Polyethylene terephthalate

[박대선]

Polyethylene terephthalate

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"PETE" redirects here. For other uses, see Pete (disambiguation).

Polyethylene terephthalateNamesIdentifiersPropertiesThermochemistryRelated compounds

IUPAC namepoly(ethylene terephthalate)
Systematic IUPAC namepoly(oxyethyleneoxyterephthaloyl)
Other namesTerylene (trademark); Dacron (trademark).
CAS Number	25038-59-9
Abbreviations	PET, PETE
ChEBI	CHEBI:53259
ChemSpider	None
ECHA InfoCard	100.121.858
UNII	5YSH70HE6K
CompTox Dashboard (EPA)	DTXSID10872790
Chemical formula	(C10H8O4)n[1]
Molar mass	10–50 kg/mol, varies
Density	1.38 g/cm3, 20 °C[2] 1.370 g/cm3,[1] amorphous 1.455 g/cm3,[1] single crystal
Melting point	> 250 °C (482 °F; 523 K)[2] 260 °C[1]
Boiling point	> 350 °C (662 °F; 623 K) (decomposes)
Solubility in water	Practically insoluble[2]
log P	0.94540[3]
Thermal conductivity	0.15[4] to 0.24 W/(m·K)[1]
Refractive index (nD)	1.57–1.58,[4] 1.5750[1]
Heat capacity (C)	1.0 kJ/(kg·K)[1]
Related Monomers	Terephthalic acid Ethylene glycol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).  verify (what is   ?) Infobox references

Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods, and thermoforming for manufacturing, and in combination with glass fibre for engineering resins.[5]

In 2016, annual production of PET was 56 million tons.[6] The biggest application is in fibres (in excess of 60%), with bottle production accounting for about 30% of global demand.[7] In the context of textile applications, PET is referred to by its common name, polyester, whereas the acronym PET is generally used in relation to packaging.[citation needed] Polyester makes up about 18% of world polymer production and is the fourth-most-produced polymer after polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC).[citation needed]

PET consists of repeating (C10H8O4) units. PET is commonly recycled, and has the digit 1 (♳) as its resin identification code (RIC). The National Association for PET Container Resources (NAPCOR) defines PET as: "Polyethylene terephthalate items referenced are derived from terephthalic acid (or dimethyl terephthalate) and mono ethylene glycol, wherein the sum of terephthalic acid (or dimethyl terephthalate) and mono ethylene glycol reacted constitutes at least 90 percent of the mass of monomer reacted to form the polymer, and must exhibit a melting peak temperature between 225°C and 255°C, as identified during the second thermal scan in procedure 10.1 in ASTM D3418, when heating the sample at a rate of 10°C/minute."[8]

Depending on its processing and thermal history, polyethylene terephthalate may exist both as an amorphous (transparent) and as a semi-crystalline polymer. The semicrystalline material might appear transparent (particle size less than 500 nm) or opaque and white (particle size up to a few micrometers) depending on its crystal structure and particle size.

One process for making PET uses bis(2-hydroxyethyl) terephthalate,[citation needed] which can be synthesized by the esterification reaction between terephthalic acid and ethylene glycol with water as a byproduct (this is also known as a condensation reaction), or by transesterification reaction between ethylene glycol and dimethyl terephthalate (DMT) with methanol as a byproduct. Polymerization is through a polycondensation reaction of the monomers (done immediately after esterification/transesterification) with water as the byproduct.[5]

Contents

• 1Uses
  • 1.1Textiles
  • 1.2Rigid packaging
  • 1.3Flexible packaging
  • 1.4Photovoltaic modules
  • 1.5Thermoplastic resins
  • 1.6Other applications
• 2History
• 3Physical properties
  • 3.1Absorption/scalping
  • 3.2Intrinsic viscosity
• 4Copolymers
• 5Production
  • 5.1Dimethyl terephthalate (DMT) process
  • 5.2Terephthalic acid (PTA) process
  • 5.3Bio-PET
  • 5.4Degradation
  • 5.5Biodegradation
• 6Environmental concerns
  • 6.1Resource depletion
  • 6.2End of life
• 7Safety
  • 7.1Antimony
• 8Bottle processing equipment
• 9Polyester recycling industry
  • 9.1PET bottle recycling
• 10See also
• 11References
• 12External links

Source[1]

Young's modulus, E	2800–3100 MPa
Tensile strength, σt	55–75 MPa
Elastic limit	50–150%
Notch test	3.6 kJ/m2
Glass transition temperature, Tg	67–81 °C
Vicat B	82 °C
Linear expansion coefficient, α	7×10−5 K−1
Water absorption (ASTM)	0.16

Uses[edit]

• 

  PET has SPI resin ID code 1

• 

  PET preform for injection stretch blow moulding of a bottle

• 

  A finished PET bottle

• 

  A PET bottle which has been heated by a candle and has recrystallized, making it opaque.

• 

  PET clamshell packaging, used to sell fruit, hardware, etc.

• 

  Polyester yarn

• 

  Microfiber towels and cleaning cloths

• 

  Aluminized Mylar balloons filled with helium

Textiles[edit]

Polyester fibres are widely used in the textile industry. The invention of the polyester fibre is attributed to J. R. Whinfield.[9] It was first commercialized in the 1940s by ICI, under the brand 'Terylene'.[10] Subsequently E. I. DuPont launched the brand 'Dacron'. As of 2022, there are many brands around the world, mostly Asian.

Polyester fibres are used in fashion apparel often blended with cotton, as heat insulation layers in thermal wear, sportswear and workwear and automotive upholstery.

Rigid packaging[edit]

Plastic bottles made from PET are widely used for soft drinks, both still and sparkling. For beverages that are degraded by oxygen, such as beer, a multilayer structure is used. PET sandwiches an additional polyvinyl alcohol (PVOH) or polyamide (PA) layer to further reduce its oxygen permeability.

Non-oriented PET sheet can be thermoformed to make packaging trays and blister packs.[11] Crystallizable PET withstands freezing and oven baking temperatures.[12]: 1378  Both amorphous PET and BoPET are transparent to the naked eye. Color-conferring dyes can easily be formulated into PET sheet.

PET is permeable to oxygen and carbon dioxide and this imposes shelf life limitations of contents packaged in PET.[13]: 104 

Flexible packaging[edit]

Biaxially oriented PET (BOPET) film (often known by one of its trade names, "Mylar") can be aluminized by evaporating a thin film of metal onto it to reduce its permeability, and to make it reflective and opaque (MPET). These properties are useful in many applications, including flexible food packaging and thermal insulation (such as space blankets).

Photovoltaic modules[edit]

BOPET is used in the backsheet of photovoltaic modules. Most backsheets consist of a layer of BOPET laminated to a fluoropolymer or a layer of UV stabilized BOPET.[14]

PET is also used as a substrate in thin film solar cells.

Thermoplastic resins[edit]

PET can be compounded with glass fibre and crystallization accelerators, to make thermoplastic resins. These can be injection moulded into parts such as housings, covers, electrical appliance components and elements of the ignition system.[15]

Other applications[edit]

• A waterproofing barrier in undersea cables.

• As a fibre, spliced into bell rope tops to help prevent wear on the ropes as they pass through the ceiling.

• Since late 2014 as liner material in type IV composite high pressure gas cylinders. PET works as a much better barrier to oxygen than earlier used (LD)PE.[16]

• As a 3D printing filament, as well as in the 3D printing plastic PETG.

• Film for tape applications, such as the carrier for magnetic tape or backing for pressure-sensitive adhesive tapes. Digitalization has caused the virtual disappeance of the magnetic audio and videotape application.

• Water-resistant paper.[17]

History[edit]

PET was patented in 1941 by John Rex Whinfield, James Tennant Dickson and their employer the Calico Printers' Association of Manchester, England. E. I. DuPont de Nemours in Delaware, United States, first used the trademark Mylar in June 1951 and received registration of it in 1952.[18] It is still the best-known name used for polyester film. The current owner of the trademark is DuPont Teijin Films.[19]

In the Soviet Union, PET was first manufactured in the laboratories of the Institute of High-Molecular Compounds of the USSR Academy of Sciences in 1949, and its name "Lavsan" is an acronym thereof (лаборатории Института высокомолекулярных соединений Академии наук СССР).[20]

The PET bottle was invented in 1973 by Nathaniel Wyeth[21] and patented by DuPont.[22]

Physical properties[edit]

Sailcloth is typically made from PET fibers also known as polyester or under the brand name Dacron; colorful lightweight spinnakers are usually made of nylon.

PET in its most stable state is a colorless, semi-crystalline resin. However it is intrinsically slow to crystallize compared to other semicrystalline polymers. Depending on processing conditions it can be formed into either amorphous or crystalline articles. Its amenability to drawing makes PET useful in fibre and film applications. Like most aromatic polymers, it has better barrier properties than aliphatic polymers. It is strong and impact-resistant. PET is hygroscopic.[23]

About 60% crystallization is the upper limit for commercial products, with the exception of polyester fibers. Transparent products can be produced by rapidly cooling molten polymer below Tg glass transition temperature to form an amorphous solid.[24] Like glass, 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 to nucleate and grow. This procedure is known as solid-state crystallization.

When allowed to cool slowly, the molten polymer forms a more crystalline material. This material has spherulites containing many small crystallites when 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, causing the resulting solid to be translucent.

Orientation also renders polymers more transparent. This is why BOPET film and bottles are both crystalline to a degree and transparent.

Amorphous PET crystallizes and becomes opaque when exposed to solvents such as chloroform or toluene.[25]

PET is stoichiometrically a mixture of carbon and H2O, and therefore has been used in an experiment involving laser-driven shock compression which created nanodiamonds and superionic water. This could be a possible way of producing nanodiamonds commercially.[26][27]

Absorption/scalping[edit]

PET has an affinity for hydrophobic flavors and drinks sometimes need to be formulated with higher dosage compared to glass to offset the flavor taken up by the container.[28]: 115 Heavy gauge PET bottles are sometimes returnable for re-use and is practiced in some EU countries, however the propensity of PET to absorb flavors makes it necessary to conduct a "sniffer" test on returned bottles to avoid cross-contamination.[28]: 115 

Intrinsic viscosity[edit]

Different applications of PET require different degrees of polymerization, which can be obtained by modifying the process conditions. The molecular weight of PET is measured by solution viscosity. The preferred method is intrinsic viscosity (IV).[29]

IV is a dimensionless measurement. It is found by extrapolating the relative viscosity (measured in (dℓ/g)) to zero concentration.

Shown below are the IV ranges for the main applications:[30]

Fibers

• 0.40–0.70: textile
• 0.72–0.98: technical eg tire cord

Films

• 0.60–0.70: biaxially oriented PET film
• 0.70–1.00: sheet grade for thermoforming

Bottles

• 0.70–0.78: general purpose bottles
• 0.78–0.85: bottles for carbonated drinks

Monofilaments, engineering plastics

• 1.00–2.00

Copolymers[edit]

PET is copolymerized with other diols or diacids to optimize the properties for particular applications.

For example, cyclohexanedimethanol (CHDM) can be added to the polymer backbone in place of ethylene glycol. Since this building block is much larger (six 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. In general, such PET is known as PETG or PET-G (polyethylene terephthalate glycol-modified). It is a clear amorphous thermoplastic that can be injection-molded, sheet-extruded or extruded as filament for 3D printing. PETG can be colored during processing.

[박대선]

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