Plastic is the general common term for a wide range of synthetic or semisynthetic organic Organic chemistry is a discipline within chemistry which involves the scientific study of the structure, properties, composition, reactions, and preparation of chemical compounds that contain carbon. These compounds may contain any number of other elements, including hydrogen, nitrogen, oxygen, the halogens as well as phosphorus, silicon and amorphous solid An "amorphous solid" is a solid in which there is no long-range order of the positions of the atoms. . Most classes of solid materials can be found or prepared in an amorphous form. For instance, common window glass is an amorphous solid, many polymers (such as polystyrene) are amorphous, and even foods such as cotton candy are amorphous materials suitable for the manufacture of industrial products. Plastics are typically polymers A polymer is a large molecule (macromolecule) composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties of high molecular weight The molecular mass of a substance, frequently referred by the older term molecular weight and abbreviated as MW, is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one isotope of carbon-12). This is distinct from the relative molecular mass of a molecule, which is the ratio of the, and may contain other substances to improve performance and/or reduce costs.

The word derives from the Greek Greek , an Indo-European language native to the southern Balkan peninsula, is the language of the Greeks. It forms an independent branch within Indo-European. It has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical Ancient Greek literature πλαστικός (plastikos) meaning fit for molding, and πλαστός (plastos) meaning molded.^[1][2] It refers to their malleability, or plasticity In physics and materials science, plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to applied forces. For example, a solid piece of metal or plastic being bent or pounded into a new shape displays plasticity as permanent changes occur within the material itself. By contrast, a permanent during manufacture, that allows them to be cast Casting is a manufacturing process by which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting materials are usually metals or various cold, pressed Death by crushing or pressing is a method of execution that has a long history during which the techniques used varied greatly from place to place. This form of execution is no longer sanctioned by any governing body, or extruded Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed or drawn through a die of the desired cross-section. The two main advantages of this process over other manufacturing processes is its ability to create very complex cross-sections and work materials that are brittle, because the material only into an enormous variety of shapes—such as films Artificial membrane also known as synthetic membrane is a syntheticly created membrane which is usually intended for separation purposes in laboratory or in industry. Synthetic membranes have been successfully used for small and large-scale industrial processes since the middle of twentieth century. A wide variety of synthetic membranes is known, fibers Synthetic fibers are the result of extensive research by scientists to improve upon naturally occurring animal and plant. In general, synthetic fibers are created by forcing, usually through extrusion, fiber forming materials through holes into the air, forming a thread. Before synthetic fibers were developed, artificially manufactured fibers were, plates, tubes, bottles, boxes, and much more.

The common word plastic should not be confused with the technical adjective plastic, which is applied to any material which undergoes a permanent change of shape (plastic deformation) when strained beyond a certain point. Aluminum, for instance, is plastic in this sense, but not a plastic in the common sense; while some plastics, in their finished forms, will break before deforming and therefore are not plastic in the technical sense.

There are two types of plastics: thermoplastics A thermoplastic is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently. Most thermoplastics are high-molecular-weight polymers whose chains associate through weak Van der Waals forces ; stronger dipole-dipole interactions and hydrogen bonding (nylon); or even stacking of aromatic rings ( and thermosets Thermosetting plastics are polymer materials that irreversibly cure. The cure may be done through heat (generally above 200 degrees Celsius), through a chemical reaction (two-part epoxy, for example), or irradiation such as electron beam processing. Thermoplastics, if exposed to enough heat, will melt. Thermosets will keep their shape until they are charred and burnt. Some examples of thermoplastics are grocery bags, piano keys and some automobile parts. Examples of thermosets are children's dinner sets and circuit boards.

Contents 1 Overview 2 Chemical structure 3 History of plastics 4 Types of plastics 4.1 Cellulose-based plastics 4.2 Bakelite 4.3 Polystyrene and PVC 4.4 Nylon 4.5 Rubber 4.6 Synthetic rubber 4.7 Other plastics 5 Toxicity 6 Environmental issues 6.1 Biodegradable (Compostable) plastics 6.2 Bioplastics 6.3 Oxo-biodegradable 7 Price, environment, and the future 8 Common plastics and uses 9 Special-purpose plastics 10 See also 11 References 12 External links

Overview

Plastics can be classified by their chemical structure, namely the molecular units In chemistry, radicals are atoms, molecules, or ions with unpaired electrons on an otherwise open shell configuration. These unpaired electrons are usually highly reactive, so radicals are likely to take part in chemical reactions. Radicals play an important role in combustion, atmospheric chemistry, polymerization, plasma chemistry, biochemistry, that make up the polymer's backbone and side chains. Some important groups in these classifications are the acrylics In organic chemistry, the acryloyl group is the functional group with structure H2C=CH–C–; it is the acyl group derived from acrylic acid. The preferred IUPAC name for the group is prop-2-enoyl, and it is also (less correctly) known as acrylyl or simply acryl. Compounds containing an acryloyl group can be referred to as "acrylic compounds&, polyesters Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate . Polyesters include naturally-occurring chemicals, such as in the cutin of plant cuticles, as well as, silicones Silicones are largely inert, man-made compounds with a wide variety of forms and uses. Typically heat-resistant, nonstick, and rubberlike, they are commonly used in cookware, medical applications, sealants, adhesives, lubricants, and insulation, polyurethanes A polyurethane, commonly abbreviated PU, is any polymer consisting of a chain of organic units joined by urethane links. Polyurethane polymers are formed through step-growth polymerization by reacting a monomer containing at least two isocyanate functional groups with another monomer containing at least two hydroxyl (alcohol) groups in the, and halogenated plastics Halocarbon compounds are chemicals in which one or more carbon atoms are linked by covalent bonds with one or more halogen atoms resulting in the formation of organofluorine compounds, organochlorine compounds, organobromine compounds, and organoiodine compounds. Chlorine halocarbons are the most common and are called organochlorides. There are. Plastics can also be classified by the chemical process used in their synthesis; e.g., as condensation A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride, methanol, or acetic acid. The word "condensation&, polyaddition Chain growth polymerisation is a polymerisation technique where unsaturated monomer molecules add on to a growing polymer chain one at a time . It can be represented with the chemical equation:, cross-linking Cross-links are bonds that link one polymer chain to another. They can be covalent bonds or ionic bonds. "Polymer chains" can refer to synthetic polymers or natural polymers . When the term "cross-linking" is used in the synthetic polymer science field, it usually refers to the use of cross-links to promote a difference in the, etc.^[3]

Other classifications are based on qualities that are relevant for manufacturing or product design. Examples of such classes are the thermoplastic and thermoset, elastomer An elastomer is a polymer with the property of elasticity. The term, which is derived from elastic polymer, is often used interchangeably with the term rubber, and is preferred when referring to vulcanisates. Each of the monomers which link to form the polymer is usually made of carbon, hydrogen, oxygen and/or silicon. Elastomers are amorphous, structural Engineering plastics are a group of plastic materials that exhibit superior mechanical and thermal properties in a wide range of conditions over and above more commonly used commodity plastics. The term usually refers to thermoplastic materials rather than thermosetting ones, biodegradable Biodegradable plastics are plastics that will decompose in the natural environment aerobic and anaerobic (landfill) environments. Biodegradation of plastics can be achieved by enabling microorganisms in the environment to metabolize the molecular structure of plastic films to produce an inert humus-like material that is less harmful to the, electrically conductive The electrical resistance of an object is a measure of its opposition to the passage of a steady electric current. An object of uniform cross section will have a resistance proportional to its length and inversely proportional to its cross-sectional area, and proportional to the resistivity of the material, etc. Plastics can also be ranked by various physical properties, such as density The density of a material is defined as its mass per unit volume. The symbol of density is ρ, tensile strength Tensile strength is indicated by the maxima of a stress-strain curve and, in general, indicates when necking will occur. As it is an intensive property, its value does not depend on the size of the test specimen. It is, however, dependent on the preparation of the specimen and the temperature of the test environment and material, glass transition temperature Glass transition or vitrification refer to the transformation of a glass-forming liquid into a glass, which usually occurs upon rapid cooling. It is a dynamic phenomenon occurring between two distinct states of matter , each with different physical properties. Upon cooling through the temperature range of glass transition (a "glass, resistance to various chemical products, etc.

Due to their relatively low cost, ease of manufacture, versatility, and imperviousness to water, plastics are used in an enormous and expanding range of products, from paper clips to spaceships. They have already displaced many traditional materials, such as wood Wood is an organic material; in the strict sense it is produced as secondary xylem in the stems of trees . In a living tree it conducts water and nutrients to the leaves and other growing tissues, and has a support function, enabling woody plants to reach large sizes or to stand up for themselves. However, wood may also refer to other plant; stone In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids; horn A horn is a pointed projection of the skin on the head of various animals, consisting of a covering of horn surrounding a core of living bone. True horns are found mainly among the ruminant artiodactyls,[citation needed] in the families Antilocapridae (pronghorn) and Bovidae (cattle, goats, antelope etc.). One pair of horns is usual, but two pairs and bone Bones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue. Because bones come in a variety of shapes and have a complex internal and external structure; leather Leather is a material created through the tanning of hides and skins of animals, primarily cattlehide. The tanning process converts the putrescible skin into a durable, long-lasting and versatile natural material for various uses. Together with wood, leather formed the basis of much ancient technology. The leather industry and the fur industry are; paper Paper is thin material mainly used for writing upon, printing upon or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets; metal In chemistry, a metal is an element, compound, or alloy characterized by high electrical conductivity. In a metal, atoms readily lose electrons to form positive ions (cations); those ions are surrounded by delocalized electrons, which are responsible for the conductivity. The thus produced solid is held by electrostatic interactions between the; glass Glass generally refers to hard, brittle, transparent material, such as those used for windows, many bottles, or eyewear. Examples of such materials include, but are not limited to, soda-lime glass, borosilicate glass, acrylic glass, sugar glass, isinglass , or aluminium oxynitride. In the technical sense, glass is an inorganic product of fusion; and ceramic A ceramic is an inorganic, non-metallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous . Because most common ceramics are crystalline, the definition of ceramic is often restricted to inorganic crystalline materials, as opposed to the non-, in most of their former uses.

The use of plastics is constrained chiefly by their organic chemistry, which seriously limits their hardness, density, and their ability to resist heat, organic solvents, oxidation Redox describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide or the reduction of carbon by hydrogen to yield methane (CH4), or it can be a complex process such as the oxidation of sugar in the human body, and ionizing radiation Ionizing radiation consists of subatomic particles or electromagnetic waves that are energetic enough to detach electrons from atoms or molecules, ionizing them. The occurrence of ionization depends on the energy of the impinging individual particles or waves, and not on their number. An intense flood of particles or waves will not cause. In particular, most plastics will melt or decompose Pyrolysis is the chemical decomposition of a condensed substance by heating. The word is coined from the Greek-derived elements pyro "fire" and lysys "decomposition" when heated to a few hundred celsius Celsius is a temperature scale that is named after the Swedish astronomer Anders Celsius (1701–1744), who developed a similar temperature scale two years before his death. The degree Celsius (°C) can refer to a specific temperature on the Celsius scale as well as serve as a unit increment to indicate a temperature interval (a difference between.^[4] While plastics can be made electrically conductive to some extent, they are still no match for metals like copper Copper is a chemical element with the symbol Cu (Latin: cuprum) and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is rather soft and malleable and a freshly-exposed surface has a pinkish or peachy color. It is used as a thermal conductor, an electrical conductor, a building material, and a or aluminum Aluminium ( ˌæljʊˈmɪniəm ) or aluminum ( /əˈluːmɪnəm/ (help·info), see spelling below) is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13. It is not soluble in water under normal circumstances. Aluminium is the most abundant metal in the Earth's crust, and the.^{[citation needed]} Plastics are still too expensive to replace wood, concrete Concrete is a construction material composed of cement as well as other cementitious materials such as fly ash and slag cement, aggregate (generally a coarse aggregate such as gravel, limestone, or granite, plus a fine aggregate such as sand), water, and chemical admixtures. The word concrete comes from the Latin word "concretus" ( and ceramic in bulky items like ordinary buildings Buildings come in a wide amount of shapes and functions, and have been adapted throughout history for a wide number of factors, from building materials available, to weather conditions, to land prices, ground conditions, specific uses and aesthetic reasons, bridges A bridge is a structure built to span a valley, road, railroad track, river, body of water, or any other physical obstacle, for the purpose of providing passage over the obstacle. Designs of bridges will vary depending on the function of the bridge and the nature of the terrain where the bridge is to be constructed, dams A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are often used in conjunction with dams to provide clean, pavement Road surface or pavement (American English) is the durable surface material laid down on an area intended to sustain traffic (vehicular or foot traffic). Such surfaces are frequently marked to guide traffic. The most common modern paving methods are asphalt and concrete. In the past, brick was extensively used, as was metalling. Today, permeable, railroad ties A railroad tie, cross tie, or railway sleeper is a rectangular object used as a base for railroad tracks. Sleepers are members generally laid transverse to the rails, on which the rails are supported and fixed, to transfer the loads from rails to the ballast and subgrade, and to hold the rails to the correct gauge, etc.^{[citation needed]}

Chemical structure

Common thermoplastics range from 20,000 to 500,000 in molecular mass, while thermosets are assumed to have infinite molecular weight. These chains are made up of many repeating molecular units, known as repeat units, derived from monomers; each polymer chain will have several thousand repeat units. The vast majority of plastics are composed of polymers of carbon and hydrogen alone or with oxygen, nitrogen, chlorine or sulfur in the backbone. (Some of commercial interests are silicon based.) The backbone is that part of the chain on the main "path" linking a large number of repeat units together. To vary the properties of plastics, both the repeat unit with different molecular groups "hanging" or "pendant" from the backbone, (usually they are "hung" as part of the monomers before linking monomers together to form the polymer chain). This customization by repeat unit's molecular structure has allowed plastics to become such an indispensable part of twenty first-century life by fine tuning the properties of the polymer.

Some plastics are partially crystalline and partially amorphous in molecular structure, giving them both a melting point (the temperature at which the attractive intermolecular forces are overcome) and one or more glass transitions (temperatures above which the extent of localized molecular flexibility is substantially increased). So-called semi-crystalline plastics include polyethylene, polypropylene, poly (vinyl chloride), polyamides (nylons), polyesters and some polyurethanes. Many plastics are completely amorphous, such as polystyrene and its copolymers, poly (methyl methacrylate), and all thermosets.

Molded plastic food replicas on display outside a restaurant in Japan.

History of plastics

This section requires expansion.

The first human-made plastic was invented by Alexander Parkes in 1862; he called this plastic Parkesine. The development of plastics has come from the use of natural plastic materials (e.g., chewing gum, shellac) to the use of chemically modified natural materials (e.g., rubber, nitrocellulose, collagen, galalite) and finally to completely synthetic molecules (e.g., bakelite, epoxy, polyvinyl chloride, polyethylene).

Types of plastics

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Cellulose-based plastics

In 1855, an Englishman from Birmingham named Alexander Parkes developed a synthetic replacement for ivory 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 (the major component of plant cell walls) treated with nitric acid and a solvent. The output of the process (commonly known as cellulose nitrate or pyroxilin) could be dissolved in alcohol and hardened into a transparent and elastic material that could be molded when heated.^[5] By incorporating pigments into the product, it could be made to resemble ivory.

Bois Durci is a plastic moulding material based on cellulose. It was patented, in Paris in 1855, by Lepage. It is made from finely ground wood flour mixed with a binder, either egg or blood albumen or gelatine. The wood is probably either ebony or rose wood, giving a black or brown result. The mixture is dried and ground to a fine powder. The powder is placed in a steel mould and compressed in a powerful hydraulic press whilst being heated by steam. The final product has a highly polished finish imparted by the surface of the steel mould.

Bakelite

Main article: Bakelite

The first plastic based on a synthetic polymer was made from phenol and formaldehyde, with the first viable and cheap synthesis methods invented in 1909 by Leo Hendrik Baekeland, a Belgian-born American living in New York state. Baekeland was searching for an insulating shellac to coat wires in electric motors and generators. 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. He continued his investigations and found that the material could be mixed with wood flour, asbestos, or slate dust to create "composite" materials with different properties. Most of these compositions 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.

Baekeland built pressure vessels to force out the bubbles and provide a smooth, uniform product. He publicly announced his discovery in 1912, naming it bakelite. It was originally used for electrical and mechanical parts, finally coming into widespread use in consumer goods in the 1920s. When the Bakelite patent expired in 1930, the Catalin Corporation acquired the patent and began manufacturing Catalin plastic using a different process that allowed a wider range of coloring.

Bakelite was the first true plastic. It was a purely synthetic material, not based on any material or even molecule found in nature. It was also the first thermosetting plastic. Conventional thermoplastics can be molded and then melted again, but thermoset plastics form bonds between polymers strands when cured, creating a tangled matrix that cannot be undone without destroying the plastic. Thermoset plastics 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. The U.S. government even considered making one-cent coins out of it when World War II caused a copper shortage.^{[citations needed]}

Phenolic plastics have been largely replaced by cheaper and less brittle plastics, but they are still used in applications requiring its insulating and heat-resistant properties. For example, some electronic circuit boards are made of sheets of paper or cloth impregnated with phenolic resin.

Phenolic sheets, rods and tubes are produced in a wide variety of grades under various brand names. The most common grades of industrial phenolic are Canvas, Linen and Paper.

Polystyrene and PVC

Main articles: Polystyrene and PVC Plastic piping and firestops being installed at Nortown Casitas, North York (Now Toronto), Ontario, Canada. Certain plastic pipes can be used in some non-combustible buildings, provided they are firestopped properly and that the flame spread ratings comply with the local building code.

After the First World War, 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 IG Farben of Germany.

Polystyrene is a rigid, brittle, inexpensive plastic that has been used to make plastic model kits and similar knick-knacks. It would also be the basis for one of the most popular "foamed" plastics, under the name styrene foam or Styrofoam. Foam plastics can be synthesized in an "open cell" form, in which the foam bubbles are interconnected, as in an absorbent sponge, and "closed cell", in which all the bubbles are distinct, like tiny balloons, as in gas-filled foam insulation and flotation devices. In the late 1950s, high impact styrene was introduced, which was not brittle. It finds much current use as the substance of toy figurines and novelties.

PVC has side chains incorporating chlorine atoms, which form strong bonds. PVC in its normal form is stiff, strong, heat and weather resistant, and is now used for making plumbing, gutters, house siding, enclosures for computers and other electronics gear. PVC can also be softened with chemical processing, and in this form it is now used for shrink-wrap, food packaging, and rain gear.

Nylon

Main article: Nylon

The real star of the plastics industry in the 1930s was polyamide (PA), far better known by its trade name nylon. Nylon was the first purely synthetic fiber, introduced by DuPont Corporation at the 1939 World's Fair in New York City.

In 1927, DuPont had begun a secret development project designated Fiber66, under the direction of Harvard chemist Wallace Carothers and chemistry department director Elmer Keiser Bolton. Carothers had been hired to perform pure research, and he worked to understand the new materials' molecular structure and physical properties. He took some of the first steps in the molecular design of the materials.

His work led to the discovery of synthetic nylon fiber, which was very strong but also very flexible. The first application was for bristles for toothbrushes. However, Du Pont's real target was silk, particularly silk stockings. Carothers and his team synthesized a number of different polyamides including polyamide 6.6 and 4.6, as well as polyesters.^[6]

General condensation polymerization reaction for nylon

It took DuPont twelve years and US$27 million to refine nylon, and to synthesize and develop the industrial processes for bulk manufacture. With such a major investment, it was no surprise that Du Pont spared little expense to promote nylon after its introduction, creating a public sensation, or "nylon mania".

Nylon mania came to an abrupt stop at the end of 1941 when the USA entered World War II. The production capacity that had been built up to produce nylon stockings, or just nylons, for American women was taken over to manufacture vast numbers of parachutes for fliers and paratroopers. After the war ended, DuPont went back to selling nylon to the public, engaging in another promotional campaign in 1946 that resulted in an even bigger craze, triggering the so called nylon riots.

Subsequently polyamides 6, 10, 11, and 12 have been developed based on monomers which are ring compounds; e.g. caprolactam.nylon 66 is a material manufactured by condensation polymerization.

Nylons still remain important plastics, and not just for use in fabrics. In its bulk form it is very wear resistant, particularly if oil-impregnated, and so is used to build gears, bearings, bushings, and because of good heat-resistance, increasingly for under-the-hood applications in cars, and other mechanical parts.

Rubber

Natural rubber is an elastomer (an elastic hydrocarbon polymer) that was originally derived from latex, a milky colloidal suspension found in the sap of some plants. It is useful directly in this form (indeed, the first appearance of rubber in Europe is cloth waterproofed with unvulcanized latex from Brazil) but, later, in 1839, Charles Goodyear invented vulcanized rubber; this a form of natural rubber heated with, mostly, sulfur forming cross-links between polymer chains (vulcanization), improving elasticity and durability.

Synthetic rubber

Main article: Synthetic rubber

The first fully synthetic rubber was synthesized by Lebedev in 1910. In World War II, supply blockades of natural rubber from South East Asia caused a boom in development of synthetic rubber, notably Styrene-butadiene rubber (a.k.a. Government Rubber-Styrene). In 1941, annual production of synthetic rubber in the U.S. was only 231 tons which increased to 840 000 tons in 1945. In the space race and nuclear arms race, Caltech researchers experimented with using synthetic rubbers for solid fuel for rockets. Ultimately, all large military rockets and missiles would use synthetic rubber based solid fuels, and they would also play a significant part in the civilian space effort.

Other plastics

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Other plastics emerged in the prewar period, though some would not come into widespread use until after the war.

By 1936, American, British, and German companies were producing Polymethyl methacrylate (PMMA), better known as acrylic glass. Although acrylics are now well known for their 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 Perspex, Plexiglas and Lucite. These were used to build aircraft canopies during the war, and its main application now is large illuminated signs such as are used in shop fronts or inside large stores, and for the manufacture of vacuum-formed bath-tubs.

Another important plastic, Polyethylene (PE), sometimes known as polythene, was discovered in 1933 by 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).

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. The ensuing litigation was not resolved until 1989.

Polypropylene managed to survive the legal process and two American chemists working for Phillips Petroleum, J. Paul Hogan and Robert Banks, are now generally credited as the primary inventors of the material. Polypropylene is similar to its ancestor, polyethylene, and shares polyethylene's low cost, but it is much more robust. It is used in everything from plastic bottles to carpets to plastic furniture, and is very heavily used in automobiles.

Polyurethane (PU) was invented by Friedrich Bayer & Company in 1937, and would come into use after the war, in blown form for mattresses, furniture padding, and thermal insulation. It is also one of the components (in non-blown form) of the fiber spandex.

In 1939, IG Farben filed a patent for polyepoxide or epoxy. Epoxies are a class of thermoset plastic that form cross-links and cure when a catalyzing agent, or hardener, is added. After the war they would come into wide use for coatings, adhesives, and composite materials.

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 less gas-permeable than other low-cost plastics and so is a popular material for making bottles for Coca-Cola and other carbonated 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 are used as a base for 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 scratch-proof 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 DuPont chemist named 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 adhesion-resistant frying pans were in demand.

Teflon was later used to synthesize the breathable fabric Gore-Tex, which can be used to manufacture wet weather clothing that is able to "breathe". Its structure allows water vapour molecules to pass, while not permitting water as liquid to enter. Gore-Tex is also used for surgical applications such as garments and 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 techniques 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 in some money. 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 ballistic rated clothing and combat helmets. Kevlar was so impressive that its manufacturer deemed it necessary to release an official statement denying alien involvement.^[7]

Toxicity

Due to their insolubility in water and relative chemical inertness, pure plastics generally have low toxicity in their finished state, and will pass through the digestive system with no ill effect (other than mechanical damage or obstruction).

However, plastics often contain a variety of toxic additives. For example, plasticizers like adipates and phthalates are often added to brittle plastics like polyvinyl chloride (PVC) to make them pliable enough for use in food packaging, children's toys and teethers, tubing, shower curtains and other items. Traces of these chemicals can leach out of the plastic when it comes into contact with food. Out of these concerns, the European Union has banned the use of DEHP (di-2-ethylhexyl phthalate), the most widely used plasticizer in PVC. Some compounds leaching from polystyrene food containers have been found to interfere with hormone functions and are suspected human carcinogens.^[8]

Moreover, while the finished plastic may be non-toxic, the monomers used in its manufacture may be toxic; and small amounts of those chemical may remain trapped in the product. The World Health Organization's International Agency for Research on Cancer (IARC) has recognized the chemical used to make PVC, vinyl chloride, as a known human carcinogen.^[8] Some polymers may also decompose into the monomers or other toxic substances when heated.

The primary building block of polycarbonates, bisphenol A (BPA), is an estrogen-like hormone disrupter that may leach into food.^[8] Research in Environmental Health Perspectives finds that BPA leached from the lining of tin cans, dental sealants and polycarbonate bottles can increase body weight of lab animals' offspring.^[9] A more recent animal study suggests that even low-level exposure to BPA results in insulin resistance, which can lead to inflammation and heart disease.^[10]

Bis(2-ethylhexyl) adipate, present in plastic wrap based on PVC, is also of concern, as are the volatile organic compounds present in new car smell. Toxic chemicals allegedly released by the reuse of water bottles have been the subject of urban legend.^[11]

Environmental issues

Further information: Marine debris

Plastics are durable and degrade very slowly; the molecular bonds that make plastic so durable make it equally resistant to natural processes of degradation. Since the 1950s, one billion tons of plastic has been discarded and may persist for hundreds or even thousands of years.^[12] In some cases, burning plastic can release toxic fumes. Burning the plastic polyvinyl chloride (PVC) creates dioxin.^[13] Also, the manufacturing of plastics often creates large quantities of chemical pollutants.

Prior to the ban on the use of CFCs in extrusion of polystyrene (and general use, except in life-critical fire suppression systems; see Montreal Protocol), the production of polystyrene contributed to the depletion of the ozone layer; however, non-CFCs are currently used in the extrusion process.

By 1995, plastic recycling programs were common in the United States and elsewhere. Thermoplastics can be remelted and reused, and thermoset plastics can be ground up and used as filler, though the purity of the material tends to degrade with each reuse cycle. There are methods by which plastics can be broken back down to a feedstock state.

To assist recycling of disposable items, the Plastic Bottle Institute of the Society of the Plastics Industry devised a now-familiar scheme to mark plastic bottles by plastic type. A plastic container using this scheme is marked with a triangle of three cyclic arrows, which encloses a number giving the plastic type:

Plastics type marks: the resin identification code

1. PET (PETE), polyethylene terephthalate: Commonly found on 2-liter soft drink bottles, water bottles, cooking oil bottles, peanut butter jars.
2. HDPE, high-density polyethylene: Commonly found on detergent bottles, milk jugs.
3. PVC, polyvinyl chloride: Commonly found on plastic pipes, outdoor furniture, siding, floor tiles, shower curtains, clamshell packaging.
4. LDPE, low-density polyethylene: Commonly found on dry-cleaning bags, produce bags, trash can liners, and food storage containers.
5. PP, polypropylene: Commonly found on bottle caps, drinking straws, yogurt containers, legos.
6. PS, polystyrene: Commonly found on "packing peanuts", cups, plastic tableware, meat trays, take-away food clamshell containers
7. OTHER, other: This plastic category, as its name of "other" implies, is any plastic other than the named #1–#6, Commonly found on certain kinds of food containers, Tupperware, and Nalgene bottles.

Unfortunately, recycling plastics has proven difficult. The biggest problem with plastic recycling is that it is difficult to automate the sorting of plastic waste, and so it is labor intensive. Typically, workers sort the plastic by looking at the resin identification code, though common containers like soda bottles can be sorted from memory. Other recyclable materials, such as metals, are easier to process mechanically. However, new mechanical sorting processes are being utilized to increase plastic recycling capacity and efficiency.

While containers are usually made from a single type and color of plastic, making them relatively easy to sort out, a consumer product like a cellular phone may have many small parts consisting of over a dozen different types and colors of plastics. In a case like this, the resources it would take to separate the plastics far exceed their value and the item is discarded. However, developments are taking place in the field of Active Disassembly, which may result in more consumer product components being re-used or recycled. Recycling certain types of plastics can be unprofitable, as well. For example, polystyrene is rarely recycled because it is usually not cost effective. These unrecycled wastes are typically disposed of in landfills, incinerated or used to produce electricity at waste-to-energy plants.

Biodegradable (Compostable) plastics

Main article: Biodegradable plastic

Research has been done on biodegradable plastics that break down with exposure to sunlight (e.g., ultra-violet radiation), water or dampness, bacteria, enzymes, wind abrasion and some instances rodent pest or insect attack are also included as forms of biodegradation or environmental degradation. It is clear some of these modes of degradation will only work if the plastic is exposed at the surface, while other modes will only be effective if certain conditions exist in landfill or composting systems. Starch powder has been mixed with plastic as a filler to allow it to degrade more easily, but it still does not lead to complete breakdown of the plastic. Some researchers have actually genetically engineered bacteria that synthesize a completely biodegradable plastic, but this material, such as Biopol, is expensive at present.^[14] The German chemical company BASF makes Ecoflex, a fully biodegradable polyester for food packaging applications.

Bioplastics

Main article: Bioplastic

Some plastics can be obtained from biomass, including:

• from pea starch film with trigger biodegradation properties for agricultural applications (TRIGGER).^[15]
• from biopetroleum.^[16]

Oxo-biodegradable

Main article: Oxo Biodegradable

This section does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be and removed. (January 2009)

Oxo-biodegradable (OBD) plastic is polyolefin plastic to which has been added very small (catalytic) amounts of metal salts. These as long as the plastic has access to oxygen (as in a littered state) these addatives catalyze the natural degradation process to speed it up so that the OBD plastic will degrade when subject to environmental conditions. On degraded to a small enough particle they can interact with biological processes to produce to water, carbon dioxide and biomass. The process is shortened from hundreds of years to months for degradation and thereafter biodegradation depends on the micro-organisms in the environment. Typically this process is not fast enough to meet ASTM D6400 standards for definition as compostable plastics.

Price, environment, and the future

The biggest threat to the conventional plastics industry is most likely to be environmental concerns, including the release of toxic pollutants, greenhouse gas, litter, biodegradable and non-biodegrable landfill impact as a result of the production and disposal of petroleum and petroleum-based plastics. Of particular concern has been the recent accumulation of enormous quantities of plastic trash in ocean gyres.

For decades one of the great appeals of plastics has been their low price. Yet in recent years the cost of plastics has been rising dramatically. A major cause is the sharply rising cost of petroleum, the raw material that is chemically altered to form commercial plastics.

With some observers suggesting that future oil reserves are uncertain, the price of petroleum may increase further. Therefore, alternatives are being sought. Oil shale and tar oil are alternatives for plastic production but are expensive. Scientists are seeking cheaper and better alternatives to petroleum-based plastics, and many candidates are in laboratories all over the world. One promising alternative may be fructose.^[17]

Common plastics and uses

Polypropylene (PP)

Food containers, appliances, car fenders (bumpers).

Polystyrene (PS)

Packaging foam, food containers, disposable cups, plates, cutlery, CD and cassette boxes.

High impact polystyrene (HIPS)

Fridge liners, food packaging, vending cups.

Acrylonitrile butadiene styrene (ABS)

Electronic equipment cases (e.g., computer monitors, printers, keyboards), drainage pipe.

Polyethylene terephthalate (PET)

Carbonated drinks bottles, jars, plastic film, microwavable packaging.

Polyester (PES)

Fibers, textiles.

Polyamides (PA) (Nylons)

Fibers, toothbrush bristles, fishing line, under-the-hood car engine mouldings.

Poly(vinyl chloride) (PVC)

Plumbing pipes and guttering, shower curtains, window frames, flooring.

Polyurethanes (PU)

Cushioning foams, thermal insulation foams, surface coatings, printing rollers. (Currently 6th or 7th most commonly used plastic material, for instance the most commonly used plastic found in cars).

Polycarbonate (PC)

Compact discs, eyeglasses, riot shields, security windows, traffic lights, lenses.

Polyvinylidene chloride (PVDC) (Saran)

Food packaging.

Polyethylene (PE)

Wide range of inexpensive uses including supermarket bags, plastic bottles.

Polycarbonate/Acrylonitrile Butadiene Styrene (PC/ABS)

A blend of PC and ABS that creates a stronger plastic. Used in car interior and exterior parts, and mobile phone bodies.

Special-purpose plastics

Polymethyl methacrylate (PMMA)

Contact lenses, glazing (best known in this form by its various trade names around the world; e.g., Perspex, Oroglas, Plexiglas), aglets, fluorescent light diffusers, rear light covers for vehicles.

Polytetrafluoroethylene (PTFE) (trade name Teflon)

Heat-resistant, low-friction coatings, used in things like non-stick surfaces for frying pans, plumber's tape and water slides.

Polyetheretherketone (PEEK) (Polyetherketone)

Strong, chemical- and heat-resistant thermoplastic, biocompatibility allows for use in medical implant applications, aerospace mouldings. One of the most expensive commercial polymers.

Polyetherimide (PEI) (Ultem)

A high temperature, chemically stable polymer that does not crystallize.

Phenolics (PF) or (phenol formaldehydes)

High modulus, relatively heat resistant, and excellent fire resistant polymer. Used for insulating parts in electrical fixtures, paper laminated products (e.g., Formica), thermally insulation foams. It is a thermosetting plastic, with the familiar trade name Bakelite, that can be moulded by heat and pressure when mixed with a filler-like wood flour or can be cast in its unfilled liquid form or cast as foam (e.g., Oasis). Problems include the probability of mouldings naturally being dark colours (red, green, brown), and as thermoset difficult to recycle.

Urea-formaldehyde (UF)

One of the aminoplasts and used as a multi-colorable alternative to Phenolics. Used as a wood adhesive (for plywood, chipboard, hardboard) and electrical switch housings.

Melamine formaldehyde (MF)

One of the aminoplasts, and used as a multi-colorable alternative to phenolics, for instance in mouldings (e.g., break-resistance alternatives to ceramic cups, plates and bowls for children) and the decorated top surface layer of the paper laminates (e.g., Formica).

Polylactic acid (PLA)

A biodegradable, thermoplastic, found converted into a variety of aliphatic polyesters derived from lactic acid which in turn can be made by fermentation of various agricultural products such as corn starch, once made from dairy products.

Plastarch material

Biodegradable and heat resistant, thermoplastic composed of modified corn starch.

See also

• Conductive polymer
• Corn construction
• Epoxy
• Molding (process)
  • Flexible mold
  • Injection molding
• Films
• Light activated resin
• Marine debris
• Nurdle
• Organic light emitting diode
• Plastic recycling
• Plastics engineering
• Plastics extrusion
• Plasticulture
• Polymer
• Progressive bag alliance
• Roll-to-roll processing
• Synthetic fiber
• Self-healing plastic
• Thermoforming
• Timeline of materials technology

References

1. ^ Plastikos, Henry George Liddell, Robert Scott, A Greek-English Lexicon, at Perseus
2. ^ Plastic, Online Etymology Dictionary
3. ^ Classification of Plastics
4. ^ Periodic Table of Polymers Dr Robin Kent - Tangram Technology Ltd.
5. ^ Celluloid, Webster's Online Dictionary, accessed on January 2009
6. ^ Kinnane, Adrian (2002). DuPont: From the banks of the Brandywine to miracles of science. Baltimore, Md.: Johns Hopkins University Press. pp. 116–125. ISBN 0-8018-7059-3.
7. ^ History of Plastic and Plastic Packaging Products - Polyethylene, Polypropylene, and More
8. ^ ^{a b c} McRandle, P.W. (March/April 2004). "Plastic Water Bottles". National Geographic. http://www.thegreenguide.com/doc/101/plastic. Retrieved on 2007-11-13.
9. ^ Perinatal Exposure to Low Doses of Bisphenol A Affects Body Weight, Patterns of Estrous Cyclicity, and Plasma LH Levels, accessed March 2009
10. ^ Alonso-Magdalena, Paloma; Morimoto, Sumiko; Ripoll, Cristina; Fuentes, Esther; Nadal, Angel (January 2006), "The Estrogenic Effect of Bisphenol A Disrupts Pancreatic β-Cell Function In Vivo and Induces Insulin Resistance", Environmental Health Perspectives 114 (1): 106–112, doi:10.1289/ehp.8451, http://www.ehponline.org/docs/2005/8451/abstract.html .
11. ^ http://www.snopes.com/medical/toxins/petbottles.asp
12. ^ Alan Weisman, "The World Without Us," St. Martin's Press, NY, 2007.
13. ^ Dioxins, Oregon Environmental Council
14. ^ Biodegradation of plastic bottles made from Biopol in an aquatic ecosystem under in situ conditions, accessed March 2009 (login required)
15. ^ CORDIS: Search CORDIS: Projects
16. ^ Spain: Scientists Close To Making Biofuel From Algae
17. ^ 'Sugar plastic' could reduce reliance on petroleum

• Substantial parts of this text originated from An Introduction To Plastics v1.0 / 1 March 2001 / greg goebel / public domain

External links

Wikimedia Commons has media related to: Plastics

• J. Harry Dubois Collection on the History of Plastics, ca. 1900-1975 Archives Center, National Museum of American History, Smithsonian Institution.
• List of over 600 plastics
• Plastics Historical Society
• History of plastics, Society of the Plastics Industry

Health issues of plastics and Polyhalogenated compounds (PHC)'s Plasticizers: Phthalates DIBP · DBP · BBP aka BBzP · DEHP aka DOP · DIDP · DINP · DIDP Other plasticizers Organophosphates · Adipate-based (DEHA · DOA) Monomers Bisphenol A (in Polycarbonates) · Vinyl chloride (in PVC) Other additives incl. PHC's PBDEs · PCBs · Organotins · PFCs Health issues Teratogen · Carcinogen · Endocrine disruptor · Diabetes · Obesity Miscellaneous PVC · Plastic recycling · Plastic bottle · Vinyl chloride · Dioxins · Polystyrene · Styrofoam · PTFE (Teflon) · California Proposition 65 (1986) · List of environmental health hazards · Persistent organic pollutant · European REACH regulation (2006) · Japan Toxic Substances Law · Toxic Substances Control Act

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