Plastics are a wide range of synthetic or semi-synthetic organic compounds that are malleable and so can be molded into solid objects.
Plasticity is the general property of all materials which can deform irreversibly without breaking but, in the class of moldable polymers, this occurs to such a degree that their actual name derives from this specific ability.
Plastics are typically organic polymers of high molecular mass and often contain other substances. They are usually synthetic, most commonly derived from petrochemicals, however, an array of variants are made from renewable materials such as polylactic acid from corn or cellulosics from cotton linters.[1]
In developed economies, about a third of plastic is used in packaging and roughly the same in buildings in applications such as piping, plumbing or vinyl siding.[2] Other uses include automobiles (up to 20% plastic[2]), furniture, and toys.[2] In the developing world, the applications of plastic may differ—42% of India's consumption is used in packaging.[2] Worldwide, about 50 kg of plastic is produced annually per person, with production doubling every ten years.
Plastics have many uses in the medical field as well, with the introduction of polymer implants and other medical devices derived at least partially from plastic. The field of plastic surgery is not named for use of plastic materials, but rather the meaning of the word plasticity, with regard to the reshaping of flesh.
The world's first fully synthetic plastic was bakelite, invented in New York in 1907, by Leo Baekeland[3] who coined the term "plastics".[4] Many chemists have contributed to the materials science of plastics, including Nobel laureate Hermann Staudinger who has been called "the father of polymer chemistry" and Herman Mark, known as "the father of polymer physics".[5]
The success and dominance of plastics starting in the early 20th century led to environmental concerns regarding its slow decomposition rate after being discarded as trash due to its composition of large molecules. Toward the end of the century, one approach to this problem was met with wide efforts toward recycling.
Contents
- 1 Etymology
- 2 Structure
- 3 Properties and classifications
- 4 Types
- 5 History
- Plastics are a wide range of synthetic or semi-synthetic organic compounds that are malleable and so can be molded into solid objects.
Plasticity is the general property of all materials which can deform irreversibly without breaking but, in the class of moldable polymers, this occurs to such a degree that their actual name derives from this specific ability.
Plastics are typically organic polymers of high molecular mass and often contain other substances. They are usually synthetic, most commonly derived from petrochemicals, however, an array of variants are made from renewable materials such as polyla
Plasticity is the general property of all materials which can deform irreversibly without breaking but, in the class of moldable polymers, this occurs to such a degree that their actual name derives from this specific ability.
Plastics are typically organic polymers of high molecular mass and often contain other substances. They are usually synthetic, most commonly derived from petrochemicals, however, an array of variants are made from renewable materials such as polylactic acid from corn or cellulosics from cotton linters.[1]
In developed economies, about a third of plastic is used in packaging and roughly the same in buildings in applications such as piping, plumbing or vinyl siding.[2] Other uses include automobiles (up to 20% plastic[2]), furniture, and toys.[2] In the developing world, the applications of plastic may differ—42% of India's consumption is used in packaging.[2] Worldwide, about 50 kg of plastic is produced annually per person, with production doubling every ten years.
Plastics have many uses in the medical field as well, with the introduction of polymer implants and other medical devices derived at least partially from plastic. The field of plastic surgery is not named for use of plastic materials, but rather the meaning of the word plasticity, with regard to the reshaping of flesh.
The world's first fully synthetic plastic was bakelite, invented in New York in 1907, by Leo Baekeland[3] who coined the term "plastics".[4] Many chemists have contributed to the materials science of plastics, including Nobel laureate Hermann Staudinger who has been called "the father of polymer chemistry" and Herman Mark, known as "the father of polymer physics".[5]
The success and dominance of plastics starting in the early 20th century led to environmental concerns regarding its slow decomposition rate after being discarded as trash due to its composition of large molecules. Toward the end of the century, one approach to this problem was met with wide efforts toward recycling.
The word plastic derives from the Greek πλαστικός (plastikos) meaning "capable of being shaped or molded" and, in turn, from πλαστός (plastos) meaning "molded".[6][7]
The plasticity, or malleability, of the material during manufacture allows it to be cast, pressed, or extruded into a variety of shapes, such as: films, fibers, plates, tubes, bottles, boxes, amongst many others.
The common noun plastic should not be confused with the technical adjective plastic. The adjective is applicable to any material which undergoes a plastic deformation, or permanent change of shape, when strained beyond a certain point. For example, aluminum which is stamped or forged exhibits plasticity in this sense, but is not plastic in the common sense. By contrast, some plastics will, in their finished forms, break before deforming and therefore are not plastic in the technical sense.
Structure
Most plastics contain organic polymers.[8] The vast majority of these polymers are formed from chains of carbon atoms, 'pure' or with the addition of: oxygen, nitrogen, or sulfur. The chains comprise many repeat units, formed from monomers. Each polymer chain will have several thousand repeating units.
The backbone is the part of the chain that is on the "main path", linking together a large number of repeat units.
To customize the properties of a plastic, different molecular groups "hang" from this backbone. These pendant units are usually "hung" on the monomers, before the monomers themselves are linked together to form the polymer chain. It is the structure of these side chains that influences the properties of the polymer.
The molecular structure of the repeating unit can be fine tuned to influence specific properties of the polymer.
Properties and classifications
Plastics are usually classified by: the chemical structure of the polymer's backbone and side chains; some important groups in these classifications are: the acrylics, polyesters, silicones, polyurethanes, and halogenated plastics.
Plastics can also be classified by: the chemical process used in their synthesis, such as: condensation, polyaddition, and cross-linking.[9]
Plastics can also be classified by: their various physical properties, such as: hardness, density, tensile strength, resistance to heat and glass transition temperature, and by their chemical properties, such as the organic chemistry of the polymer and its resistance and reaction to various chemical products and processes, such as: organic solvents, oxidation, and ionizing radiation. In particular, most plastics will melt upon heating to a few hundred degrees celsius.[10]
Other classifications are based on qualities that are relevant for manufacturing or product design. Examples of such qualities and classes are: thermoplastics and thermosets, conductive polymers, biodegradable plastics and engineering plastics and other plastics with particular structures, such as elastomers.
Thermoplastics and thermosetting polymers
plasticity, or malleability, of the material during manufacture allows it to be cast, pressed, or extruded into a variety of shapes, such as: films, fibers, plates, tubes, bottles, boxes, amongst many others.
The common noun plastic should not be confused with the technical adjective plastic. The adjective is applicable to any material which undergoes a plastic deformation, or permanent change of shape, when strained beyond a certain point. For example, aluminum which is stamped or forged exhibits plasticity in this sense, but is not plastic in the common sense. By contrast, some plastics will, in their finished forms, break before deforming and therefore are not plastic in the technical sense.
Most plastics contain organic polymers.[8] The vast majority of these polymers are formed from chains of carbon atoms, 'pure' or with the addition of: oxygen, nitrogen, or sulfur. The chains comprise many repeat units, formed from monomers. Each polymer chain will have several thousand repeating units.
The backbon
The backbone is the part of the chain that is on the "main path", linking together a large number of repeat units.
To customize the properties of a plastic, different molecular groups "hang" from this backbone. These pendant units are usually "hung" on the monomers, before the monomers themselves are linked together to form the polymer chain. It is the structure of these side chains that influences the properties of the polymer.
The molecular structure of the repeating unit can be fine tuned to influence specific properties of the polymer.
Plastics are usually classified by: the chemical structure of the polymer's backbone and side chains; some important groups in these classifications are: the acrylics, polyesters, silicones, polyurethanes, and halogenated plastics.
Plastics can also be classified by: the chemical process used in their synthesis, such as: condensation, polyaddition, and cross-linking.[9]
Plastics can also be classified by: their various physical properties, such as: hardness, density, tensile strength, resistance to heat and glass transition temperature, and by their chemical properties, such as the organic chemistry of the polymer and its resistance and reaction to various chemical products and processes, such as: organic solvents, oxidation, and ionizing radiation. In particular, most plastics will melt upon heating to a few hundred degrees celsius.[10]
Other classifications are based on qualities that are relevant for manufacturing or product design. Examples of such qualities and classes are: thermoplastics and thermosets, conductive polymers, biodegradable plastics and engineering plastics and other plastics with particular structures, such as elastomers.
One important classification of plastics is by the permanence or impermanence of their form, or whether they are: thermoplastics or thermosetting polymers. Thermoplastics are the plastics that, when heated, do not undergo chemical change in their composition and so can be molded again and again. Examples include: polyethylene (PE), polypropylene (PP), polystyrene (PS) and polyvinyl chloride (PVC).[11] Common thermoplastics range from 20,000 to 500,000 amu, while thermosets are assumed to have infinite molecular weight.
Thermosets, or thermosetting polymers, can melt and take shape only once: after they have solidified, they stay solid.[12] If heated again, they do not melt; they decompose instead. In the thermosetting process, a chemical reaction occurs that is irreversible. The vulcanization of rubber is an example of a thermosetting process: before heating with sulfur, the polyisoprene is a tacky, slightly runny material; after vulcanization, the product is rigid and non-tacky.
Amorphous plastics and crystalline plastics
Many plastics are completely amorphous,[13] such as: all thermosets; polystyrene and its copolymers; and poly[12] If heated again, they do not melt; they decompose instead. In the thermosetting process, a chemical reaction occurs that is irreversible. The vulcanization of rubber is an example of a thermosetting process: before heating with sulfur, the polyisoprene is a tacky, slightly runny material; after vulcanization, the product is rigid and non-tacky.
Many plastics are completely amorphous,[13] such as: all thermosets; polystyrene and its copolymers; and polymethyl methacrylate.
However, some plastics are partially crystalline and partiall
However, 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 also one or more glass transitions, the temperatures above which the extent of localized molecular flexibility is substantially increased. These so-called semi-crystalline plastics include: polyethylene, polypropylene, polyvinyl chloride, polyamides (nylons), polyesters and some polyurethanes.
Intrinsically Conducting Polymers (ICP) are organic polymers that conduct electricity. While plastics can be made electrically conductive, with a conductivity of up to 80 kS/cm in stretch-oriented polyacetylene,[14] they are still no match for most metals like copper which have a conductivity of several hundred kS/cm. Nevertheless, this is a developing field.
Biodegradable
Biodegradable plastics are plastics that degrade, or break down, upon exposure to: sunlight or ultra-violet radiation, water or dampness, bacteria, enzymes or wind abrasion. In some instances, rodent, pest, or insect attack can also be considered as forms of biodegradation or environmental degradation.
Some modes of degradation require that the plastic be exposed at the surface (aerobic), whereas other modes will only be effective if certain conditions exist in landfill or composting systems (Some modes of degradation require that the plastic be exposed at the surface (aerobic), whereas other modes will only be effective if certain conditions exist in landfill or composting systems (anaerobic).
Some companies produce biodegradable additives, to enhance biodegradation. Plastic can have starch powder added as a filler to allow it to degrade more easily, but this still does not lead to the complete breaking down of the plastic.
Some researchers have genetically engineered bacteria to synthesize completely biodegradable plastics, such as Biopol; however, these are expensive at present.[15]
While most plastics are produced from petrochemicals, bioplastics are made substantially from renewable plant materials such: as cellulose and starch.[16] Due both to the finite limits of the petrochemical reserves and to the threat of global warming, the development of bioplastics is a growing field.
However, bioplastic development begins from a very low base and, as yet, does not compare significantly with petrochemical production. Estimates of the global production capacity for bio-derived materials is
However, bioplastic development begins from a very low base and, as yet, does not compare significantly with petrochemical production. Estimates of the global production capacity for bio-derived materials is put at 327,000 tonnes/year. In contrast, global production of polyethylene (PE) and polypropylene (PP), the world's leading petrochemical derived polyolefins, was estimated at over 150 million tonnes in 2015.[17]
This category includes both commodity plastics, or standard plastics, and engineering plastics.
- Polyamides (PA) or (nylons) – fibers, toothbrush bristles, tubing, fishing line and low-strength machine parts such as engine parts or gun frames
- Polycarbonate (PC) – compact discs, eyeglasses, riot shields, security windows, traffic lights and lenses
- Polyester (PES) – fibers and textiles
- Polyethylene (PE) – a wide range of inexpensive uses including supermarket bags and plastic bottles
- High-density polyethylene (HDPE) – detergent bottles, milk jugs and molded plastic cases
- Low-density polyethylene (LDPE) – outdoor furniture, siding, floor tiles, shower curtains and clamshell packaging
- Polyethylene terephthalate (PET) – carbonated drinks bottles, peanut butter jars, plastic film and microwavable packaging
- Polypropylene (PP) – bottle caps, drinking straws, yogurt containers, appliances, car fenders (bumpers) and plastic pressure pipe systems
- The development of plastics has evolved from the use of natural plastic materials (e.g., chewing gum, shellac) to the use of chemically modified, natural materials (e.g., natural rubber, nitrocellulose, collagen, galalite) and finally to completely synthetic molecules (e.g., bakelite, epoxy, polyvinyl chloride). Early plastics were bio-derived materials such as egg and blood proteins, which are organic polymers. In around 1600 BC, Mesoamericans used natural rubber for balls, bands, and figurines.[2] Treated cattle horns were used as windows for lanterns in the Middle Ages. Materials that mimicked the properties of horns were developed by treating milk-proteins (casein) with lye.
In the nineteenth century, as industrial chemistry developed during the Industrial Revolution, many materials were reported. The development of plastics also accelerated with Charles Goodyear's discovery of vulcanization to thermoset materials derived from natural rubber.
Blue plaque commemorating Parkes on the Birmingham Science Museum.Parkesine (nitrocellulose) is considered the first man-made plastic. The plastic material was patented by Alexander Parkes, in Birmingham, England in 1856.[19] It was unveiled at the 1862 Great International Exhibition in London.[20] Parkesine 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 as 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.[21] By incorporating pigments into the product, it could be made to resemble ivory.
In 1897, the Hanover, Germany mass printing press owner Wilhelm Krische was commissioned to develop an alternative to blackboards.[22] The resultant horn-like plastic made from the milk protein casein was developed in cooperation with the Austrian chemist (Friedrich) Adolph Spitteler (1846–1940). The final result was unsuitable for the original purpose.[23] In 1893, French chemist Auguste Trillat discovered the means to insolubilize casein by immersion in formaldehyde, producing material marketed as galalith.[22]
In the early 1900s, Bakelite, the first fully synthetic thermoset, was reported by Belgian chemist Leo Baekeland by using phenol and formaldehyde.
After World War I, improvements in chemical technology led to an explosion in new forms of plastics, with mass production beginning in the 1940s and 1950s (around World War II).[24] Among the earliest examples in the wave of new polymers were polystyrene (PS), first produced by BASF in the 1930s,[2] and polyvinyl chloride (PVC), first created in 1872 but commercially produced in the late 1920s.[2] In 1923, Durite Plastics Inc. was the first manufacturer of phenol-furfural resins.[25] In 1933, polyethylene was discovered by Imperial Chemical Industries (ICI) researchers Reginald Gibson and Eric Fawcett.[2]
In 1954, polypropylene was discovered by Giulio Natta and began to be manufactured in 1957.[2]
In 1954, expanded polystyrene (used for building insulation, packaging, and cups) was invented by Dow Chemical.[2] The discovery of polyethylene terephthalate (PET) is credited to employees of the Calico Printers' Association in the UK in 1941; it was licensed to DuPont for the US and ICI otherwise, and as one of the few plastics appropriate as a replacement for glass in many circumstances, resulting in widespread use for bottles in Europe.[2]
Plastics industry
Use of monobloc plastic chairs in a rural area of Cameroon. The monobloc produced in polypropylene is one of the most produced chair designs in the world.[26][27]Plastics manufacturing is a major part of the chemical industry, and some of the world's largest chemical companies have been involved since the earliest days, such as the industry leaders BASF and Dow Chemical.
In 2014, sales of the top fifty companies amounted to US$961,300,000,000.[28] The firms came from some eighteen countries in total, with more than half of the companies on the list being headquartered in the US. Many of the top fifty plastics companies were concentrated in just three countries:
- United States: 12
- Japan: 8
- Germany: 6
BASF was the world's largest chemical producer for the ninth year in a row.[28]
Trade associations which represent the industry in the US include the American Chemistry Council.
However, the COVID-19 pandemic has had a devastating effect on the fossil fuel and petrochemical industry. Natural gas prices have dropped so low that gas producers were burning if off on-site (not being worth the cost to transport it to cracking facilities). In addition, bans on single-use consumer plastic (in China, the European Union, Canada, and many countries in Africa), and bans on plastic bags (in several states in the USA) has reduced demand for plastics considerably. Many cracking facilities in the USA have been suspended. The petrochemical industry has b
In the nineteenth century, as industrial chemistry developed during the Industrial Revolution, many materials were reported. The development of plastics also accelerated with Charles Goodyear's discovery of vulcanization to thermoset materials derived from natural rubber.
Parkesine (nitrocellulose) is considered the first man-made plastic. The plastic material was patented by Alexander Parkes, in Birmingham, England in 1856.[19] It was unveiled at the 1862 Great International Exhibition in London.[20] Parkesine 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 as 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.[21] By incorporating pigments into the product, it could be made to resemble ivory.
In 1897, the Hanover, Germany mass printing press owner Wilhelm Krische was commissioned to develop an alternative to blackboards.[22] The resultant horn-like plastic made from the milk protein casein was developed in cooperation with the Austrian chemist (Friedrich) Adolph Spitteler (1846–1940). The final result was unsuitable for the original purpose.[23] In 1893, French chemist Auguste Trillat discovered the means to insolubilize casein by immersion in formaldehyde, producing material marketed as galalith.[22]
In the early 1900s, [22] The resultant horn-like plastic made from the milk protein casein was developed in cooperation with the Austrian chemist (Friedrich) Adolph Spitteler (1846–1940). The final result was unsuitable for the original purpose.[23] In 1893, French chemist Auguste Trillat discovered the means to insolubilize casein by immersion in formaldehyde, producing material marketed as galalith.[22]
In the early 1900s, Bakelite, the first fully synthetic thermoset, was reported by Belgian chemist Leo Baekeland by using phenol and formaldehyde.
After World War I, improvements in chemical technology led to an explosion in new forms of plastics, with mass production beginning in the 1940s and 1950s (around World War II).[24] Among the earliest examples in the wave of new polymers were polystyrene (PS), first produced by BASF in the 1930s,[2] and polyvinyl chloride (PVC), first created in 1872 but commercially produced in the late 1920s.[2] In 1923, Durite Plastics Inc. was the first manufacturer of phenol-furfural resins.[25] In 1933, polyethylene was discovered by Imperial Chemical Industries (ICI) researchers Reginald Gibson and Eric Fawcett.[2]
In 1954, polypropylene was discovered by Giulio Natta and began to be manufactured in 1957.[2]
In 1954, expanded polystyrene (used for building insulation, packaging, and cups) was invented by Dow Chemical.[2] The discovery of polyethylene terephthalate (PET) is credited to employees of the Calico Printers' Association in the UK in 1941; it was licensed to DuPont for the US and ICI otherwise, and as one of the few plastics appropriate as a replacement for glass in many circumstances, resulting in widespread use for bottles in Europe.[2]
Plastics manufacturing is a major part of the chemical industry, and some of the world's largest chemical companies have been involved since the earliest days, such as the industry leaders BASF and Dow Chemical.
In 2014, sales of the top fifty companies amounted to US$961,300,000,000.[28] The firms came from some eighteen countries in total, with more than half of the companies on the list being headquartered in the US. Many of the top fifty plastics companies were concentrated in just three countries:
- United States: 12
- Japan: 8
- Germany: 6
BASF was the world's largest chemical producer for the ninth year in a row.[28]
Trade associations which represent the industry in the US include the American Chemistry Council.
However, the COVID-19 pandemic has had a devastating effect on the fossil fuel and petrochemical industry. Natural gas prices have dropped so low that gas producers were burning if off on-site (not being worth the cost to transport it to cracking facilities).
In 2014, sales of the top fifty companies amounted to US$961,300,000,000.[28] The firms came from some eighteen countries in total, with more than half of the companies on the list being headquartered in the US. Many of the top fifty plastics companies were concentrated in just three countries:
BASF was the world's largest chemical producer for the ninth year in a row.[28]
Trade associations which represent the industry in the US include the American Chemistry Council.
However, the COVID-19 pa
Trade associations which represent the industry in the US include the American Chemistry Council.
However, the COVID-19 pandemic has had a devastating effect on the fossil fuel and petrochemical industry. Natural gas prices have dropped so low that gas producers were burning if off on-site (not being worth the cost to transport it to cracking facilities). In addition, bans on single-use consumer plastic (in China, the European Union, Canada, and many countries in Africa), and bans on plastic bags (in several states in the USA) has reduced demand for plastics considerably. Many cracking facilities in the USA have been suspended. The petrochemical industry has been trying to save itself by attempting to rapidly expand demand for plastic products worldwide (i.e. through pushbacks on plastic bans and by increasing the number of products wrapped in plastic in countries where plastic use is not already as widespread (i.e. developing nations)).[29]
Many of the properties of plastics are determined by standards specified by ISO, such as:
- ISO 306 – T
Many of the properties of plastics are determined by the UL Standards, tests specified by Underwriters Laboratories (UL), such as:
- Flammability – inorganic compounds. The average content of additives is a few percent. Many of the controversies associated with plastics actually relate to the additives:[30] organotin compounds are particularly toxic.[31]
Typical additives include:
Stabilizers
Polymer stabilizers prolong the lifetime of the polymer by suppressing degradation that results from UV-light, oxidation, and other phenomena. Typical stabilizers thus absorb UV light or function as antioxidants.
Typical additives include:
Polymer stabilizers prolong the lifetime of the polymer by suppressing degradation that results from UV-light, oxidation, and other phenomena. Typical stabilizers thus absorb UV light or function as antioxidants.
Fillers
Many
Many plastics[citation needed] contain fillers, to improve performance or reduce production costs.[32] Typically fillers are mineral in origin, e.g., chalk. Other fillers include: starch, cellulose, wood flour, ivory dust and zinc oxide.
- most fillers are relatively Plasticizers are, by mass, often the most abundant additives.[31] These oily but nonvolatile compounds are blended in to plastics to improve rheology, as many organic polymers are otherwise too rigid for particular applications.
Plastic colorants are chemical compounds used to color plastic. Those compounds come in a form of dyes and pigments. The type of a colorant is chosen based on the type of a polymeric resin, that needs to be colored.[citation needed] Dyes are usually used with polycarbonates, polystyrene and acrylic polymers. Pigments are better suited for use with polyolefins.[34] [35]The colorant must satisfy various constraints, for example, the compound must be[36] chemically compatible with the base resin, be a suitable match with a color standard (see e.g. International Color Consortium), be chemically stable, which in this case means being able to survive the stresses and processing temperature (heat stability) in the fabrication process and be durable enough to match the life duration of the product.
The parameters of the compound vary with a desired effect, which may include the final product being pearlescent, metallic, fluorescent, phosphorescent, thermochromic or photochromic.[37]
The exact chemical formula will furthermore depend on the type of application: general purpose, food contact item, The colorant must satisfy various constraints, for example, the compound must be[36] chemically compatible with the base resin, be a suitable match with a color standard (see e.g. International Color Consortium), be chemically stable, which in this case means being able to survive the stresses and processing temperature (heat stability) in the fabrication process and be durable enough to match the life duration of the product.
The parameters of the compound vary with a desired effect, which may include the final product being pearlescent, metallic, fluorescent, phosphorescent, thermochromic or photochromic.[37]
The exact chemical formula will furthermore depend on the type of application: general purpose, food contact item, toy, package subject to CONEG,[38] etc.[37]
Pure plastics have low toxicity due to their insolubility in water and because they are biochemically inert, due to a large molecular weight. Plastic products contain a variety of additives, some of which can be toxic.[41] For example, plasticizers like adipates and phthalates are often added to brittle plastics like polyvinyl chloride to make them pliable enough for use in food packaging, toys, and many other items. Traces of these compounds can leach out of the product. Owing to concerns over the effects of such leachates, the European Union has restricted the use of DEHP (di-2-ethylhexyl phthalate) and other phthalates in some applications, and the United States has limited the use of DEHP, DPB, BBP, DINP, DIDP, and DnOP in children's toys and child care articles with the Consumer Product Safety Improvement Act. Some compounds leaching from polystyrene food containers have been proposed to interfere with hormone functions and are suspected human carcinogens.[42] Other chemicals of potential concern include alkylphenols.[31]
Whereas the finished plastic may be non-toxic, the monomers used in the manufacture of the parent polymers may be toxic. In some cases, small amounts of those chemicals can remain trapped in the product unless suitable processing is employed. For example, the World Health Organization's International Agency for Research on Cancer (IARC) has recognized vinyl chloride, the precursor to PVC, as a human carcinogen.[42]
World Health Organization's International Agency for Research on Cancer (IARC) has recognized vinyl chloride, the precursor to PVC, as a human carcinogen.[42]
Some polymers may also decompose into the monomers or other toxic substances when heated. In 2011, it was reported that "almost all plastic products" sampled released chemicals with estrogenic activity, although the researchers identified plastics which did not leach chemicals with estrogenic activity.[43]
The primary building block of polycarbonates, polycarbonates, bisphenol A (BPA), is an estrogen-like endocrine disruptor that may leach into food.[42] 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.[44] 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.[45]
As of January 2010, the LA Times newspaper reports that the United States FDA is spending $30 million to investigate indications of BPA being linked to cancer.[46]
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.
The European Union has a permanent ban on the use of phthalates in toys. In 2009, the United States government banned certain types of phthalates commonly used in plastic.[47]
Most plastics are durable and degrade very slowly, as their chemical structure renders them resistant to many natural processes of degradation. There are differing estimates of how much plastic waste has been produced in the last century. By one estimate, one billion tons of plastic waste have been discarded since the 1950s.[48] Others estimate a cumulative human production of 8.3 billion tons of plastic of which 6.3 billion tons is waste, with a recycling rate of only 9%.[49] Much of this material may persist for centuries or longer, given the demonstrated persistence of structurally similar natural materials such as amber.
The Ocean Conservancy reported that China, Indonesia, Philippines, Thailand, and Vietnam dump more plastic in the sea than all other countries combined.[50] The rivers Yangtze, Indus, Yellow River, Hai River, Nile, Ganges, Pearl River, Amur, Niger, and the Mekong "transport 88–95% of the global [plastics] load into the sea."[51][52]
The presence of plastics, particularly microplastics, within the food chain is increasing. In the 1960s microplastics were observed in the guts of seabirds, and since then have been found in increasing concentrations.[53] The long-term effects of plastic in the food chain are poorly understood. In 2009, it was estimated that 10% of modern waste was plastic,[24]
The Ocean Conservancy reported that China, Indonesia, Philippines, Thailand, and Vietnam dump more plastic in the sea than all other countries combined.[50] The rivers Yangtze, Indus, Yellow River, Hai River, Nile, Ganges, Pearl River, Amur, Niger, and the Mekong "transport 88–95% of the global [plastics] load into the sea."[51][52]
The presence of plastics, particularly microplastics, within the food chain is increasing. In the 1960s microplastics were observed in the guts of seabirds, and since then have been found in increasing concentrations.[53] The long-term effects of plastic in the food chain are poorly understood. In 2009, it was estimated that 10% of modern waste was plastic,[24] although estimates vary according to region.[53] Meanwhile, 50–80% of debris in marine areas is plastic.[53]
Prior to the Montreal Protocol, CFCs were commonly used in the manufacture of polystyrene, and as such the production of polystyrene contributed to the depletion of the ozone layer.
Microplastics are very small pieces of plastic that pollute the environment.[54] Microplastics are not a specific kind of plastic, but rather any type of plastic fragment that is less than 5 mm in length according to the U.S. National Oceanic and Atmospheric Administration (NOAA) [55][56] and the European Chemicals Agency.[57] They enter natural ecosystems from a variety of sources, including cosmetics, clothing, and industrial processes.
Two classifications of microplastics currently exist. Primary microplastics are any plastic fragments or particles that are already 5.0 mm in size or less before entering the environment. These include microfibers from clothing, microbeads, and plastic pellets (also known as nurdles).[58][59][60] Secondary microplastics are microplastics that are created from the degradation of larger plastic products once they enter the environment through natural weathering processes. Such sources of secondary microplastics include water and soda bottles, fishing nets, and plastic bags.[60][61] Both types are recognized to persist in the environment at high levels, particularly in aquatic and marine ecosystems.microfibers from clothing, microbeads, and plastic pellets (also known as nurdles).[58][59][60] Secondary microplastics are microplastics that are created from the degradation of larger plastic products once they enter the environment through natural weathering processes. Such sources of secondary microplastics include water and soda bottles, fishing nets, and plastic bags.[60][61] Both types are recognized to persist in the environment at high levels, particularly in aquatic and marine ecosystems.[62] The term macroplastics is used to differentiate larger plastic waste, such as plastic bottles.
Additionally, plastics degrade slowly, often over hundreds if not thousands of years. This increases the probability of microplastics being ingested and incorporated into, and accumulated in, the bodies and tissues of many organisms.[63][64] The entire cycle and movement of microplastics in the environment is not yet known, but research is currently underway to investigate this issue.
absorption and adsorption. Polymer degradation takes much longer as a result of saline environments and the cooling effect of the sea. These factors contribute to the persistence of plastic debris in certain environments.[53] Recent studies have shown that plastics in the ocean decompose faster than was once thought, due to exposure to sun, rain, and other environmental conditions, resulting in the release of toxic chemicals such as bisphenol A. However, due to the increased volume of plastics in the ocean, decomposition has slowed down.[65] The Marine Conservancy has predicted the decomposition rates of several plastic products. It is estimated that a foam plastic cup will take 50 years, a plastic beverage holder will take 400 years, a disposable nappy will take 450 years, and fishing line will take 600 years to degrade.[66]In 2018, a survey by the Global Oceanic Environmental Survey (GOES) Foundation found that the ecosystem in seas and oceans may collapse in the next 25 years, potentially causing failure of terrestrial ecosystem and "very possibly the end of life on Earth as we know it";[67] the main agents of this prediction were hypothesized to be plastic, ocean acidification, and ocean pollution. In order to prevent such a catastrophe, experts have proposed a total single-use plastic ban, wood burning bans while planting "as many trees as possible," "pollution-free recycling of electronics, and by 2030 all industries to be zero toxic discharge." One British scientist advocates "special protection and perservation of peat bogs, wetlands, marshlands and mangrove swamps to ensure carbon dioxide is absorbed from the atmosphere."[67]
Microbial species capable of degrading plastics are known to science, and some are potentially useful for the disposal of certain classes of plastic waste.
- In 1975 a team of Japanese scientists studying ponds containing waste water from a nylon factory, discovered a strain of Flavobacterium tha
In 2018, a survey by the Global Oceanic Environmental Survey (GOES) Foundation found that the ecosystem in seas and oceans may collapse in the next 25 years, potentially causing failure of terrestrial ecosystem and "very possibly the end of life on Earth as we know it";[67] the main agents of this prediction were hypothesized to be plastic, ocean acidification, and ocean pollution. In order to prevent such a catastrophe, experts have proposed a total single-use plastic ban, wood burning bans while planting "as many trees as possible," "pollution-free recycling of electronics, and by 2030 all industries to be zero toxic discharge." One British scientist advocates "special protection and perservation of peat bogs, wetlands, marshlands and mangrove swamps to ensure carbon dioxide is absorbed from the atmosphere."[67]
Microbial species capable of degrading plastics are known to science, and some are potentially useful for the disposal of certain classes of plastic waste.
When different types of plastics are melted together, they tend to phase-separate, like oil and water, and set in these layers. The phase boundaries cause structural weakness in the resulting material, meaning that polymer blends are useful in only limited applications. This is in part, why the plastics industry has developed the resin identification codes. The two most widely manufactured plastics, polypropylene and polyethylene, behave this way, which limits their utility for recycling. Each time plastic is recycled, additional virgin materials must be added to help improve the integrity of the material. So, even recycled plastic has new plastic material added in. Moreover, the same piece of plastic can only be recycled about 2–3.[92] Thus, even when plastics have a resin code, or are collected for recycling, only a small portion of that material is actually recycled. For example, as of 2017, only 8% of US plastic was recycled.[93]
Since the majority of plastic is non-biodegradable, recycling can be part of reducing plastic in the waste stream. This is important, for example, for reducing the approximately 8 million metric tons of waste plastic that enters the Earth's ocean every year.[94][95] However, because of the complexity of recycling, a substantial amount of plastic that is collected for recycling is processed in other ways, such as through trash incineration, or not processed at all.
Climate change
In 2019, the Center for International Environmental Law published a new report on the impact of plastic on climate change. According to the report plastic will contribute Greenhouse gases in the equivalent of 850 million tons of Carbon dioxide (CO2) to the atmosphere in 2019. In current trend, annual emissions will grow to 1.34 billion tons by 2030. By 2050 plastic could emit 56 billion tons of Greenhouse gas emissions, as much as 14 percent of the earth's remaining carbon budget.[96]
The effect of plastics on global warming is mixed. Plastics are generally made from petroleum. If the plastic is incinerated, it increases carbon emissions; if it is placed in a landfill, it becomes a carbon sink[97] although biodegradable plastics have caused methane emissions. [98] Due to the lightness of plastic versus glass or metal, plastic may reduce energy consumption. For example, packaging beverages in PET plastic rather than glass or metal is estimated to save 52% in transportation energy.[2]
Production of plastics
Production of plastics from crude oil requires 62 to 108 MJ/Kg (taking into account the average efficiency of US utility stations of 35%). Producing silicon and semiconductors for modern electronic equipment is even more energy consuming: 230 to 235 MJ/Kg of silicon, and about 3,000 MJ/Kg of semiconductors.[99] This is much higher than the energy needed to produce many other materials, e.g. iron (from iron ore) requires 20-25 MJ/Kg of energy, glass (from sand, etc.) 18–35 MJ/Kg, steel (from iron) 20–50 MJ/Kg, paper (from timber) 25–50 MJ/Kg.[100]
Incineration of plastics
Controlled high-temperature incineration, above 850 °C for two seconds[citation needed], performed with selective additional heating, breaks down toxic dioxins and furans from burning plastic, and is widely used in municipal solid waste incineration. Municipal solid waste incinerators also normally include flue gas treatments to reduce pollutants further. This is needed because uncontrolled incineration of plastic produces polychlorinated dibenzo-p-dioxins, a carcinogen (cancer causing chemical). The problem occurs because the heat content of the waste stream varies.[101] Open-air burning of plastic occurs at lower temperatures, and normally releases such toxic fumes.
Pyrolytic disposal
Plastics can be pyrolyzed into hydrocarbon fuels, since plastics include hydrogen and carbon. One kilogram of waste plastic produces roughly a liter of hydrocarbon.[102]
Representative polymers
Plastic piping and firestops being installed in Ontario. 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.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 1907, by Leo Hendrik Baekeland, a Belgian-born American living in New York state. Baekeland was looking for an insulating shellac to coat wires in electric motors and generators. He found that combining phenol (C6H5OH) and formaldehyde (HCOH) formed a sticky mass and later found that the material could be mixed with wood flour, asbestos, or slate dust to create strong and fire resistant "composite" materials. The new material tended to foam during synthesis, requiring that Baekeland build pressure vessels to force out the bubbles and provide a smooth, uniform product, as he announced in 1909, in a meeting of the American Chemical Society.[103] Bakelite was originally used for electrical and mechanical parts, coming into widespread use in consumer goods and jewelry in the 1920s. Bakelite was a purely synthetic material, not derived from living matter. It was also an early thermosetting plastic.
Polystyrene
Unplasticised polystyrene is a rigid, brittle, inexpensive plastic that has been used to make plastic model kits and similar knick-knacks. It also is the basis for some of the most popular "foamed" plastics, under the name styrene foam or Styrofoam. Like most other foam plastics, foamed polystyrene can be manufactured 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 s
In 2019, the Center for International Environmental Law published a new report on the impact of plastic on climate change. According to the report plastic will contribute Greenhouse gases in the equivalent of 850 million tons of Carbon dioxide (CO2) to the atmosphere in 2019. In current trend, annual emissions will grow to 1.34 billion tons by 2030. By 2050 plastic could emit 56 billion tons of Greenhouse gas emissions, as much as 14 percent of the earth's remaining carbon budget.[96]
The effect of plastics on global warming is mixed. Plastics are generally made from petroleum. If the plastic is incinerated, it increases carbon emissions; if it is placed in a landfill, it becomes a carbon sink[97] although biodegradable plastics have caused methane emissions. [98] Due to the lightness of plastic versus glass or metal, plastic may reduce energy consumption. For example, packaging beverages in PET plastic rather than glass or metal is estimated to save 52% in transportation energy.[2]
Production of plastics
Production of plastics from crude oil requires 62 to 108 MJ/Kg (taking into account the average efficiency of US utility stations of 35%). Producing silicon and semic
The effect of plastics on global warming is mixed. Plastics are generally made from petroleum. If the plastic is incinerated, it increases carbon emissions; if it is placed in a landfill, it becomes a carbon sink[97] although biodegradable plastics have caused methane emissions. [98] Due to the lightness of plastic versus glass or metal, plastic may reduce energy consumption. For example, packaging beverages in PET plastic rather than glass or metal is estimated to save 52% in transportation energy.[2]
Production of plastics from crude oil requires 62 to 108 MJ/Kg (taking into account the average efficiency of US utility stations of 35%). Producing silicon and semiconductors for modern electronic equipment is even more energy consuming: 230 to 235 MJ/Kg of silicon, and about 3,000 MJ/Kg of semiconductors.[99] This is much higher than the energy needed to produce many other materials, e.g. iron (from iron ore) requires 20-25 MJ/Kg of energy, glass (from sand, etc.) 18–35 MJ/Kg, steel (from iron) 20–50 MJ/Kg, paper (from timber) 25–50 MJ/Kg.[100]
Incineration of plasticsControlled high-temperature incineration, above 850 °C for two seconds[citation needed], performed with selective additional heating, breaks down toxic dioxins and furans from burning plastic, and is widely used in municipal solid waste incineration. Municipal solid waste incinerators also normally include flue gas treatments to reduce pollutants further. This is needed because uncontrolled incineration of plastic produces polychlorinated dibenzo-p-dioxins, a carcinogen (cancer causing chemical). The problem occurs because the heat content of the waste stream varies.[101] Open-air burning of plastic occurs at lower temperatures, and normally releases such toxic fumes.
Pyrolytic disposal
Plastics
Plastics can be pyrolyzed into hydrocarbon fuels, since plastics include hydrogen and carbon. One kilogram of waste plastic produces roughly a liter of hydrocarbon.[102]
The first plastic based on a synthetic polymer was made from phenol and formaldehyde, with the first viable and cheap synthesis methods invented in 1907, by Leo Hendrik Baekeland, a Belgian-born American living in New York state. Baekeland was looking for an insulating shellac to coat wires in electric motors and generators. He found that combining phenol (C6H5OH) and formaldehyde (HCOH) formed a sticky mass and later found that the material could be mixed with wood flour, asbestos, or slate dust to create strong and fire resistant "composite" materials. The new material tended to foam during synthesis, requiring that Baekeland build pressure vessels to force out the bubbles and provide a smooth, uniform product, as he announced in 1909, in a meeting of the American Chemical Society.[103] Bakelite was originally used for electrical and mechanical parts, coming into widespread use in consumer goods and jewelry in the 1920s. Bakelite was a purely synthetic material, not derived from living matter. It was also an early thermosetting plastic.Polystyrene
Unplasticised polystyrene is a rigid, brittle, inexpensive plastic that has been used to make plastic model kits and similar knick-knacks. It also is the basis for some of the most popular "foamed" plastics, under the name styrene foam or Styrofoam. Like most other foam plastics, foamed polystyrene can be manufactured 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.
Polyvinyl chloride
plastic model kits and similar knick-knacks. It also is the basis for some of the most popular "foamed" plastics, under the name styrene foam or Styrofoam. Like most other foam plastics, foamed polystyrene can be manufactured 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.
Polyvinyl chloride
Polyvinyl chloride (PVC, commonly called "vinyl")Polyvinyl chloride (PVC, commonly called "vinyl")[104] incorporates chlorine atoms. The C-Cl bonds in the backbone are hydrophobic and resist oxidation (and burning). PVC is stiff, strong, heat and weather resistant, properties that recommend its use in devices for 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.
All PVC polymers are degraded by heat and light. When this happens, hydrogen chloride is released into the atmosphere and oxidation of the compound occurs.[105] Because hydrogen chloride readily combines with water vapor in the air to form hydrochloric acid,[106] polyvinyl chloride is not recommended for long-term archival storage of silver, photographic film or paper (mylar is preferable).[107]
Nylon
The plastics indus
All PVC polymers are degraded by heat and light. When this happens, hydrogen chloride is released into the atmosphere and oxidation of the compound occurs.[105] Because hydrogen chloride readily combines with water vapor in the air to form hydrochloric acid,[106] polyvinyl chloride is not recommended for long-term archival storage of silver, photographic film or paper (mylar is preferable).[107]
The plastics industry was revolutionized in the 1930s with the announcement of 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
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.[108]
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 US 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
Nylon mania came to an abrupt stop at the end of 1941 when the US 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, plain bearings, valve seats, seals and because of good heat-resistance, increasingly for under-the-hood applications in cars, and other mechanical parts.
Poly(methyl methacrylate) (PMMA), also known as acrylic or acrylic glass as well as by the trade names Plexiglas, Acrylite, Lucite, and Perspex among several others (see below), is a transparent thermoplastic often used in sheet form as a lightweight or shatter-resistant alternative to glass. The same material can be utilised as a casting resin, in inks and coatings, and has many other uses.
Rubber
Natural rubber is an elastomer (an elastic hydrocarbon polymer) that originally was derived from latex, a milky colloidal s
Natural rubber is an elastomer (an elastic hydrocarbon polymer) that originally was derived from latex, a milky colloidal suspension found in specialised vessels in some plants. It is useful directly in this form (indeed, the first appearance of rubber in Europe was cloth waterproofed with unvulcanized latex from Brazil). However, in 1839, Charles Goodyear invented vulcanized rubber; a form of natural rubber heated with sulfur (and a few other chemicals), forming cross-links between polymer chains (vulcanization), improving elasticity and durability.
In 1851, Nelson Goodyear added fillers to natural rubber ma
In 1851, Nelson Goodyear added fillers to natural rubber materials to form ebonite.[33]
The first fully synthetic rubber was synthesized by Sergei 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. In 1941, annual production of synthetic rubber in the U.S. was only 231 tonnes which increased to 840,000 tonnes 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.
See also
- In 1975 a team of Japanese scientists studying ponds containing waste water from a nylon factory, discovered a strain of Flavobacterium tha
- most fillers are relatively Plasticizers are, by mass, often the most abundant additives.[31] These oily but nonvolatile compounds are blended in to plastics to improve rheology, as many organic polymers are otherwise too rigid for particular applications.
- Flammability – inorganic compounds. The average content of additives is a few percent. Many of the controversies associated with plastics actually relate to the additives:[30] organotin compounds are particularly toxic.[31]
plasticity
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plastic model
