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Polyethylene: A
product of Brain and Brawn The invention of polyethylene, today's highest volume commodity plastic, took muscle power, risk-taking youths, and the understanding of polymers and polymerization. Eric William Fawcett and Reginald Oswald Gibson are the two young British scientists who can be credited with polymerizing the first few grams of polyethylene at the Winnington ICI laboratories in England. Fawcett was a young Oxford graduate who was only twenty years old and had to have his father come to the Winnington laboratories to sign for him his employment contract with ICI. Gibson had just returned from Amsterdam, where he had worked with Professor Anton Michels, the world-leading expert on high-pressure vessel design. They both worked in Lab Z, a small ICI laboratory that housed a pressure vessel that everyone called "the bomb". It was no coincidence that the assistants that worked in Lab Z were all young men in great physical shape. It took significant muscle power to operate the hand pump that could pressurize the bomb to up to 2,500 atmospheres (almost 37,000 psi). After pressurizing various liquids and finding that they remained unfazed, they decided to switch to gases, which they hoped would lead to more exciting reactions. Late on a Friday afternoon, March 24 of 1933, they filled the bomb with ethylene gas, raised the temperature to 170°C and pressurized it to 1,900 atmospheres. They turned off the lights and went home for the weekend. Since they couldn't wait all weekend for their results, Fawcett and Gibson went back to the lab on Saturday morning and found that the pressure inside the vessel had dropped to 100 atmospheres, a sure sign for a chemical reaction having taken place. Again they pumped the bomb up to 1,900 atmospheres, and left for the remainder of the weekend. On Monday, they found the pressure dials marking 0 atmospheres. They found out that, in addition to the polymerization reaction that took place inside the vessel, the pressure drop was also due to a leak that sprang around an oil tube connection. After opening the vessel, they saw that its inside was covered with a waxy white powder, of which they were able to scrape out 0.4 grams of polyethylene. They quickly fixed the leak and repeated the experiment, recovering a total of 4 grams of polyethylene. They now had collected enough material that they were able to spin a couple of fibers and form a small thin film. In the third try, the bomb exploded. Even though the explosion did not harm anyone, the managers did not find these experiments as important as Fawcett and Gibson knew they were, and Lab Z was put to rest and the young men were given other tasks. Two years later, Fawcett attended The Faraday Society of London polymer congress in Cambridge where Wallace Carothers, Herman Mark, Kurt Meyer and Hermann Staudinger were the main guests and speakers. In the proceedings, Fawcett saw how the future Nobel Prize winner Staudinger claimed that it was not possible to polymerize ethylene. Fawcett got his courage together and went up to Staudinger's room at the University Arms Hotel to attempt to set him straight. There he told the prominent scientist that under certain conditions it was possible to polymerize ethylene. Staudinger ignored him and gave his talk as planned. After the talk Mark even supported Staudinger's findings. Undaunted by the prominence and belief of his opponents the young man rose and tolled the audience that ethylene polymerizes if maintained at 170°C under very high pressures. This bold move impressed Carothers, a well-known American Scientist, who offered Fawcett a job and took him to the DuPont laboratories in Wilmington, Delaware. Soon after, ICI resumed their high-pressure vessel work, reproducing Fawcett and Gibson's experiments and patenting polyethylene in February of 1936. ICI continued to produce polyethylene using their high-pressure polymerization process. Soon, their operation had been scaled-up sufficiently to produce several kilograms of polyethylene every hour. In the meantime they had also discovered that this new plastic had excellent dielectric properties, which made it ideal when insulating thin wires for telecommunications applications. In 1940, the British were at war. The Germans were bombing major English cities, and although ground radars detected the bombers, it was usually too late. A major breakthrough came when the British were able to reduce the weight of a radar from several tons to just under 600 pounds with the use of polyethylene as a wire insulator. This allowed them to place radars inside their fighter planes, enabling them to detect Nazi planes, before they saw them, shooting them out of the air at the same rate as they were crossing the British Channel. This put the British at an advantage, saving their cities from destruction. Twenty years after Fawcett and Gibson produced polyethylene inside the bomb, the German professor and future Nobel Prize winner, Karl Ziegler, found a way to polymerize ethylene at low pressures using catalysts. His catalysts were metal based compounds that act as vehicles as they drive through a sea of ethylene, picking up each monomer in an orderly fashion resulting in long chains of polyethylene. One was now able to produce this versatile material at much higher rates under safer conditions and lower energy costs. Ziegler sold his patent to several resin producers who immediately jumped into production. However, they soon found out that their new process produced polyethylene that cracked easily, rendering the first few thousand tons of high-density polyethylene useless. Luckily, in 1957 along came a small California toy manufacturer, The Wham-O Company, who proposed to use the inferior HDPE on their new toy: the Hula-Hoop. While Wham-O was using up the world supply of imperfect polyethylene, and America was buying the hoops by the millions, the chemical companies were successfully working out the kinks in their polymerization processes. Soon, polyethylene Hula-Hoops, Tupperware, and plastic bags became everyday items. As the years passed, catalysts not only produced other polymers but also allowed us to tailor an ultra high molecular weight high density polyethylene that can be spun into fibers that are stronger than steel. Today, UHMWHDPE is used to manufacture artificial hip joint replacements that have given many people a quality of life otherwise thought to be impossible.
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