plastics

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Perhaps the most prevalent manufactured material in society today is plastics. About 200 billion pounds of plastics are produced annually in the world, 90 billion pounds in the United States alone. In the 1967 movie The Graduate, the title character, played by Dustin Hoffman, was offered one word of advice for future success: "plastics." It is difficult to imagine society without plastics. Plastics come in innumerable forms, types, and items. They can take the form of adhesives, casting resins, coating compounds, laminates, or molded plastics. They are formed through extrusion, injection, compression, blowing, transfer (fusing), or by a vacuum. There are thermoplastics of nylon, polyester, polyethylene, polypropylene, polyvinyl chloride, polystyrene, and many other substances. There are also thermoset plastics, made of phenols, urea-formaldehydes, melamines, or epoxies. A single object may involve many different types of plastics. For example, the plastics in a car include phenolic and glass (fiberglass), acetal, nylon, polypropylene, fluorocarbon, polyethylene, acrylic, butyrate, and melamine. Plastic can be a natural substance or a synthetic one. In other words, "plastics" can mean any number of different substances and products.

History

Resin is the key to plastics. Until the mid-nineteenth century, societies used natural plastic materials such as amber, sealing wax, shellac, or animal horns. These materials could be softened and molded. When cooled, they retained the new shape. Sealing wax was used to close documents with a personal mark. Items made from animal horns included buttons, cups, hornbooks, and lantern windows. Shellac (a gutta-percha molded plastic) was often used for lamination and for phonograph records (until vinyl was introduced).

In the mid-nineteenth century, the organic chemical industry began, which led to a study of the chemical makeup of materials and many man-made products. Early plastics were created from cellulose wood fibers treated with nitrate. A German, Christian Friedrich Schönbein, was one of the first to develop cellulose nitrate plastics in 1846. Later, in England, Alexander Parkes developed Parkesine, a pressure-molded collodoin (cellulose nitrate in ethanol). He displayed many Parkesine objects at the 1862 London International Exhibition. However, as happened with so many inventions from Europe, it was the Americans who developed them as commercial successes. John Wesley Hyatt and his brother created the Celluloid Manufacturing Company in Newark, New Jersey, in 1872; this company became the renowned Celanese Corporation of America, renamed CelaneseAG in 1999. Hyatt used camphor as a plasticizer with cellulose, which proved safer and, therefore, more commercially viable. Camphor is still used as a natural plasticizer. Hyatt also introduced injection molding, extrusion molding (forcing molten plastics through an opening), and blow molding (like glass blowing). His work in celluloid made possible motion picture film for Thomas Edison, photographic film for George Eastman, and other products such as collars, eyeglass frames, and side curtains for automobiles. The great disadvantage of celluloid nitrate was its flammability. However, by World War I (1914–1918) the Tennessee Eastman Corporation had developed cellulose fibers mixed with acetate, which proved much less flammable and was used widely on airplane wings.

Leo Baekeland, a Belgian who came to the United States in 1889, developed the first commercial synthetic resin and the first thermoset resin in the early 1900s. He created a substance from phenolics (found in coal tar) and formaldehyde to impregnate fibrous sheets. His new synthetic was called Bakelite, which became the foremost name in plastics.

The work of Hermann Staudinger in Zurich in the 1920s was critical in explaining how the plastic molecules, polymers, were created. Once his work was accepted in the 1930s, the plastics industry developed rapidly with diversified products for commercial uses. In the 1930s the new plastics materials included urea resins, acrylics, and polyethylene in 1931; vinyl resins in 1933; melamine, fiberglass, and styrene in 1937; Teflon and epoxy in 1938; and nylon in 1939. After World War II (1939–1945), society entered the "Plastics Age."

What Are Plastics?

Plastics are inexpensive substances that are soft and malleable during manufacturing and are fabricated into lightweight, tough, rigid or flexible, clear or opaque, corrosive-resistant objects. There are some inorganic substances that conform to this definition—concrete, mortar, and plaster of Paris for example. However, as we think of them, plastics are organic substances made up of huge molecules called polymers. The organic material generally used is coal, oil, natural gas, or wood. Plastics have a high molecular weight; for instance, the molecular weight of oxygen is 32, and that of a polymer is between 10,000 and 500,000. Chemicals are used to distill and modify the organic substance. Chemicals found in plastics include carbon, hydrogen, oxygen, and nitrogen. Chlorine, fluorine, sulfur, or silicon may also be present. To make the polymers more flexible or tougher, a plasticizer is added. There are many different plasticizers, and it is important to use the right one in the right amount for the particular substance or object desired. If the wrong plasticizer is used, the polymer loses its plasticity in a short time. In the early days of the plastics industry, this happened often with raincoats, handbags, curtains, and other objects, which soon became brittle and cracked.

There are two types of plastics—thermoplastics and thermoset plastics. Thermoplastics are formed from long linear chains of molecules (polymers). These polymers can be softened and when cooled regain a solid state. These plastics can be first formed as sheets, pellets, films, tubes, rods, or fibers. These forms can then be reheated and molded into other shapes. For example, nylon thread can be made into fabric. The various chemical and molecular properties of thermoplastics determine whether they are called nylon, polyester, polypropylene, polystyrene, polyethylene, polyvinyl chloride (PVC), or other names.

Thermoset plastics are different. These polymers are formed from two directions and produce three-dimensional networks of molecules, not linear chains. Such substances cannot be remelted. They are formed through compression molding or casting. Thermoset plastics include phenolic laminates (the original Bakelite), urethane, melamine, epoxy, acrylic, silicone, fluorocarbons, and others.

Uses of Plastics

Plastics are prolific and have many advantages over other heavier, easily corroded, breakable, or more expensive materials. A home provides a good example of the ubiquity and versatility of plastics. The house may use vinyl concrete, vinyl siding, vinyl window frames, vinyl wallpaper, and vinyl venetian blinds. These are long lasting and require little upkeep. The wiring in the house could be polyethylene with epoxy coating. The insulation may be silicone or polystyrene. The house will also have polyvinyl chloride pipes. The outdoor furniture is likely to be molded PVC. Windows may be acrylic and so, too, the sofa. Seat cushions and pillows will likely be made with urea-formaldehyde foam; the carpets, nylon. The tables and cabinets may be polyurethane. Dishes may be melamine, which is easily dyed, durable, and very scratch resistant. The family car is also likely to be melamine coated. Pots and pans often use Teflon, a fluorocarbon invented in 1943. Serving dishes may be the acrylic Lucite, and small windows may be of another acrylic, Plexiglas. Clothing may also be of plastics, including nylon stockings and nylon underwear. In the late 1960s, clothing often was all polyester; today, polyester fibers are often mixed with natural fibers such as wool or cotton for a more natural look. The home's air ducts are also likely to be polyester, and if there is a boat, it is most likely fiberglass, made from polyester and glass fiber mix. The glass fibers reinforce the plastics and allow for repairs. Foods in a home, especially meats, are packaged in Styrofoam, made from polystyrene, as are some carry-out containers. Polystyrenes are thermoplastics that are easily molded, rigid, and good insulators.

The five most prevalent plastics are all thermoplastics and account for 90 percent of the plastics of the early twenty-first century. These include polyethylene, used in all types of bags, diaper liners, agricultural covers, and milk and juice jugs; polyethylene terephthalate (PET), used principally for soda bottles and videotapes; polystyrene, used as clear packaging, as a foam (Styrofoam), or for furniture, toys, utensils, and dishes; polypropylene, used for battery cases, crates, film, molded car parts, appliances, fish nets, and wire coating; and polyvinyl chloride, used as a flexible substance in film, hoses, rainwear, and wall coverings, or as a rigid substance in pipes, buildings, and credit cards. The most prevalent thermoset plastics are phenolics, used with formaldehyde and fillers in plywood, fiberglass, and circuit boards; and urea resins, used in polyurethane foam fillers.

The uses of plastics are always expanding and new polymers are being created. One example of thermoset plastics whose uses are expanding is silicone. It is an oxygen-based, and not the usual carbon-based, substance. Because it is highly resistant to ozone, chemicals, sunlight, and aging, it has a wide variety of uses, such as polishes, insulation, waterproofing, adhesives, and implants. Two very versatile thermoplastics are polyethylene and polycarbonate. Polyethylene is used for toys, electronic devices, wires, and milk carton coatings. Polyethylene is also now used widely in medical procedures, for example, to replace aortas or as prosthetic devices. Polycarbonates are fairly new polymers that are formed from bonding oxygen and silicon. Polycarbonates are easy to use yet highly rigid and very corrosive resistant. They have replaced phenol laminates in spacecraft, automobiles, and ships.

Disadvantages of Plastics

Though plastics are ubiquitous and versatile, they also have several disadvantages. The original plastic, cellulose nitrate, was highly flammable; celluloid acetate lessened that danger. Later plastics have included flame retardants, which delay the outbreak of flames but not the decomposition before reaching flammable temperatures. Because of the flame retardants, plastics produce thick, dense smoke that is acrid from the chemicals, especially carbon monoxide. In some of the most disastrous fires, more people suffocated from the plastics smoke and soot than died from the flames. Also, once plastic does flame, it burns faster and hotter than natural substances.

Decomposition is another issue. Because plastics are made from long chains of molecules that receive high heat to set or mold them, decomposition can emerge as weaknesses in the chain. When thermoplastics are remolded, weaknesses can increase. Some plastics also decompose more rapidly than others, especially the less expensive plastics such as PVC and urethane foam. Some critics claim that the phthalate plasticizers used in PVC create low-level toxicity. The urethane foam cushions begin to break down fairly quickly, leaving bits of foam and dust. Leaving plastics exposed to sunlight and heat also causes decomposition and cracking. As plastics decompose, they release chemicals such as carbon monoxide, chlorine, and benzene into the air. For example, the "office worker's illness" is caused by decomposing polymers of the air ducts, furniture, and equipment, and too little fresh air.

Future

Another problem with plastics is waste disposal. In the United States alone, some 60 billion pounds of plastics are discarded annually and over 90 percent of the waste is not yet recycled. Thermoset plastics cannot be reused; neither can some thermoplastics because of impurities (including disposable diapers, food packaging, and trash bags). Nevertheless, in the United States and Europe plastics recycling has become a major industry, tripling in the United States since 1990. Recycled bottles alone have grown from 411 million pounds in 1990 to 1,511 million pounds in 2000. There are over 1,400 products made from recycled plastics, most of the same items as new synthetic plastics—furniture, packaging, household items—but also new items such as lumber and posts.

Composting is a principal method of recycling plastics. Synthetic plastics may decompose through photo-degradation, oxidation, or hydrolysis—naturally or chemically. Success in composting depends on the environment and the chemicals used in the plastics. Some, such as the polyolefins, are hydrophobic (water-resistant) and thus highly resistant to biodegradation.

The newest research and development in plastics is in bioplastics, biodegradable plastics whose components are principally derived from renewable raw materials. This often means a return to many of the natural polymers used in the nineteenth century, with late-twentieth or twenty-first-century technology added. In 1941 Henry Ford produced a prototype Ford made of soybean plastics. Due to war needs and the rise of synthetic plastics, the work was abandoned, but such innovation is typical of today's research and development. Bioplastics are already used in a wide variety of products including all types of bags, packaging, fishnet and lines, pet toys, wall coverings, razors, and golf tees.

Starch is a prolific raw material that makes a good plastic. It is now used in many fast-food containers and for the "peanuts" used in shipping. The water solubility of starch is both an advantage for decomposition and a limitation, which technology may overcome. For example, some eating utensils are now made of 55 percent cornstarch and 45 percent poly (lactic acid), which is insoluble in water but biodegradable in seawater. Poly (lactic acid) is a polyester synthesized from lactic acid. It shows solid commercial production growth and is used, for example, in compost bags, agricultural films, fibers, and bone repair. Cellulose is another bioplastic from the past. It is contained in 40 percent of organic matter and thus is renewable. Its limitation is that it is not thermoplastic, though it can be made into films.

Though bioplastics have limitations such as tensile strength, solubility, and cost, they produce less toxicity to humans and the environment and are based on renewable resources. Improved technology may overcome the limitations.

Bibliography

Hooper, Rodney. Plastics for the Home Craftsman. London: Evans Brothers, 1953.

Simonds, Herbert R., and James M. Church. A Concise Guide to Plastics. New York: Reinhold Publishing Company, 1963.

Stevens, E. S. Green Plastics: An Introduction to the New Science of Biodegradable Plastics. Princeton, N.J.: Princeton University Press, 2002.

Wallace, Deborah. In the Mouth of the Dragon. Garden City Park, N.Y.: Avery Publishing Group, 1990.

Paranormally obtained plastics may be divided into two groups: imprints and molds. The first may be produced in any soft, yielding substance or on smoked or chemically treated surfaces; for the second, melted paraffin wax is employed.

Paranormal Imprints

Johann C. F. Zöllner, in his experiments with the medium Henry Slade, placed a dish filled to the brim with flour under the table hoping the spirit hand that took hold of him might leave an impression in the flour. Baron Lazar Hellenbach testified to having seen an impression of a hand larger than Slade's or any other individual present. None of their hands had any trace of flour. Zöllner also obtained the imprint of a foot on two sheets of paper covered with lamp black between two closed slates.

The imprint of a hand with four fingers, the imprint of a bird, two feet, and a materialized butterfly were supposedly obtained during the George Valiantine-Bradley sittings in 1925, in England. Charles Sykes, the British sculptor, was unable to give an explanation, as was Noel Jaquin, a fingerprint expert. In 1931, however, the same experts claimed to have caught Valiantine in a fraud. They smeared printing ink in secret on the modeling wax, stripped Valiantine after the séance and found a large stain on his left elbow corresponding with the lines of the imprint. Other imprints were found identical to those of his toes.

Palladino's Mediumship

Eusapia Palladino produced hand and face imprints in putty and clay. Reportedly they bore her characteristics, although she was held at a distance from the tray while the impression was made. Numerous imprints were obtained by the psychical researchers Cesare Lombroso, Enrico Morselli, Er-cole Chiaia, and Guillaume de Fontenay.

Camille Flammarion claimed to be a witness of the process at Monfort-l'Amaury in 1897. Supposedly the resemblance of the spirit head to the medium was undeniable, yet seemingly she could not have imprinted her face in the putty. Besides having been physically controlled, Ms. Z. Blech kissed Palladian on the cheeks, searching for the odor of putty on her face.

Julien Ochorowitz wrote of Palladino's mediumship at Rome: "The imprint of this face was obtained in darkness, yet at a moment when I held two hands of Eusapia, while my arms were entirely around her. Or, rather, it was she who clung to me in such a way that I had accurate knowledge of the position of all her limbs. Her head rested against mine even with violence. At the moment of the production of the phenomena a convulsive trembling shook her whole body, and the pressure of her head on my temples was so intense that it hurt me."

Paranormal Molds

In normal wax molding, the technical process of the production of paraffin wax casts begins with the placement of buckets of hot and cold water placed side by side. The hot water will melt the paraffin. If one dips a hand in and withdraws it, a thin shell of the liquid will settle and congeal. If a hand is dipped alternately into the hot paraffin and into the cold water the shell will thicken. When the hand is freed, a wax glove is left behind. These gloves are fragile. They must be filled with plaster of Paris to preserve. Then if the paraffin wax is melted off, the texture of the skin appears in the plaster. The hand freed from the paraffin shell must be washed in soap and water before another experiment, or the second shell will stick to the fingernails. Altogether, it takes about twenty minutes to deliver a finished shell. The fingers of the hand must be held fairly straight, otherwise they will break the shell when withdrawn. For the same reason no full cast, up to the wrist, can be obtained.

Supposedly molds obtained by psychical researchers in séances with mediums have bent fingers, joined hands, and wrists. These molds are fine and delicate, whereas those obtained from living hands are thick and solid.

The first paraffin wax casts were obtained by William Denton in 1875, in Boston with the medium Mary M. Hardy. Hardy produced the paraffin wax gloves in public halls. To test Hardy's ability, the dish of paraffin was weighed before the mold appeared and after. In later years, another test was devised, locking up the liquid paraffin wax and cold water in a wire cage. After Denton, Epes Sargent investigated Hardy.

In England, William Oxley produced the first psychic molds in 1876 with Elizabeth d'Esperance and later with Mrs. A. H. Firman and the Rev. Francis W. Monck. Similar success was claimed with the Davenport Brothers, William Eglinton, and Annie Fairlamb around the same time. T. P. Barkas of Newcastle, England, mixed magenta dye in the paraffin wax during experiments with Fairlamb in 1876. The gloves had traces of the dye.

The psychical researcher Alexander Aksakof hypothesized that the plaster casts showed similar characteristics between the medium and the materialization. He noted that Oxley made similar observations and quoted his letter: "It is a curious fact that one always recognises in the casts the distinctive token of youth or age. This shows that the materialised limbs, whilst they preserve their juvenile form, evince peculiarities which betray the age of the medium. If you examine the veins of the hand you will find in them characteristic indications which indisputably are associated with the organism of the medium."

It had been suggested the wax gloves may have been prepared from inflated rubber gloves. Gustav Geley produced some casts using rubber gloves for comparison. They were also put on display. The charge that the gloves may have been made previous to the séance could not be sustained.

One variety of plastics is the working of linen into the semblance of human features by psychic means. Reportedly Dr. Eliakim Phelps left a well-detailed description of an instance, including the appearance of 11 figures of "angelic beauty." Occasionally similar phenomena have been reported as a manifestation in haunted houses, with cushions assuming the shape of human forms.

There are also artistic efforts under the heading of direct paintings —the paint appears to give three-dimensional effects. Many such pictures were produced during the late nineteenth and early twentieth centuries.

There are various methods to produce imprints. Mrs. Albert Blanchard, an American medium, produced imprints by depositing sediment under water in a dish. F. Bligh Bond discussed her work in Psychic Research (October 1930) using data collected from Horace Newhart. Blanchard put clay and water in a shallow dish, stirred the sediment with her fingers, and let it settle. When the water evaporated, supposedly the clay had assumed the outlines of a human face or head in low relief.

Major categories of plastics used in modern boatbuilding
Widespread use of plastic in pleasure boats during the last 50 years has made boats cheaper, more numerous, and practically indestructible. In harbors where a few wooden boats once bobbed gracefully at moorings, there are now huge marinas cramming hundreds of plastic boats into congested berths.Twenty or more forms of plastic are used in modern boat-building, many combined with materials such as glass or carbon fibers for strength and flexibility. Following are some of the major categories:

• acetals: resilient and tough; high melting point; used in water pumps, through-hull fittings, and interior panels

• acrylics: clear and resistant to sunlight; used in port lights, windshields, dodgers, and paint

• alkyds: form tough skins in paint and varnish; make good electrical insulation

• aminos: very scratch-resistant and heatproof; melamine and urea are examples; used for countertops and tableware

• epoxies: tough, gap-filling adhesives; form high-grade laminates with glassfiber and other materials; used extensively in paints and barrier coats, but adversely affected by sun

• fluorocarbons: very slippery, they eliminate much friction; used in engines, blocks, and as insulating material to prevent galvanic action between different metals

• nylons: very strong, light, but stretchy; used for light-weather sails, anchor rodes, chocks, and bushings

• polycarbonates: tough, stable, and resistant to chemicals; used in windows, pumps, and engines

• polyesters: the resins mixed with fine glass fibers, most commonly used to build boat hulls, and known as fiberglass or glass-reinforced plastic (GRP); also the basis of Dacron fibers for rope and sails that are more stable than nylon but not quite as strong

• polyolefins: best known are polyethylene and polypropylene; very light and strong; used for floating ropes, fuel and water tanks, fenders, and galleyware; adversely affected by sunlight

• polystyrenes: very light; used for flotation, fenders, and insulating and packing material; adversely affected by sunlight

• polyurethanes: best known as tough, flexible sealant-adhesives; also form ultradurable and glossy paints, as well as flotation material and cushions

• silicones: form long-lasting flexible gaskets and bedding for port lights and deck fittings; also used as lubricants and to waterproof fabrics

• vinyls: expensive but very waterproof resin; often used on hulls below the waterline to discourage osmosis; ubiquitous as surface coverings, inflatable boats, rain gear, water hoses, paint, and so on