Synthetic Rubber Turns the Corner

by HARLAND MANCHESTER

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THE rubber shortage, the gravest material crisis this country has ever faced, is at last on the road to solution. Synthetic rubber has turned the corner. Big factories are rapidly coming into production, and already the first of the five million “GR-S” tires to be produced in 1943, concocted by chemists from petroleum and farm alcohol, have been released to essential civilian drivers.

This does not mean that we can leap into our cars and go joy-riding. It does not mean that the war of materials is over. Rigid economy in all rubber uses must still be observed. We are being saved by the skin of our teeth from a nation-wide paralysis of vital transportation, and from a stoppage of transport on battle fronts which might easily have lost us the war.

Only a miracle of research and production has saved the complacent American public from a fate which few fully realized and many have carelessly abetted. After the Japanese raided Pearl Harbor, the Far Eastern plantations which supplied 90 per cent of our rubber were suddenly lost to the enemy. Our very national existence was at the mercy of a dwindling stockpile—and the ingenuity of our technical men. Our production of all synthetic rubbers totaled a mere 12,000 tons a year — one fiftieth of our pre-war annual needs. A few synthetic rubber tires had been made, but large-scale production was only a gleam in the eyes of chemists and engineers.

To fill the gap in our industrial economy caused by Japan’s conquests, every possible source of rubber, both natural and synthetic, has been exploited regardless of cost. Wild rubber has been rushed by plane from the Amazon, plantations still under Allied control have been double-tapped, scrap has been collected, and thousands of acres of latexbearing guayule shrubs and Cryptostegia vines have been planted in California and Latin America. But the major burden of the program falls upon synthetic rubber. Of the 308,000 tons of new rubber supplies which Mr. Jeffers is now able to predict for 1943, more than 82 per cent will come from the man-made rubbers.

This triumph of swift conversion has been accomplished in a number of ways. About a third of the butadiene gas upon which most of the new rubber is based is made from alcohol derived from farm products. The rest comes from petroleum, and the present and future of synthetic rubber depend largely upon the magic by which a fraction of crude oil is chemically cracked, cooked, tortured, and teased until it emerges at the end of the line as sheets of rubber hardly distinguishable from the product of the tree.

Forty-eight plants, many of them performing only one step iu the entire program, are springing up all over the country, and in another t welve months they will be turning out more rubber than the country ever used in a peacetime year. A few of them are integrated plants, located near oil fields, where petroleum stored underground for centuries is drawn through a scries of monstrous and complicated refining columns, reactors, and processing machines, and never sees the light of day until it emerges as rubber ready to ship to the tire factories.

One of the most spectacular of these continuousprocess plants is located on a 1200-acre lot on the east bank of the Mississippi near Baton Rouge. It is a part of the great Standard Oil of Louisiana refineries where high-octane aviation fuel and toluene for TNT are also produced. Crude oil from three states is pumped to the network of grumbling metal towers and broken down into components from which it is possible to make anything from an automobile tire to a lady’s evening gown.

For oil is composed of an infinite variety ot hydrocarbon molecules. Chemists will draw you pictures of them made up of “C’s” and “II’s” arranged in various patterns. Some molecules, with the carbon and hydrogen atoms rearranged, will make explosives, some will make plastics, some will improve the performance of an engine, and others form the basis of synthetic rubber.

The whole secret of making rubber out of oil is in juggling the “C’s” and “H’s” so that the right pattern eventually emerges. This sounds very simple, but so far the equipment needed for the rubber program has cost $48,500,000 in the Baton Rouge plant alone.

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THE visitor to Baton Rouge who traces the progress of oil into rubber sees some of t he newest and most spectacular discoveries in operation. First the crude oil has to be cracked to yield a series of major components, which range all the way from heavy sludge at the bottom of a 150-foot steel tower to valuable light gases at the top. Among these gases is butylene, and the extraction of this gas from petroleum is the first step in rubber-making. An efficient new process which went into operation shortly after Pearl Harbor has increased the amount of butylene which can be obtained from each barrel of oil, thus contributing to the speed-up of the entire rubber program.

The next step of the oil-into-rubber process at Baton Rouge is the conversion of butylene into butadiene, one of the two staples of the new tire rubber. Butylene has two superfluous hydrogen atoms which have to be removed to make t he rubber ingredient . (Butylene is represented by the symbol CJIs, and butadiene is C4HG.) There are a number of ways of making butadiene, but under the government program by far the largest amount will come from Standard’s efficient new dehydrogenation process, which since early 1941 has been rushed from the glass-retort state to large-scale production. Its bewildering maze of pipes and containers exists for the sole purpose of removing the two unneeded atoms. In an attempt to illustrate the complexities of the task, R. E. Wilson of Pan American Petroleum put it this way: —

“Imagine a big hall with ten billion fleas in it. They send you in with a sledge hammer and a crowbar and tell you to knock off the right hind leg and the left front whisker of each flea — and then, when you’ve finished, to sort out all the fleas that you’ve maimed in the process.”

When the colorless, invisible butadiene gas finally emerges in the great procession of processes, we are getting closer to the smell of rubber. That volatile gas, which would vanish in the air if not confined, makes up three quarters of the tough, Buna S tire rubber that will soon be rolling on the highways. The other quarter is styrene, a liquid chemical made from coal or petroleum; its production raises no major difficulty.

Just across the fence from the new butadiene plant is the factory of the Copolymer Corporation, where the ingredients are mixed and the rubber actually made. Here the stream of material gradually evolves from a scientific witches’ brew that one must take on faith, and there are peepholes through which the newborn rubber can be seen. Big vats called reactors are filled with water, soap, styrene, butadiene, and chemical “salt and pepper” and agitated by giant egg-beaters for sixteen hours or so, while the butadiene and styrene are encouraged to join hands in long chains to form the molecules of the Buna S tire rubber, otherwise known as “Government Rubber-S,” or “GR-S.”

A small part of the mixture always refuses to “jell” on its first trip through the reactor, and is separated and piped back to join the supply lines. The rest comes out as latex. The work of the rubber tree has at last been approximated, for this white, milky liquid is similar to the stuff that runs into the cup when a plantation tree is tapped. The latex is run into a coagulating vat with a little brine and acid and stirred by a paddle, and rubber particles appear in much the same way that butter globules are formed when cream is churned. The new rubber is carried on endless belts through a wringer which squeezes out. the water, and through a hot drier; then it is pressed and baled for shipment to the tire and rubber goods plants.

Complicated as it is, the making of crude Buna S is only half the battle. It has been no easy task to fabricate it into tires. Not that Akron was caught flat-footed by the rubber famine: for years a number of tire company chemists had kept abreast of synthetic developments here and abroad.

Long before Pearl Harbor a number of tire and chemical companies experimented with synthetic rubber tires, and some were placed on the market. They did well in road tests and provided invaluable experience. There are rubber men who for years have been using various synthetic tires on their cars, with good results. It was not. hard to make a few good tires that would stand up in service, but that is a long way from turning them out by the million in mass production.

Go to Akron and talk with a compounder in one of the big plants if you wish to hear of the trials of tire-making with synthetic rubber. The compounder is the master chef who brews the mix from which the tires are made. He is the czar of tiremaking. You see him in his shirtsleeves, cutting off a piece of rubber with his knife, smelling it, biting it, and stretching it. Then he looks either satisfied or worried. Laboratory tests give him a complete report on the sample, but a prodigious memory and a sixth sense born of years at his job often tell him whether the rubber will make a good tire.

Buna S turned this man’s world upside down. It was deceptive. It seemed all right but it had a will of its own. Before the war the skilled compounder knew the habits of rubber from every spot on earth, and knew how to blend and treat it to make it behave. Using batteries of chemical tricks invented by research men, he had increased tire mileage about 400 per cent in two decades. He had begun to think that he knew his job; then came Pearl Harbor, and they gave him some stuff that wasn’t rubber at all, but something like it, and told him to make tires from it on rubber machinery with men trained to work in rubber.

When treated like tree rubber, Buna S turned out to be so hard and unworkable that it took three times as long to make a tire. This rate of production would not fill the demand unless the industry tripled its number of tire machines, and with metals hard to get, that was out of the question. Buna S can be made with various characteristics, so the compounders demanded softer rubber. This meant some sacrifice of quality in the tire, but there had to be a compromise somewhere, as there is in almost every product. Another headache: natural rubber slicks to itself when layers are built up on the tire mold; Buna S does not. The problem was solved ingeniously by devising a semi-automatic machine which places a thin film of nat ural rubber cement between the plies. These examples are only a hint of the tribulations of the rubber chefs when their old reliable cookbooks became suddenly obsolete.

Company barriers were forgotten as the tire makers pooled their resources to meet the challenge of the new material. They are emerging victorious. Buna S passenger-car tires are now rolling off the lines in rapidly increasing numbers.

And how do the new tires stand up in service? To answer this question we do not have to depend on guesses and hopes. Thousands of Buna S passenger-car tires have been tested on roads flat and hilly, curved and straight, wet and dry, paved and unpaved, and there are fat notebooks full of figures showing their performance under all conditions. A look at the record shows both pluses and minuses. The new tires may outwear natural rubber at high speeds, but they often give somewhat poorer mileage at low speeds. They are more brittle and chip more easily. They hold the road much better than natural rubber on wet pavements, but since water does not lubricate them, they wear out faster under those conditions.

Balance the books and you can safely say that the new tires are already nearly as good as those made from tree rubber. In fact, the average passenger-car driver will hardly know the difference between the new tires and the old. The difference in wear will be less than he now notices between his rear right tire and his front left one, and he will have less trouble with skidding.

The making of heavy-duty tires for trucks and buses is a more difficult problem, and the whole industry is working toward a solution. Buna S builds up more internal heat than tree rubber, and the bigger the tire the hotter it gets, with greater danger of fabric failure. This heat problem is being partially solved by using a special rayon in place of cotton cord to reinforce the tires. Rayon is stronger than cotton, especially when hot. By strengthening the tire structure, it reduces the amount of rubber needed, thus making thinner walls which carry off the heat faster, adding thousands of miles to the life of the tire.

Recent experiments indicate that nylon cords may make the big tires still lighter and cooler in operation. This weight-saving is especially important in the tires of military planes, where every pound saved increases range or load. At present, about 30 per cent of natural rubber is being used in heavyduty tires. With much of the drain on our stockpile and imports being relieved by synthetics, this compromise will keep the big vehicles rolling until the war is won or the fast-working research men solve the heat problem.

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APID as the advance has been, chemists have barely scratched the surface in synthetic rubber research. When war came, three hundred different rubber substitutes were known to them. Buna S seemed to be the most logical material for tires, and became the bulwark of the government program, but thousands of possibilities in this one synthetic remain to be explored. By varying formulas and processes, it can be made as soft as molasses or as hard as a plank, and a wide variation of other qualities can be built into it. Multiply this research program by three hundred, and bear in mind the limitless opportunities still latent in the hydrocarbon molecule, and it is easy to believe that man-made rubber will eventually be tailored to fill any need.

Spectacular progress has already been made in making synthetics for hundreds of special jobs which natural rubber cannot do at all, or cannot do so well. Perbumm, or Buna N, was a miserable failure when the Germans tried to make tires from it, but it has other virtues which have saved the lives of many airmen. Oil does not rot it the way it does natural rubber, and that makes it just the thing for lining the new airplane tanks which do not lose their fuel when punctured with bullets.

Two kinds of rubber are used in these tanks: an inner lining which resists oil, and a sandwich filling which sponges up quickly and fills the bullet holes when the escaping gasoline strikes it. The construction is so effective that many planes have come safely home with their tanks riddled like sieves but only a few drops of fuel lost. Another merit of Perbunan — built into it by chemists — is that it remains flexible in the coldest weather. So it has a thousand and one uses for planes operating in the Arctic or in frigid high altitudes, where fuel connections and other rubber parts must withstand temperatures of 60 below.

Back in 1037 two young chemists named William J. Sparks and Robert M. Thomas spent a Saturday half-holiday in their laboratory at Bayway, New Jersey, and discovered the key to Butyl rubber, one of the most promising of the synthetics now being manufactured under the government program. It does not wear so well in tires as Buna S, but research men have discovered that it holds air much longer. The result: better gas masks, better barrage balloons and life rafts, and a promise of inner tubes that will have to be inflated only twice a year.

Nor should Butyl be dismissed as a future tiro rubber. Tested on highways three years ago, Butyl tires ran only 5000 miles or so. Then the compounders tried out thousands of recipes, and in recent road tests some of the tires covered 25,000 miles at 40 miles an hour, with some rubber left on the treads. Because of the need of concentrating on a definite program, Butyl tires have been shelved for the duration, but if research men keep on improving them, they may eventually compete with Buna S.

For Butyl can be made more quickly and cheaply. It is made directly from isobutylene cracked from petroleum, by-passing some of the expensive and time-consuming steps necessary in making Buna S. For this reason, some experts are predicting that Butyl may sell cheaply enough to enable it to wage a stiff battle even with rubber from the tree.

Another important place in the government rubber program is held by du Font’s neoprene, whicli is made from acetylene obtained from coal. Neoprene is the oldest and in many ways the aristocrat of American synthetic rubbers. First-class tires were made from it years ago, but its cost of production has barred it from the mass-production tire field. It can be made highly resistant to oil, sunlight, age, and below-zero weather. It has many war uses where quality is paramount.

For example, when today’s fast, acrobatic fighting planes were in the blueprint stage, a new floatless carburetor was needed to make upside-down flying safer. The carburetor could not be made until the designers found a material for a gasoline-resistant diaphragm that would remain flexible and could be turned out uniformly with a thickness of a thousandth of an inch. A fabric coated with neoprene served the purpose as nothing else would.

And neoprene withstands the fierce sunlight of high altitudes so well that it is used to coat the rubber de-icers on airplane wings. The war curtailed production of neoprene waterproof garments, boots and shoes, hot-water bottles, tennis balls, and dozens of other peacetime products. Tests indicate that neoprene washers for household water faucets will last for a generation without a drip, and this accomplishment by itself should assure a brilliant future.

There are also a number of new synthetic materials — “stretchable plastics,” they might be called — which are easing the shortage by doing many important jobs tree rubber used to do. One of these is the Monsanto Chemical Company’s Gaflex, once used in safety windshields and now used to waterproof army raincoats. Another is Koroseal, developed by Dr. Waldo Semon of the B. F. Goodrich Company. It is made by another of those mystifying processes in which a formless gas is turned into a liquid, then into a powder, and finally emerges as tough, flexible stuff with some of the properties of rubber. Electrical insulation is now one of its most important wartime uses. Unlike natural rubber, it is not inflammable, so it is widely used in insulating wires in naval vessels. In case of a direct hit, fire will not follow the wires.

Plastics of this sort are no mere rubber savers. They are being groomed for many post-war uses which rubber was never equal to. For example, flexible pipes made from the new plastics are being used in industry, and may be used in the house of the future.

An accidental discovery made by a man who knew what he was about ushered in Thiokol, a chemical rubber with invaluable war uses. In the twenties, Dr. Joseph C. Patrick of Kansas City, a medical man turned industrial chemist, was trying to make an anti-freeze solution from ethylene gas. then a waste by-product of oil-refining. One of his mixt arcs thickened when he thought it should not, and the result was Thiokol, which the Dow Chemical Company is now manufacturing for the Thiokol Corporation.

Thiokol is inexpensive and gasoline does not rot it — two facts which have boomed its production. Since 1940, the Navy has built a number of vast underground storage tanks to hold lubricating oil and high-octane aviation fuel. In anticipation of a steel shortage, it was planned to construct the great caverns of concrete. But aviation fuel depreciates in octane rating through contact with concrete, and there is some seepage through the walls. So the tanks were lined with large black sheets of Thiokol, which were cemented like wallpaper to walls, floors, and columns.

Now portable “gas stations” made of Thiokol, holding up to 10,000 gallons of fuel or oil, are set up in a few minutes on foreign shores as soon as the troops land. Great supporting tubs of canvas reinforced with wood slats are staked to the ground, and inner bladders of Thiokol hold the fuel.

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No MATTER how cheap and plentiful tree rubber may become in the future, it is clear that many of these man-made varieties designed for special purposes have come to stay. In a few short years they have been adapted to tasks from which natural rubber is barred forever, and it is fair to assume that they will be greatly improved.

The future of the Buna S plants in competition with natural rubber is another matter. As a general rule, synthetic products become better and cheaper with the years, and it is reasonable to believe that Buna S will follow the same trend — that the tires will do as well as those of tree rubber, at a cost that will not be prohibitive. In other words, we have shown Japan that we can get along without the rubber plantations which she has seized — permanently if necessary. But we are fighting for an open world market, among other things, and we can conceive of no peace settlement which does not include unrestricted access to the products of the Far East.

With the law of supply and demand in operation once more, an annual crop of a million or more tons of natural rubber will be looking for buyers. Despite mad fluctuations in the price of this rubber for the last two decades, many experts agree that under pre-war conditions it could be delivered in New York for 10 cents a pound at a good profit. By way of comparison, Mr. Jeffers suggests 8 to 15 cents as a possible future price for Buna S. Figures like these point to a close race.

But rubber scientists have not limited their work to synthetics — they have also been improving the rubber tree. Twenty years ago, a yield of 230 pounds of rubber per acre was considered good; by 1940 the better plantations were yielding GOO pounds, and there are acres of “prima donnas” which are producing 1500 and even 2000 pounds a year. Firestone has constantly increased its plantings in Liberia, getting high yields and cutting the sea haulage by 7600 miles.

In South and Central America, Goodyear, the United Fruit Company, and the Department of Agriculture are conducting experimental plantations to combat the leaf disease and pave the way for the re-establishment of the rubber tree in its original home. Inexpensive equipment has been devised for the “family-size” rubber plantation which would give the small farmer a supplementary cash income like that of the Vermonter with his maple sugar lot, and would stimulate post-war trade with our neighbors to the South.

All signs point toward a greatly increased production of natural rubber after the war. Harried tire workers would be delighted to return to their old familiar material; and in view of the industry’s record, we may expect far better tires of natural rubber than we have yet seen.

This would by no means sound the death knell of the new synthetic rubber industry. Ever since Charles Goodyear learned how to vulcanize rubber in 1839, its use has doubled with every decade. The war has brought a bumper crop of new applications. In many war vehicles, the twisting of rubber cylinders mounted near the axles takes up road shock, supplanting metal springs. These may be adapted to automobiles. Sanitary Airfoam cushions, used in tanks and planes, may make big inroads in the mattress field. Inexpensive rugs and carpets with the nap fixed in a rubber base are waiting only for the victory. Conveyers of endless rubberized belts now carry minerals for many miles from mine to factory, and even rubber-surfaced streets have been proposed.

Synthetic rubbers will be adaptable to many of the new uses, and even if the tire turns again to the tree, a big market for the new rubbers appears certain. In addition, the new industry should serve two vital national purposes: it should establish a price ceiling for natural rubber to curb the rapaciousness of plantation barons, and it should act as permanent insurance that American wheels will keep turning.