Plastics

Introduction

As used here, plastics are polymers of hydrocarbon monomers that in a liquid state can be molded or extruded into objects, films or fibers.   Plastics vary greatly in heat tolerance, hardness, and resiliency.   Their uniform composition, lightness, and low cost make them useful in many industries, offices, and homes as substitutes for other materials, like wood, steel, and glass.   Most modern plastics are products of petroleum refining, using about 4% of its production. ^{Word n.p.}   Plastics contributed to higher American living standards by replacing more expensive glass, wood, and steel products with low cost products available to more people.

Plastics can be grouped into several classes: ^{Word n.p.}

1   Natural polymers are made of cellulose.   Examples of their uses are wax, shellac, rubber, flax, hemp, and cotton that can be spun into clothing fibers, rope, burlap bags, etc.

2   Cellulose based plastics, e.g., Celluloid and Rayon (trade names).   Celluloid examples are (formerly) shirt collars and cuffs (made them waterproof), corsets (replaced metal stays that rusted), movie film, billiard balls (replacing ivory) and (now) ping pong balls.   The invention of celluloid began the plastics "revolution".   Rayon, now replaced by other plastics, was used for sheet wrapping (cellophane) and clothing fibers.

3   Bakelite (a phenolic, which is a ring of six carbon atoms joined by alternating single and double bonds).   Bakelite is a purely synthetic material, i.e., not made partly with molecules found in nature.   It was also the first thermoset plastic.   Conventional thermoplastics can be molded and then melted again, but thermoset plastics form bonds between polymers strands when cured, creating a matrix that cannot be undone without destroying the plastic.   Thermoplastics are tough and temperature-resistant.   Bakelite was cheap, strong and durable.   It was molded into thousands of forms, such as radios, telephones, clocks, and billiard balls.   Phenolic plastics are still in widespread use, e.g., some electronic circuit boards are made of sheets of paper or cloth impregnated with phenolic resin.   Bakelite was replaced by other plastics that were easier and cheaper to produce.

4   Polypropylene is used on bottle caps, drinking straws, and other throwaways.   Polystyrene is used on packaging pellets or "styrofoam peanuts," cups, plastic tableware, meat trays, take away food containers.   PVC (Polyvinyl Chloride), an extremely versatile and useful plastic, was formerly used to replace wood, metals, concrete, etc. for plastic pipes, outdoor furniture, shrink wrap, water bottles, salad dressing and liquid detergent containers, but now its use is curtailed because it is a carcinogen.

5   Nylon.   This is polyamide (PA), but better known by its trade name, "nylon".   It was the first synthetic nylon fiber, very strong and flexible.   The first application was for bristles for toothbrushes.   However, Du Pont's wanted it as a silk substitute, particularly for expensive silk stockings.   In WW II, silk stockings were put aside while nylon was made into parachutes for aviators and paratroopers.   After the war, silk stocking mania began again.   Nylon is today an important plastic, and not just for making clothing and luggage fabrics.   In its bulk form, it is very strong and wear-resistant, so is used to build gears, bearings, bushings, and other mechanical parts.

6   Neoprene is the trade name DuPont gave to its synthesis of the polymer polychloroprene, used as a synthetic rubber.   Its monomer is chloroprene, a common name for the organic compound 2-chloro-1,3-butadiene, which has the chemical formula CH₂=CCl-CH=CH₂.   Neoprene is highly resistant to heat and chemicals such as oil and gasoline, and is used in fuel hoses and as an insulating material in machinery.   It is also used for wetsuits, electrical insulation, and car fan belts.

7   Acrylic.   Although acrylics are well-known for their use in paints and synthetic fibers, such as "fake furs", in bulk form they are actually very hard and more transparent than glass, so they are sold as glass replacements under trade names such as Plexiglas and Lucite.   Plexiglas was used to build aircraft canopies during WW II; commercially, it is used as an inexpensive marble replacement for countertops.

8   Polyethylene and polypropylene.   This material evolved into two forms, "low density polyethylene" (LDPE), and "high density polyethylene" (HDPE).   PEs are cheap, flexible, durable, and chemically resistant.   LDPE is used to make films and packaging materials, such as, dry cleaning bags, produce bags, trash can liners, food storage containers.   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 tougher by exposing it to fluorine gas, which modified the surface layer of the container into the much tougher polyfluoroethylene.   Polypropylene is similar to polyethylene, and shares polyethylene's low cost, but it is much tougher.   It is used in everything from plastic bottles to carpets to plastic furniture, and is very heavily used in automobiles.   Earl Tupper's "tupperware", is a complete line of sealable polyethylene food containers.   The tupperware line of products greatly reduced spoilage of foods in storage.   Thin-film "plastic wrap" polyethylene rolls keep food fresh.

9   Polyurethane is used in blown form for mattresses, furniture padding, and thermal insulation.   In non-blown form, it is used sportswear as "lycra".

10   Epoxies are a class of thermoset plastic that form cross-links and cure when a hardener is added.   After WW II, they would be used in coatings, adhesives, and composite materials.   Composites using epoxy as a matrix include glass-reinforced plastic, where the structural element is glass fiber, and "arbon-epoxy composites, in which the structural element is carbon fiber.   Fiberglass is now often used to build sports equipment and boats, and carbon-epoxy composites are an increasingly important structural element in aircraft, as they are lightweight, strong, and heat-resistant.

11   Polyethylene terephthalate (PET or PETE) is used for synthetic fibers, with names such as "polyester", "dacron", and "terylene".   PET is more impermeable than other low-cost plastics and resists acid corrosion, so is a popular material for making bottles for carbonated beverages, and for acidic drinks, such as, fruit or vegetable juices, cooking oil bottles, peanut butter jars.   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 MylarŽ, are used to make recording tape.   It is also one of the most important raw material for synthetic fibers.

12   Polytetrafluoroethylene (PTFE), better known as "teflon", can be deposited on metal surfaces as a scratchproof and corrosion-resistant, low-friction protective coating.   During WW II, teflon was used in gaseous-diffusion processes to refine uranium for the atomic bomb, as the process was highly corrosive.   Teflon coating has the lowest coefficient of friction of any substance, so it is used on "no-stick" metal frying pans and its strands are used for dental floss.   Teflon was later used to synthesize the miracle fabric "GoreTex", which can be used to build raingear that "breathes" (allows air to enter and lets wearer's moisture out).   GoreTex is also used for surgical implants.

13   FormicaŽ is a plastic laminate that is used to surface furniture and cabinetry.   Formica was durable, attractive, non-absorbent, and easily cleaned of food stains, so it is useful as a kitchen counter and table covering to inexpensive, lightweight plywood.

14   Lexan is a high-impact polycarbonate plastic used as a glass substitute.

15   Kevlar is an extremely strong, high-impact polycarbonate plastic, fiber that was best-known for its use in bullet-proof vests and combat helmets.

16   Polystyrene is made mainly as expanded polystyrene, which is a mixture of about 5% polystyrene and 95% air.   It is used in throwaway coffee cups and takeaway food containers, insulation in building structures, and also in crafts and model building, particularly architectural models.   Polystyrene is a rigid, brittle plastic that is now used to make plastic model kits, disposable eating utensils, and similar articles.   It would also be the basis for one of the most popular "foamed" plastics, under the name styrene foam or styrofoam.

Environmental Impact of Plastics.   Although plastics had a remarkable impact on American (and other) living standards, they are safety and environmental hazards.   The first controversy arose in the late 1950s and early 1960s.   Infants and small children crawled into plastic bags used by launderers to cover clothing and suffocated.   The plastics industry launched a massive public education campaign that eventually suceeded in preventing these disasters.   The massive consumption of plastic-encased products led to problems of litter and waste disposal, since it was durable and degraded very slowly.   By the 1990s, plastic recycling programs were common in the United States, although this accounts for only about 5% of plastic products because of the difficulty of sorting different kinds of plastics in trash, which must be done by hand.   Also, a single consumer product may contain many different kinds and colors of plastics.   When feasible to collect, thermoplastics can be remelted and reused, and thermoset plastics can be ground up and used as filler.   Plastics can be decomposed chemically and used as animal feed. ^{Word n.p.}

To 1834

Plastics in use at this time are natural polymers, like rubber, wax, shellac, cotton, flax, hemp, etc.

1830-1839

Polyvinyl chloride was accidentally discovered in 1838 by Henri Victor Regnault. ^{Word n.p.}   No commercial use was made of this product at this time (see 1926).

In 1839, the American inventor, Charles Goodyear, was experimenting with the sulfur treatment of natural rubber when he dropped a piece of sulfur-treated rubber on a stove.   The rubber had improved properties, and Goodyear followed up with further experiments to develop a process known as "vulcanization" that involved cooking the rubber with sulfur.   Compared to untreated natural rubber, Goodyear's "vulcanized rubber" was stronger, more resistant to abrasion, more elastic, much less sensitive to temperature changes, impermeable to gases, and highly resistant to deterioration from chemicals and electricity.   Vulcanization creates sulfur bonds that link separate isoprene polymers together, improving the material's structural integrity and its other properties. ^{Word n.p.}   Vulcanized rubber eventually was replaced by a totally synthetic rubber, called neoprene.

1840-1849

1850-1859

1860-1869

An Englishman, Alexander Parkes, developed a synthetic ivory as a substitute for real ivory, which was (and is) expensive.   He named it "pyroxlin", which he marketed under the trade name "Parkesine", and which won a bronze medal at the 1862 World's fair in London.   Parkesine was made from cellulose that was treated with nitric acid and a solvent, which hardened into a hard, ivory-like material that could be molded when heated.   However, Parkes was not able to scale up the process to a commercial manufacturing level, and products made from Parkesine quickly warped and cracked after a short period of use. ^{Word n.p.}   However, it was a precursor to later improvements.

An American printer and amateur inventor, John Wesley Hyatt, continued Parkes' work.   Whereas Parkes failed to find a proper solvent, Hyatt discovered that camphor worked well.   Since cellulose was the main constituent used in the synthesis of his new material, Hyatt named it celluloid and introduced it in 1863.   (Hyatt was somewhat of an industrial genius who understood what could be done with such a shapeable, or plastic, materials and proceeded to design much of the basic industrial machinery needed to produce good-quality plastic materials in quantity. ) ^{Word n.p.}

1870-1879

In 1870, John W. Hyatt, Jr. and Isaiah S. Hyatt of Albany, NY, were awarded a patent for producing celluloid. ^{Carruth 305}

Polyvinyl chloride was accidentally rediscovered (see 1838) in 1872 by Eugen Baumann. ^{Word n.p.}   No commercial use was made of this product at this time (see 1926).

1880-1889

In 1884, a French chemist, the Comte de Chardonnay, introduced a cellulose-based fabric that was called "Chardonnay silk", meant to replace the expensive real silk.   Although attractive like celluloid, it was very flammable and was taken off the market after some severe accidents. ^{Word n.p.}

1890-1899

In 1894, three British inventors, Charles Cross, Edward Bevan, and Clayton Beadle, patented a new "artificial silk" or "art silk" that was much safer than "Chardonnay silk".   The three men sold the rights for the new fabric to the French Courtald Company, a major manufacturer of silk, which put it into production in 1905, using cellulose from wood pulp as the feedstock material. ^{Word n.p.}

Polyethylene was first synthesized by the German chemist, Hans von Pechmann, who prepared it by accident in 1898 while heating diazomethane.   When his colleagues Eugen Bamberger and Friedrich Tschirner characterized the white, waxy subsance he had created, they recognized that it contained long -CH2- chains and termed it polymethylene. ^{Word n.p.}

1900-1909

By 1900, movie film was a major market for celluloid. ^{Word n.p.}

The limitations of celluloid led to the next major advance in plastics, "phenolic" or "phenol-formaldehyde" plastics.   Leo Hendrik Baekeland, a Belgian-born American chemist , was searching for an insulating shellac to coat wires in electric motors and generators when he found that mixtures of phenol (C₆H₅OH) and formaldehyde (HCOH) formed a sticky mass when mixed together and heated, and the mass became extremely hard if allowed to cool and dry.   Baekeland also found that the material could be mixed with wood flour, asbestos, or slate dust to create composite materials with different properties, most of which were strong and fire-resistant.   The only problem was that the material tended to foam during synthesis, and the resulting product was of unacceptable quality.   Baekelund built pressure vessels to force out the bubbles and provide a smooth, uniform product. He publicly announced his discovery in 1909, naming it bakelite. It was originally used for electrical and mechanical parts, finally coming into widespread use in consumer goods in the 1920s. ^{Word n.p.}

After WW I, improvements in chemical technology led to an explosion in new forms of plastics. Among the earliest examples in the wave of new plastics were polystyrene (PS) and polyvinyl chloride (PVC), developed by the I.G. Farben company of Germany. ^{Word n.p.}

1920-1929

In 1923, DuPont Corp. began to produce cellophane through the patent of Jacques F. Brandenberger. ^{Carruth 455}

In 1926, Waldo Semon of B.F. Goodrich developed a method to plasticize PVC by blending it with various additives.   The result was a more flexible and more easily processed material that soon achieved widespread commercial use. ^{Word n.p.}

When the Bakelite patent expired in 1927, the Catalin Corporation acquired the patent and began manufacturing Catalin plastic using a different process that allowed a wider range of coloring. ^{Word n.p.}

Practical synthetic rubber grew out of studies published in 1930 written independently by Carothers and the German scientist, Hermann Staudinger.   These studies led in 1931 to one of the first successful synthetic rubbers, known as neoprene. ^{Word n.p.}

Another important plastic, polyethylene (PE), sometimes known as "polythene", was discovered in 1933 by the Reginald Gibson and Eric Fawcett at Imperial Chemical Industries (ICI). ^{Word n.p.}

In 1934, Dr. Wallace H. Carothers of Du Pont Laboratories invented nylon (polymer 66).   Patents were granted in 1938.   The first commercial nylon product was a toothbrush with nylon bristles.   ^{Carruth 489,501}

In 1935, German chemists synthesized the first of a series of synthetic rubbers known as "Buna rubbers".   These were "copolymers", meaning that their polymers were made up from, not one, but two monomers, in alternating sequence.   One such copolymer, Buna rubber, known as "GR-S" ("Government Rubber Styrene, commercially "neoprene"), a copolymer of butadiene and styrene, became the basis for US synthetic rubber production during World War II. ^{Word n.p.}

In 1935, another ICI chemist, Michael Perrin, developed a reproducible high-pressure synthesis for polyethylene that became the basis for industrial LDPE production beginning in 1939. ^{Word n.p.}

By 1936, American, British, and German companies were producing polymethyl methacrylate (PMMA), better known as acrylic. ^{Word n.p.}

Polyurethane was invented by Friedrich Bayer & Company of Germany in 1937. ^{Word n.p.}

A Du Pont chemist, Roy Plunkett, discovered teflon by accident in 1938. ^{Word n.p.}

In 1939, nylon stockings went on the market. ^{Carruth 507}

In 1939, I.G. Farben Industrie of Germany filed a patent for polyepoxide or epoxy. ^{Word n.p.}

Polystyrene was first manufactured by BASF in the 1930s. ^{Word n.p.}

1940-1949

Two chemists, Rex Whinfield and James Dickson, working at a small English company, Calico Printer's Association, in Manchester, England, developed polyethylene terephthalate (PET or PETE) in 1941. ^{Word n.p.}

Worldwide natural rubber supplies were limited, and by mid-1942 in WW II, most of the rubber-producing regions were under Japanese control.   Military trucks needed rubber for tires, and rubber was used in almost every other war machine.   The US government launched a major effort to increase synthetic rubber production, and by 1944 a total of 50 factories were manufacturing it, producing a volume of the material twice that of the world's natural rubber production before the beginning of the war. ^{Word n.p.}

After the WW II (1945), natural rubber plantations no longer had a stranglehold on rubber supplies, particularly after chemists learned to synthesize isoprene.   GR-S (neoprene) remains the primary synthetic rubber for the manufacture of tires. ^{Word n.p.}

Teflon was introduced as a commercial product in 1946. ^{Word n.p.}

1950-1959

After WW II, polyethylene would lead 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.   Two American chemists working for Phillips Petroleum of the Netherlands, Paul Hogan and Robert Banks, are now generally credited as the "official" inventors of the material. ^{Word n.p.}

FormicaŽ began to be used on home counters and tables in the 1950s. ^{Word n.p.}

1960-1969

By the early 1960s, teflon "non-stick" frying pans were in wide demand by consumers. ^{Word n.p.}

1970-1979

General Electric introduced lexan and Du Pont developed kevlar, a high-impact polycarbonate plastic, in the 1970s. ^{Word n.p.}

1980-1989

1990-1999