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[[File:Plastic household items.jpg|thumb|upright=1.35|Household items made of various types of plastics]]
'''Plastics''' are a wide range of [[synthetic polymers|synthetic]] or semi-synthetic materials that use [[polymer]]s as a main ingredient. Their [[Plasticity (physics)|plasticity]] makes it possible for plastics to be [[Injection moulding|
9.2 billion
The success and dominance of plastics starting in the early 20th century has caused widespread environmental problems,<ref>{{cite web |date=October 2020 |title=The environmental impacts of plastics and micro-plastics use, waste and pollution: EU and national measures |url=https://www.europarl.europa.eu/RegData/etudes/STUD/2020/658279/IPOL_STU(2020)658279_EN.pdf |website=europarl.europa.eu}}</ref> due to their slow decomposition rate in natural ecosystems. Most plastic produced has not been reused, or is incapable of reuse, either being captured in [[landfill]]s or persisting in the environment as [[plastic pollution]] and [[microplastics]]. Plastic pollution can be [[Marine plastic pollution|found in all the world's major water bodies]], for example, creating [[garbage patch]]es in all of the world's oceans and contaminating terrestrial ecosystems. Of all the plastic discarded so far, some 14% has been incinerated and less than 10% has been recycled.<ref name=":0" />
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====Biodegradable plastics====
{{Main|Biodegradable plastic}}
[[Biodegradable]] plastics are plastics that degrade (break down) upon exposure to sunlight or [[ultra-violet radiation]]; water or dampness; bacteria; enzymes; or wind abrasion. Attack by insects, such as waxworms and mealworms, can also be considered as forms of biodegradation. [[aerobic digestion|Aerobic]] degradation requires that the plastic be exposed at the surface, whereas [[anaerobic digestion|anaerobic]] degradation would be effective in landfill or composting systems. Some companies produce [[biodegradable additives]] to enhance biodegradation. Although starch powder can be added as a filler to allow some plastics to degrade more easily, such treatment does not lead to complete breakdown. Some researchers have [[Genetic engineering|genetically engineered]] bacteria to synthesize completely biodegradable plastics, such as polyhydroxy butyrate (PHB); however, these
====Bioplastics====
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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.<ref name=PlasEU /> 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.<ref name=":0" />
In 2017, the global plastics market was dominated by [[thermoplastic]]s– polymers that can be melted and recast. Thermoplastics include [[polyethylene]] (PE), [[polyethylene terephthalate]] (PET), [[polypropylene]] (PP), [[polyvinyl chloride]] (PVC), [[polystyrene]] (PS) and synthetic
===Compounding===
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The compounding of thermosetting plastic is relatively straightforward; as it remains liquid until it is [[Curing (chemistry)|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 {{Convert|150-320|C|F|round=5}}. 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
===Converting===
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:[[File:Symbol Resin Code 06 PS.svg|35px]] [[Polystyrene]] (PS)
[[Polyurethane]]s (PUR) and PP&A
A huge number of plastics exist beyond the commodity plastics, with many having exceptional properties.
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===High-performance plastics===
[[High-performance plastics]] are usually expensive, with their use limited to
*[[Aramid]]s: best known for their use in making [[body armor]], this class of heat-resistant and strong synthetic fibers are also used in aerospace and military applications, includes [[Kevlar]] and [[Nomex]], and [[Twaron]].
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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|
Kinder Joy 01.jpg|[[Kinder Joy]] shell made of polypropylene
Red Polypropylene Chair with Stainless Steel Structure.JPG|A polypropylene chair
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==Additives==
Additives are chemicals blended into plastics to change their performance or appearance, making it possible to alter the properties of plastics to better suit their intended applications.<ref name="Additive-rev">{{cite journal | vauthors = Hahladakis JN, Velis CA, Weber R, Iacovidou E, Purnell P | title = An overview of chemical additives present in plastics: Migration, release, fate and environmental impact during their use, disposal and recycling | journal = Journal of Hazardous Materials | volume = 344 | pages = 179–199 | date = February 2018 | pmid = 29035713 | doi = 10.1016/j.jhazmat.2017.10.014 | doi-access = free | bibcode = 2018JHzM..344..179H }}</ref><ref>{{cite journal |last1=Marturano |first1=Valentina |last2=Cerruti |first2=Pierfrancesco |last3=Ambrogi |first3=Veronica |title=Polymer additives |journal=Physical Sciences Reviews |date=June 27, 2017 |volume=2 |issue=6 |page=130 |doi=10.1515/psr-2016-0130|bibcode=2017PhSRv...2..130M |s2cid=199059895 |doi-access=free }}</ref> Additives are therefore one of the reasons why plastic is used so widely.<ref>{{cite journal |last1=Pfaendner |first1=Rudolf |title=How will additives shape the future of plastics? |journal=Polymer Degradation and Stability |date=September 2006 |volume=91 |issue=9 |pages=2249–2256 |doi=10.1016/j.polymdegradstab.2005.10.017}}</ref> 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.<ref name=":0" />
In the EU, over 400 additives are used in high volumes.<ref>{{cite web |title=Mapping exercise – Plastic additives initiative - ECHA |url=https://echa.europa.eu/mapping-exercise-plastic-additives-initiative |website=echa.europa.eu |access-date=May 3, 2022}}</ref><ref name=":0" /> 5500 additives were found in a global market analysis.<ref>{{Cite journal |last1=Wiesinger |first1=Helene |last2=Wang |first2=Zhanyun |last3=Hellweg |first3=Stefanie |date=July 6, 2021 |title=Deep Dive into Plastic Monomers, Additives, and Processing Aids |journal=[[Environmental Science & Technology]] |volume=55 |issue=13 |pages=9339–9351 |doi=10.1021/acs.est.1c00976|pmid=34154322 |bibcode=2021EnST...55.9339W |hdl=20.500.11850/495854 |s2cid=235597312 |hdl-access=free }}</ref> At a minimum, all plastic contains some [[polymer
=== Leaching ===
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=== Recycling ===
{{Main|Plastic recycling}}
As additives change the properties of plastics they have to be considered during recycling. Presently, almost all recycling is performed by simply remelting and reforming used plastic into new items. Additives present risks in recycled products, as they are difficult to remove. When plastic products are recycled, it is highly likely that the additives will be integrated into the new products. Waste plastic, even if it is all of the same polymer type, will contain varying types and amounts of additives. Mixing these together can give a material with inconsistent properties, which can be unappealing to industry. For example, mixing different
Absence of transparency and reporting across the value chain often results in lack of knowledge concerning the chemical profile of the final products. For example, products containing brominated flame retardants have been incorporated into new plastic products. Flame retardants are a group of chemicals used in electronic and electrical equipment, textiles, furniture and construction materials which should not be present in food packaging or child care products. A recent study found brominated dioxins as unintentional contaminants in toys made from recycled plastic [[electronic waste]] that contained brominated flame retardants. Brominated dioxins have been found to exhibit toxicity similar to that of chlorinated dioxins. They can have negative developmental effects and negative effects on the nervous system and interfere with mechanisms of the endocrine system.<ref name=":0" />
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| Impact modifiers || 10–40 || Improved toughness and resistance to damage<ref>{{cite journal |title=Impact modifiers: how to make your compound tougher |journal=Plastics, Additives and Compounding |date=May 2004 |volume=6 |issue=3 |pages=46–49 |doi=10.1016/S1464-391X(04)00203-X}}</ref> || Typically some other [[elastomeric]] polymer, e.g. rubbers, styrene copolymers || [[Chlorinated polyethylene]] is used for PVC || 5%
|-
| [[Antioxidant]]s || 0.05–3 || Protects against degradation during processing || [[Phenols]], [[phosphite ester]]s, certain [[thioethers]] || The most widely used type of additives, all plastics will contain [[polymer
|-
| [[Colorant]]s || 0.001-10 || Imparts
|-
| [[Lubricant]]s || 0.1-3 || Assist in forming/molding the plastic, includes processing aids (or flow aids), [[release agent]]s, slip additives || Hazardous [[PFASs]]. [[Paraffin wax]], [[wax ester]]s, metal stearates (i.e. [[zinc stearate]]), long-chain [[fatty acid amide]]s ([[oleamide]], erucamide) || Very common. All examples form a coating between the plastic and machine parts during production. Reduces pressure and power usage in the extruder. Reduces imperfections. || 2%
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==Toxicity==
Pure plastics have low toxicity due to their insolubility in water, and because they have a large molecular weight, they are biochemically inert. Plastic products contain a variety of additives, however, some of which can be toxic.<ref name=additives>{{cite journal | vauthors = Hahladakis JN, Velis CA, Weber R, Iacovidou E, Purnell P | title = An overview of chemical additives present in plastics: Migration, release, fate and environmental impact during their use, disposal and recycling | journal = Journal of Hazardous Materials | volume = 344 | pages = 179–199 | date = February 2018 | pmid = 29035713 | doi = 10.1016/j.jhazmat.2017.10.014 | doi-access = free | bibcode = 2018JHzM..344..179H }}{{open access}}</ref> For example, plasticizers like [[Adipic_acid#Adipate_salts_and_esters|adipates]] and [[phthalate]]s are often added to brittle plastics like PVC 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 [[leachate]]s, the EU has restricted the use of [[Bis(2-ethylhexyl) phthalate|DEHP]] (di-2-ethylhexyl phthalate) and other phthalates in some applications, and the US has limited the use of DEHP, [[Dibutyl phthalate|DPB]], [[Benzyl butyl phthalate|BBP]], [[Diisononyl phthalate|DINP]], [[Diisodecyl phthalate|DIDP]], and [[Di(n-octyl) phthalate|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).<ref name="NationalGeographic" /> Other chemicals of potential concern include [[alkylphenol]]s.<ref name=Transportandrelease/>
While a finished plastic may be non-toxic, the monomers used in the manufacture of its 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.<ref name="NationalGeographic">{{cite web| vauthors = McRandle PW |title = Plastic Water Bottles|publisher = [[National Geographic Society|National Geographic]]|date = March–April 2004|url = http://www.thegreenguide.com/doc/101/plastic|access-date = November 13, 2007}}</ref>
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Because the chemical structure of most plastics renders them durable, they are resistant to many natural degradation processes. Much of this material may persist for centuries or longer, given the demonstrated persistence of structurally similar natural materials such as [[amber]].
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.<ref>{{cite book| vauthors = Weisman A |title=The world without us|date=2007|publisher=Thomas Dunne Books/St. Martin's Press|location=New York|isbn=978-1-4434-0008-4}}</ref> 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.<ref>{{cite journal | vauthors = Geyer R, Jambeck JR, Law KL | title = Production, use, and fate of all plastics ever made | journal = Science Advances | volume = 3 | issue = 7 | pages = e1700782 | date = July 2017 | pmid = 28776036 | pmc = 5517107 | doi = 10.1126/sciadv.1700782 | bibcode = 2017SciA....3E0782G }}</ref>
It is estimated that this waste is made up of 81% polymer resin, 13% polymer
The [[Ocean Conservancy]] reported that China, Indonesia, Philippines, Thailand, and Vietnam dump more plastic into the sea than all other countries combined.<ref>{{cite news | vauthors = Leung H |title=Five Asian Countries Dump More Plastic Into Oceans Than Anyone Else Combined: How You Can Help |url=https://www.forbes.com/sites/hannahleung/2018/04/21/five-asian-countries-dump-more-plastic-than-anyone-else-combined-how-you-can-help/#1d663de71234 |access-date=June 23, 2019 |work=[[Forbes]] |date=April 21, 2018 |language=en |quote=China, Indonesia, the Philippines, Thailand, and Vietnam are dumping more plastic into oceans than the rest of the world combined, according to a 2017 report by Ocean Conservancy}}</ref> 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."<ref>{{cite journal | vauthors = Schmidt C, Krauth T, Wagner S | title = Export of Plastic Debris by Rivers into the Sea | journal = Environmental Science & Technology | volume = 51 | issue = 21 | pages = 12246–12253 | date = November 2017 | pmid = 29019247 | doi = 10.1021/acs.est.7b02368 | bibcode = 2017EnST...5112246S | url = http://oceanrep.geomar.de/43169/4/es7b02368_si_001.pdf | quote = The 10 top-ranked rivers transport 88–95% of the global load into the sea }}</ref><ref>{{cite news | vauthors = Franzen H |title=Almost all plastic in the ocean comes from just 10 rivers |url=https://p.dw.com/p/2oTF6 |access-date=December 18, 2018 |work=[[Deutsche Welle]] |date=November 30, 2017 |quote=It turns out that about 90 percent of all the plastic that reaches the world's oceans gets flushed through just 10 rivers: The Yangtze, the Indus, Yellow River, Hai River, the Nile, the Ganges, Pearl River, Amur River, the Niger, and the Mekong (in that order).}}</ref>{{Verify quote|date=February 2021|type=quote punctuation|text=Should the full stop in this quote be placed outside of it instead? See Wikipedia:Manual_of_Style#Punctuation for more information.}}
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.<ref name=Accumulation/> The long-term effects of plastics in the food chain are poorly understood. In 2009 it was estimated that 10% of modern waste was plastic,<ref name=PlasticAge/> although estimates vary according to region.<ref name="Accumulation">{{cite journal | vauthors = Barnes DK, Galgani F, Thompson RC, Barlaz M | title = Accumulation and fragmentation of plastic debris in global environments | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 364 | issue = 1526 | pages = 1985–98 | date = July 2009 | pmid = 19528051 | pmc = 2873009 | doi = 10.1098/rstb.2008.0205 }}</ref> Meanwhile, 50% to 80% of debris in marine areas is plastic.<ref name=Accumulation/> Plastic is often used in agriculture. There is more plastic in the soil than in the oceans. The presence of plastic in the environment hurts ecosystems and human health.<ref>{{cite news |last1=Carrington |first1=Damian |title='Disastrous' plastic use in farming threatens food safety – UN |url=https://www.theguardian.com/environment/2021/dec/07/disastrous-plastic-use-in-farming-threatens-food-safety-un |access-date=December 8, 2021 |agency=The Guardian |date=December 7, 2021}}</ref>
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Quickly burning plastics at very high temperatures breaks down many toxic components, such as [[Dioxins and dioxin-like compounds|dioxins]] and [[furan]]s. This approach is widely used in municipal solid [[Incineration|waste incineration]]. Municipal solid waste incinerators also normally treat the [[flue gas]] to decrease pollutants further, which is needed because uncontrolled incineration of plastic produces [[carcinogen]]ic [[Polychlorinated dibenzodioxins|polychlorinated dibenzo-p-dioxins]].<ref>{{cite journal | vauthors = Halden RU | title = Plastics and health risks | journal = Annual Review of Public Health | volume = 31 | pages = 179–94 | date = 2010 | pmid = 20070188 | doi = 10.1146/annurev.publhealth.012809.103714 | doi-access = free }}</ref> Open-air burning of plastic occurs at lower temperatures and normally releases such [[toxicity|toxic]] fumes.
In the European Union, municipal waste incineration is regulated by the [[Industrial Emissions Directive]],<ref>{{Cite journal |last1=Romero |first1=Lina M. |last2=Lyczko |first2=Nathalie |last3=Nzihou |first3=Ange |last4=Antonini |first4=Gérard |last5=Moreau |first5=Eric |last6=Richardeau |first6=Hubert |last7=Coste |first7=Christophe |last8=Madoui |first8=Saïd |last9=Durécu |first9=Sylvain |date=July 2020 |title=New insights on mercury abatement and modeling in a full-scale municipal solid waste incineration flue gas treatment unit |journal=Waste Management |language=en |volume=113 |pages=270–279 |doi=10.1016/j.wasman.2020.06.003|pmid=32559697 |bibcode=2020WaMan.113..270R |s2cid=219948357 |doi-access=free }}</ref> which stipulates a minimum temperature of 850 °C for at least two seconds.<ref>{{Cite journal |last1=Janhäll |first1=Sara |last2=Petersson |first2=Mikaela |last3=Davidsson |first3=Kent |last4=Öman |first4=Tommy |last5=Sommertune |first5=Jens |last6=Kåredal |first6=Monica |last7=Messing |first7=Maria E. |last8=Rissler |first8=Jenny |date=October 2021 |title=Release of carbon nanotubes during combustion of polymer nanocomposites in a pilot-scale facility for waste incineration |journal=NanoImpact |language=en |volume=24 |pages=100357 |doi=10.1016/j.impact.2021.100357|pmid=35559816 |s2cid=239252029 |doi-access=free |bibcode=2021NanoI..2400357J }}</ref>
==History==
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