivory." Meantime he has turned out several hundred other inventions, many of them much more useful and profitable, but I imagine that he takes less satisfaction in any of them than he does in having solved the problem that he undertook fifty years ago.
The reason for the prize was that the game on the billiard table was getting more popular and the game in the African jungle was getting scarcer, especially elephants having tusks more than 2-7/16 inches in diameter. The raising of elephants is not an industry that promises as quick returns as raising chickens or Belgian hares. To make a ball having exactly the weight, color and resiliency to which billiard players have become accustomed seemed an impossibility. Hyatt tried compressed wood, but while he did not succeed in making billiard balls he did build up a profitable business in stamped checkers and dominoes.
Setting type in the way they did it in the sixties was hard on the hands. And if the skin got worn thin or broken the dirty lead type were liable to infect the fingers. One day in 1863 Hyatt, finding his fingers were getting raw, went to the cupboard where was kept the "liquid cuticle" used by the printers. But when he got there he found it was bare, for the vial had tipped over—you know how easily they tip over—and the collodion had run out and solidified on the shelf. Possibly Hyatt was annoyed, but if so he did not waste time raging around the office to find out who tipped over that bottle. Instead he pulled off from the wood a bit of the dried film as big as his thumb nail and examined it with that "'satiable curtiosity," as Kipling calls it, which is characteristic of the born inventor. He found it tough and elastic and it occurred to him that it might be worth $10,000. It turned out to be worth many times that.
Collodion, as I have explained in previous chapters, is a solution in ether and alcohol of guncotton (otherwise known as pyroxylin or nitrocellulose), which is made by the action of nitric acid on cotton. Hyatt tried mixing the collodion with ivory powder, also using it to cover balls of the necessary weight and solidity, but they did not work very well and besides were explosive. A Colorado saloon keeper wrote in to complain that one of the billiard players had touched a ball with a lighted cigar, which set it off and every man in the room had drawn his gun.
The trouble with the dissolved guncotton was that it could not be molded. It did not swell up and set; it merely dried up and shrunk. When the solvent evaporated it left a wrinkled, shriveled, horny film, satisfactory to the surgeon but not to the man who wanted to make balls and hairpins and knife handles out of it. In England Alexander Parkes began working on the problem in 1855 and stuck to it for ten years before he, or rather his backers, gave up. He tried mixing in various things to stiffen up the pyroxylin. Of these, camphor, which he tried in 1865, worked the best, but since he used castor oil to soften the mass articles made of "parkesine" did not hold up in all weathers.
Another Englishman, Daniel Spill, an associate of Parkes, took up the problem where he had dropped it and turned out a better product, "xylonite," though still sticking to the idea that castor oil was necessary to get the two solids, the guncotton and the camphor, together.
But Hyatt, hearing that camphor could be used and not knowing enough about what others had done to follow their false trails, simply mixed his camphor and guncotton together without any solvent and put the mixture in a hot press. The two solids dissolved one another and when the press was opened there was a clear, solid, homogeneous block of—what he named—"celluloid." The problem was solved and in the simplest imaginable way. Tissue paper, that is, cellulose, is treated with nitric acid in the presence of sulfuric acid. The nitration is not carried so far as to produce the guncotton used in explosives but only far enough to make a soluble nitrocellulose or pyroxylin. This is pulped and mixed with half the quantity of camphor, pressed into cakes and dried. If this mixture is put into steam-heated molds and subjected to hydraulic pressure it takes any desired form. The process remains essentially the same as was worked out by the Hyatt brothers in the factory they set up in Newark in 1872 and some of their original machines are still in use. But this protean plastic takes innumerable forms and almost as many names. Each factory has its own secrets and lays claim to peculiar merits. The fundamental product itself is not patented, so trade names are copyrighted to protect the product. I have already mentioned three, "parkesine," "xylonite" and "celluloid," and I may add, without exhausting the list of species belonging to this genus, "viscoloid," "lithoxyl," "fiberloid," "coraline," "eburite," "pulveroid," "ivorine," "pergamoid," "duroid," "ivortus," "crystalloid," "transparene," "litnoid," "petroid," "pasbosene," "cellonite" and "pyralin."
Celluloid can be given any color or colors by mixing in aniline dyes or metallic pigments. The color may be confined to the surface or to the interior or pervade the whole. If the nitrated tissue paper is bleached the celluloid is transparent or colorless. In that case it is necessary to add an antacid such as urea to prevent its getting yellow or opaque. To make it opaque and less inflammable oxides or chlorides of zinc, aluminum, magnesium, etc., are mixed in.
Without going into the question of their variations and relative merits we may consider the advantages of the pyroxylin plastics in general. Here we have a new substance, the product of the creative genius of man, and therefore adaptable to his needs. It is hard but light, tough but elastic, easily made and tolerably cheap. Heated to the boiling point of water it becomes soft and flexible. It can be turned, carved, ground, polished, bent, pressed, stamped, molded or blown. To make a block of any desired size simply pile up the sheets and put them in a hot press. To get sheets of any desired thickness, simply shave them off the block. To make a tube of any desired size, shape or thickness squirt out the mixture through a ring-shaped hole or roll the sheets around a hot bar. Cut the tube into sections and you have rings to be shaped and stamped into box bodies or napkin rings. Print words or pictures on a celluloid sheet, put a thin transparent sheet over it and weld them together, then you have something like the horn book of our ancestors, but better.
Nowadays such things as celluloid and pyralin can be sold under their own name, but in the early days the artificial plastics, like every new thing, had to resort to camouflage, a very humiliating expedient since in some cases they were better than the material they were forced to imitate. Tortoise shell, for instance, cracks, splits and twists, but a "tortoise shell" comb of celluloid looks as well and lasts better. Horn articles are limited to size of the ceratinous appendages that can be borne on the animal's head, but an imitation of horn can be made of any thickness by wrapping celluloid sheets about a cone. Ivory, which also has a laminated structure, may be imitated by rolling together alternate white opaque and colorless translucent sheets. Some of the sheets are wrinkled in order to produce the knots and irregularities of the grain of natural ivory. Man's chief difficulty in all such work is to imitate the imperfections of nature. His whites are too white, his surfaces are too smooth, his shapes are too regular, his products are too pure.
The precious red coral of the Mediterranean can be perfectly imitated by taking a cast of a coral branch and filling in the mold with celluloid of the same color and hardness. The clear luster of amber, the dead black of ebony, the cloudiness of onyx, the opalescence of alabaster, the glow of carnelian—once confined to the selfish enjoyment of the rich—are now within the reach of every one, thanks to this chameleon material. Mosaics may be multiplied indefinitely by laying together sheets and sticks of celluloid, suitably cut and colored to make up the picture, fusing the mass, and then shaving off thin layers from the end. That chef d'œuvre of the Venetian glass makers, the Battle of Isus, from the House of the Faun in Pompeii, can be reproduced as fast as the machine can shave them off the block. And the tesserae do not fall out like those you bought on the Rialto.
The process thus does for mosaics, ivory and coral what printing does for pictures. It is a mechanical multiplier and only by such means can we ever attain to a state of democratic luxury. The product, in cases where the imitation is accurate, is equally valuable except to those who delight in thinking that coral insects, Italian craftsmen and elephants have been laboring for years to put a trinket into their hands. The Lord may be trusted to deal with such selfish souls according to their deserts.
But it is very low praise for a synthetic product that it can pass itself off, more or less acceptably, as a natural product. If that is all we could do without it. It must be an improvement in some respects on anything to be found in nature or it does not represent a real advance. So celluloid and its congeners are not confined to the shapes of shell and coral and crystal, or to the grain of ivory and wood and horn, the colors of amber and amethyst and lapis lazuli, but can be given forms and textures and tints that were never known before 1869.
Let me see now, have I mentioned all the uses of celluloid? Oh, no, there are handles for canes, umbrellas, mirrors and brushes, knives, whistles, toys, blown animals, card cases, chains, charms, brooches, badges, bracelets, rings, book bindings, hairpins, campaign buttons, cuff and collar buttons, cuffs, collars and dickies, tags, cups, knobs, paper cutters, picture frames, chessmen, pool balls, ping pong balls, piano keys, dental plates, masks for disfigured faces, penholders, eyeglass frames, goggles, playing cards—and you can carry on the list as far as you like.
Celluloid has its disadvantages. You may mold, you may color the stuff as you will, the scent of the camphor will cling around it still. This is not usually objectionable except where the celluloid is trying to pass itself off for something else, in which case it deserves no sympathy. It is attacked and dissolved by hot acids and alkalies. It softens up when heated, which is handy in shaping it though not so desirable afterward. But the worst of its failings is its combustibility. It is not explosive, but it takes fire from a flame and burns furiously with clouds of black smoke.
But celluloid is only one of many plastic substances that have been introduced to the present generation. A new and important group of them is now being opened up, the so-called "condensation products." If you will take down any old volume of chemical research you will find occasionally words to this effect: "The reaction resulted in nothing but an insoluble resin which was not further investigated." Such a passage would be marked with a tear if chemists were given to crying over their failures. For it is the epitaph of a buried hope. It likely meant the loss of months of labor. The reason the chemist did not do anything further with the gummy stuff that stuck up his test tube was because he did not know what to do with it. It could not be dissolved, it could not be crystallized, it could not be distilled, therefore it could not be purified, analyzed and identified.
What had happened was in most cases this. The molecule of the compound that the chemist was trying to make had combined with others of its kind to form a molecule too big to be managed by such means. Financiers call the process a "merger." Chemists call it "polymerization." The resin was a molecular trust, indissoluble, uncontrollable and contaminating everything it touched.
But chemists—like governments—have learned wisdom in recent years. They have not yet discovered in all cases how to undo the process of polymerization, or, if you prefer the financial phrase, how to unscramble the eggs. But they have found that these molecular mergers are very useful things in their way. For instance there is a liquid known as isoprene (C5H8). This on heating or standing turns into a gum, that is nothing less than rubber, which is some multiple of C5H8.
For another instance there is formaldehyde, an acrid smelling gas, used as a disinfectant. This has the simplest possible formula for a carbohydrate, CH2O. But in the leaf of a plant this molecule multiplies itself by six and turns into a sweet solid glucose (C6H12O6), or with the loss of water into starch (C6H10O5) or cellulose (C6H10O5).
But formaldehyde is so insatiate that it not only combines with itself but seizes upon other substances, particularly those having an acquisitive nature like its own. Such a substance is carbolic acid (phenol) which, as we all know, is used as a disinfectant like formaldehyde because it, too, has the power of attacking decomposable organic matter. Now Prof. Adolf von Baeyer discovered in 1872 that when phenol and formaldehyde were brought into contact they seized upon one another and formed a combine of unusual tenacity, that is, a resin. But as I have said, chemists in those days were shy of resins. Kleeberg in 1891 tried to make something out of it and W.H. Story in 1895 went so far as to name the product "resinite," but nothing came of it until 1909 when L.H. Baekeland undertook a serious and systematic study of this reaction in New York. Baekeland was a Belgian chemist, born at Ghent in 1863 and professor at Bruges. While a student at Ghent he took up photography as a hobby and began to work on the problem of doing away with the dark-room by producing a printing paper that could be developed under ordinary light. When he came over to America in 1889 he brought his idea with him and four years later turned out "Velox," with which doubtless the reader is familiar. Velox was never patented because, as Dr. Baekeland explained in his speech of acceptance of the Perkin medal from the chemists of America, lawsuits are too expensive. Manufacturers seem to be coming generally to the opinion that a synthetic name copyrighted as a trademark affords better protection than a patent.
Later Dr. Baekeland turned his attention to the phenol condensation products, working gradually up from test tubes to ton vats according to his motto: "Make your mistakes on a small scale and your profits on a large scale." He found that when equal weights of phenol and formaldehyde were mixed and warmed in the presence of an alkaline catalytic agent the solution separated into two layers, the upper aqueous and the lower a resinous precipitate. This resin was soft, viscous and soluble in alcohol or acetone. But if it was heated under pressure it changed into another and a new kind of resin that was hard, inelastic, unplastic, infusible and insoluble. The chemical name of this product is "polymerized oxybenzyl methylene glycol anhydride," but nobody calls it that, not even chemists. It is called "Bakelite" after its inventor.
The two stages in its preparation are convenient in many ways. For instance, porous wood may be soaked in the soft resin and then by heat and pressure it is changed to the bakelite form and the wood comes out with a hard finish that may be given the brilliant polish of Japanese lacquer. Paper, cardboard, cloth, wood pulp, sawdust, asbestos and the like may be impregnated with the resin, producing tough and hard material suitable for various purposes. Brass work painted with it and then baked at 300° F. acquires a lacquered surface that is unaffected by soap. Forced in powder or sheet form into molds under a pressure of 1200 to 2000 pounds to the square inch it takes the most delicate impressions. Billiard balls of bakelite are claimed to be better than ivory because, having no grain, they do not swell unequally with heat and humidity and so lose their sphericity. Pipestems and beads of bakelite have the clear brilliancy of amber and greater strength. Fountain pens made of it are transparent so you can see how much ink you have left. A new and enlarging field for bakelite and allied products is the making of noiseless gears for automobiles and other machinery, also of air-plane propellers.
Celluloid is more plastic and elastic than bakelite. It is therefore more easily worked in sheets and small objects. Celluloid can be made perfectly transparent and colorless while bakelite is confined to the range between a clear amber and an opaque brown or black. On the other hand bakelite has the advantage in being tasteless, odorless, inert, insoluble and non-inflammable. This last quality and its high electrical resistance give bakelite its chief field of usefulness. Electricity was discovered by the Greeks, who found that amber (electron) when rubbed would pick up straws. This means simply that amber, like all such resinous substances, natural or artificial, is a non-conductor or di-electric and does not carry off and scatter the electricity collected on the surface by the friction. Bakelite is used in its liquid form for impregnating coils to keep the wires from shortcircuiting and in its solid form for commutators, magnetos, switch blocks, distributors, and all sorts of electrical apparatus for automobiles, telephones, wireless telegraphy, electric lighting, etc.
Bakelite, however, is only one of an indefinite number of such condensation products. As Baeyer said long ago: "It seems that all the aldehydes will, under suitable circumstances, unite with the aromatic hydrocarbons to form resins." So instead of phenol, other coal tar products such as cresol, naphthol or benzene itself may be used. The carbon links (-CH2-, methylene) necessary to hook these carbon rings together may be obtained from other substances than the aldehydes, for instance from the amines, or ammonia derivatives. Three chemists, L.V. Kedman, A.J. Weith and F.P. Broek, working in 1910 on the Industrial Fellowships of the late Robert Kennedy Duncan at the University of Kansas, developed a process using formin instead of formaldehyde. Formin—or, if you insist upon its full name, hexa-methylene-tetramine—is a sugar-like substance with a fish-like smell. This mixed with crystallized carbolic acid and slightly warmed melts to a golden liquid that sets on pouring into molds. It is still plastic and can be bent into any desired shape, but on further heating it becomes hard without the need of pressure. Ammonia is given off in this process instead of water which is the by-product in the case of formaldehyde. The product is similar to bakelite, exactly how similar is a question that the courts will have to decide. The inventors threatened to call it Phenyl-endeka-saligeno-saligenin, but, rightly fearing that this would interfere with its salability, they have named it "redmanol."
A phenolic condensation product closely related to bakelite and redmanol is condensite, the invention of Jonas Walter Aylesworth. Aylesworth was trained in what he referred to as "the greatest university of the world, the Edison laboratory." He entered this university at the age of nineteen at a salary of $3 a week, but Edison soon found that he had in his new boy an assistant who could stand being shut up in the laboratory working day and night as long as he could. After nine years of close association with Edison he set up a little laboratory in his own back yard to work out new plastics. He found that by acting on naphthalene—the moth-ball stuff—with chlorine he got a series of useful products called "halowaxes." The lower chlorinated products are oils, which may be used for impregnating paper or soft wood, making it non-inflammable and impregnable to water. If four atoms of chlorine enter the naphthalene molecule the product is a hard wax that rings like a metal.
Condensite is anhydrous and infusible, and like its rivals finds its chief employment in the insulation parts of electrical apparatus. The records of the Edison phonograph are made of it. So are the buttons of our blue-jackets. The Government at the outbreak of the war ordered 40,000 goggles in condensite frames to protect the eyes of our gunners from the glare and acid fumes.
The various synthetics played an important part in the war. According to an ancient military pun the endurance of soldiers depends upon the strength of their soles. The new compound rubber soles were found useful in our army and the Germans attribute their success in making a little leather go a long way during the late war to the use of a new synthetic tanning material known as "neradol." There are various forms of this. Some are phenolic condensation products of formaldehyde like those we have been considering, but some use coal-tar compounds having no phenol groups, such as naphthalene sulfonic acid. These are now being made in England under such names as "paradol," "cresyntan" and "syntan." They have the advantage of the natural tannins such as bark in that they are of known strength and can be varied to suit.
This very grasping compound, formaldehyde, will attack almost anything, even molecules many times its size. Gelatinous and albuminous substances of all sorts are solidified by it. Glue, skimmed milk, blood, eggs, yeast, brewer's slops, may by this magic agent be rescued from waste and reappear in our buttons, hairpins, roofing, phonographs, shoes or shoe-polish. The French have made great use of casein hardened by formaldehyde into what is known as "galalith" (i.e., milkstone). This is harder than celluloid and non-inflammable, but has the disadvantages of being more brittle and of absorbing moisture. A mixture of casein and celluloid has something of the merits of both.
The Japanese, as we should expect, are using the juice of the soy bean, familiar as a condiment to all who patronize chop-sueys or use Worcestershire sauce. The soy glucine coagulated by formalin gives a plastic said to be better and cheaper than celluloid. Its inventor, S. Sato, of Sendai University, has named it, according to American precedent, "Satolite," and has organized a million-dollar Satolite Company at Mukojima.
The algin extracted from the Pacific kelp can be used as a rubber surrogate for water-proofing cloth. When combined with heavier alkaline bases it forms a tough and elastic substance that can be rolled into transparent sheets like celluloid or turned into buttons and knife handles.
In Australia when the war shut off the supply of tin the Government commission appointed to devise means of preserving fruits recommended the use of cardboard containers varnished with "magramite." This is a name the Australians coined for synthetic resin made from phenol and formaldehyde like bakelite. Magramite dissolved in alcohol is painted on the cardboard cans and when these are stoved the coating becomes insoluble.
Tarasoff has made a series of condensation products from phenol and formaldehyde with the addition of sulfonated oils. These are formed by the action of sulfuric acid on coconut, castor, cottonseed or mineral oils. The products of this combination are white plastics, opaque, insoluble and infusible.
Since I am here chiefly concerned with "Creative Chemistry," that is, with the art of making substances not found in nature, I have not spoken of shellac, asphaltum, rosin, ozocerite and the innumerable gums, resins and waxes, animal, mineral and vegetable, that are used either by themselves or in combination with the synthetics. What particular "dope" or "mud" is used to coat a canvas or form a telephone receiver is often hard to find out. The manufacturer finds secrecy safer than the patent office and the chemist of a rival establishment is apt to be baffled in his attempt to analyze and imitate. But we of the outside world are not concerned with this, though we are interested in the manifold applications of these new materials.
There seems to be no limit to these compounds and every week the journals report new processes and patents. But we must not allow the new ones to crowd out the remembrance of the oldest and most famous of the synthetic plasters, hard rubber, to which a separate chapter must be devoted.