Plastic

The word plastic derives from the Ancient Greek (), meaning "capable of being shaped or molded," which itself comes from (), meaning "molded" or "formed." In modern usage, the word plastic most commonly refers to the solid synthetic products of petrochemical-derived manufacturing. The word plasticity, as a noun, specifically refers to the deformability of the materials used in the manufacture of plastics. Plasticity allows molding, extrusion, or compression into a variety of shapes, including films, fibers, plates, tubes, bottles, and boxes, among many others. In materials science, plasticity also has a more technical definition, describing the nonreversible change in form of solid substances when subjected to external forces. However, this definition extends beyond the scope of this article. == Structure ==

Most plastics contain organic polymers. The vast majority of these polymers are formed from chains of carbon atoms, with or without the attachment of oxygen, nitrogen or sulfur atoms. These chains comprise many repeating units formed from monomers. Each polymer chain consists of 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 called side chains hang from this backbone; they are usually attached to the monomers before the monomers themselves are linked together to form the polymer chain. The structure of these side chains influences the properties of the polymer. ==Classifications==

Plastics are usually classified by their chemical structure of the polymer's backbone and side chains. Important groups classified in this way include the acrylics, polyesters, silicones, polyurethanes, and halogenated plastics. Plastics can be classified by the chemical process used in their synthesis, such as condensation, polyaddition, and cross-linking. They can also be classified by their physical properties, including hardness, density, tensile strength, thermal resistance, and glass transition temperature. Plastics can additionally be classified by their resistance and reactions to various substances and processes, such as exposure to organic solvents, oxidation, and ionizing radiation. Other classifications of plastics are based on qualities relevant to manufacturing or product design for a particular purpose. Examples include thermoplastics, thermosets, conductive polymers, biodegradable plastics, engineering plastics and elastomers. Thermoplastics and thermosetting polymers One important classification of plastics is the degree to which the chemical processes used to make them are reversible or not. Thermoplastics do not undergo chemical change in their composition when heated and thus can be molded repeatedly. Examples include polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC). Thermosetting polymers, also known as thermosets, can melt and take shape only once: after they have solidified, they stay solid and retain their shape permanently. If reheated, thermosets decompose rather than melt. Examples of thermosets include epoxy resin, polyimide, and Bakelite. The vulcanization of rubber is an example of this process. Before heating in the presence of sulfur, natural rubber (polyisoprene) is a sticky, slightly runny material, and after vulcanization, the product is dry and rigid. : Commodity, engineering, and high-performance plastics Commodity plastics Commodity plastics or commodity polymers are plastics produced in high volumes for applications such as packaging, food containers, and household products, including both disposable products and durable goods. In contrast to engineering plastics, commodity plastics tend to be inexpensive to produce and exhibit relatively weak mechanical properties. Widely used commodity plastics include polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), poly(methyl methacrylate) (PMMA), and polyethylene terephthalate (PET). Products made from commodity plastics include disposable plates, disposable cups, photographic and magnetic tape, clothing, reusable bags, medical trays, and seeding trays. Approximately 80% of global plastic production includes commodity plastics, a type of plastics primarily chosen for their low cost and ease of manufacturing. These plastics are mass-produced and ubiquitous in packaging, food containers, and single-use items. Most commodity plastics are identifiable by their Resin Identification Codes (RICs), a standardized numbering system developed by ASTM International. : Polyethylene terephthalate (PET or PETE) : High-density polyethylene (HDPE or PE-HD) : Polyvinyl chloride (PVC or V) : Low-density polyethylene (LDPE or PE-LD), : Polypropylene (PP) : Polystyrene (PS) Beyond the six most widely recognized listed above, there are more commodity plastics that are also mass-produced and commonly used, such as polyurethanes (PURs). PURs are a class of plastics also designated as commodity plastics due to their low cost, ease of manufacturing, and versatility. However, they lack RICs because they encompass many chemically diverse formulations such as foams and adhesives. Packaging represents the largest application of commodity plastics, consuming 146 million metric tons (36% of global production) in 2015 alone. Beyond packaging, however, these plastics are critical in various other fields such as agriculture, construction, consumer goods, and healthcare. Although many traits such as durability and resistance to biodegradability are desirable in various applications, they have led to significant environmental issues. An estimated 8 to 12 million tons of plastic enter oceans annually, primarily from mismanaged packaging waste. Commodity plastics account for the majority of this pollution, as their recycling rates remain low (e.g., only ~9% of all plastics are recycled globally). Microplastics derived from their degradation further threaten ecosystems and human health. The roughly 20% of remaining plastics are engineering and high-performance plastics, valued for their strength, heat resistance, chemical resistance, and other exceptional qualities. These kinds of plastics are more expensive, less common, and often used in more specialized applications. Engineering plastics Engineering plastics are more robust and are used to manufacture products such as vehicle parts, building and construction materials, and some machine parts. In some cases, they are polymer blends consisting mixtures of polymers. • Acrylonitrile butadiene styrene (ABS): electronic equipment cases (e.g., computer monitors, printers, keyboards) and drainage pipes • High-impact polystyrene (HIPS): refrigerator liners, food packaging, and vending cups • Polycarbonate (PC): compact discs, eyeglasses, riot shields, security windows, traffic lights, and lenses • 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 in mobile phone bodies • Polyethylene + acrylonitrile butadiene styrene (PE + ABS): a slippery blend of PE and ABS used in low-duty dry bearings • Polymethyl methacrylate (PMMA) (acrylic): contact lenses (of the original "hard" variety), glazing (best known in this form by its various trade names around the world; e.g. Perspex, Plexiglas, and Oroglas), fluorescent-light diffusers, and rear light covers for vehicles. It also forms the basis of artistic and commercial acrylic paints, when suspended in water with the use of other agents. • Silicones (polysiloxanes): heat-resistant resins used mainly as sealants but also used for high-temperature cooking utensils and as a base resin for industrial paints • Urea-formaldehyde (UF): one of the aminoplasts used as a multi-colorable alternative to phenolics: used as a wood adhesive (for plywood, chipboard, hardboard) and electrical switch housings High-performance plastics High-performance plastics are a category of polymers exhibiting superior properties compared to commodity and engineering plastics. These plastics can withstand high temperatures, often above 302°F (150°C), are highly resistant to chemical corrosion and degradation, have excellent mechanical and electric properties, and are lightweight and versatile. • Polyphenylene sulfide (PPS): extreme chemical resistance, flame retardancy, and thermal stability (up to 428°F). • Polyethersulfone (PES): best known for their clarity, high-temperature resistance (up to 392°F), and biocompatibility. Commonly used in medical devices, food-grade equipment, and aerospace lighting. • Polyvinylidene fluoride (PVDF): a nonreactive thermoplastic fluoropolymer known for extreme chemical resistance, ultraviolet stability, and piezoelectric properties. Commonly used in semiconductor tubing, lithium-ion battery binders, and architectural coatings. • Liquid-crystal polymers (LCPs): a class of polymers combining the properties of both liquids and crystals, known for extreme dimensional stability, low thermal expansion, and high dielectric strength. Commonly used in miniature electronics, fiber-optic cables, and surgical devices. • Polyimides (PIs): a class of high-performance thermosets, able to operate up to 572°F and best known for their excellent dielectric properties and radiation resistance. Commonly used in flexible printed circuits, space suit layers, and jet engine components. • Polybenzimidazole (PBI): extremely high heat resistance (up to 752°F short-term), low outgassing, and flame resistance. Commonly used in firefighting gear, semiconductor tools, and aerospace thermal shields. • Bismaleimide (BMI): known for its high glass transition temperature (around 482°F) and low moisture absorption. Commonly used in composite aircraft matrices and military radar systems. • Cyanate esters: known for their low dielectric loss and space-grade radiation resistance. Commonly used in satellite components and radar antennas. Amorphous and crystalline plastics Many plastics are amorphous, meaning they lack a highly ordered molecular structure. Crystalline plastics exhibit a pattern of more regularly spaced atoms, such as high-density polyethylene (HDPE), polybutylene terephthalate (PBT), and polyether ether ketone (PEEK). However, some plastics are partially amorphous and partially crystalline in molecular structure, giving them both a melting point and one or more glass transitions (the temperature 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. Conductive polymers Conductive polymers include certain kinds of polyacetylene, which attracted much academic interest. Conductivities as high as 80 kilosiemens per centimeter (kS/cm) have been achieved in such materials, although that value is not comparable to that of copper (60 MS/cm). A practical conductive plastic is poly(3,4-ethylenedioxythiophene) polystyrene sulfonate.--> Bioplastics While most plastics are produced from petrochemicals, bioplastics are made substantially from renewable plant materials like cellulose and starch. Due both to the finite limits of fossil fuel reserves and to rising levels of greenhouse gases caused primarily by the burning of those fuels, the development of bioplastics is a growing field. Global production capacity for bio-based plastics is estimated at 327,000 tonnes per 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. ==Plastic industry==

The plastic industry includes the global production, compounding, conversion and sale of plastic products. Although the Middle East and Russia produce most of the required petrochemical raw materials, the production of plastic is concentrated in the global East and West. The plastic industry comprises a huge number of companies and can be divided into several sectors: Production Between 1950 and 2017, 9.2 billion tonnes of plastic are estimated to have been made, with more than half of this having been produced since 2004. Since the birth of the plastic industry in the 1950s, global production has increased enormously, reaching 400 million tonnes a year in 2021; this is up from 381 million metric tonnes in 2015 (excluding additives). From the 1950s, rapid growth occurred in the use of plastics for packaging, in building and construction, and in other sectors. This includes a mixture of private and state-owned enterprises. Roughly half of all production takes place in East Asia, with China being the largest single producer. Major international producers include: • Dow Chemical • LyondellBasell • ExxonMobil • SABIC • BASF • Sibur • Shin-Etsu Chemical • Indorama Ventures • Sinopec • Braskem Historically, Europe and North America have dominated global plastics production. However, since 2010 Asia has emerged as a significant producer, with China accounting for 31% of total plastic resin production in 2020. Regional differences in the volume of plastics production are driven by user demand, the price of fossil fuel feedstocks, and investments made in the petrochemical industry. For example, since 2010 over US$200 billion has been invested in the United States in new plastic and chemical plants, stimulated by the low cost of raw materials. In the European Union (EU), too, heavy investments have been made in the plastics industry, which employs over 1.6-million people with a turnover of more than 360 billion euros per year. In China in 2016 there were over 15,000 plastic manufacturing companies, generating more than US$366 billion in revenue. In 2017, the global plastics market was dominated by thermoplastics– polymers that can be melted and recast. Thermoplastics include polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS) and synthetic fibers, which together represent 86% of all plastics. Compounding material Plastic is not sold as a pure unadulterated substance but is instead mixed with various chemicals and other materials. These additives include substances such as stabilizers, plasticizers, and dyes, which are intended to improve the lifespan, workability, or appearance of the final item. In some cases, two types of polymers are combined to form a polymer blend, such as high impact polystyrene. Large companies may do their own compounding prior to production, but some producers have it done by a third party. Companies that specialize in this work are known as Compounders. The compounding of thermosetting plastic is relatively straightforward; as it remains liquid until it is cured into its final form. For thermosoftening materials, which are used to make the majority of products, it is necessary to melt the plastic in order to mix-in the additives. This involves heating it to anywhere between . Molten plastic is viscous and exhibits laminar flow, leading to poor mixing. Compounding is therefore done using extrusion equipment, which is able to supply the necessary heat and mixing to give a properly dispersed product. The concentrations of most additives are usually quite low, however high levels can be added to create Masterbatch products. The additives in these are concentrated but still properly dispersed in the host resin. Masterbatch granules can be mixed with cheaper bulk polymer and will release their additives during processing to give a homogeneous final product. This can be cheaper than working with a fully compounded material and is particularly common for the introduction of color. Converting Converters (sometimes known as processors) are companies or specialists that fabricate finished plastic products from raw materials, often in the form of resins, pellets, or films. • Injection molding: involves injecting molten plastic into a mold cavity under high pressure. The plastic solidifies in the mold to form the desired shape. • Blow molding: involves heating a plastic tube called a parison and inflating it inside a mold to form hollow products such as bottles and toys. • Rotational molding: involves rotating a mold on two axes while it is heated. Plastic powder is added to the mold and melts and sticks to the walls as the mold is rotated, which forms thick-walled hollow parts such as intermediate bulk containers. • Casting: involves pouring liquid resin into a mold where it solidifies into a predesigned shape. • Film blowing: involves heating a polymer and blowing it into a thin, continuous sheet. Commonly used for making polyethylene and polypropylene films used in packaging. • Spinning: involves transforming a polymer melt or solution into continuous strands • 3D printing: involves three-dimensionally printing an object layer by layer following a digital model using computer-aided design software. For thermosetting materials, the process is slightly different, as the plastics are liquid to begin with and but must be cured to give solid products, but much of the equipment is broadly similar. The most commonly produced plastic consumer products include packaging made from LDPE (e.g. bags, containers, food packaging film), containers made from HDPE (e.g. milk bottles, shampoo bottles, ice cream tubs), and PET (e.g. bottles for water and other drinks). Together these products account for around 36% of plastics use in the world. Most of them (e.g. disposable cups, plates, cutlery, takeaway containers, carrier bags) are used for only a short period, many for less than a day. The use of plastics in building and construction, textiles, transportation and electrical equipment also accounts for a substantial share of the plastics market. Plastic items used for such purposes generally have longer life spans. They may be in use for periods ranging from around five years (e.g. textiles and electrical equipment) to more than 20 years (e.g. construction materials, industrial machinery). Plastic consumption differs among countries and communities, with some form of plastic having made its way into most people's lives. North America (i.e. the North American Free Trade Agreement or NAFTA region) accounts for 21% of global plastic consumption, closely followed by China (20%) and Western Europe (18%). In North America and Europe, there is high per capita plastic consumption (94 kg and 85 kg/capita/year, respectively). In China, there is lower per capita consumption (58 kg/capita/year), but high consumption nationally because of its large population. ==Gallery==

PET Bottle Water.jpg|Water bottles made of PET File:HDPE bottles and containers.png|High density polythene (HDPE) is used for making sturdy containers; transparent containers may be made of PET. Pulling on the hood of the Tyveck suit (5429334133).jpg|Disposable suits can be made from non-woven HDPE fabric. Registered Mail Royal Mail - Great Britain-Germany 2017 - envelope front side.jpg|Plastic mailing envelopes made of HDPE A Ziploc bag made from LDPE.jpg|A Ziploc bag made of LDPE Daujėnų naminė duona.JPG|Food wrap made of LDPE Image-from-rawpixel-id-5957725-original.jpg|Metalized polypropylene film is a commonly used snack pack material. Kinder Joy 01.jpg|Kinder Joy shell made of polypropylene Red Polypropylene Chair with Stainless Steel Structure.JPG|A polypropylene chair Hanoi Vietnam The-omnipresent-plastic-chairs-01.jpg|Stools made of HDPE Polistirolo.JPG|Expanded polystyrene foam ("Thermocol") Styrofoam-grey-board.jpg|Extruded polystyrene foam ("Styrofoam") Have a Nice Day! styrofoam food container.JPG|Thermocol take-away food container Plastic egg carton.jpg|Egg tray made of PETE LDPE Foam.jpg|A piece of packaging foam made of LDPE Urethane sponge1.jpg|A kitchen sponge made of polyurethane foam Frying pan.jpeg|Non-stick cookware with Teflon coating IPhone 5c blue back.jpg|iPhone 5c, a smartphone with a polycarbonate "unibody" shell KelpAquarium.jpg|To withstand the extreme water pressure, this deep Monterey Bay Aquarium tank has windows made of acrylic glass up to 33 cm thick. Plastic tubing.jpg|alt=|PVC pipes Pills in blister pack.jpg|PVC blister pack ==Applications==

The largest application for plastics is as packaging materials, but they are used in a wide range of other sectors, including: construction (pipes, gutters, door and windows), textiles (stretchable fabrics, fleece), consumer goods (toys, tableware, toothbrushes), transportation (headlights, bumpers, body panels, wing mirrors), electronics (phones, computers, televisions) and as machine parts. ==Additives==

Additives are chemicals blended into plastics to improved their performance or appearance. Additives are therefore one of the reasons why plastic is used so widely. Plastics are composed of chains of polymers. Many different chemicals are used as plastic additives. A randomly chosen plastic product generally contains around 20 additives. The identities and concentrations of additives are generally not listed on products. At a minimum, all plastic contains some polymer stabilizers which permit them to be melt-processed (molded) without suffering polymer degradation.Additives in polyvinyl chloride (PVC), used widely for sanitary plumbing, can constitute up to 80% of the total volume. Additives may also degrade to form other compounds that could be more benign or more toxic. Plastic fragmentation into microplastics and nanoplastics can allow chemical additives to move in the environment far from the point of use. Once released, some additives and derivatives may persist in the environment and bioaccumulate in organisms. They can have adverse effects on human health and biota. A recent review by the United States Environmental Protection Agency (US EPA) revealed that out of 3,377 chemicals potentially associated with plastic packaging and 906 likely associated with it, 68 were ranked by ECHA as "highest for human health hazards" and 68 as "highest for environmental hazards". "When birds ingest small pieces of plastic, they found, it inflames the digestive tract. Over time, the persistent inflammation causes tissues to become scarred and disfigured, affecting digestion, growth and survival." Types of additive ==Health effects==

Plastics per se have low toxicity due to their insolubility in water and because they have a large molecular weight. They are biochemically inert. Additives in plastic products can be more problematic. For example, plasticizers like adipates and phthalates are often added to brittle plastics like PVC to make them pliable. Traces of these compounds can leach out of the product. Owing to concerns over the effects of such leachates, the EU has restricted the use of DEHP (di-2-ethylhexyl phthalate) and other phthalates in some applications, and the US has limited the use of DEHP, DPB, BBP, DINP, DIDP, and DnOP in children's toys and child-care articles through 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 (cancer-causing substances). Bisphenol A (BPA) Some plastic products degrade to chemicals with estrogenic activity. The primary building block of polycarbonates, bisphenol A (BPA), is an estrogen-like endocrine disruptor that may leach into food. 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. As of January 2010, the Los Angeles Times reported that the US Food and Drug Administration (FDA) is spending $30 million to investigate indications of BPA's link to cancer. 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 EU has a permanent ban on the use of phthalates in toys. In 2009, the US government banned certain types of phthalates commonly used in plastic. ==Environmental effects==

Estimates differ as to the amount of plastic waste produced in the last century. By one estimate, one billion tons of plastic waste have been discarded since the 1950s. Others estimate a cumulative human production of 8.3-billion tons of plastic, of which 6.3-billion tons is waste, with only 9% getting recycled. It is estimated that this waste is made up of 81% polymer resin, 13% polymer fibers and 32% additives. In 2018 more than 343 million tons of plastic waste were generated, 90% of which was composed of post-consumer plastic waste (industrial, agricultural, commercial and municipal plastic waste). The rest was pre-consumer waste from resin production and manufacturing of plastic products (e.g. materials rejected due to unsuitable color, hardness, or processing characteristics). The rivers Yangtze, Indus, Yellow, Hai, Nile, Ganges, Pearl, Amur, Niger, and Mekong "transport 88% to 95% of the global [plastics] load into the sea." 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. Meanwhile, 50% to 80% of debris in marine areas is plastic. Research on the environmental impacts has typically focused on the disposal phase. However, the production of plastics is also responsible for substantial environmental, health and socioeconomic impacts. Prior to the Montreal Protocol, CFCs had been commonly used in the manufacture of the plastic polystyrene, the production of which had contributed to depletion of the ozone layer. Efforts to minimize environmental impact of plastics may include lowering of plastics production and use, waste- and recycling-policies, and the proactive development and deployment of alternatives to plastics such as for sustainable packaging. Microplastics Decomposition of plastics Plastics degrade by a variety of processes, the most significant of which are hydrolysis and photo-oxidation. Chemical structure determines the fate of a polymers. 400 °C, PVC degrades at {{cite journal | vauthors = Li MX, Yang SS, Ding J, Ding MQ, He L, Xing DF, Criddle CS, Benbow ME, Ren NQ, Wu WM |title= Cockroach Blaptica dubia biodegrades polystyrene plastics: Insights for superior ability, microbiome and host genes |journal= J Hazard Mater |date=November 5, 2024 | volume = 479| issue = |article-number=135756|doi=10.1016/j.jhazmat.2024.135756 ==History==

The development of plastics has evolved from the use of naturally plastic materials (e.g., gums and shellac) to the use of the chemical modification of those materials (e.g., natural rubber, cellulose, collagen, and milk proteins), and finally to completely synthetic plastics (e.g., Bakelite, epoxy, and PVC). 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. 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 with lye. In the nineteenth century, as chemistry developed during the Industrial Revolution, many materials were reported. The development of plastics accelerated with Charles Goodyear's 1839 discovery of vulcanization to harden natural rubber. Parkesine, invented by Alexander Parkes in 1855 and patented the following year, is considered the first man-made plastic. It was manufactured 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. By incorporating pigments into the product, it could be made to resemble ivory. Parkesine was unveiled at the 1862 International Exhibition in London and garnered for Parkes the bronze medal. In 1893, French chemist Auguste Trillat discovered the means to insolubilize casein (milk proteins) by immersion in formaldehyde, producing material marketed as galalith. The resultant horn-like plastic made from casein was developed in cooperation with the Austrian chemist (Friedrich) Adolph Spitteler (1846–1940). Although unsuitable for the intended purpose, other uses would be discovered. Among the earliest examples in the wave of new polymers were polystyrene (first produced by BASF in the 1930s) In 1933, polyethylene was discovered by Imperial Chemical Industries (ICI) researchers Reginald Gibson and Eric Fawcett. In the 1980s and 1990s, plastic recycling and the development of biodegradable plastics began to flourish to mitigate environmental impacts. From 2000 to the present, bioplastics from renewable sources and awareness of microplastics have spurred extensive research and policies to control plastic pollution. == Policy ==

Work is currently underway to develop a global treaty on plastic pollution. On March 2, 2022, UN Member States voted at the resumed fifth UN Environment Assembly (UNEA-5.2) to establish an Intergovernmental Negotiating Committee (INC) with the mandate of advancing a legally-binding international agreement on plastics. The resolution is entitled "End plastic pollution: Towards an international legally binding instrument." The mandate specifies that the INC must begin its work by the end of 2022 with the goal of "completing a draft global legally binding agreement by the end of 2024." == See also ==