PlasticFrom Wikipedia, thefree encyclopediaFor other uses, seePlastic (disambiguation)."Age of Plastics" redirects here. For the album byThe Buggles, seeThe Age of Plastic.

Household items made of various types of plasticIUPAC definitionGeneric term used in the case of polymericmaterialthat may contain other substancesto improve performance and/or reduce costs.Note 1: The use of this term instead ofpolymeris a source of confusion and thus isnot recommended.Note 2: This term is used in polymer engineering for materials often compounded thatcan be processed by flow.[1]Plasticis a material consisting of any of a wide range ofsyntheticor semi-syntheticorganicsthat aremalleableand can bemoldedinto solid objects of diverse shapes. Plastics are typicallyorganic polymersof highmolecular mass, but they often contain other substances. They are usually synthetic, most commonly derived frompetrochemicals, but many are partially natural.[2]Plasticityis the general property of all materials that are able to irreversibly deform without breaking, but this occurs to such a degree with this class of moldablepolymersthat their name is an emphasis on this ability.Due to their relativelylow cost, ease of manufacture, versatility, and imperviousness to water, plastics are used in an enormous and expanding range of products, from paper clips to spaceships. They have already displaced many traditional materials, such aswood,stone,hornandbone,leather,paper,metal,glass, andceramic, in most of their former uses. In developed countries, about a third of plastic is used in packaging and another third in buildings such aspipingused inplumbingorvinyl siding.[3]Other uses include automobiles (up to 20% plastic[3]), furniture, and toys.[3]In the developing world, the ratios may be different - for example, reportedly 42% of India's consumption is used in packaging.[3]Plastics have many uses in the medical field as well, to include polymer implants, however the field ofplastic surgeryis not named for use of plastic material, but rather themoregeneric meaning of the word plasticity in regards to the reshaping of flesh.The world's first fully synthetic plastic wasbakelite, invented in New York in 1907 byLeo Baekeland[4]who coined the term 'plastics'.[5]Many chemists contributed to thematerials scienceof plastics, includingNobel laureateHermann Staudingerwho has been called "the father ofpolymer chemistry" andHerman Mark, known as "the father ofpolymer physics".[6]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 very large molecules. Toward the end of the century, one approach to this problem was met with wide efforts towardrecycling.Contents[hide] 1Etymology 2Common plastics and uses 3Special purpose plastics 4History 5Composition 5.1Fillers 5.2Plasticizers 5.3Colorants 6Classification 6.1Thermoplastics and thermosetting polymers 6.2Other classifications 6.2.1Biodegradability 6.2.2Natural vs synthetic 6.2.3Crystalline vs amorphous 7Ebonite 7.1Bakelite 8Representative polymers 8.1Polystyrene 8.2Polyvinyl chloride 8.3Nylon 8.4Rubber 8.5Synthetic rubber 9Properties of plastics 9.1UL Standards 9.2ISO 10Toxicity 10.1Bisphenol A 11Environmental effects 11.1Climate change 11.2Production of plastics 11.3Incineration of plastics 11.4Pyrolytic disposal 11.5Recycling 12See also 13References 14External linksEtymologyThe wordplasticis derived from theGreek (plastikos) meaning "capable of being shaped or molded", from (plastos) meaning "molded".[7][8]It refers to their malleability, orplasticityduring manufacture, that allows them to becast,pressed, orextrudedinto a variety of shapessuch asfilms,fibers, plates, tubes, bottles, boxes, and much more.The common wordplasticshould not be confused with the technical adjectiveplastic, which is applied to any material which undergoes a permanent change of shape (plastic deformation) when strained beyond a certain point.Aluminumwhich is stamped or forged, for instance, exhibits plasticity in this sense, but is not plastic in the common sense; in contrast, in their finished forms, some plastics will break before deforming and therefore are not plastic in the technical sense.Common plastics and uses

A chair made with a polypropylene seat Polyester(PES) Fibers,textiles. Polyethylene terephthalate(PET) Carbonated drinks bottles, peanut butter jars, plastic film, microwavable packaging. Polyethylene(PE) Wide range of inexpensive uses including supermarket bags, plastic bottles. High-density polyethylene(HDPE) Detergent bottles, milk jugs, and molded plastic cases. Polyvinyl chloride(PVC) Plumbing pipesand guttering,shower curtains, window frames, flooring. Polyvinylidene chloride(PVDC) (Saran) Food packaging. Low-density polyethylene(LDPE) Outdoor furniture, siding, floor tiles, shower curtains,clamshell packaging. Polypropylene(PP) Bottle caps, drinking straws, yogurt containers, appliances,carfenders (bumpers),plastic pressure pipe systems. Polystyrene(PS) Packaging foam/"peanuts", food containers, plastic tableware, disposable cups, plates, cutlery, CD and cassette boxes. High impact polystyrene(HIPS) -: Refrigerator liners, food packaging, vending cups. Polyamides(PA) (Nylons) Fibers, toothbrush bristles, tubing,fishing line, low strength machine parts: under-the-hood carengine partsor gun frames. Acrylonitrile butadiene styrene(ABS) Electronic equipment cases (e.g., computer monitors, printers, keyboards),drainage pipe. Polyethylene/Acrylonitrile Butadiene Styrene (PE/ABS) A slippery blend of PE and ABS used in low-duty dry bearings. Polycarbonate(PC) Compact discs,eyeglasses,riot shields,security windows, traffic lights, lenses. Polycarbonate/Acrylonitrile Butadiene Styrene (PC/ABS) A blend of PC and ABS that creates a stronger plastic. Used incar interiorand exterior parts, and mobilephonebodies. Polyurethanes(PU) Cushioning foams, thermal insulation foams, surface coatings, printing rollers (Currently 6th or 7th most commonly used plastic material, for instance the most commonly used plastic in cars).Special purpose plasticsSee also:High performance plastics Maleimide/BismaleimideUsed in high temperature composite materials. Melamine formaldehyde(MF) One of the aminoplasts, and used as a multi-colorable alternative to phenolics, for instance in moldings (e.g., break-resistance alternatives to ceramic cups, plates and bowls for children) and the decorated top surface layer of the paper laminates (e.g., Formica). Plastarch material Biodegradable and heat resistant, thermoplastic composed ofmodified corn starch. Phenolics(PF) or (phenol formaldehydes) Highmodulus, relatively heat resistant, and excellent fire resistant polymer. Used for insulating parts in electrical fixtures, paper laminated products (e.g.,Formica), thermally insulation foams. It is a thermosetting plastic, with the familiar trade name Bakelite, that can be molded by heat and pressure when mixed with a filler-like wood flour or can be cast in its unfilled liquid form or cast as foam (e.g., Oasis). Problems include the probability of moldings naturally being dark colors (red, green, brown), and as thermoset it is difficult torecycle. Polyepoxide(Epoxy) Used as an adhesive, potting agent for electrical components, and matrix for composite materials with hardeners includingamine,amide, andBoron Trifluoride. Polyetheretherketone(PEEK) Strong, chemical- and heat-resistant thermoplastic,biocompatibilityallows for use inmedical implantapplications, aerospace moldings. One of the most expensive commercial polymers. Polyetherimide(PEI) (Ultem) A high temperature, chemically stable polymer that does not crystallize. PolyimideA High temperature plastic used in materials such asKaptontape. Polylactic acid(PLA) A biodegradable, thermoplastic found converted into a variety of aliphatic polyesters derived fromlactic acidwhich in turn can be made by fermentation of various agricultural products such ascorn starch, once made from dairy products. 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, Oroglas, Plexiglas), aglets, fluorescent light diffusers, rear light covers for vehicles. It forms the basis of artistic and commercialacrylic paintswhen suspended in water with the use of other agents. Polytetrafluoroethylene(PTFE) Heat-resistant, low-friction coatings, used in things like non-stick surfaces for frying pans, plumber's tape and water slides. It is more commonly known as Teflon. Urea-formaldehyde(UF) One of the aminoplasts and used as a multi-colorable alternative to phenolics. Used as a wood adhesive (for plywood, chipboard, hardboard) and electrical switch housings. FuranResin based on Furfuryl Alcohol used in foundry sands and biologically derived composites. SiliconeHeat resistant resin used mainly as a sealant but also used for high temperature cooking utensils and as a base resin for industrial paints. PolysulfoneHigh temperature melt processable resin used in membranes, filtration media, water heater dip tubes and other high temperature applications.History

Plastic (LDPE) bowl, by GEECO, Made in England, c1950.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.,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 areorganic polymers. In 1600 BC,Mesoamericansused natural rubber for balls, bands, and figurines.[3]Treated cattle horns were used as windows for lanterns in theMiddle Ages. Materials that mimicked the properties of horns were developed by treating milk-proteins (casein) with lye.In the 1800s, asindustrial chemistrydeveloped during theIndustrial Revolution, many materials were reported. The development of plastics also accelerated withCharles Goodyear's discovery ofvulcanizationto thermoset materials derived from natural rubber.Parkesineis considered the first man-made plastic. The plastic material was patented byAlexander Parkes, InBirmingham,UKin 1856.[9]It was unveiled atthe 1862 Great International ExhibitioninLondon.[10]Parkesinewon a bronze medal at the 1862World's fairinLondon. Parkesine was made fromcellulose(the major component of plant cell walls) treated withnitric acidas a solvent. The output of the process (commonly known as cellulose nitrate or pyroxilin) could be dissolved inalcoholand hardened into a transparent and elastic material that could be molded when heated.[11]By incorporating pigments into the product, it could be made to resembleivory.In the early 1900s,Bakelite, the first fully synthetic thermoset, was reported by Belgian chemistLeo Baekeland.AfterWorld War I, improvements in chemical technology led to an explosion in new forms of plastics, with mass production beginning in the 1940s and 1950s (aroundWorld War II).[12]Among the earliest examples in the wave of new polymers werepolystyrene(PS), first produced byBASFin the 1930s,[3]andpolyvinyl chloride(PVC), first created in 1872 but commercially produced in the late 1920s.[3]In 1923, Durite Plastics Inc. was the first manufacturer of phenol-furfural resins.[13]In 1933,polyethylenewas discovered byImperial Chemical Industries(ICI) researchers Reginald Gibson and Eric Fawcett.[3]In 1954,Polypropylenewas found byGiulio Nattaand began to be manufactured in 1957.[3]In 1954, expanded polystyrene (used for building insulation, packaging, and cups) was invented byDow Chemical.[3]Polyethylene terephthalate(PET)'s discovery is credited to employees of theCalico Printers' Associationin the UK in 1941; it was licensed toDuPontfor the USA 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.[3]CompositionMost plastics containorganicpolymers. The vast majority of these polymers are based on chains ofcarbonatoms alone or withoxygen,sulfur, ornitrogenas well. The backbone is that part of the chain on the main "path" linking a large number of repeat units together. To customize the properties of a plastic, different molecular groups "hang" from the backbone (usually they are "hung" as part of the monomers before the monomers are linked together to form the polymer chain). The structure of these "side chains" influence the properties of the polymer. This fine tuning of the repeating unit's molecular structure influences the properties of the polymer.Most plastics contain other organic orinorganic compoundsblended in. The amount of additives ranges from zero percentage (for example in polymers used to wrap foods) to more than 50% for certain electronic applications. The average content of additives is 20% by weight of the polymer[citation needed].Many of the controversies associated with plastics are associated with the additives.[14]Organotin compoundsare particularly toxic.[15]FillersFillersimprove performance and/or reduce production costs.Stabilizing additivesincludefire retardantsto lower the flammability of the material. Many plastics contain fillers, relatively inert and inexpensive materials that make the product cheaper by weight.Typically fillers are mineral in origin, e.g.,chalk. Some fillers are more chemically active and are called reinforcing agents. Other fillers include zinc oxide, wood flour, ivory dust, cellulose and starch.[16]PlasticizersSince many organic polymers are too rigid for particular applications, they are blended withplasticizers(the largest group of additives[15]), oily compounds that confer improvedrheology.ColorantsColorants are common additives, although their weight contribution is small.ClassificationPlastics are usually classified by theirchemical structureof the polymer's backbone andside chains. Some important groups in these classifications are theacrylics,polyesters,silicones,polyurethanes, andhalogenated plastics. Plastics can also be classified by the chemical process used in their synthesis, such ascondensation,polyaddition, andcross-linking.[17]Thermoplastics and thermosetting polymersThere are two types of plastics:thermoplasticsandthermosetting polymers. Thermoplastics are the plastics that do not undergo chemical change in their composition when heated and can be molded again and again. Examples includepolyethylene,polypropylene,polystyreneandpolyvinyl chloride.[18]Common thermoplastics range from 20,000 to 500,000amu, while thermosets are assumed to have infinite molecular weight. These chains are made up of many repeating molecular units, known asrepeat units, derived frommonomers; each polymer chain will have several thousand repeating units.Thermosets can melt and take shape once; after they have solidified, they stay solid. In the thermosetting process, a chemical reaction occurs that is irreversible. The vulcanization of rubber is a thermosetting process. Before heating with sulfur, the polyisoprene is a tacky, slightly runny material, but after vulcanization the product is rigid and non-tacky.Other classificationsOther classifications are based on qualities that are relevant for manufacturing orproduct design. Examples of such classes are the thermoplastic and thermoset,elastomer,structural,biodegradable, andelectrically conductive. Plastics can also be classified by variousphysical properties, such asdensity,tensile strength,glass transition temperature, and resistance to various chemical products.BiodegradabilityMain article:Biodegradable plasticBiodegradableplastics break down (degrade) upon exposure to sunlight (e.g.,ultra-violet radiation), water or dampness, bacteria, enzymes, wind abrasion, and in some instances, rodent, pest, or insect attack are also included as forms ofbiodegradationorenvironmental degradation. Some modes of degradation require that the plastic be exposed at the surface, whereas other modes will only be effective if certain conditions exist in landfill or composting systems.Starchpowder has been mixed with plastic as a filler to allow it to degrade more easily, but it still does not lead to complete breakdown of the plastic. Some researchers have actuallygenetically engineeredbacteria that synthesize a completely biodegradable plastic, but this material, such asBiopol, is expensive at present.[19]Companies have madebiodegradable additivesto enhance the biodegradation of plastics.Natural vs syntheticMain article:BioplasticMost plastics are produced frompetrochemicals. Motivated by the finiteness of petrochemical reserves and threat ofglobal warming, bioplastics are being developed. Bioplastics are made substantially from renewable plant materials such as cellulose and starch.[20]In comparison to the global consumption of all flexible packaging, estimated at 12.3 million tonnes/year, estimates put global production capacity at 327,000 tonnes/year for related bio-derived materials.[21][22]Crystalline vs amorphousSome plastics are partiallycrystallineand partiallyamorphousinmolecularstructure, giving them both amelting point(the temperature at which the attractiveintermolecular forcesare overcome) and one or more glass transitions (temperatures above which the extent of localized molecular flexibility is substantially increased). The so-calledsemi-crystallineplastics include polyethylene, polypropylene, poly (vinyl chloride), polyamides (nylons), polyesters and some polyurethanes. Many plastics are completely amorphous, such as polystyrene and its copolymers, poly (methyl methacrylate), and all thermosets.

Molded plastic food replicas on display outside a restaurant inJapanEboniteIn 1851, Nelson Goodyear added fillers to natural rubber materials to formebonite.[16]BakeliteMain article:BakeliteThe first plastic based on a synthetic polymer was made fromphenolandformaldehyde, with the first viable and cheap synthesis methods invented in 1907, byLeo Hendrik Baekeland, aBelgian-born Americanliving inNew 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.[23]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.Representative polymersPolystyreneMain articles:PolystyreneandPVC

Plasticpipingandfirestopsbeing installed inOntario. 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 localbuilding code.Unplasticised polystyrene is a rigid, brittle, inexpensive plastic that has been used to makeplastic modelkits and similar knick-knacks. It also is the basis for some of the most popular "foamed" plastics, under the namestyrene foamorStyrofoam. 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 impactstyrene was introduced, which was not brittle. It finds much current use as the substance of toy figurines and novelties.

Styrene polymerizationPolyvinyl chloridePolyvinyl chloride (PVC, commonly called "vinyl")[24]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 forplumbing, 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 forshrink-wrap, food packaging, and rain gear.

Vinylchloride polymerizationAll PVC polymers are degraded by heat and light. When this happens, hydrogen chloride is released into the atmosphere and oxidation of the compound occurs.[25]Because hydrogen chloride readily combines with water vapor in the air to form hydrochloric acid,[26]polyvinyl chloride is not recommended for long-term archival storage of silver, photographic film or paper (mylaris preferable).[27]NylonMain article:NylonThe plastics industry was revolutionized in the 1930s with the announcement ofpolyamide(PA), far better known by its trade namenylon. Nylon was the first purely synthetic fiber, introduced byDuPont Corporationat the1939 World's FairinNew York City.In 1927, DuPont had begun a secret development project designated Fiber66, under the direction of Harvard chemistWallace Carothersand chemistry department directorElmer 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 fortoothbrushes. However, Du Pont's real target wassilk, particularly silkstockings. Carothers and his team synthesized a number of different polyamides including polyamide 6.6 and 4.6, as well as polyesters.[28]

General condensation polymerization reaction for nylonIt 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 majorINVESTMENT, it was no surprise that Du Pont spared little expense to promote nylon after its introduction, creating a public sensation, or "nylon mania".Nylon mania came to an abrupt stop at the end of 1941 when the USA enteredWorld War II. The production capacity that had been built up to producenylon stockings, or justnylons, 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-callednylon 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 bycondensation 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.RubberNatural rubberis an elastomer (an elastic hydrocarbon polymer) that originally was derived fromlatex, a milkycolloidal suspensionfound 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 Goodyearinvented 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.Synthetic rubberMain article:Synthetic rubberThe first fully synthetic rubber was synthesized bySergei Lebedevin 1910. In World War II, supply blockades of natural rubber fromSouth East Asiacaused a boom in development of synthetic rubber, notablystyrene-butadiene rubber. In 1941, annual production of synthetic rubber in theU.S.was only 231 tonnes which increased to 840,000 tonnes in 1945. In thespace raceandnuclear arms race,Caltechresearchers 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.Properties of plasticsThe properties of plastics are defined chiefly by the organic chemistry of the polymer such as hardness, density, and resistance to heat, organic solvents,oxidation, andionizing radiation. In particular, most plastics will melt upon heating to a few hundred degreescelsius.[29]While plastics can be made electrically conductive, with the conductivity of up to 80 kS/cm in stretch-orientedpolyacetylene,[30]they are still no match for most metals likecopperwhich have conductivities of several hundreds kS/cm.UL StandardsMany properties of plastics are determined by tests as specified byUnderwriters Laboratories, such as: Flammability-UL94 High voltage arc tracking rate-UL746A Comparative Tracking IndexISOMany properties of plastics are determined by standards as specified by ISO, such as: ISO 306- ThermoplasticsToxicityPure 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. For example,plasticizerslikeadipatesandphthalatesare 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, theEuropean Unionhas restricted the use ofDEHP(di-2-ethylhexyl phthalate) and other phthalates in some applications, and the United States has limited the use of DEHP,DPB,BBP,DINP,DIDP, andDnOPin children's toys and child care articles with theConsumer Product Safety Improvement Act. Some compounds leaching from polystyrene food containers have been proposed to interfere with hormone functions and are suspected human carcinogens.[31]Other chemicals of potential concern includealkylphenols.[15]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, theWorld Health Organization'sInternational Agency for Research on Cancer(IARC) has recognizedvinyl chloride, the precursor to PVC, as a humancarcinogen.[31]Bisphenol ASome 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.[32]The primary building block ofpolycarbonates,bisphenol A(BPA), is anestrogen-likeendocrine disruptorthat may leach into food.[31]Research inEnvironmental Health Perspectivesfinds that BPA leached from the lining of tin cans,dental sealantsand polycarbonate bottles can increase body weight of lab animals' offspring.[33]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.[34]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.[35]Bis(2-ethylhexyl) adipate, present inplastic wrapbased on PVC, is also of concern, as are thevolatile organic compoundspresent innew car smell.The European Union has a permanent ban on the use ofphthalatesin toys. In 2009, the United States government banned certain types of phthalates commonly used in plastic.[36]Environmental effectsSee also:Plastic pollution,Marine debrisandGreat Pacific Garbage PatchMost plastics are durable anddegradevery slowly; the very chemical bonds that make them so durable tend to make them resistant to most natural processes of degradation. However, microbial species and communities capable of degrading plastics are discovered from time to time, and some show promise as being useful for bioremediating certain classes of plastic waste. In 1975 a team of Japanese scientists studying ponds containingwaste waterfrom anylonfactory, discovered a strain ofFlavobacteriumthat digested certain byproducts ofnylon 6manufacture, such as the linear dimer of6-aminohexanoate.[37]Nylon 4 or polybutyrolactam can be degraded by the (ND-10 and ND-11) strands of Pseudomonas sp. found in sludge. This produced -aminobutyric acid (GABA) as a byproduct.[38] Several species of soil fungi can consumepolyurethane.[39]This includes two species of the Ecuadorian fungusPestalotiopsisthat can consume polyurethane aerobically and also in anaerobic conditions such as those at the bottom of landfills.[40] Methanogenic consortiadegradestyrene, using it as a carbon source.[41]Pseudomonas putidacan convertstyreneoil into variousbiodegradablepolyhydroxyalkanoates.[42][43][44] Microbial communities isolated from soil samples mixed with starch have been shown to capable of degradingpolypropylene.[45] The fungusAspergillus fumigatuseffectively degrades plasticized PVC.[46]Phanerochaete chrysosporiumwas grown on PVC in a mineral salt agar.[47]Phanerochaete chrysosporium,Lentinus tigrinus,Aspergillus niger, andAspergillus sydowiican also effectively degrade PVC.[48]Phanerochaete chrysosporiumwas grown on PVC in a mineral salt agar.[47] Acinetobacterhas been found to partially degrade low molecular weightpolyethyleneoligomers.[49]When used in combination,Pseudomonas fluorescensandSphingomonascan degrade over 40% of the weight of plastic bags in less than three months.[50][51]The thermophilic bacteriumBrevibacillus borstelensis(strain 707) was isolated from a soil sample and found capable of using low-densitypolyethyleneas a sole carbon source when incubated at 50 degrees Celsius. Pre-exposure of the plastic toultravioletradiation broke chemical bonds and aided biodegradation; the longer the period of UV exposure, the greater the promotion of the degradation.[52] Less desirably, hazardous molds have been found aboard space stations, molds that degrade rubber into a digestible form.[53] Several species of yeasts, bacteria, algae and lichens have been found growing on synthetic polymer artifacts in museums and at archaeological sites.[54] In the plastic-polluted waters of theSargassosea, bacteria have been found that consume various types of plastic; however it is unknown to what extent these bacteria effectively clean up poisons rather than simply releasing them into the marine microbial ecosystem. Plastic eating microbes also have been found in landfills.[55] Nocardiacan degrade PET with an esterase enzyme.[56] The fungiGeotrichum candidum, found in Belize, has been found to consume thepolycarbonateplastic found in CD's.[57][58] Phenol-formaldehyde, commonly known as bakelite, is degraded by the white rot fungusPhanerochaete chrysosporium[59] Thefuturohouse was made of fibreglass-reinforced polyesters, polyester-polyurethane, and poly(methylmethacrylate.) One such house was found to be harmfully degraded by Cyanobacteria and Archaea.[60][61]Since the 1950s, one billion tons of plastic have been discarded and some of that material might persist for centuries or much longer, as is demonstrated by the persistence of natural materials such as amber.[62]Serious environmental threats from plastic have been suggested in the light of the increasing presence ofmicroplasticsin the marine food chain along with many highly toxic chemical pollutants that accumulate in plastics. They also accumulate in larger fragmented pieces of plastic callednurdles.[63]In the 1960s the latter were observed in the guts of seabirds, and since then have been found in increasing concentration.[64]In 2009, it was estimated that 10% of modern waste was plastics,[12]although estimates vary according to region.[64]Meanwhile, 50-80% of debris in marine areas is plastic.[64]Before the ban on the use ofCFCsin extrusion of polystyrene (and in general use, except in life-critical fire suppression systems; seeMontreal Protocol), the production of polystyrene contributed to the depletion of theozone layer, but current extrusion processes use non-CFCs.Climate changeThe 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[65]although biodegradable plastics have caused methane emissions.[66]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.[3]Production of plasticsProduction of plastics from crude oil requires 62 to 108MJof energy per kilogram (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 per 1 kilogram of silicon, and about 3,000 MJ per kilogram of semiconductors.[67]This is much higher, compared to many other materials, e.g. production of iron from iron ore requires 20-25 MJ of energy, glass (from sand, etc.) - 18-35 MJ, steel (from iron) - 20-50 MJ, paper (from timber) - 25-50 MJ per kilogram.[68]Incineration of plasticsControlled high-temperatureincineration, above 850C for two seconds,[69]performed with selective additional heating, breaks down toxic dioxins and furans from burning plastic, and is widely used in municipal solid waste incineration.[69]Municipal solid waste incinerators also normally include flue gas treatments to reduce pollutants further.[69]This is needed because uncontrolled incineration of plastic produces polychlorinated dibenzo-p-dioxins, a carcinogen (cancer causing chemical). The problem occurs as the heat content of the waste stream varies.[70]Open-air burning of plastic occurs at lower temperatures, and normally releases suchtoxicfumes.Pyrolytic disposalPlastics can bepyrolyzedintohydrocarbonfuels, since plastics have hydrogen and carbon. One kilogram of waste plastic produces roughly a liter of hydrocarbon.[71]RecyclingThermoplastics can be remelted and reused, and thermoset plastics can be ground up and used as filler, although the purity of the material tends to degrade with each reuse cycle. There are methods by which plastics can be broken back down to a feedstock state.The greatest challenge to the recycling of plastics is the difficulty of automating the sorting of plastic wastes, making itlabor-intensive. Typically, workers sort the plastic by looking at the resin identification code, although common containers like soda bottles can be sorted from memory. Typically, the caps for PETE bottles are made from a different kind of plastic which is not recyclable, which presents additional problems to the automated sorting process. Other recyclable materials such as metals are easier to process mechanically. However, new processes of mechanical sorting are being developed to increase capacity and efficiency of plastic recycling.While containers are usually made from a single type and color of plastic, making them relatively easy to be sorted, a consumer product like a cellular phone may have many small parts consisting of over a dozen different types and colors of plastics. In such cases, the resources it would take to separate the plastics far exceed their value and the item is discarded. However, developments are taking place in the field ofactive disassembly, which may result in more consumer product components being re-used or recycled. Recycling certain types of plastics can be unprofitable, as well. For example, polystyrene is rarely recycled because it is usually not cost effective. These unrecycled wastes are typically disposed of inlandfills,incineratedor used to produce electricity atwaste-to-energyplants.A first success in recycling of plastics isVinyloop, a recycling process and an approach of the industry to separate PVC from other materials through a process of dissolution, filtration and separation of contaminations. A solvent is used in a closed loop to elute PVC from the waste. This makes it possible to recycle composite structure PVC waste which normally is being incinerated or put in a landfill. Vinyloop-based recycled PVC's primary energy demand is 46 percent lower than conventional produced PVC. The global warming potential is 39 percent lower. This is why the use of recycled material leads to a significant better ecological footprint.[72]This process was used after theOlympic Gamesin London 2012. Parts of temporary Buildings like theWater Polo Arenaor theRoyal Artillery Barrackswere recycled. This way, the PVC Policy could be fulfilled which says that no PVC waste should be left after the games.[73]In 1988, to assist recycling of disposable items, the Plastic Bottle Institute of theSociety of the Plastics Industrydevised a now-familiar scheme to mark plastic bottles by plastic type. A plastic container using this scheme is marked with a triangle of three "chasing arrows", which encloses a number giving the plastic type:Plastics type marks: theresin identification code[74]1. PET(PETE),polyethylene terephthalate2. HDPE,high-density polyethylene3. PVC,polyvinyl chloride4. LDPE,low-density polyethylene,5. PP,polypropylene6. PS,polystyrene7. Other types of plastics (see list,below)See also Conductive polymer Corn construction Molding (process) Flexible mold Injection molding Films Light activated resin Nurdle Organic light emitting diode Plastics engineering Plastics extrusion Plastic film Plastic recycling Plasticulture Progressive bag alliance Roll-to-roll processing Self-healing plastic Thermoforming Timeline of materials technologyReferences

Harmful Chemicals in our EnvironmentOver the past century humans have introduced a large number of chemical substances into the environment.Some are the waste from industrial and agricultural processes. Some have been designed as structural materials and others have been designed to perform various functions such as healing the sick or killing pests and weeds. Obviously some chemicals are useful but many are toxic and their harm to the environment and our health far outweighs their benefit to society. We need to manage the risks better by only using chemicals, which are safe.Chemicals enter air as emissions and water as effluent. Industrial and motorvehicleemissions of nitrogen and sulphur oxides cause acid rain, which poisons fish and other aquatic organisms in rivers and lakes and affects the ability of soil to support plants. Carbon dioxide causes the greenhouse effect and climate change. Chlorofluorocarbons (CFCs) cause the destruction of ozone in the stratosphere and create the possibility of serious environmental damage from ultraviolet radiation. Chemical fertilisers and nutrients run-off from farms and gardens cause the build up of toxic algae in rivers, making them uninhabitable to aquatic organisms and unpleasant for humans. Some toxic chemicals find their way from landfill waste sites into our groundwater, rivers and oceans and induce genetic changes that compromise the ability of life to reproduce and survive.The impact of human activities on the environment is complex and affects a chain of interconnecting ecosystems. The extinction of species all along the chain may mean the loss of useful genetic material or life saving cancer drugs or safer alternatives to the dangerous chemicals in use at the moment.OrganochlorinesOrganochlorine compounds such as polychlorinated biphenyls or PCBs were developed originally for use in electric equipment as cooling agents and are very dangerous chemicals. During the manufacture and disposal of products containing PCBs, and as a result of accidents, millions of gallons of PCB oil have leaked out. Although their manufacture in theUnitedStates was halted in the 1970s and they are being phased out, they are difficult to detect, are nearly indestructible and large quantities remain in existence and they will remain in the environment for a long time. They accumulate in the food chain and significant levels of them have been found in marine species, particularly mammals and sea birds, decades after their production was discontinued. They are carcinogenic and capable of damaging the liver, nervous system and the reproductive system in adults. When PCBs are burned, evenmoretoxic dioxins are formed.DioxinsDioxins, are a class of super-toxic chemicals formed as a by-product of the manufacture, moulding, or burning of organic chemicals and plastics that contain chlorine. They are the most toxic man-made organic chemicals known. They cause serious health effects even at levels as low as a few parts per trillion. Only radioactive waste is more toxic. They are virtually indestructible and are excreted by the body extremely slowly. Dioxins became known when Vietnam War veterans and Vietnamese civilians, exposed to dioxin-contaminated Agent Orange, became ill.Dioxins enter the body in food and accumulate in body fat. They bind to cell receptors and disrupt hormone functions in the body and they also affect gene functions. Our bodies have no defence against dioxins which may cause a wide range of problems, from cancer to reduced immunity to nervous system disorders to miscarriages and birth deformity. The effects can be very obvious or subtle. Because they change gene functions, they can cause genetic diseases to appear and they can interfere with child development.Attention Deficit Disorder,diabetes, endometriosis, chronic fatigue syndrome, rare nervous and blood disorders have been linked to exposure to dioxins and PCBs.Over the past 40 years there has been a dramatic increase in the manufacture and use of chlorinated organic chemicals in plastics, insecticides and herbicides. Dioxins have been found in high concentrations near to the sites where these chemicals have been produced and where insecticides and herbicides have been heavily used, such as on farms, orchards, or along electric and railway lines. They have also been a found downstream from paper mills where chlorine chemicals have been used to bleach wood pulp.In the last few years we have begun to discard our unfashionable household plastic products, together with industrial andmedical wasteby burning them in incinerators. Dioxins formed during the combustion process have been carried for hundreds of miles on tiny specks of ash and contaminated the countryside. They settle on pastures and crops and get eaten by cows, pigs and chickens. They get into lakes, streams, and ocean and are taken up by fish. They go through the food chain and appear in meat and milk and accumulate in the fat cells of our bodies.CadmiumCadmium occurs naturally in the earth's crust combined with other elements. It is usually formed as a mineral such as cadmium oxide, cadmium chloride, or cadmium sulphate and although these compounds are highly toxic they are less harmful when bound to rocks. They are present in coal and in the soil.Cadmium is useful because it doesn't corrode easily. It is used in batteries, plastics, pigments and metal coatings. Cadmium gets into the environment through landfills, poorwaste disposalmethods and leaks athazardous wastesites. It is produced by mining and other industrial activities. Cadmium particles enter our air when we burn coal for energy and incinerate household waste. The particles cantravelfar before falling to the ground or water. Each year many tonnes of cadmium are discharged into our seas and oceans. Animals and plants take up cadmium when it is in the environment. If we consume food contaminated with cadmium it can irritate our digestive system and cause vomiting and diarrhoea. If inhaled it can damage our lungs. Even when levels of exposure are low, over time, cadmium accumulates in the body and it can be difficult to get rid of. Accumulated cadmium can cause kidneys and bone disease.We take cadmium into our body by: Inhaling it when working in factories that make batteries or do welding, brazing or soldering Inhaling it when nearpowerstations or factories burning of fossil fuels Eating foods in which it accumulates such as shellfish, liver and kidney Drinking water that is contaminated Smoking cigarettesConclusionPotentially dangerous chemicals such as these are being introduced into the environment all the time. As in the case of PCBs their effect on living things may not be known until many years after their release. Hundreds of thousands of different chemicals are marketed worldwide. Of these 5000 are produced in quantities over 10 tonnes a year and 1500 are produced in quantities over 1000 tonnes year.We do not have enough information about the environmental effects of these industrial chemicals and their effects on humans. The balance between human activity and ecological sustainability is wrong.What you can doUse biodegradable products. Make your own cleaning agent using safe materials. Dispose ofchemical wastecarefully. Do not put them down the sink. Be wise withhome maintenanceand in the garden. Do not burn plastics.Avoid all organic chemicals that have "chloro" as part of their names including wood preservatives, herbicides and insecticides. Avoid chlorine bleach (sodium hypochlorite) and products containing it. Use oxygen bleach instead. Use unbleached paper products.Avoid "Permethrin" flea sprays for pets. Avoid products made of or packaged in polyvinyl chloride (PVC). Avoid cling flim plastic wraps unless they are clearly identified as non-chlorinated plastic.To minimise your risk of dioxins accumulating in your body avoid all full-fat dairy products and fatty meats such as beef or pork. Wash all fruits and vegetables to remove chlorophenol pesticide residue. Avoid grapes and raisins unless they are clearly labelled as organically grown. Avoid soaps, toothpaste and deodorants containing "triclosan," a chlorophenol.We can reduce the dioxins if we stop producing PVCs and other chlorinated chemicals. If your local government sends its waste to an incinerator, request that they stop burning plastics and introduce a comprehensive recycling service. Write to companies and ask them to use safe substitutes to chlorinated plastics. Ask your supermarket to sell Totally Chlorine Free (TCF) products. Join or form a local environmental group campaigning against hazardous chemicals.People who work with cadmium should take care not to inhale cadmium-containing dust and should avoid carrying it home from work on their clothes, skin or hair. Eat from a wide range of foods to prevent the risk of ingesting toxic levels of cadmium.Link to Green Sowers solutions for this problemRetrieve green groups directly addressing Chemical Pollution from the databaseBioplastics and biodegradable plastics byChris Woodford.Last updated: May 27, 2014.From cars to food wrap and from planes to pens, you can make anything and everything fromplasticsunquestionably the world's most versatile materials. But there's a snag. Plastics are synthetic (artificially created) chemicals that don't belong in our world and don't mix well with nature. Discarded plastics are a big cause ofpollution, clutteringrivers, seas, and beaches, killing fish, choking birds, and making our environment a much less attractive place. Public pressure to clean up has produced plastics that seem to be more environmentally friendly. But are they all they're cracked up to be?Photo: A typical eco-friendly bag made using EPI chemical additives. Added to normal plastics in small quantities (about 23 percent), they cause the plastic to break down after exposure to sunlight, heat, or after repeated stresses and strains through regular use.The global plastics problem

Plastics are carbon-basedpolymers(long-chain molecules that repeat their structures over and over) and we make them mostly from petroleum. They're incredibly versatileby definition: the word plastic, which means flexible, says it all. The trouble is that plastic is just too good. We use it for mostly disposable, low-value items such as food-wrap and product packaging, but there's nothing particularly disposable about most plastics. On average, we use plastic bags for 12 minutes before getting rid of them, yet they can take fully 500 years to break down in the environment (quite how anyone knows this is a mystery, since plastics have been around only about a century).Getting rid of plastics is extremely difficult. Burning them can give off toxic chemicals such as dioxins, while collecting andrecyclingthem responsibly is also difficult, because there are many different kinds and each has to be recycled by a different process. If we used only tiny amounts of plastics that wouldn't be so bad, but we use them in astounding quantities. In Britain alone (one small island in a very big world), people use 8 billion disposable plastic bags each year. If you've ever taken part in a beach clean, you'll know that about 80 percent of the waste that washes up on the shore is plastic, including bottles, bottle tops, and tiny odd fragments known as "mermaids' tears."We're literally drowning in plastic we cannot get rid of. And we're making most of it from oila non-renewableresource that's becoming increasingly expensive. It's been estimated that 200,000 barrels of oil are used each day to make plastic packaging for the United States alone.Photo: A biodegradable fruit and vegetable bag produced by d2w for the UK's Co-op chain of grocery stores.Making better plasticsIronically, plastics are engineered to last. You may have noticed that some plastics do, gradually, start to go cloudy or yellow after long exposure to daylight (more specifically, in theultraviolet lightthat sunlight contains). To stop this happening, plastics manufacturers generally introduce extra stabilizing chemicals to give their products longer life. With society's ever-increasing focus on protecting the environment, there's a new emphasis on designing plastics that will disappear much more quickly.Broadly speaking, so-called "environmentally friendly" plastics fall into three types: Bioplasticsmade from natural materials such as corn starch Biodegradable plasticsmade from traditional petrochemicals, which are engineered to break down more quickly Eco/recycled plastics, which are simply plastics made from recycled plastic materials rather than raw petrochemicals.We'll look at each of these in turn.Bioplastics

Photo: Some bioplastics can be harmlessly composted. Others leave toxic residues or plastic fragments behind, making them unsuitable for composting if your compost is being used to grow food.The theory behind bioplastics is simple: if we could make plastics from kinder chemicals to start with, they'd break down more quickly and easily when we got rid of them. The most familiar bioplastics are made from natural materials such ascorn starchand sold under such names as EverCornand NatureWorkswith a distinct emphasis on environmental credentials. Some bioplastics look virtually indistinguishable from traditional petrochemical plastics.Polylactide acid (PLA)looks and behaves like polyethylene and polypropylene and is now widely used for food containers. According to NatureWorks, making PLA saves two thirds theenergyyou need to make traditional plastics. Unlike traditional plastics and biodegradable plastics, bioplastics generally do not produce a net increase in carbon dioxide gas when they break down (because the plants that were used to make them absorbed the same amount of carbon dioxide to begin with). PLA, for example, produces almost 70 percent lessgreenhouse gaseswhen it degrades in landfills.Another good thing about bioplastics is that they're compostable: they decay into natural materials that blend harmlessly with soil. Some bioplastics can break down in a matter of weeks. The cornstarch molecules they contain slowly absorb water and swell up, causing them to break apart into small fragments that bacteria can digest more readily.A recipe for PLA bioplastics1. Take some corn kernels (lots of them).2. Process and mill them to extract the dextrose (a type of sugar) from their starch.3. Use fermenting vats to turn the dextrose into lactic acid.4. In a chemical plant, convert the lactic acid into lactide.5. Polymerize the lactide to make long-chain molecules of polylactide acid (PLA).Biodegradable plasticsIf you're in the habit of reading what supermarkets print on their plastic bags, you may have noticed a lot of environmentally friendly statements appearing over the last few years. Some stores now use what are described asphotodegradable,oxydegradable, or just biodegradable bags (in practice, whatever they're called, it often means the same thing). As the name suggests, these biodegradable plastics contain additives that cause them to decay more rapidly in the presence of light and oxygen (moisture and heat help too). Unlike bioplastics, biodegradable plastics are made of normal (petrochemical) plastics and don't always break down into harmless substances: sometimes they leave behind a toxic residue and that makes them generally (but not always) unsuitable for composting.Photo: A typical message on a biodegradable bag. This one, made from Eco Film, is compostable too.Recycled plasticsOne neat solution to the problem of plastic disposal is to recycle old plastic materials (like used milk bottles) into new ones (such as items of clothing). A product called ecoplastic is sold as a replacement forwoodfor use in outdoor garden furniture and fence posts. Made from high-molecular polyethylene, the manufacturers boast that it's long-lasting, attractive, relatively cheap, and nice to look at.

Photo: This "wooden" public bench looks much like any other until you look at the grain really closely. Then you can see the wood is actually recycled plastic. The surface texture is convincing, but the giveaway is the ends of the "planks," which don't look anything like the grain of wood.But there are two problems with recycled plastics. First, plastic that's recycled is generally not used to make the same items the next time around: old recycled plastic bottles don't go to make new plastic bottles, but lower-grade items such as plastic benches and fence posts. Second, you can't automatically assume recycled plastics are better for the environment unless you know they've been made with a net saving of energy and water, a net reduction in greenhouse gas emissions, or some other overall benefit to the environment. Keeping waste out of a landfill and turning it into new things is great, but what if it takes a huge amount of energy to collect and recycle the plasticmore even than making brand new plastic products?Are bioplastics good or bad?Anything that helps humankind solve the plastics problem has to be a good thing, right? Unfortunately, environmental issues are never quite so simple. Actions that seem to help the planet in obvious ways sometimes have major drawbacks and can do damage in other ways. It's important to see things in the round to understand whether "environmentally friendly" things are really doing more harm than good.Bioplastics and biodegradable plastics have long been controversial. Manufacturers like to portray them as a magic-bullet solution to the problem of plastics that won't go away. Bioplastics, for example, are touted as saving 3080 percent of thegreenhouse gas emissionsyou'd get from normal plastics and they can give food longer shelf-life in stores. But here are some of the drawbacks: When some biodegradable plastics decompose in landfills, they produce methane gas. This is a very powerful greenhouse gas that adds to the problem of global warming. Biodegradable plastics and bioplastics don't always readily decompose. Some need relatively high temperatures and, in some conditions, can still take many years to break down. Even then, they may leave behind toxic residues. Bioplastics are made from plants such as corn and maize, so land that could be used to grow food for the world is being used to "grow plastic" instead. By 2014, almost a quarter of US grain production is expected to be turned over tobiofuelsand bioplastics production, potentially causing a significant rise in food prices that will hit the poorest people hardest. Some bioplastics, such as PLA, are made from genetically modified corn. Mostenvironmentalistsconsider GM (genetically modified) crops to be inherently harmful to the environment. Bioplastics and biodegradable plastics cannot be easily recycled. To most people, PLA looks very similar to PET (polyethylene terephthalate) but, if the two are mixed up in a recycling bin, the whole collection becomes impossible to recycle. There are fears that increasing use of PLA may undermine existing efforts to recycle plastics.How to cut down on plastics

Why is life never simple? If you're keen on helping the planet, complications like this sound completely exasperating. But don't let that put you off. As many environmental campaigners point out, there are some very simple solutions to the plastics problem that everyone can bear in mind to make a real difference. Instead of simply sending your plastics waste for recycling, remember the saying "Reduce, repair, reuse, recycle". Recycling, though valuable, is only slightly better than throwing something away: you still have to use energy and water to recycle things and you probably create toxic waste products as well. It's far better to reduce our need for plastics in the first place than to have to dispose of them afterwards.Photo: Recycling, though sensible, is not always the best option. Generally it's better to reduce, reuse, and repair if you can and recycle only if you can't do these things.You can make a positive difference by actively cutting down on the plastics you use. For example: Get a reusable cotton bag and take that with you ever time you go shopping. Buy your fruit and vegetables loose, avoiding the extra plastic on pre-packaged items. Use long-lasting items (such as razors and refillable pens) rather than disposable ones. It can work out far cheaper in the long run. If you break something, can you repair it simply and carry on using it? Do you really have to buy a new one? Can you give unwanted plastic items a new lease of life? Ice cream tubs make great storage containers; vending machine cups can be turned into plant pots; and you can use old plastic supermarket bags for holding your litter. When you do have to buy new things, why not buy ones made from recycled materials? By helping to create a market for recycled products, you encourage more manufacturers to recycle.One day, we may have perfect plastics that break down in a trice. Until then, let's be smarter about how we use plastics and how we get rid of them when we've finished with them.DioxinChemical compoundWritten by:The Editors of Encyclopdia Britannica 2 READ EDIT VIEW HISTORY FEEDBACKAlternate titles:dibenzo-p-dioxin; polychlorinated dibenzodioxin; TCDDRead More: organohalogen compound science matter chemical element DDT tear gas chemical compound chloral hydrateDioxin,also calledpolychlorinated dibenzodioxin, any of a group of aromatichydrocarboncompounds known to beenvironmental pollutantsthat are generated as undesirable by-products in the manufacture ofherbicides,disinfectants, and other agents. In popular terminology, dioxin has become a synonym for one specific dioxin, 2,3,7,8-tetrachlorodibenzo-para-dioxin (2,3,7,8-TCDD).

Chemical characteristics and productionThe family of dioxins is characterized chemically by the presence of twobenzenerings connected by a pair ofoxygenatoms. Each of the eightcarbonatoms on the rings that are not bonded to oxygen can bind withhydrogenatoms or atoms of other elements. By convention these positions are assigned the numbers 1 through 4 and 6 through 9. Themoretoxic dioxins carrychlorineatoms at these positions, and the best-known one has chlorine atoms at the2,3,7, and 8 positions. Thisisomer2,3,7,8-TCDDis extremely stable chemically. It is virtually insoluble inwaterand in mostorganic compoundsbut is soluble in oils. It is this combination of properties that allows this dioxin insoilto resist dilution with rainwater and causes it to seek and enter fatty tissue in the body if it is absorbed.Dioxin serves no useful purpose but is formed as an undesirable by-product during the synthesis of2,4,5-trichlorophenol and some other useful compounds. The chemical 2,4,5-trichlorophenol serves as a raw material for making the herbicides Silvex (fenoprop) and 2,4,5-T (2,4,5-trichlorophenoxyacetic acid). The latter is a major active ingredient ofAgent Orange, a defoliant formerly used in Vietnam by the U.S. military and in theUnited Statesto kill unwanted vegetation. This 2,4,5-trichlorophenol is used in the production of hexachlorophene, an antibacterial agent formerly used in deodorants and soaps.Toxicityin humansThe recognition in the early 1980s that residential sites at Times Beach and elsewhere inMissouri, U.S., had been contaminated by improper disposal ofchemical wastescontaining2,3,7,8-TCDDled to intense public scrutiny of its possible toxic effects. Toxicologists concluded from studies on laboratory animals that TCDD is a persistent toxin, and they recommended that soil levels in excess of one part per billion might constitute a health risk to humans. Animal studies indicated that human exposure to the chemical might be associated with muscular dysfunction,inflammation,impotence,birth defects, geneticmutations, and nervous system disorders. Those investigations also suggested a potential link between exposure to TCDD and the development of variouscancersin humans.Although the actual physiological effects of TCDD toxicity in humans remain amatterof debate, in 1997 the International Agency forResearchon Cancer (IARC) upgraded the classification of TCDD from a Group 2B possiblecarcinogen(cancer-causing substance) in humans to a Group 1 known carcinogen in humans. The upgrade came after consideration of extensive epidemiological studies of TCDD carcinogenicity in humans, in which chronic exposure to high levels of the chemical was found to be associated with an increase in overall cancer mortality. The data from those studies did not link TCDD exposure directly to the development of any specific type of cancer. Typical exposure to TCDD appears to be less of a carcinogenic risk than similar exposure toasbestos,radon, orcigarettesmoke. Among humans, short-term exposure to high levels of TCDD can cause chloracne, a serious skin rash.TCDDs toxicity is derived from the chemicals ability to bind to areceptorprotein known as the aryl hydrocarbon receptor, which is present inside certain cells within the body. The resulting TCDD-receptor complex can enter the cellsnucleusand bind with itsDNA, thereby disrupting the cells machinery for producing proteins. The wide and rather puzzling array of toxic effects induced in animals by high levels of TCDD are apparently all receptor-mediated responses to the chemical. Such animals immune systems are those most often affected, being apparently weakened or compromised by TCDD.Accumulation in thefoodchainDioxins are of particular concern in regard to environmental andhuman healthbecause they are persistent environmentalpollutantsand therefore accumulate within thefood chain. Because of their lipophilic properties, the chemicals are readily absorbed into fatty tissue, and thus they have a tendency to accumulate in animalsfor example, infish, as a result of the chemicals presence in aquatic environments, and incattleand otherlivestock, as a result of the chemicals release into terrestrial environments. Consumption of potentially contaminated foods, such as beef and dairy products, is the primary route for dioxin entry into the human body. In fact, more than 90 percent of human dioxin exposure is attributed to dietary ingestion. Once in the human body, dioxins are absorbed into fat cells, where they persist for long periods of time; the half-life of dioxin in humans has been estimated to be between 7 and 11 years.The incineration of dioxins generated as by-products in manufacturing processes is an effective method for controlling the release of the chemicals into the environment.

What is Dioxin?How to Avoid Toxin DioxinDECODING HOUSEHOLD CHEMICALS

Found everywhere, dioxin is public enemy number one. To give you an idea of how common dioxin exposure is, consider bleached coffee filters. The EPA says that 40% to 70% of the dioxins contained in bleached coffee filters get transferred to your coffee. Therefore, the simple routine of using bleached coffee filters results in a lifetime of unsafe exposure to dioxin.According to theWorld Health Organization, dioxins are highly toxic. They cause reproductive and developmental problems, damage the immune system, disrupt hormones and cause cancer.The Skinny Science:Dioxin is an organic chemical that consists of a pair of benzene rings. Because of their chemical stability and their ability to be dissolved by fat tissue, they can exist in the body for years. Highly potent in small quantities, it is measured in parts per trillion, not the parts per million we usually hear. Dioxins are categorized as persistentenvironmentalpollutants. This means two things: they do not degrade in the environment, and they exist indefinitely once released.Word to the Wise:Manufacturing processes are the root cause of our dioxin issues today. This includes smelting, chlorine bleaching of paper pulp, manufacturing of herbicides and pesticides, and uncontrolled waste incinerators. Sadly they are found throughout the world, even in hundred-year-old Greenland Sharks that live in some of the most pristine waters of the Arctic Ocean.Green your Routine:How do you avoid this seemingly omnipresent substance? A major source of dioxin exposure is eating animal products, because of dioxin's ability to persist in fats. In addition to changing your diet, here are some other strategies you can incorporate: Avoid eating animal products. Eat organically grown fruits and vegetables. Pesticide and herbicide residues found on non-organically grown food harbors dioxin. Whengardening, avoid using pesticides and herbicides that contain dioxin. When cleaning, avoidchlorine bleach. It forms dioxin aftercontactwith organic compounds. In personal care products, avoidtriclosan, an antibacterial agent. It degrades into dioxin. With coffee supplies, use unbleached coffee filters, metal filters, or a French press. Dioxin is a by-product of the bleaching process. Avoid bleached paper products like disposable diapers, napkins, tissue and paper towels.Prevention is the Best Cure:Because of the ubiquitous nature of dioxin, the usual prevention advice is challenging. Dioxin is present in every aspect of life: water, air, soil and food. That said, dioxin concentrations vary, so the best advice may be to avoid foods with the highest concentration of dioxins. Since dioxin accumulates in fat -- in both our own and the animals we eat people with diets high in vegetables and low in animal products have lower dioxin levels.High dioxin level foods: dairy products meat fish shellfishLow dioxin level foods: vegetables fruitExtra Tidbits: Alternative names quick list: DLC (dioxin-like compound),TCDD (the most toxic dioxin), PCDD, PCDF, and some dioxin-like PCBs. Dioxin is categorized as one of the "dirty dozen" chemicals. Dioxin made headlines when it was used in an assassination attempt to poison former Ukrainian president, Viktor Yushchenko,leaving him severely disfigured. Agent Orange made dioxin infamous in the 1980s. Formoreinformation, check out these sources:UnitedStates Department of Agriculture,EnvironmentalProtection Agency.

As always, stay informed and green your routine to what fits you best.

Dioxins & why you dont want to be burning plastic02 June, 2008 / bypolythenepam/ in04.1 PLASTIC PROBLEMSThe image showsplastictrash being burnt inKhatmanduSo, is it safe to burn plastic?Well it never burns easily it melts and bubbles. It will burn eventually but you have to keep heating it clickhereif you want to know why.And, when you do set fire to plastic it gives off a terrible smell at least in my experience, as a child, playing round the back of the derelict garages I hasten to add.>But is it bad for you? It could be lethal.The smell according to thenaked scientistcould be anything. They sayThere are lots of different plastics, and they will give off lots of different vapours when they decompose.It could be just a simple hydrocarbon, or it could contain cyanides, orPCBs,or lots of other substances. Without knowing what the plastic was ..it would be difficult to know what are the likely volatiles it would create. volatiles given off from plastics in house fires are a major cause of death.PCBs? thats a dioxin and dioxins are nasty! Eeek!So, to conclude, it depends on the plastic then?

Setting fire to plastic filled ditchesYes it is apparently safe to burn polythene it can even be reprocessed as briquettes to make a very efficient fuel (ifenergy).But its a big NO if its a halogenated plastics, i.e one of those made from chlorine or fluorineHalogenated plasticsinclude:Chlorine based plastics:Chlorinated polyethylene (CPE)Chlorinated polyvinyl chloride (CPVC)Chlorosulfonated polyethylene (CSPE)Polychloroprene (CR or chloroprene rubber, marketed under the brand name of Neoprene)PVCFluorine based plastics:Fluorinated ethylene propylene (FEP)Burning these plastics can release dioxins.Dioxinsare unintentionally, but unavoidably produced during the manufacture of materials containing chlorine, including PVC and other chlorinated plastic feedstocks.Dioxinis a known human carcinogen and the most potent synthetic carcinogen ever tested in laboratory animals. A characterization by theNational Instituteof Standards andTechnologyof cancer causing potential evaluated dioxin as over 10,000 timesmorepotent than the next highest chemical (diethanol amine), half a million times more than arsenic and a million or more times greater than all others.TheWorld HealthOrganization saidOncedioxinshave entered the environment or body, they are there to stay due to their uncanny ability to dissolve in fats and to their rock-solid chemical stability.That is because dioxinsare classed as one of the persistant organic pollutants, POPs,also known as asPBTs(Persistent,Bioaccumulativeand Toxic) orTOMPs(Toxic Organic Micro Pollutants.)POPs are a small set of toxic chemicals that remainintact in the environment for long periods and accumulate in the fatty tissues of animals. They are extremely toxic and cause all manner of illnesses. You canfind out more about POPS hereThe Uk Government states on their websiteBurning plastic, rubber or painted materials creates poisonous fumes and can have damaging health effects for people who have asthmatic or heart conditions.This is covered under the Environmental Protection Act 1990.Environmental Protection Act 1990IN CONCLUSIONIts best not to be burning plastic on an open fire unless you knowexactlywhat it is made up of.While there are some plastics that are supposed to be safe to burn, personally I wont be burning plastic on my bonfire.But is it safe to send off to my localwaste disposalplant where they burn it in an incinerator?It is claimed that all plastics can be burnt safely in the modern industrial incinerators but only those built to high specifications.Opinions vary wildly as to wether this is the case withenvironmentalists saying we are poisoning the very air that we breathe.Many of these plants generate electricity from the heat produced so in effect the plastic is recycled.The resulting ash from incineration plants has to be disposed of and so presnets yet another waste disposal challenge.For more information go toWikkipediaWaste Plastic Blogspotabout the technology behind waste incinerators.Zero Waste Americaa crtiqua of waste incinerators.Burning Binsthe problems of trash being burnt on open firesPLASTICSThe quality of plasticity is one that had been used to great effect in the crafts of metallurgy and ceramics. The use of the wordplasticsas a collective noun, however, refers not so much to the traditional materials employed in these crafts as to new substances produced by chemical reactions and molded or pressed to take a permanent rigid shape. The first such material to be manufactured wasParkesine, developed by the British inventorAlexander Parkes. Parkesine, made from a mixture of chloroform andcastor oil, was a substance hard as horn, but as flexible as leather, capable of being cast or stamped, painted, dyed or carved. The words are from a guide to the International Exhibition of 1862 in London, at which Parkesine won a bronze medal for its inventor. It was soon followed by other plastics, butapart from celluloid, a cellulose nitrate composition using camphor as a solvent and produced in solid form (as imitation horn for billiard balls) and in sheets (for mens collars and photographic film)these had little commercial success until the 20th century.The early plastics relied upon the large molecules in cellulose, usually derived from wood pulp.Leo H. Baekeland, a Belgian American inventor, introduced a new class of large molecules when he took out his patent forBakelitein 1909. Bakelite is made by the reaction between formaldehyde and phenolic materials at high temperatures; the substance is hard, infusible, and chemically resistant (the type known as thermosetting plastic). As a nonconductor of electricity, it proved to be exceptionally useful for all sorts of electrical appliances. The success of Bakelite gave a great impetus to the plastics industry, to the study ofcoal tarderivatives and other hydrocarbon compounds, and to the theoretical understanding of the structure of complex molecules. This activity led to new dyestuffs and detergents, but it also led to the successful manipulation of molecules to produce materials with particular qualities such as hardness or flexibility. Techniques were devised, often requiring catalysts and elaborate equipment, to secure these polymersthat is, complex molecules produced by the aggregation of simpler structures. Linear polymers give strong fibres, film-forming polymers have been useful in paints, and mass polymers have formed solid plastics.SYNTHETIC FIBRESThe possibility of creating artificial fibres was another 19th-century discovery that did not become commercially significant until the 20th century, when such fibres were developed alongside the solid plastics to which they are closely related. The first artificial textiles had been made fromrayon, a silklike material produced by extruding a solution of nitrocellulose in acetic acid into a coagulating bath of alcohol, and various other cellulosic materials were used in this way. But later research, exploiting the polymerization techniques being used in solid plastics, culminated in the production of nylon just before the outbreak of World War II.Nylonconsists of long chains of carbon-based molecules, giving fibres of unprecedented strength and flexibility. It is formed by melting the component materials and extruding them; the strength of thefibreis greatly increased by stretching it when cold. Nylon was developed with the womens stocking market in mind, but the conditions of war gave it an opportunity to demonstrate its versatility and reliability as parachute fabric and towlines. This and other synthetic fibres became generally available only after the war.SYNTHETICRUBBERThe chemical industry in the 20th century put a wide range of new materials at the disposal of society. It also succeeded in replacing natural sources of some materials. An important example of this is the manufacture of artificial rubber to meet a world demand far in excess of that which could be met by the existing rubber plantations. This technique was pioneered in Germany during World War I. In this effort, as in the development of other materials such as high explosives and dyestuffs, the consistent German investment in scientific and technical education paid dividends, for advances in all these fields of chemical manufacturing were prepared by careful research in the laboratory.PLASTICSCell wall plastics such aslignin,cutin, andsuberin all contain a variety of organic compounds cross-linked into tight three-dimensional networks that strengthen cell walls and make them more resistant to fungal and bacterial attack. Lignin is the general name for a diverse group of polymers of aromaticalcohols. Deposited mostly in secondary cell walls and providing the rigidity of terrestrial vascular plants, it accounts for up to 30 percent of a plants dry weight. The diversity of cross-links between the polymersand the resulting tightnessmakes lignin a formidable barrier to the penetration of most microbes.Cutin and suberin are complex biopolyesters composed offatty acidsand aromatic compounds. Cutin is the major component of thecuticle, the waxy, water-repelling surface layer of cell walls exposed to the environment aboveground. By reducing the wetability of leaves and stemsand thereby affecting the ability of fungalsporesto germinateit plays an important part in the defense strategy of plants. Suberin serves with waxes as a surface barrier of underground parts. Its synthesis is also stimulated in cells close to wounds, thereby sealing off the wound surfaces and protecting underlying cells from dehydrationPlastic pollution,accumulation in theenvironmentof man-madeplasticproducts to the point where they create problems for wildlife and theirhabitatsas well as for human populations. In 1907 the invention ofBakelitebrought about a revolution in materials by introducing truly syntheticplasticresinsinto world commerce. By the end of the 20th century, however, plastics were found to be persistent polluters of many environmental niches, fromMount Everestto the bottom of the sea. Whether being mistaken forfoodby animals, flooding low-lying areas by clogging drainage systems, or simply causing significant aesthetic blight, plastics have attracted increasing attention as a large-scalepollutant. IMAGES QUIZZES LISTS The problem of plasticsPlastic is apolymeric materialthat is, a material whose molecules are very large, often resembling long chains made up of a seemingly endless series of interconnected links. Natural polymers such asrubberandsilkexist in abundance, but natures plastics have not been implicated in environmentalpollution, because they do not persist in theenvironment. Today, however, the average consumer comes into daily contact with all kinds of man-made plastic materials that have been developed specifically to defeat natural decay processesmaterials derived mainly frompetroleumthat can be molded, cast, spun, or applied as a coating. Since synthetic plastics are largely nonbiodegradable, they tend to persist in natural environments. Moreover, many lightweight, single-use plastic products and packaging materials, which account for approximately 50 percent of all plastics produced, are not deposited in containers for subsequent removal tolandfills,recyclingcentres, orincinerators. Instead, they are improperly disposed of at or near the location where they end their usefulness to the consumer. Dropped on the ground, thrown out of a car window, heaped onto an already full rubbish bin, or inadvertently carried off by a gust ofwind, they immediately begin to pollute the environment. Indeed, landscapes littered by plastic packaging have become common in many parts of the world. (Illegal dumping of plastic and overflowing of containment structures also play a role.) Studies from around the world have not shown any particular country or demographic group to be most responsible, though population centres generate the most litter. The causes and effects of plastic pollution are truly worldwide.According to the trade association PlasticsEurope, world plastic production grew from some 1.5 million tons in 1950 to an estimated 275 million tons in 2010; some 4 million to 12 million tons is discarded into the oceans annually by countries with ocean coastlines. Compared with materials in common use in the first half of the 20th century, such asglass,paper,iron, andaluminum, plastics have a low recovery rate. That is, they are relatively inefficient to reuse as recycled scrap in the manufacturing process, due to significant processing difficulties such as a low melting point, which prevents contaminants from being driven off during heating and reprocessing. Most recycled plastics are subsidized below the cost of raw materials by various deposit schemes, or their recycling is simply mandated by government regulations. Recycling rates vary dramatically from country to country, with only northern European countries obtaining rates greater than 50 percent. In any case, recycling does not really address plastic pollution, since recycled plastic is properly disposed of, whereas plastic pollution comes from improper disposal.Plastic,polymericmaterialthat has the capability of being molded or shaped, usually by the application of heat and pressure. This property ofplasticity, often found in combination with other special properties such as lowdensity, low electrical conductivity, transparency, and toughness, allows plastics to be made into a great variety of products. These include tough and lightweight beverage bottles made ofpolyethylene terephthalate(PET), flexible garden hoses made ofpolyvinyl chloride(PVC), insulatingfoodcontainers made of foamedpolystyrene, and shatterproof windows made ofpolymethyl methacrylate. IMAGES VIDEOS QUIZZES LISTS In this article a brief review of the essential properties of plastics is provided, followed by a more detailed description of their processing into useful products and subsequentrecycling. For a fuller understanding of the materials from which plastics are made,seechemistry of industrial polymers.The composition, structure, and properties of plasticsMany of the chemical names of the polymers employed as plastics have become familiar to consumers, although some are better known by their abbreviations or trade names. Thus, polyethylene terephthalate and polyvinyl chloride are commonly referred to as PET and PVC, while foamedpolystyreneand polymethyl methacrylate are known by their trademarked names, Styrofoam and Plexiglas (or Perspex).Industrial fabricators of plastic products tend to think of plastics as either commodity resins or specialty resins. (The termresindates from the early years of the plastics industry; it originally referred to naturally occurring amorphous solids such asshellacand rosin.) Commodity resins are plastics that are produced at high volume and low cost for the most common disposable items and durable goods. They are represented chiefly bypolyethylene,polypropylene, polyvinyl chloride, and polystyrene. Specialty resins are plastics whose properties are tailored to specific applications and that are produced at low volume and higher cost. Among this group are the so-calledengineeringplastics, or engineering resins, which are plastics that can compete with die-cast metals inplumbing, hardware, and automotive applications. Important engineering plastics, less familiar to consumers than the commodity plastics listed above, arepolyacetal,polyamide(particularly those known by the trade namenylon),polytetrafluoroethylene(trademark Teflon),polycarbonate, polyphenylene sulfide,epoxy, and polyetheretherketone. Another member of the specialty resins isthermoplasticelastomers, polymers that have the elastic properties ofrubberyet can be molded repeatedly upon heating. Thermoplastic elastomers are described in the articleelastomer.Plastics also can be divided into two distinct categories on the basis of their chemical composition. One category is plastics that are made up of polymers having only aliphatic (linear)carbonatoms in their backbone chains. All the commodity plastics listed above fall into this category. The structure ofpolypropylenecan serve as an example; here attached to every other carbon atom is a pendant methyl group (CH3):

The other category of plastics is made up ofheterochain polymers. These compounds contain atoms such as oxygen, nitrogen, or sulfur in their backbone chains, in addition to carbon. Most of the engineering plastics listed above are composed of heterochain polymers. An example would be polycarbonate, whose molecules contain two aromatic (benzene) rings:

The distinction between carbon-chain and heterochain polymers is reflected in the table, in which selected properties and applications of the most important carbon-chain and heterochain plastics are shown and from which links are provided directly to entries that describe these materials in greater detail. It is important to note that for eachpolymertype listed in the table there can be many subtypes, since any of a dozen industrial producers of any polymer can offer 20 or 30 different variations for use in specific applications. For this reason the properties indicated in the table must be taken as approximations.Properties and applications of commercially important plasticspolymer family and typedensity(g/cm3)degree ofcrystallinityglasstransitiontemperature(C)crystalmeltingtemperature(C)deflectiontemperatureat 1.8 MPa(C)

Thermoplastics

Carbon-chain

high-density polyethylene (HDPE)0.950.97high120137

low-density polyethylene (LDPE)0.920.93moderate120110

polypropylene (PP)0.900.91high20176

polystyrene (PS)1.01.1nil100

acrylonitrile-butadiene-styrene (ABS)1.01.1nil90120

polyvinyl chloride, unplasticized (PVC)1.31.6nil85

polymethyl methacrylate (PMMA)1.2nil115

polytetrafluoroethylene (PTFE)2.12.2moderate-high126327

Heterochain

polyethylene terephthalate (PET)1.31.4moderate69265

polycarbonate (PC)1.2low145230

polyacetal1.4moderate50180

polyetheretherketone (PEEK)1.3nil185

polyphenylene sulfide (PPS)1.35moderate88288

cellulose diacetate1.3low120230

polycaprolactam (nylon 6)1.11.2moderate50210220

Thermosets*

Heterochain

polyester (unsaturated)1.32.3nil200

epoxies1.11.4nil110250

phenol formaldehyde1.72.0nil175300

urea and melamine formaldehyde1.52.0nil190200

polyurethane1.05low90100

polymer family and typetensilestrength(MPa)elongationat break(%)flexuralmodulus(GPa)typical products and applications

Thermoplastics

Carbon-chain

high-density polyethylene (HDPE)2030101,00011.5milk bottles, wire and cable insulation, toys

low-density polyethylene (LDPE)8301006500.250.35packaging film, grocery bags, agricultural mulch

polypropylene (PP)30401006001.21.7bottles, food containers, toys

polystyrene (PS)3550122.63.4eating utensils, foamed food containers

acrylonitrile-butadiene-styrene (ABS)1555301000.93.0appliance housings, helmets, pipe fittings

polyvinyl chloride, unplasticized (PVC)40502802.13.4pipe, conduit, home siding, window frames

polymethyl methacrylate (PMMA)50752102.23.2impact-resistant windows, skylights, canopies

polytetrafluoroethylene (PTFE)20352004000.5self-lubricated bearings, nonstick cookware

Heterochain

polyethylene terephthalate (PET)5075503002.43.1transparent bottles, recording tape

polycarbonate (PC)65751101202.32.4compact discs, safety glasses, sporting goods

polyacetal7025752.63.4bearings, gears, shower heads, zippers

polyetheretherketone (PEEK)70105301503.9machine, automotive, and aerospace parts

polyphenylene sulfide (PPS)50901103.84.5machine parts, appliances, electrical equipment

cellulose diacetate15656701.5photographic film

polycaprolactam (nylon 6)40170303001.02.8bearings, pulleys, gears

Thermosets*

Heterochain

polyester (unsaturated)2070