PLASTICS EXPLOSION
| Index | |
| SR No. | Content |
| 1 | INTRODUCTION |
| 2 | Brand Names |
| 3 | Listings |
| 4 | IMPORTANT PLASTICS AND THEIR USES |
| 5 | REFERENCES |
INTRODUCTION
Synthetic polymers are often referred to as "plastics", such as the well-known polyethylene and nylon. However, most of them can be classified in at least three main categories: thermoplastics, thermosets and elastomers.
Man-made polymers are used in a bewildering array of applications: food packaging, films, fibers, tubing, pipes, etc. The personal care industry also uses polymers to aid in texture of products, binding, and moisture retention (e.g. in hair gel and conditioners).
Plastics explosion: Acrylic, Polyethylene, etc...
BRAND NAMES
These polymers are often better known through their brand names, for instance:
Kevlar
Kynar, e.g. PVDF
Mylar, e.g. polyethylene terephthalate
Nylon, e.g. polyamide 6,6
Rilsan, e.g. polyamide 11 & 12
Teflon, e.g. PTFE
Ultem, e.g. polyimide
Vectran
Viton
Zylon
LISTINGS
Plastics explosion: Acrylic, Polyethylene, etc...
Other plastics emerged in the prewar period, though some wouldn't come into widespread use until after the war.
By 1936, American, British, and German companies were producing "polymethyl methacrylate" (PMMA), better known as "acrylic". Although acrylics are now well-known for the use in paints and synthetic fibers, such as "fake furs", in their bulk form they are actually very hard and more transparent than glass, and are sold as glass replacements under trade names such as "Plexiglas" and "Lucite". Plexiglas was used to built aircraft canopies during the war, and it is also now used as a marble replacement for countertops.
Another important plastic, "polyethylene" (PE), sometimes known as "polythene", was discovered in 1933 by the Reginald Gibson and Eric Fawcett at the British industrial giant Imperial Chemical Industries (ICI). This material evolved into two forms, "low density polyethylene" (LDPE), and "high density polyethylene" (HDPE).
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ethylene monomer polyethylene polymer
PEs are cheap, flexible, durable, and chemically resistant. LDPE is used to make films and packaging materials, while HDPE is used for containers, plumbing, and automotive fittings. While PE has low resistance to chemical attack, it was found later that a PE container could be made much more robust by exposing it to fluorine gas, which modified the surface layer of the container into the much tougher "polyfluoroethylene".
Polyethylene would lead after the war to an improved material, "polypropylene" (PP), which was discovered in the early 1950s by Giulio Natta. It is common in modern science and technology that the growth of the general body of knowledge can lead to the same inventions in different places at about the same time, but polypropylene was an extreme case of this phenomenon, being separately invented about nine times. It was a patent attorney's dream scenario, and litigation wasn't resolved until 1989.
Polypropylene managed to survive the legal process, and two American chemists working for Phillips Petroleum of the Netherlands
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propylene monomer polypropylene polymer
Polyurethane was invented by Friedrich Bayer & Company of Germany
In 1939, I.G. Farben Industrie of Germany
Composites using epoxy as a matrix include glass-reinforced plastic, where the structural element is glass fiber, and "carbon-epoxy composites", in which the structural element is carbon fiber. Fiberglass is now often used to build sport boats, and carbon-epoxy composites are an increasingly important structural element in aircraft, as they are lightweight, strong, and heat-resistant.
Two chemists named Rex Whinfield and James Dickson, working at a small English company with the quaint name of the "Calico Printer's Association" in Manchester, developed "polyethylene terephthalate" (PET or PETE) in 1941, and it would be used for synthetic fibers in the postwar era, with names such as "polyester", "dacron", and "terylene".
PET is more impermeable than other low-cost plastics and so is a popular material for making bottles for Coca-Cola and other "fizzy drinks", since carbonation tends to attack other plastics, and for acidic drinks such as fruit or vegetable juices. PET is also strong and abrasion resistant, and is used for making mechanical parts, food trays, and other items that have to endure abuse. PET films, tradenamed "mylar", are used to make recording tape.
One of the most impressive plastics used in the war, and a top secret, was "polytetrafluoroethylene" (PTFE), better known as "teflon", which could be deposited on metal surfaces as a scratchproof and corrosion-resistant, low-friction protective coating. The polyfluoroethylene surface layer created by exposing a polyethylene container to fluorine gas is very similar to teflon.
A Du Pont chemist name Roy Plunkett discovered teflon by accident in 1938. During the war, it was used in gaseous-diffusion processes to refine uranium for the atomic bomb, as the process was highly corrosive. By the early 1960s, teflon "non-stick" frying pans were a hot consumer item.
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tetrafluoroethylene monomer teflon polymer
Teflon was later used to synthesize the miracle fabric "GoreTex", which can be used to build raingear that in principle "breathes" to keep the wearer's moisture from building up. GoreTex is also used for surgical implants; teflon strand is used to make dental floss; and teflon mixed with fluorine compounds is used to make "decoy" flares dropped by aircraft to distract heat-seeking missiles.
After the war, the new plastics that had been developed entered the consumer mainstream in a flood. New manufacturing were developed, using various forming, molding, casting, and extrusion processes, to churn out plastic products in vast quantities. American consumers enthusiastically adopted the endless range of colorful, cheap, and durable plastic gimmicks being produced for new suburban home life.
One of the most visible parts of this plastics invasion was Earl Tupper's "tupperware", a complete line of sealable polyethylene food containers that Tupper cleverly promoted through a network of housewives who sold Tupperware as a means of bringing some money. The tupperware line of products was well thought out and highly effective, greatly reducing spoilage of foods in storage. Thin-film "plastic wrap" that could be purchased in rolls also helped keep food fresh.
Another prominent element in 1950s homes was "Formica®", a plastic laminate that was used to surface furniture and cabinetry. Formica was durable and attractive. It was particularly useful in kitchens, as it did not absorb, and could be easily cleaned of, stains from food preparation, such as blood or grease. With formica, a very attractive and well-built table could be built using low-cost and lightweight plywood with formica covering, rather than expensive and heavy hardwoods like oak or mahogany.
Composite materials like fiberglass came into use for building boats and, in some cases, cars. Polyurethane foam was used to fill mattresses, and styrofoam was used to line ice coolers and make float toys.
Plastics continue to be improved. General Electric introduced "lexan", a high-impact "polycarbonate" plastic, in the 1970s. Du Pont developed "kevlar", an extremely strong synthetic fiber that was best-known for its use in bullet-proof vests and combat helmets. Kevlar was so remarkable that Du Pont officials actually had to release statements to deny rumors that the company had received the recipe for it from space aliens.
One of the most potentially important new developments in plastic are circuits out of plastics is conductive polymers. Electronic circuitry fabricated using plastics or other materials that could be simply printed on a substrate could be incredibly cheap, opening the door to throwaway electronic devices that would cost pennies, or to applications hardly dreamed of now.
So far, electronic devices made with such materials have not been acceptable for production, but in 2001, prototypes of flat-panel displays based on such technologies were being publicly demonstrated, with predictions of commercial introduction in two or three years.
Exotic new engineering plastics are being introduced on a regular basis. Recent inventions include GE's Ultem family and Victrex's PEEK. Both are highly chemical-resistant and are often used in medical and liquid-chromatography equipment.
IMPORTANT PLASTICS AND THEIR USES
acrylics -Molding compound, glazing.
epoxies -Protective coatings, adhesives, laminating compounds, composites.
melamine-formaldehyde (aminos) -Molding compounds.
nylon -Filaments, fibers, bristles, engineering applications.
phenol-formaldehyde (phenolics) - Molding and laminating compounds, adhesives, cast sheets, rods, tubes.
polyesters, saturate - Fabrics, food packaging, molding compounds, engineering applications.
polyesters, unsaturated - Laminating and molding compounds, protective coatings, castings.
polyethylene - Film, extruded tubing, sheets.
polystyrene, or styrene - Molding compounds, foamed resins.
polyurethanes - Protective coatings, adhesives, foamed resins.
polyvinyl chloride - Film, sheets, extruded tubing, casting.
silicones - Rubber compounds, molding compounds, protective coatings, paints, varnishes.
urea-formaldehyde (aminos) - Textile-treating compounds, molding compounds, foamed resins.
vinyls (several types) - Protective coatings, extruded tubing, film, molding compounds, foamed resins.
REFERENCES
1. Processes and Materials of Manufacture by R.A. LINDBERG
2. SEMINAR TOPIC FROM :: www.edufive.com/seminartopics.html
3. www.pcmag.com/encyclopedia
4. www.me.sc.edu
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