http://www.abipet.org.br/index.html?method=mostrarInstitucional&id=71Garrafas - FabricaoFabricao das Garrafas e Frascos: o Sopro das PreformasA transformao da resina PET em garrafas, frascos, potes ou outros tipos de embalagem, ocorre em7 etapasdistintas e as trs ltimas so aquelas referentes produo da garrafa propriamente dita:Secagem

Alimentao

Plastificao

Injeo

Condicionamento

Sopro

Ejeo do produto.

5- No condicionamentoa pr-forma recebe um tratamento trmico diferenciado, aquecendo-se mais onde for necessrio conforme o desenho da embalagem - otimizando o sopro. Esse condicionamento pode ser realizado de duas maneiras diferentes, conforme o sistema adotado para o sopro das embalagens:a)um estgio (tambm conhecido como integradoou ciclo quente)b)dois es tgios (tambm conhecido comociclo frio)No sistema de um estgio (a) possvel variar mais a produo de formas e tamanhos para os frascos e garrafas, embora a produtividade seja inferior.Neste sistema, a preforma segue do molde de injeodiretamentepara o condicionamento a uma temperatura emtorno de 100C.No sistema de dois estgios (b) a prioridade a velocidade de produo, assim, as preformas so injetadas (primeiro estgio) em grandes quantidades e estocadas, sendo enviadas posteriormentepara o local onde o sopro ser feito (segundo estgio) conforme a necessidade. Neste sistema, a preforma injetada previamente. Para ser soprada, chega fria do estoque e entra no forno, onde a regio a ser estirada ser condicionada. Uma vez atingida as temperaturas ideais, a preforma est preparada e otimizada para etapa seguinte.6- No sopro, a pr-forma colocada, geralmente com o auxlio de robs, dentro do molde, cuja cavidade tem a forma final da embalagem.
Um pino penetra no gargalo da pr-forma para estir-la, e soprado o ar comprimido no seu interior.O corpo da preforma inflado de forma controlada com a ajuda de uma haste de estiramento. Desta maneira, a pr-forma estirada, orientando as molculas de PET nas direes radial e axial, isto , bi-orientada, at que encoste na cavidade do molde de sopro e adquira sua forma final.

7- Finalmente, a embalagem soprada retirada ou ejetada da mquina, pronto para o envase.A produo de Garrafas de PET normalizada pela Associao Brasileira de Normas Tcnicasatravs da NBR15395:2006. O documento pode ser adquirido diretamente com a ABNT.A Abipet recomenda a leitura do guia Diretrizes para Projeto de Garrafa, disponvel no site para download.

Preformas - VariedadePreformas de PET: variedade para todos os finsAntes da garrafa pronta, como a conhecemos nos mercados, necessrio produziruma PREFORMA. Trata-se de uma pea em forma de tubo com rosca - que ser,posteriormente, soprada para chegar ao fomato final do produto um frasco, umpote, uma garrafa e a absoluta maioria das embalagens de PET existentes.

Com fcil observar em qualquer supermercado, h uma grande variedade deprodutos envasados em PET. Desde os tradicionais e pioneiros refrigerantesat produtos de limpeza, remdios e muitos outros. Cada produto exige umdeterminado desempenho de sua embalagem: resistncia mecnica, transparncia, resistncia qumica e tamanhos variados.

Para atender tantas especificaes, foram desenvolvidas vrias preformas de PETe cada uma dar origem a um frasco, garrafa ou poe de caractersticas prprias.

Cada uma tem um tipo de finish (a parte da rosca da garrafa), podem ser maisleves, ter a boca larga (adequadas para potes) e mais uma srie de caractersticasque fazem de cada embalagem um exerccio de tecnologia, inteligncia eplanejamento. Com isso, ganham consumidores, indstria e o meio ambiente, j que o uso de material ser sempre racionalmente pensado para cada caso.

A produo das Preformas de PET normalizada pela Associao Brasileira deNormas Tcnicas atravs da ABNT NBR 15588:2008. O documento pode seradquirido diretamente com a ABNT.

A Abipet recomenda a leitura do guia Diretrizes para Projeto de Garrafa, disponvelno site para leitura ou download (link para pgina publicaes).

Preformas - FabricaoA fabricao das preformas de PETAo utilizarmos uma embalagem de PET, no percebemos a tecnologia envolvida no seu processo produtivo, tampouco as vrias etapas necessrias at a obteno do produto final.Antes da garrafa, necessrio produzir uma PREFORMA. Trata-se de uma pea em forma de tubo com rosca - que ser, posteriormente, soprada para chegar ao formato final do produto um frasco, um pote, uma garrafa e a absoluta maioria das embalagens de PET existentes.A transformao da resina PET em garrafas, frascos ou potes ocorre em7 etapasdistintas, sendo que as 4 primeiras dizem respeito fabricao das preformas:Secagem

Alimentao

Plastificao

Injeo

Condicionamento

Sopro

Ejeo do produto.

1- A secagemda resina uma das etapas mais importantes e crticas. PET um material higroscpico, que absorve gua do meio ambiente durante seu armazenamento. A umidade dos gro de PET pode atingir nveis elevados de at 0,6% em peso, se expostos sem nenhuma proteo s intempries por longos perodos.

Na prtica, se a resina for mantida em locais fechados por curtos perodos de tempo, o valor de umidade normalmente menor, podendo ser inferior a 0,1%.

Se a resina for submetida fuso com esses nveis de umidade, sofre uma rpida degradao (hidrlise), reduzindo o seu peso molecular, o que refletido na perda da viscosidade intrnseca (VI) e conseqente perda de suas propriedades fsicas. Portanto, a secagem cuidadosa e controlada das resinas PET uma operao essencial antes de sua transformao.

As recomendaes prticas para se ter um processo de secagem eficiente e confivel so:

- Manter a temperatura efetiva dos gros entre 160 / 180C (medida na sada do secador);
- A temperatura do ar seco no deve exceder 190C (medido na entrada do secador). Esse limite deve ser respeitado para evitar degradao termo-oxidativa que muito rpida acima desta temperatura. Este fenmeno, quando ocorre, percebido atravs do amarelamento do gro;
- O ponto de orvalho deve ser inferior a 30C (medido na entrada do secador);
- Normalmente o secador operado acima de 3 Nm3(cbicos) de ar/kg de PET/h, na temperatura e ponto de orvalho de operao;
- O tempo de residncia dos gros deve ser superior a 4h. Na faixa de temperatura recomendada para a secagem, a velocidade de degradao termo-oxidativa baixa, mas o uso de tempos muitos longos pode tornar essa degradao significativa.2- A alimentao a transio entre o silo que armazena a resina e a entrada doPET na injetora. Nesta etapa, quando necessrio, so dosados aditivos resina PET (protetores aos raios ultravioleta, concentrados de cor, etc.), atravs de equipamentos especficos para esta finalidade. Aqui o material est slido, seco e a uma temperatura, preferencialmente, acima de 100 C.

3- A plastificao muito importante e delicada. Nesta etapa a resina PET muda de estado fsico para ser injetado. Ele aquecido e plastificado dentro do canho da injetora com o auxilio de um parafuso sem fim, com passo de rosca e zonas de presso bem determinados.

As temperaturas de trabalho, geralmente controladas por resistncias, variam conforme o equipamento e esto entre 265 e 305oC.

4- Injeo,ou, a etapa de transfernciada resina PET plastificada para o molde de preformas. O molde deve estar abaixa temperatura, devido circulao em seu interior de gua gelada. O PET no molde de injeo endurece rapidamente devido a esta baixa temperatura. Se o resfriamento fosse lento, o PET poderia retornar parcialmente ao estado cristalizado, podendo debilitar algumas propriedades do produto final.
Ao final desta etapa, a preforma est pronta, com o gargalo em sua forma definitiva e o corpo que, na etapa seguinte, ser transformado no corpo da embalagem final.A produo das Preformas de PET normalizada pelaAssociao Brasileira de Normas Tcnicasatravs daABNT NBR 15588:2008.O documento pode ser adquirido diretamente com a ABNT.A Abipet recomenda a leitura do guia Diretrizes para Projeto de Garrafa, disponvel no site para leitura ou download.

Resina PET - HistriaHistria da Resina PETO Poli(Tereftalato de Etileno), ou, simplesmente PET, um polmero termoplstico da famlia dos polisteres. Embora seja muito conhecidoh oje atravs das garrafas plsticas, o material iniciou sua trajetria na indstria txtil.A primeira amostra da resina foi desenvolvida pelos ingleses Whinfield e Dickson, em 1941. Aps a Segunda Grande Guerra, o desabastecimento afetou - tambm - a Indstria txtil da poca, ainda baseada em fibras como algodo, linho, l, entre outras.Assim, as pesquisas que levaram produo em larga escala do polister comearam logo aps a Segunda Grande Guerra nos EUA e Europa e baseavam-se nas aplicaes txteis. A idia era criar alternativas viveis para as fibras at ento usadas, cujos campos estavam destrudos pela guerra. O polister apresentou-se como um excelente substituto para o algodo funo que cumpre muito bem at hoje, inclusive a partir das garrafas recicladas.O PET continuou a ser desenvolvido e novas aplicaes foram surgindo. Sua resistncia mecnica foi comprovada quando o polister passou a ser utilizado na indstria de pneus, em 1962.As primeiras embalagens de PET surgiram nos Estados Unidos e logo aps na Europa no incio dos anos 70.
O PET chegou ao Brasil em 1988 e seguiu uma trajetria semelhante ao resto do mundo, sendo utilizado primeiramente na indstria txtil. Apenas a partir de 1993 passou a ter forte expresso no mercado de embalagens, notadamente para os refrigerantes. Atualmente o PET est presente nos mais diversos produtos.

Resina PET - FabricaoProduo da Resina PETO Poli (Etileno Tereftalato), conhecido pela sigla em ingls PET, classificado quimicamente como um polmero polister termoplstico.O PET produzido industrialmente por esterificaodireta do cido tereftlico purificado (PTA) com monoetileno glicol (MEG). Ouseja, esses dois elementos (PTA e MEG) so misturados, formando uma pasta que, durante o processo de fabricao, reagiro entre si, passando por cristalizao e formando o PET como conhecemos: gros brancos e opacos.

A resina PET para embalagens rgidas caracterizada por possuir uma viscosidade intrnseca (VI) maior do que a do PET para aplicaes de filmes e fibras. A viscosidade intrnseca, comumente expressa em dl/g, diretamente proporcional ao peso molecular.
A resina PET produzidas em duas fases:

1-O PET amorfo obtido pela polimerizao no estado lquido com VI em torno de 0,6.

Nesta etapa formado o bis-2-hidroxietil-tereftalato (BHET), tambm chamado demonmero da polimerizao. Nesta operao forma-se gua, que retirada continuamente do meio.

O monmero ento transferido para a polimerizao, onde, sob alto vcuo, ocorre a policondensao lquida.
Nesta operao, o glicol eliminado da reao com o aumento da VI do polmero(reao 2).
Neste ponto, o polmero amorfo retirado do polimerizador, resfriado, solidificado, cortado e ento armazenado.
2-Na ps-condensao no estadoslido a resina PET amorfa - obtida na primeira fase de fabricao - cristalizada e polimerizada continuamente (reao 3). Nesse processo, a VI do polmero aumentada tipicamente a 0,8dl/g.A resina ento embalada, estando pronta para ser comercializada.

CARACTERSTICAS DO PET

Peso Molecular:- A propriedade mais significativa do PET. O peso um indicativo do nmero mdio de unidades de repetio PET individuais que so agrupadas para formar uma corrente molecular nica.

Viscosidade intrnseca do PET:- o modo pelo qual podemos definir oseu peso molecular corretamenteA Morfologia do PETA morfologia dos polmeros envolve o arranjo, o formato, o tamanho e o efeito do cristal no polmero slido. Esta morfologia importante pelo seu efeito nas propriedades finais do polmero slido.

Os polmeros podem ser:

- Amorfos: so aqueles que no possuem capacidade de cristalizar, sendo amorfo sem qualquer condio ou histria trmica.
- Semicristalinos: geralmente chamados de polmeros cristalinos, so polmeros formados por regies amorfas e regies cristalinas. A regio amorfa aquela caracterizada por completa desordem de molculas, ao contrrio das regies cristalinas, em que segmentos de cadeias moleculares esto estendidas, arranjadas de uma maneira ordenada, formando um empacotamento regular chamado cristalito. Normalmente, os polmeros nunca so 100% cristalinos. O PET enquadra-se na categoria dos polmeros semi-cristalinos.

O modelo tradicional usado para visualizar a morfologia e explicar as propriedades dos polmeros semi cristalinos a Micela Franjada.Em determinados trechos, os segmentos de cadeias moleculares esto perfeitamente ordenados, formando as regies cristalinas e em outros segmentos dessas mesmas molculas esto desordenados, correspondendo s regies amorfas. A molcula , portanto, muito maior do que o comprimento do cristalito.

As propriedades do PET dependem:

- Da frao das regies cristalinas (grau de cristalizao)
- Tipo e tamanho dos cristais
- Orientao das cadeias moleculares e dos cristais.

A morfologia do PET depende das condies do processamento. O PET completamente amorfo ou com baixo grau de cristalizao obtido aps rpido resfriamento do polmero fundido, tal como acontece com o extrudado do reator de polimerizao e com a pr-formas injetadas.
O PET amorfo obtido um slido transparente com baixas propriedades fsicas (baixa barreira a gases) e mecnicas (baixa resistncia mecnica e baixo mdulode elasticidade).

A morfologia do PET semi cristalino varia conforme o processo de obteno, existindo basicamente duas cristalizaes bem distintas:

- Cristalizao trmica, e
- Cristalizao induzida por tenso.

A cristalizao trmica realizada por resfriamento lento do PET fundido ou por aquecimento formando cristais de estrutura esferultica. A cristalizao esferultica resulta em um slido branco, opaco, frgil, com maior resistncia trmica e mecnica do que o PET amorfo.

Devido o maior empacotamento das molculas, a cristalizao aumenta a densidade e reduz o volume do slido obtido.Caractersticas finais do produtoA resina PET um dos mais recentes materiais para embalagem. Embora seja largamente utilizada em todo o mundo para a fabricao de embalagens, notadamente garrafas para bebidas carbonatadas (refrigerantes, guas com gs, cervejas, etc), tem vrias outras utilidades, sendo encontrada em diversos segmentos de mercado.O alto desempenho em resistncia mecnica, brilho e transparncia, faz desse termoplstico o preferido de muitos setores.A leveza do PET permite produzir garrafas e frascos de alta capacidade volumtrica, com perfeita manuteno da segurana em todas as etapas (envase, empacotamento, distribuio, utilizao final pelo consumidor).Os benefcios ambientais proporcionados pelas embalagens de PET no pr-consumo so:- Reduo do desperdcio de produtos e embalagens - j que no se quebram mesmo aps quedas considerveis;- Extrema reduo nas emisses durante o transporte;- Economia de gua no envase de refrigerantes e outras bebidas, por dispensar a lavagem de cascos vazios como ilustrao, so necessrios 6 litros de gua para cada litro de refrigerante produzido em sistemas de embalagens retornveis, enquanto o sistema que utiliza as garrafas reciclveis de PET precisam de apenas 2 litros.

No ps-consumo, a indstria do PET trabalha incessantemente para desenvolver aplicaes para o PET reciclado. Esse trabalho reflete-se no ndice brasileiro de reciclagem de PET, um dos maiores do mundo, e na vasta gama de produtos que utilizam o PET reciclado, sendo encontrveis no dia-a-dia das pessoas comuns inmeros itens como bancos de nibus, carpetes de carros, vassouras, cordas,roupas, aparelhos de telefone celular, novas embalagens entre muitos outros.

http://pt.wikipedia.org/wiki/PET_(pl%C3%A1stico)

Politereftalato de etileno, ouPET, umpolmerotermoplstico, desenvolvido por dois qumicosbritnicosWhinfieldeDicksonem1941, formado pela reao entre ocido tereftlicoe oetileno glicol, originando umpolmero, termoplstico. Utiliza-se principalmente na forma de fibras para tecelagem e de embalagens para bebidas.Possui propriedades termoplsticas, isto , pode ser reprocessado diversas vezes pelo mesmo ou por outro processo de transformao. Quando aquecidos a temperaturas adequadas, esses plsticos amolecem, fundem e podem ser novamente moldados.As garrafas produzidas com este polmero s comearam a ser fabricadas nadcada de 70, aps cuidadosa reviso dos aspectos de segurana e meio ambiente.No comeo dosanos 80, osEstados Unidose oCanadiniciaram a coleta dessas garrafas, reciclando-as inicialmente para fazer enchimento de almofadas. Com a melhoria da qualidade do PET reciclado, surgiram aplicaes importantes, como tecidos, lminas e garrafas para produtos no alimentcios.Mais tarde nadcada de 90, o governo americano autorizou o uso destes material reciclado em embalagens de alimentos.Reciclagem

Uma garrafa PET demora no meio ambiente cerca de 400 anos para se degradar.Pode ser reciclado, pelo processo de termoreao, ou a quente, aonde a determinada temperatura, o polmero fica lquido, podendo ento ser moldado, extrusado, comprimido ou em outra forma.As garrafas produzidas com este polmero podem permanecer na natureza por at 800 anos.No comeo dadcada de 1980, osEstados UnidoseCanadiniciaram a coleta dessas garrafas, reciclando-as inicialmente para fazer enchimento de almofadas.Com a melhoria da qualidade do PET reciclado, surgiram aplicaes importantes, como tecidos, lminas e garrafas para produtos no alimentcios.Mais tarde nadcada de 1990, o governo norte americano autorizou o uso destes materiais reciclados em embalagens de alimentos.A produo cresceu mais, a reciclagem no acompanhou a produo, gerando uma invaso de garrafas de todos os tamanhos e formatos, hoje a produo de pet avanou e um dos maiores viles do meio ambiente, poluindo matas,riosecrregos[3].ContaminantesOs principaiscontaminantesdo PET reciclado so os adesivosplsticosA base ou ("base cup") - a famosa base de alguns refrigerantes dePolipropileno. A maioria dos processos de lavagens no impede que traos destes produtos indesejveis permaneam no floco de PET.A cola age como catalisador dedegradao hidrolticaquando o material submetido alta temperatura no processo deextruso, alm de escurecer e endurecer o reciclado. O mesmo pode ocorrer com opolicloreto de vinilo(PVC), que compe outros tipos de garrafas e no pode misturar-se com a sucata de PET, pois o PVC reage com o PET, transformando-o em outra substncia.Oalumnioexistente em algumas tampas s tolerado com teor de at 50 partes por milho no reciclado.SelecoA seleco e pr-processamento da sucata muito importante para a garantia de qualidade do reciclado. A seleco pode ser feita pelo smbolo que identifica o material ou pela cor (cristal, mbar ou verde). A separao pode seguir processos manuais ou mecnicos, como sensores pticos.No pr-processamento, aps a prensagem, preciso retirar os contaminantes, separando-os por diferena de densidade em fluxo de gua (levigao) ou ar. Alm do rtulo (polietileno de alta densidade), devem ser retirados da sucata os resduos de refrigerantes e demais detritos, por meio de processos de lavagem.Os diferentes tipos de garrafas tambm podem ser um problema na reciclagem. As garrafas que so usadas para envase de bebidas carbonatadas, precisam de um ndice de viscosidade maior que o de uma garrafa de gua, por exemplo. Dependendo da aplicao da resina reciclada, a mistura dos dois tipos de garrafas pode dar um efeito complicador no futuro processamento.Vantagens da ReciclagemReduo do volume de lixo nos aterros sanitrios e melhoria nos processos de decomposio de matrias orgnicas nos mesmos. O PET acaba por prejudicar a decomposio pois impermeabiliza certas camadas de lixo, no deixando circularem gases e lquidos.

Embalagens plsticas depositadas ematerro sanitrio.Economia depetrleopois o plstico um derivado.

Economia de energia na produo de novo plstico.

Gerao de renda e empregos.

Reduo dos preos para produtos que tm como base materiais reciclados.

No caso do PET de 2 litros, a relao entre o peso da garrafa (cerca de 54g) e o contedo uma das mais favorveis entre os descartveis. Por esse motivo torna-se rentvel sua reciclagem.

O material no pode ser transformado emadubo. Plstico e derivados no podem ser usados como adubo, pois no hbactriana natureza capaz de degradar rapidamente o plstico.

altamente combustvel, com valor de cerca de 20Megajoules/quilo , e libera gases residuais comomonxidoedixido de carbono,acetaldedo,benzoato de vinilaecido benzico. Esses gases podem ser usados na indstria qumica.

muito difcil a sua degradao em aterros sanitrios.

Produo de PET no Brasil para garrafas

Uma garrafa PET derefrigerante.Em toneladas1994 - 80.000

1995 - 120.000

1996 - 150.000

1997 - 185.700

1998 - 223.600

1999 - 244.800

2000 - 255.100

2001 - 270.000

2002 - 300.000

2003 - 330.000

2004 - 360.000

2005 - 374.000

2006 - 402.000

2007 - 407.000

2008 - 469.700

Reciclagem de PET no Brasil(fonte ABIPET)ANO - RECICLAGEM ps-consumo|ndice1994 - 13.000 ton | 18,80%

1995 - 18.000 ton | 25,40%

1996 - 22.000 ton | 21,00%

1997 - 30.000 ton | 16,20%

1998 - 40.000 ton | 17,90%

1999 - 50.000 ton | 20,42%

2000 - 67.000 ton | 26,27%

2001 - 89.000 ton | 32,90%

2002 - 105.000 ton | 35,00%

2003 - 141.500 ton | 43,00%

2004 - 167.000 ton | 47,00%

2005 - 174.000 ton | 47,00%

2006 - 194.000 ton | 51,30%

Refernciasab(emingls) J. G. Speight, Norbert Adolph Lange,Lange's handbook of chemistry, McGraw-Hill, 2005, 1610{{{1}}}Predefinio:Abrviation, 1623Predefinio:Abreviao discretaISBN 0071432205,Predefinio:P.2.807 et 2.758Predefinio:COinS bibliographique

abcRecord ofPolyethylenterephthalatin the GESTIS Substance Database from theBGIA

Garrafas pet e ecologia

Politereftalato de etileno
Alerta sobre risco sade

Nome IUPACpoly(ethylene terephthalate)

Identificadores

Nmero CAS25038-59-9

Propriedades

Densidade1,3 gcm3(20C)[2]

Ponto de fuso> 250C[2]

Solubilidadeemguapraticamente insolvel[2]

Condutividade trmica0.15 W m-1K-1[1]

ndice de refraco(nD)20= 1.57 - 1.58[1]

Compostos relacionados

PolmerosrelacionadosPolinaftalato de etileno(PEN, formado por cido naftaleno dicarboxlico e etilenoglicol)
Politereftalado de trimetileno(PTT, formado por cido tereftlico e propano-1,3-diol)
`Politereftalato de butileno(PBT, formado por cido tereftlico e butano-1,4-diol)

Compostos relacionadoscido tereftlicoeEtilenoglicol(monmeros)

Excepto onde denotado, os dados referem-se a
materiais sobcondies PTN
Referncias e avisos gerais sobre esta caixa.
Alerta sobre risco sade.

http://en.wikipedia.org/wiki/Polyethylene_terephthalate

Polyethylene terephthalate

From Wikipedia, the free encyclopedia

Polyethylene terephthalate(sometimes written poly(ethylene terephthalate)), commonly abbreviatedPET,PETE, or the obsolete PETP or PET-P, is athermoplasticpolymerresin of thepolyesterfamily and is used insynthetic fibers; beverage, food and other liquidcontainers; thermoforming applications; and engineering resins often in combination with glass fiber.Depending on its processing and thermal history, polyethylene terephthalate may exist both as an amorphous (transparent) and as asemi-crystalline polymer. The semicrystalline material might appear transparent (particle size < 500nm) or opaque and white (particle size up to a few microns) depending on its crystal structure and particle size. Its monomer (bis--hydroxyterephthalate) can be synthesized by theesterificationreaction betweenterephthalic acidandethylene glycolwith water as a byproduct, or bytransesterificationreaction betweenethylene glycolanddimethyl terephthalatewithmethanolas a byproduct. Polymerization is through apolycondensationreaction of the monomers (done immediately after esterification/transesterification) with ethylene glycol as the byproduct (the ethylene glycol is directly recycled in production).The majority of the world's PET production is for synthetic fibers (in excess of 60%) with bottle production accounting for around 30% of global demand. In discussing textile applications, PET is generally referred to as simply "polyester" while "PET" is used most often to refer to packaging applications. The polyester industry makes up about 18% of world polymer production and is third afterpolyethylene(PE) andpolypropylene(PP).PET consists ofpolymerizedunits of the monomerethyleneterephthalate, with repeating C10H8O4units. PET is commonly recycled, and has the number "1" as itsrecycling symbol.UsesPET can be semi-rigid to rigid, depending on its thickness, and it is very lightweight. It makes a good gas and fair moisture barrier, as well as a good barrier toalcohol(requires additional "barrier" treatment) andsolvents. It is strong andimpact-resistant. It is naturally colorless with a high transparency.Plastic bottlesmade from PET are excellent barrier materials and are widely used forsoft drinks(seecarbonation). For certain specialty bottles, PET sandwiches an additionalpolyvinyl alcoholto further reduce itsoxygenpermeability.Biaxially oriented PETfilm (often known by one of its trade names, "Mylar") can bealuminizedbyevaporatingathin filmof metal onto it to reduce its permeability, and to make it reflective and opaque (MPET). These properties are useful in many applications, including flexible foodpackagingandthermal insulation, such as "space blankets". Because of its high mechanical strength, PET film is often used in tape applications, such as the carrier formagnetic tapeor backing forpressure sensitive adhesive tapes.Non-oriented PET sheet can bethermoformedto make packaging trays andblisters. If crystallizable PET is used, the trays can be used forfrozen dinners, since they withstand both freezing and oven baking temperatures.When filled withglassparticlesorfibers, it becomes significantlystifferand more durable. This glass-filled plastic, in a semi-crystalline formulation, is sold under the tradenameRynite,Arnite,Hostadur, andCrastin.1-PETEWhile most thermoplastics can, in principle, be recycled,PET bottle recyclingis more practical than many other plastic applications. The primary reason is that plastic carbonated soft drink bottles andwater bottlesare almost exclusively PET. PET has aresin identification codeof 1. One of the uses for a recycled PET bottle is for the manufacture ofpolar fleecematerial. Among its many uses, companies such asEnglish Retreadsuse the PET material to line their products. It can also make fiber for polyester products.Because of the recyclability of PET and the relative abundance of post-consumer waste in the form of bottles, PET is rapidly gaining market share as a carpet fiber.Mohawk Industriesreleased everSTRAND in 1999, a 100% post-consumer recycled content PET fiber. Since that time, more than 17 billion bottles have been recycled into carpet fiber.[4]Pharr Yarns, a supplier to numerous carpet manufacturers including Looptex, Dobbs Mills, and Berkshire Flooring,[5]produces a BCF (bulk continuous filament) PET carpet fiber containing a minimum of 25% post-consumer recycled content.PET, as with many plastics, is also an excellent candidate for thermal disposal (incineration), as it is composed of carbon, hydrogen, and oxygen, with only trace amounts of catalyst elements (but no sulfur). PET has the energy content of soft coal.PET was patented in 1941 by the Calico Printers' Association ofManchester. The PET bottle was patented in 1973 byNathaniel Wyeth.[6Intrinsic viscosityOne of the most important characteristics of PET is referred to asintrinsic viscosity(IV)[7]The intrinsic viscosity of the material, measured indecilitersper gram (d/g) is dependent upon the length of its polymer chains. The longer the polymer chains, the more entanglements between chains and therefore the higher the viscosity. The average chain length of a particular batch of resin can be controlled duringpolycondensation.The intrinsic viscosity range of PET[8]Fibergrade0.40 0.70 d/g Textile0.72 0.98 d/g Technical,tirecordFilmgrade0.60 0.70 d/gBoPET(biaxially oriented PET film)0.70 1.00 d/gSheetgrade forthermoformingBottlegrade0.70 0.78 d/gWaterbottles (flat)0.78 0.85 d/g Carbonatedsoft drinkgradeMonofilament,engineering plastic1.00 2.00 d/gDryingPET ishygroscopic, meaning that it naturally absorbs water from its surroundings. However, when this 'damp' PET is then heated, the waterhydrolyzesthe PET, decreasing its resilience. This means that before the resin can be processed in a molding machine, as much moisture as possible must be removed from the resin. This is achieved through the use of adesiccantor dryers before the PET is fed into the processing equipment.Inside the dryer, hot dry air is pumped into the bottom of the hopper containing the resin so that it flows up through the pellets, removing moisture on its way. The hot wet air leaves the top of the hopper and is first run through an after-cooler, because it is easier to remove moisture from cold air than hot air. The resulting cool wet air is then passed through adesiccantbed. Finally the cool dry air leaving the desiccant bed is re-heated in a process heater and sent back through the same processes in a closed loop. Typically, residual moisture levels in the resin must be less than 5 parts per million (parts of water per million parts of resin, by weight) before processing. Dryer residence time should not be shorter than about four hours. This is because drying the material in less than 4 hours would require a temperature above 160 C, at which levelhydrolysiswould begin inside the pellets before they could be dried out.PET can also be dried in compressed air resin dryers. Compressed air dryers do not reuse drying air. Dry, heated compressed air is circulated through the PET pellets as in the desiccant dryer, then released to the atmosphere.CopolymersIn addition to pure (homopolymer) PET, PET modified bycopolymerizationis also available.In some cases, the modified properties of copolymer are more desirable for a particular application. For example,cyclohexane dimethanol(CHDM) can be added to the polymer backbone in place ofethylene glycol. Since this building block is much larger (6 additional carbon atoms) than the ethylene glycol unit it replaces, it does not fit in with the neighboring chains the way an ethylene glycol unit would. This interferes with crystallization and lowers the polymer's melting temperature. Such PET is generally known as PETG (Eastman Chemical and SK Chemicals are the only two manufacturers). PETG is a clear amorphous thermoplastic that can be injection molded or sheet extruded. It can be colored during processing.Another common modifier isisophthalic acid, replacing some of the 1,4-(para-) linkedterephthalateunits. The 1,2-(ortho-) or 1,3-(meta-) linkage produces an angle in the chain, which also disturbs crystallinity.Such copolymers are advantageous for certain molding applications, such asthermoforming, which is used for example to make tray or blister packaging from co-PET film, or amorphous PET sheet (A-PET) orPETG sheet. On the other hand, crystallization is important in other applications where mechanical and dimensional stability are important, such asseat belts. For PET bottles, the use of small amounts of isophthalic acid, CHDM, DEG or other comonomers can be useful: if only small amounts of comonomers are used, crystallization is slowed but not prevented entirely. As a result, bottles are obtainable viastretch blow molding("SBM"), which are both clear and crystalline enough to be an adequate barrier to aromas and even gases, such as carbon dioxide in carbonated beverages.CrystalsCrystallization of polymersoccurs when polymer chains fold up on themselves in a repeating, symmetrical pattern. Long polymer chains tend to become entangled on themselves, which prevents full crystallization in all but the most carefully controlled circumstances. PET is no exception to this rule; About 60% crystallization is the upper limit for commercial products, with the exception of polyester fibers. Besides, about 60% crystalline polymer about 40% of the polymer chains remaining amorphous. Therefore PET is commonly called asemi-crystalline polymer.PET in its natural state is a semi-crystalline resin. Clear products can be produced by rapidly cooling molten polymer below Tgglass transition temperatureto form anamorphous solid. Likeglass, amorphous PET forms when its molecules are not given enough time to arrange themselves in an orderly, crystalline fashion as the melt is cooled. At room temperature the molecules are frozen in place, but if enough heat energy is put back into them by heating above Tg, they begin to move again, allowing crystals tonucleateand grow. This procedure is known as solid-statecrystallization.Like most materials, PET tends to producespherulitescontaining many smallcrystalliteswhen crystallized from an amorphous solid, rather than forming one large single crystal. Light tends to scatter as it crosses the boundaries between crystallites and the amorphous regions between them. This scattering means that crystalline PET is opaque and white in most cases.Fiber drawingis among the few industrial processes that produce a nearly single-crystal product.DegradationPET is subject to various types of degradations during processing. The main degradations that can occur are hydrolytic, thermal and, probably most important, thermal oxidation. When PET degrades, several things happen: discoloration, chain scissions resulting in reduced molecular weight, formation ofacetaldehydeandcross-links("gel" or "fish-eye" formation). Discoloration is due to the formation of various chromophoric systems following prolonged thermal treatment at elevated temperatures. This becomes a problem when the optical requirements of the polymer are very high, such as in packaging applications. The thermal and thermooxidative degradation results in poor processibility characteristics and performance of the material.One way to alleviate this is to use acopolymer. Comonomers such as CHDM orisophthalic acidlower the melting temperature and reduce the degree of crystallinity of PET (especially important when the material is used for bottle manufacturing). Thus the resin can be plastically formed at lower temperatures and/or with lower force. This helps to prevent degradation, reducing the acetaldehyde content of the finished product to an acceptable (that is, unnoticeable) level. Seecopolymers, above. Other ways to improve the stability of the polymer is by using stabilizers, mainly antioxidants such as phosphites. Recently, molecular level stabilization of the material using nanostructured chemicals has also been considered.AcetaldehydeAcetaldehyde is normally a colorless, volatile substance with a fruity smell. It forms naturally in fruit, but it can cause an off-taste inbottled water. Acetaldehyde forms in PET through the "abuse" of the material. High temperatures (PET decomposes above 300 C or 570 F), high pressures, extruder speeds (excessive shear flow raises temperature) and long barrel residence times all contribute to the production of acetaldehyde. When acetaldehyde is produced, some of it remains dissolved in the walls of a container and thendiffusesinto the product stored inside, altering the taste and aroma. This is not such a problem for non-consumables (such as shampoo), for fruit juices (which already contain acetaldehyde), or for strong-tasting drinks likesoft drinks. For bottled water, however, low acetaldehyde content is quite important, because if nothing masks the aroma, even extremely low concentrations (1020 parts per billion in the water) of acetaldehyde can produce an off-taste.AntimonyAntimony(Sb) is acatalystthat is often used asantimony trioxide(Sb2O3) or antimony triacetate in the production of PET. After manufacturing a detectable amount of antimony can be found on the surface of the product. This residue can be removed with washing. Antimony also remains in the material itself and can thus migrate out into food and drinks. Exposing PET to boiling or microwaving can increase the levels of antimony significantly, possibly above USEPA maximum contamination levels.[9]The drinking water limit in the USA for antimony is 6 parts per billion.[10]Although antimony trioxide is of low toxicity when taken orally,[11]its presence is still of concern. The Swiss Federal Office of Public Health investigated the amount of antimony migration, comparing waters bottled in PET and glass: the antimony concentrations of the water in PET bottles were higher, but still well below the allowed maximumconcentration. The Swiss Federal Office of Public Health concluded that small amounts of antimony migrate from the PET into bottled water, but that the health risk of the resulting low concentrations is negligible (1% of the "tolerable daily intake" determined by theWHO). A later (2006) but more widely publicized study found similar amounts of antimony in water in PET bottles.[12]The WHO has published a risk assessment for antimony in drinking water.[11]Fruit juiceconcentrates (for which no guidelines are established), however, that were produced and bottled in PET in the UK were found to contain up to 44.7g/L of antimony, well above the EU limits fortap waterof 5g/L.[13][14Possible toxicity of PETCommentary published inEnvironmental Health Perspectivesin April 2010 suggested that PET might yieldendocrine disruptorsunder conditions of common use and recommended[15]research on this topic. Proposed mechanisms include leaching ofphthalatesas well as leaching of antimony. Other authors (FRANZ and WELLE) published evidence based on mathematical modeling, indicating that it is quite unlikely that PET yields endocrine disruptors in mineral water.[16]Bottle processing equipmentThere are two basic molding methods for PET bottles, one-step and two-step. In two-step molding, two separate machines are used. The first machine injection molds thepreform, which resembles a test tube, with the bottle-cap threads already molded into place. The body of the tube is significantly thicker, as it will be inflated into its final shape in the second step usingstretch blow molding.In the second step, the preforms are heated rapidly and then inflated against a two-part mold to form them into the final shape of the bottle. Preforms (uninflated bottles) are now also used as containers for candy, and by someRed Crosschapters to distribute to homeowners to store medical history for emergency responders.[17]In one-step machines, the entire process from raw material to finished container is conducted within one machine, making it especially suitable for molding non-standard shapes (custom molding), includingjars, flat oval, flask shapes etc. Its greatest merit is the reduction in space, product handling and energy, and far higher visual quality than can be achieved by the two-step system.Polyester recycling industryWhenrecyclingpolyethylene terephthalate or PET or polyester, two ways generally have to be differentiated:The chemical recycling back to the initial raw materials purifiedterephthalic acid(PTA) ordimethyl terephthalate(DMT) andethylene glycol(EG) where the polymer structure is destroyed completely, or in process intermediates like bis--hydroxyterephthalate

The mechanical recycling where the original polymer properties are being maintained or reconstituted.

Chemical recycling of PET will become cost-efficient only applying high capacity recycling lines of more than 50,000 tons/year. Such lines could only be seen, if at all, within the production sites of very large polyester producers. Several attempts of industrial magnitude to establish such chemical recycling plants have been made in the past but without resounding success. Even the promising chemical recycling in Japan has not become an industrial break through so far. The two reasons for this are: at first, the difficulty of consistent and continuous waste bottles sourcing in such a huge amount at one single site, and, at second, the steadily increased prices and price volatility of collected bottles. The prices of baled bottles increased for instance between the years 2000 and 2008 from about 50 Euro/ton to over 500 Euro/ton in 2008.Mechanical recycling or direct circulation of PET in the polymeric state is operated in most diverse variants today. These kinds of processes are typical of small and medium-sized industry. Cost-efficiency can already be achieved with plant capacities within a range of 5 000 20 000 tons/year. In this case, nearly all kinds of recycled-material feedback into the material circulation are possible today. These diverse recycling processes are being discussed hereafter in detail.Besides chemical contaminants anddegradationproducts generated during first processing and usage, mechanical impurities are representing the main part of quality depreciating impurities in the recycling stream. Recycled materials are increasingly introduced into manufacturing processes, which were originally designed for new materials only. Therefore, efficient sorting, separation and cleaning processes become most important for high quality recycled polyester.When talking about polyester recycling industry, we are concentrating mainly on recycling of PET bottles which are meanwhile used for all kinds of liquid packaging like water, carbonated soft drinks, juices, beer, sauces, detergents, household chemicals and so on. Bottles are easy to distinguish because of shape and consistency and separate from waste plastic streams either by automatic or hand sorting processes. The established polyester recycling industry consists of three major sections:PET bottle collection and waste separationwaste logistics

Production of clean bottle flakesflake production

Conversion of PET flakes to final productsflake processing

Intermediate product from the first section is baled bottle waste with a PET content greater than 90%. Most common trading form is the bale but also bricked or even loose, pre-cut bottles are common in the market. In the second section the collected bottles are converted to clean PET bottle flakes. This step can be more or less complex and complicated depending on required final flake quality. During third step PET bottle flakes are processed to any kind of products like film, bottles, fiber, filament, strapping or intermediates like pellets for further processing and engineering plastics.Besides this external (post-consumer) polyester bottle recycling, numbers of internal (pre-consumer) recycling processes exist, where the wasted polymer material does not exit the production site to the free market, and instead is reused in the same production circuit. In this way, fiber waste is directly reused to produce fiber, preform waste is directly reused to produce preforms, and film waste is directly reused to produce film.PET bottle recyclingMain article:PET bottle recycling[edit]Purification and decontaminationThe success of any recycling concept is hidden in the efficiency of purification and decontamination at the right place during processing and to the necessary or desired extent.Generally, the following applies: the sooner foreign substances are removed, in the process, and the more thoroughly this is done, the more efficient the process is.The highplasticizationtemperature of PET in the range of 280C is the reason why almost all common organic impurities such asPVC,PLA,polyolefin, chemical wood-pulp and paper fibers,polyvinyl acetate, melt adhesive, coloring agents,sugarandproteinresidues are transformed into colored degradation products which, in their turn, might release reactive degradation products additionally. Then, the number of defects in the polymer chain increases considerably. Naturally, the particle size distribution of impurities is very wide, the big particles of 601000mwhich are visible by naked eye and easy to filterrepresenting the lesser evil since their total surface is relatively small and the degradation speed is therefore lower. The influence of the microscopic particles, whichbecause they are manyincrease the frequency of defects in the polymer, is comparable bigger.The motto "What the eye does not see the heart cannot grieve over" is considered to be very important in many recycling processes. Therefore besides efficient sorting the removal of visible impurity particles by melt filtration processes is playing a particular part in this case.In general, one can say that the processes to make PET bottle flakes from collected bottles are as versatile as the different waste streams are different in their composition and quality. In view of technology there isn't just one way to do it. There are meanwhile many engineering companies which are offering flake production plants and components, and it is difficult to decide for one or other plant design. Nevertheless there are processes which are sharing most of these principles. Depending on composition and impurity level of input material, the general following process steps are applied.[18]Bale opening, briquette opening

Sorting and selection for different colors, foreign polymers especially PVC, foreign matter, removal of film, paper, glass, sand, soil, stones and metals

Pre-washing without cutting

Coarse cutting dry or combined to pre-washing

Removal of stones, glass and metal

Air sifting to remove film, paper and labels

Grinding, dry and / or wet

Removal of low-density polymers (cups) by density differences

Hot wash

Caustic wash

Caustic surface etching, maintaining intrinsic viscosity and decontamination

Rinsing

Clean water rinsing

Drying

Air sifting of flakes

Automatic flake sorting

Water circuit and water treatment technology

Flake quality control

[edit]Impurities and material defectsThe number of possible impurities and material defects which accumulate in the polymeric material is increasing permanentlywhen processing as well as when using polymerstaking into account a growing service life time, growing final applications and repeated recycling. As far as recycled PET bottles are concerned, the defects mentioned can be sorted in the following groups:Reactive polyester OH- or COOH- end groups are transformed into dead or non-reactive end groups, e.g. formation of vinyl ester end groups through dehydration or decarboxylation of terephthalate acid, reaction of the OH- or COOH- end groups with mono-functional degradation products like mono-carbonic acids or alcohols. Results are decreased reactivity during re-polycondensation or re-SSP and broadening the molecular weight distribution.

The end group proportion shifts toward the direction of the COOH end groups built up through a thermal and oxidative degradation. The results are decrease in reactivity, and increase in the acid autocatalytic decomposition during thermal treatment in presence of humidity.

Number of poly-functional macromolecules increases. Accumulation of gels and long-chain branching defects.

Number, concentration and variety of non polymer-identical organic and inorganic foreign substances are increasing. With every new thermal stress, the organic foreign substances will react by decomposition. This is causing the liberation of further degradation-supporting substances and coloring substances.

Hydroxide and peroxide groups build up at the surface of the products made of polyester in presence of air (oxygen) and humidity. This process is accelerated by ultraviolet light. During an ulterior treatment process, hydro peroxides are a source of oxygen radicals which are source of oxidative degradation. Destruction of hydro peroxides is to happen before the first thermal treatment or during plasticization and can be supported by suitable additives like antioxidants.

Taking into consideration the above-mentioned chemical defects and impurities, there is an ongoing modification of the following polymer characteristics during each recycling cycle, which are detectable by chemical and physical laboratory analysis.In particular:Increase of COOH end groups

Increase of color number b

Increase of haze (transparent products)

Increase of oligomer content

Reduction in filterability

Increase of by-products content such as acetaldehyde, formaldehyde

Increase of extractable foreign contaminants

Decrease in color L

Decrease ofintrinsic viscosityor dynamic viscosity

Decrease of crystallization temperature and increase of crystallization speed

Decrease of the mechanical properties like tensile strength, elongation at break orelastic modulus

Broadening of molecular weight distribution

The recycling of PET-bottles is meanwhile an industrial standard process which is offered by a wide variety of engineering companies.[19][edit]Processing examples for recycled polyesterRecycling processes with polyester are almost as varied as the manufacturing processes based on primary pellets or melt. Depending on purity of the recycled materials polyester can be used today in most of the polyester manufacturing processes as blend with virgin polymer or increasingly as 100% recycled polymer. Some exceptions like BOPET-film of low thickness, special applications like optical film or yarns through FDY-spinning at > 6000 m/min or microfilaments and micro-fibers are produced from virgin polyester only.[edit]Simple re-pelletizing of bottle flakesThis process consists in transforming bottle waste into flakes, by drying and crystallizing the flakes, by plasticizing and filtering, as well as by pelletizing. Product is an amorphous re-granulate of an intrinsic viscosity in the range of 0.550.7 d/g, depending on how complete pre-drying of PET flakes has been done.Special feature are: acetaldehyde and oligomers are contained in the pellets at lower level; the viscosity is reduced somehow, the pellets are amorphous and have to be crystallized and dried before further processing.Processing to:A-PET film forthermoforming,

Addition to PET virgin production,

BoPETpackaging film,

PET Bottleresinby SSP,

Carpet yarn,

Engineering plastic,

Filaments,

Non-woven,

Packaging stripes,

Staple fibre,

Choosing the re-pelletizing way means having an additional conversion process which is at the one side energy intensive, cost consuming and causes thermal destruction. At the other side the pelletizing step is providing the following advantages:Intensive melt filtration

Intermediate quality control

Modification by additives.

Product selection and separation by quality

Processing flexibility increased

Quality uniformization

[edit]Manufacture of PET-pellets for bottles (bottle to bottle) and A-PETThis process is, in principle, similar to the one described above; however, the pellets produced are directly (continuously or discontinuously) crystallized and then subjected to a solid-state polycondensation (SSP) in a tumbling drier or a vertical tube reactor. During this processing step, the corresponding intrinsic viscosity of 0.80 0.085 d/g is rebuild again and, at the same time, the acetaldehyde content is reduced to < 1 ppm.The fact that some machine manufacturers and line builders in Europe and USA make efforts to offer independent recycling processes, e.g. the so called bottle-to-bottle (B-2-B) process, such as URRC or BHLER, aims at generally furnishing proof of the "existence" of the required extraction residues and of the removal of model contaminants according to FDA applying the so called challenge test, which is necessary for the application of the treated polyester in the food sector. Besides this process approval it is nevertheless necessary that any user of such processes has to constantly check the FDA-limits for the raw materials manufactured by himself for his process.[edit]Direct conversion of bottle flakesIn order to save costs, one[who?]is working on the direct use of the PET-flakes, from the treatment of used bottles, with a view to manufacturing an increasing number of polyester intermediates. For the adjustment of the necessary viscosity, besides an efficient drying of the flakes, it is possibly necessary to also reconstitute the viscosity through polycondensation in the melt phase or solid-state polycondensation of the flakes. The latest PET flake conversion processes are applying twin screw extruders, multi-screw extruders or multi-rotation systems and coincidental vacuum degassing to remove moisture and avoid flake pre-drying. These processes allow the conversion of undried PET flakes without substantial viscosity decrease caused by hydrolysis.Looking at the consumption of PET bottle flakes, the main portion of about 70% is converted to fibers and filaments. When using directly secondary materials such as bottle flakes in spinning processes, there are a few processing principles to obtain.High speed spinning processes for the manufacture of POY normally need a viscosity of 0.620.64 d/g. Starting from bottle flakes, the viscosity can be set via the degree of drying. The additional use of TiO2is necessary for full dull or semi dull yarn. In order to protect the spinnerets, an efficient filtration of the melt is, in any case is necessary. For the time being the amount of POY made of 100% recycling polyester is rather low because this process requires high purity of spinning melt. Most of the time a blend of virgin and recycled pellets is used.Staple fibers are spun in an intrinsic viscosity range which rather lies somewhat lower and which should be between 0.58 and 0.62 d/g. In this case too, the required viscosity can be adjusted via drying or vacuum adjustment in case of vacuum extrusion. For adjusting the viscosity, however, an addition of chain length modifier like ethylene glycol or diethylene glycol can also be used.Spinning non-woven in the fine titer field for textile applications as well as heavy spinning non-woven as basic materials, e.g. for roof covers or in road building can be manufactured by spinning bottle flakes. The spinning viscosity is again within a range of 0.580.65 d/g.One field of increasing interest where recycled materials are used is the manufacture of high tenacity packaging stripes, and monofilaments. In both cases, the initial raw material is a mainly recycled material of higher intrinsic viscosity. High tenacity packaging stripes as well as monofilament are then manufactured in the melt spinning process.[edit]Recycling back to the initial raw materials[edit]Glycolysis and partial glycolysisThe polyester which has to be recycled is transformed into an oligomer by adding ethylene glycol or other glycols during thermal treatment. The aim and advantage of this way of processing is the possibility of separating the mechanical deposits directly and efficient through a progressive and stepwise filtration. The filtration fineness of the last filtration step has a decisive effect on the quality of the end product. Taking partial recycling with partialglycolysisas an example, it is to be demonstrated how bottle waste can successfully be recycled in a continuously operating polyester line which is manufacturing pellets for bottle applications.The task consists in feeding 1025% bottle flakes while maintaining the quality of the bottle pellets which are manufactured on the line. This aim is solved by degrading the PET bottle flakes already during their first plasticization which can be carried out in a single- or multi-screw extruder to an intrinsic viscosity of about 0.30 d/g by adding small quantities of ethylene glycol and by subjecting the low viscosity melt stream to an efficient filtration directly after plasticization. Furthermore, temperature is brought to the lowest possible limit. In addition, with this way of processing, the possibility of a chemical decomposition of the hydro peroxides is possible by adding a corresponding P-stabilizer directly when plasticizing. The destruction of the hydro peroxide groups is, with other processes, already carried out during the last step of flake treatment for instance by adding H3PO3.[20]The partially glycolyzed and finely filtered recycled material is continuously fed to the esterification or prepolycondensation reactor, the dosing quantities of the raw materials are being adjusted accordingly.The treatment of polyester waste through total glycolysis to convert the polyester to bis-beta hydroxy-terephthalate, which is vacuum distilled and can be used, instead of DMT or PTA, as a raw material for polyester manufacture, has been executed on an industrial scale in Japan as experimental production.[edit]HydrolysisRecycling processes, through hydrolysis of the PET to PTA and MEG, are operating under high pressures under supercritical conditions. In this case, PET-waste will be directly hydrolyzed applying for instance supercritical water steam. Purification of crude terephthalic acid will be carried out by re-crystallization inacetic acid/ water mixtures similar to PTA purification. Industrial-scale lines based on this chemistry have not been known to date.[edit]MethanolysisMethanolysis is the recycling process which has been practiced and tested on a large scale for many years in the past. In this case, polyester waste is transformed with methanol into DMT, under pressure and in presence of catalysts. After this an efficient filtration of the methanolysis product is applied. Finally the crude DMT is purified by vacuum distillation. The methanolysis is only rarely carried out in industry today because polyester production based on DMT shrunk tremendously and with this DMT producers disappeared step by step during the last decade.[21]

Notes^abcdefghA.K. van der Vegt & L.E. Govaert, Polymeren, van keten tot kunstof,ISBN 90-407-2388-5

^abJ. G. Speight, Norbert Adolph Lange (2005). McGraw-Hill. ed.Lange's handbook of chemistry(16 ed.). pp.2.8072.758.ISBN0071432205.

^abcRecord ofPolyethylenterephthalatin the GESTIS Substance Database from theIFA

^Carpet-inspectors-experts.com

^Simply Green Carpet A Berkshire Flooring Brand

^Nathaniel C. Wyeth Biaxially Oriented Poly(ethylene terephthalate) BottleUS patent 3733309, Issued May 1973

^Ulrich K. Thiele; Polyester Bottle Resins, Production, Processing, Properties and Recycling, pp. 85 ff, Heidelberg, Germany,2007,ISBN 978-3-9807497-4-9

^Stoyko Fakirov; Handbook of Thermoplastic Polyesters, Chapter 7 by V.B. Gupta, Z. Bashir, p. 320, ISBN 978352730113

^Cheng, X; Shi, H; Adams, CD; Ma, Y (2010). "Assessment of metal contaminations leaching out from recycling plastic bottles upon treatments.".Environmental science and pollution research international17(7): 132330.doi:10.1007/s11356-010-0312-4.PMID20309737.

^Consumer Factsheet on: Antimony, EPA

^abGuidelines for drinking water quality

^Shotyk, William; Krachler, Michael; Chen, Bin (2006). "Contamination of Canadian and European bottled waters with antimony from PET containers" (free access).Journal of Environmental Monitoring8(2): 28892.doi:10.1039/b517844b.PMID16470261.

^Hansen, Claus; Tsirigotaki, Alexandra; Bak, Sren Alex; Pergantis, Spiros A.; Strup, Stefan; Gammelgaard, Bente; Hansen, Helle Rsz (17 February 2010). "Elevated antimony concentrations in commercial juices".Journal of Environmental Monitoring12(4): 8224.doi:10.1039/b926551a.PMID20383361.

^Borland, Sophie (1. March 2010)."Fruit juice cancer warning as scientists find harmful chemical in 16 drinks".Daily Mail.

^Sax, Leonard (Apr 2010). "Polyethylene Terephthalate May Yield Endocrine Disruptors".Environmental Health Perspectives118(4).doi:10.1289.ehp.0901253.

^Franz, Roland and Welle, Frank (2009)."Can Migration of Endocrine Disruptors from Plastic Bottles be the Cause of Estrogenic Burden Recently Determined in Bottled Mineral Water?".Deutsche Lebensmittel-Rundschau105(5): 315.

^Red Cross "Vial of Life" using preform

^PET-Recycling Forum;"Current Technological Trends in Polyester Recycling; 9th International Polyester Recycling Forum Washington, 2006; Sao Paulo;ISBN 3-00-019765-6

^Ulrich K. Thiele,Polyester Bottle Resins Production, Processing, Properties and Recycling, pp. 259 ff, PETplanet Publisher GmbH, Heidelberg, 2007, GermanyISBN 978-3-9807497-4-9

^DE-Patent DE19503055

^Stoyko Fakirov; "Handbook of Thermoplastic Polyesters", pp. 1223 ff; Wiley-VCH, Weinheim, 2002,ISBN 3-527-30113-5

Polyethylene terephthalate

IUPAC namepoly(ethylene terephthalate)

Identifiers

CAS number25038-59-9

Properties

Molecular formula(C10H8O4)n[1]

Density1.4 g/cm3(20C),[3]amorphous: 1.370 g/cm3,[1]crystalline: 1.455 g/cm3[1]

Melting point> 250C,[3]260C[1]

Solubilityinwaterpractically insoluble[3]

Thermal conductivity0.15 W m1K1,[2]0.24 W m1K1[1]

Refractive index(nD)1.571.58,[2]1.5750[1]

Thermochemistry

Specific heat capacity,C1.0 kJ/(kgK)[1]

Related compounds

RelatedMonomersTerephthalic acid
Ethyleneglycol

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Except where noted otherwise, data are given for materials in theirstandard state (at 25C, 100kPa)

Infobox references

PET

Young's modulus(E)28003100MPa

Tensile strength(t)5575 MPa

Elastic limit50150%

notch test3.6kJ/m2

Glass temperature75C

VicatB170 C

linear expansion coefficient ()7105/K

Water absorption(ASTM)0.16

Source[1

http://es.wikipedia.org/wiki/Politereftalato_de_etilenoTereftalato de polietilenoElTereftalato de polietileno,politereftalato de etileno,polietilentereftalatoopolietileno Tereftalato(ms conocido por sus siglas en ingls PET,Polyethylene Terephtalate) es un tipo deplsticomuy usado en envases debebidasytextiles. Algunas compaas manufacturan el PET y otros polisteres bajo diferentes marcas comerciales, por ejemplo, en los Estados Unidos y Gran Bretaa usan los nombres deMylaryMelinex.Qumicamente el PET es unpolmeroque se obtiene mediante unareaccin de policondensacinentre elcido tereftlicoy eletilenglicol. Pertenece al grupo de materialessintticosdenominadospolisteres.Es un polmerotermoplsticolineal, con un alto grado decristalinidad. Como todos los termoplsticos puede ser procesado medianteextrusin,inyeccin,inyeccin y soplado,soplado de preformaytermoconformado. Para evitar el crecimiento excesivo de las esferulitas y lamelas de cristales, este material debe ser rpidamente enfriado, con esto se logra una mayortransparencia, la razn de su transparencia al enfriarse rpido consiste en que los cristales no alcanzan a desarrollarse completamente y su tamao no interfiere (scattering en ingls) con la trayectoria de lalongitud de ondade laluz visible, de acuerdo con lateora cuntica.PropiedadesPresenta como caractersticas ms relevantes:Alta transparencia, aunque admite cargas de colorantes.

Alta resistencia al desgaste y corrosin.

Muy buen coeficiente de deslizamiento.

Buena resistencia qumica y trmica.

Muy buena barrera a CO2, aceptable barrera a O2y humedad.

Compatible con otros materiales barrera que mejoran en su conjunto la calidad barrera de los envases y por lo tanto permiten su uso en mercados especficos.

Reciclable, aunque tiende a disminuir su viscosidad con lahistoria trmica.

Aprobado para su uso en productos que deban estar en contacto con productos alimentarios.

Las propiedades fsicas del PET y su capacidad para cumplir diversas especificaciones tcnicas han sido las razones por las que el material haya alcanzado un desarrollo relevante en la produccin de fibras textiles y en la produccin de una gran diversidad de envases, especialmente en la produccin debotellas,bandejas, flejes ylminas.[editar]HistoriaFue producido por primera vez en1941por los cientficos britnicos Whinfield y Dickson, quienes lo patentaron como polmero para la fabricacin defibras. Se debe recordar que su pas estaba en plenaguerray exista una apremiante necesidad de buscar sustitutos para elalgodnproveniente deEgipto.A partir de1946se empez a utilizar industrialmente como fibra y su uso textil ha proseguido hasta el presente. En1952se comenz a emplear en forma de filme para envasar alimentos. Pero la aplicacin que le signific su principal mercado fue en envases rgidos, a partir de1976. Pudo abrirse camino gracias a su particular aptitud para la fabricacin de botellas para bebidas poco sensibles aloxgenocomo por ejemplo elagua mineraly los refrescos carbonatados. Desde principios de losaos 2000se utiliza tambin para el envasado decerveza.[editar]Aspectos positivos del uso de tereftalato de polietilenoComo algunos de los aspectos positivos que encontramos para el uso de este material, principalmente empleado en envases de productos destinados a la venta, podemos destacar:Que acta como barrera para los gases, como el CO2, humedad y el O2

Es transparente y cristalino, aunque admite algunos colorantes

Irrompible

Liviano

Impermeable

No txico, cualidad necesaria para este tipo de productos que estn al alcance del pblico en general (Aprobado para su uso en productos que deban estar en contacto con productos alimentarios)

Inerte (al contenido)

Resistencia esfuerzos permanentes y al desgaste, ya que presenta alta rigidez y dureza

Alta resistencia qumica y buenas propiedades trmicas, posee una gran indeformabilidad al calor

Totalmente reciclable

Superficie barnizable

Estabilidad a la intemperie

Alta resistencia al plegado y baja absorcin de humedad que lo hacen muy adecuado para la fabricacin de fibras

PET

Formula Molecular(C10H8O4)n

Densidadamorfa1,370 g/cm3

Densidadcristalina1,455 g/cm3

Mdulo de Young (E)(E)28003100MPa

Presin(t)5575 MPa

Lmite elstico50150%

notch test3,6kJ/m2

Glass temperature75 C

Punto de fusin260 C

VicatB170 C

Conductividad trmica0,24 W/(mK)

Coeficiente de dilatacin lineal ()7105/K

Calor especfico(c)1,0 kJ/(kgK)

Absorcin de agua(ASTM)0,16

ndice de refraccin1,5750

Coste0,51,25 /kg

Source: A.K. vam der Vegt & L.E. Govaert, Polymeren, van keten tot kunstof,ISBN 90-407-2388-5