Polyester is a category of polymers A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a wide variety of properties which contain the ester Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH (hydroxyl) group is replaced by an -O-alkyl (alkoxy) group, and most commonly from carboxylic acids and alcohols. Basically, esters are functional group In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of. However, its relative reactivity can be in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate Polyethylene terephthalate (sometimes written poly), commonly abbreviated PET, PETE, or the obsolete PETP or PET-P), is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination with glass fiber (PET). Polyesters include naturally-occurring chemicals, such as in the cutin Cutin is one of two waxy polymers that are the main components of the plant cuticle which covers all aerial surfaces of plants. The other major cuticle polymer is cutan, which is much more readily preserved in the fossil record,. Cutin consists of omega hydroxy acids and their derivatives which are interlinked via ester bonds, forming a polyester of plant cuticles Plant cuticles are a protective waxy covering produced only by the epidermal cells of leaves, young shoots and all other aerial plant organs without periderm. The cuticle tends to be thicker on the top of the leaf, but is not always thicker in xerophytic plants living in dry climates than in mesophytic plants from wetter climates, despite a, as well as synthetics through step-growth polymerization Step-growth polymerization refers to a type of polymerization mechanism in which bi-functional or multifunctional monomers react to form first dimers, then trimers, longer oligomers and eventually long chain polymers. Many naturally occurring and some synthetic polymers are produced by step-growth polymerization, e.g. polyesters, polyamides, such as polycarbonate Polycarbonates are a particular group of thermoplastic polymers. They are easily worked, moulded, and thermoformed; as such, these plastics are very widely used in the modern chemical industry. Their interesting features position them between commodity plastics and engineering plastics. Polycarbonates do not have a unique plastic identification and polybutyrate Polybutyrate is a biodegradable aliphatic-aromatic polyester plastic. Natural polyesters and a few synthetic ones are biodegradable, but most synthetic polyesters are not.

Depending on the chemical structure polyester can be a thermoplastic A thermoplastic, also known as thermosoftening plastic, is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently. Most thermoplastics are high-molecular-weight polymers whose chains associate through weak Van der Waals forces ; stronger dipole-dipole interactions and hydrogen bonding (nylon); or or thermoset A thermosetting plastic, also known as a thermoset, is polymer material that irreversibly cures. The cure may be done through heat (generally above 200 °C ), through a chemical reaction (two-part epoxy, for example), or irradiation such as electron beam processing, however the most common polyesters are thermoplastics.^[1]

Fabrics woven from polyester thread or yarn are used extensively in apparel and home furnishings, from shirts and pants to jackets and hats, bed sheets, blankets and upholstered furniture. Industrial polyester fibers, yarns and ropes are used in tyre reinforcements, fabrics for conveyor belts, safety belts, coated fabrics and plastic reinforcements with high-energy absorption. Polyester fiber is used as cushioning and insulating material in pillows, comforters and upholstery padding.

While synthetic clothing in general is perceived by many as having a less-natural feel compared to fabrics woven from natural fibres (such as cotton Cotton is a soft, fluffy staple fiber that grows in a boll around the seeds of the cotton plant. The plant is a shrub native to tropical and subtropical regions around the world, including the Americas, Pakistan, India and Africa. The fiber most often is spun into yarn or thread and used to make a soft, breathable textile, which is the most widely and wool The term wool is usually restricted to describing the fibrous protein derived from the specialized skin cells called follicles in sheep), polyester fabrics can provide specific advantages over natural fabrics, such as improved wrinkle resistance, durability and high color retention. As a result, polyester fibres are sometimes spun together with natural fibres to produce a cloth with blended properties. Synthetic fibres also can create materials with superior water, wind and environmental resistance compared to plant-derived fibres.

Polyesters are also used to make "plastic" bottles, films, tarpaulin A tarpaulin is a large sheet of strong, flexible, water-resistant or waterproof material, often cloth such as canvas or polyester coated with urethane, or made of plastics such as polyethylene. In some places such as Australia, and in military slang, a tarp may be known as a hootchie. Tarpaulins often have reinforced grommets at the corners and, canoes, liquid crystal displays, holograms Holography is a technique that allows the light scattered from an object to be recorded and later reconstructed so that it appears as if the object is in the same position relative to the recording medium as it was when recorded. The image changes as the position and orientation of the viewing system changes in exactly the same way as if the, filters In chemistry and common usage, a filter is a device that is designed to physically block certain objects or substances while letting others through. Filters are often used to remove solid substances suspended in fluids, for example to remove air pollution, to make water drinkable, and to prepare coffee. Some devices that are called filters may, dielectric A dielectric is an electrical insulator that may be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material, as in a conductor, but only slightly shift from their average equilibrium positions causing dielectric polarization. Because of dielectric polarization, film for capacitors A capacitor is a passive electronic component consisting of a pair of conductors separated by a dielectric (insulator). When there is a potential difference (voltage) across the conductors a static electric field develops in the dielectric that stores energy and produces a mechanical force between the conductors. An ideal capacitor is, film insulation An insulator, also called a dielectric, is a material that resists the flow of electric current. An insulating material has atoms with tightly bonded valence electrons. These materials are used in parts of electrical equipment, also called insulators or insulation, intended to support or separate electrical conductors without passing current for wire A wire is a single, usually cylindrical, string of metal. Wires are used to bear mechanical loads and to carry electricity and telecommunications signals. Wire is commonly formed by drawing the metal through a hole in a die or draw plate. Standard sizes are determined by various wire gauges. The term wire is also used more loosely to refer to a and insulating tapes Electrical tape is a type of pressure-sensitive tape used to insulate electrical wires and other material that conduct electricity. It can be made of many plastics, but vinyl is most popular; it stretches well and gives an effective and long lasting insulation. Electrical tape may also be called PVC electrical insulation tape, insulating tape, or.

Liquid crystalline polyesters are among the first industrially-used liquid crystalline polymers. They are used for their mechanical properties and heat-resistance. These traits are also important in their application as an abradable seal in jet engines.

Polyesters are widely used as a finish on high-quality wood products such as guitars The guitar is a plucked string instrument, played either with fingers or a pick. The guitar consists of a body with a rigid neck to which the strings, generally six in number but sometimes more, are attached. Guitars are traditionally constructed of various woods and strung with animal gut or, more recently, with either nylon or steel strings, pianos The piano is a musical instrument played by means of a keyboard. It is widely known as one of the most popular instruments in the world. Widely used in Classical music for solo performances, ensemble use, chamber music, and accompaniment, the piano is also very popular as an aid to composing and rehearsal. Although not portable and often expensive, and vehicle / yacht interiors. Burns Guitars Burns London is a guitar-making company originally formed in 1960 as Ormston Burns Ltd. It was founded by James Ormston Burns , who has been described as the British Leo Fender. Burns guitars were reintroduced in 1992, and the product line now includes a collector's edition of the first model the company produced, Rolls Royce Bentley models were produced mostly in parallel with the above cars. The Bentley Continental coupés did not have Rolls-Royce equivalents. Very expensive Rolls-Royce Phantom limousines were also produced and Sunseeker Sunseeker International, is a UK luxury motor yacht manufacturer. Their headquarters and assembly factory is in Poole Harbour, at Poole in Dorset, England. The company has been making motor boats since 1979 are a few companies that use polyesters to finish their products. Thixotropic Thixotropy is the property of certain gels or fluids that are thick under normal conditions, but flow (become thin, less viscous) over time when shaken, agitated, or otherwise stressed. In more technical language: some non-Newtonian pseudoplastic fluids show a time-dependent change in viscosity; the longer the fluid undergoes shear stress, the properties of spray-applicable polyesters make them ideal for use on open-grain timbers, as they can quickly fill wood grain, with a high-build film thickness per coat. Cured polyesters can be sanded and polished to a high-gloss, durable finish.

Types

Polyesters as thermoplastics may change shape after the application of heat. While combustible at high temperatures, polyesters tend to shrink away from flames and self-extinguish upon ignition. Polyester fibres have high tenacity Tenacity is the customary measure of strength of a fiber or yarn. In the U.S. it is usually defined as the ultimate strength of the fiber (in gram-force units) divided by the denier and E-modulus In solid mechanics, Young's modulus, also known as the tensile modulus, is a measure of the stiffness of an isotropic elastic material. It is defined as the ratio of the uniaxial stress over the uniaxial strain in the range of stress in which Hooke's Law holds. This can be experimentally determined from the slope of a stress-strain curve created as well as low water absorption and minimal shrinkage in comparison with other industrial fibres.

Unsaturated polyesters Polyester resins are unsaturated resins formed by the reaction of dibasic organic acids and polyhydric alcohols. Among other sheet moulding compound, bulk moulding compound and the toner of laser printers. - - Unsaturated polyesters are condensation polymers formed by the reaction of polyols (also known as polyhydric alcohols, organic compounds (UPR) are thermosetting resins Resin is a hydrocarbon secretion of many plants, particularly coniferous trees. It is valued for its chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials for organic synthesis; and as constituents of incense and perfume. In perfumery such products. They are used as casting Casting is a manufacturing process by which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting materials are usually metals or various cold materials, fiberglass Fiberglass, , is material made from extremely fine fibers of glass. It is used as a reinforcing agent for many polymer products; the resulting composite material, properly known as fiber-reinforced polymer (FRP) or glass-reinforced plastic (GRP), is called "fiberglass" in popular usage. Glassmakers throughout history have experimented laminating resins and non-metallic auto-body fillers. Fibreglass-reinforced unsaturated polyesters find wide application in bodies of yachts and as body parts of cars.

According to the composition of their main chain, polyesters can be:

Increasing the aromatic parts of polyesters increases their glass transition temperature Glass transition or vitrification refers to the transformation of a glass-forming liquid into a glass, which usually occurs upon rapid cooling. It is a dynamic phenomenon occurring between two distinct states of matter , each with different physical properties. Upon cooling through the temperature range of glass transition (a "glass, melting temperature, thermal stability, chemical stability...

Polyesters can also be telechelic A telechelic polymer is a polymer carrying two functionalized endgroups. Telechelic polymers can be used as prepolymers, e.g., for the synthesis of block co-polymers oligomers In chemistry, an oligomer consists of a few monomer units , in contrast to a polymer that, at least in principle, consists of an unlimited number of monomers. Dimers, trimers and tetramers are oligomers. Many oils are oligomeric, such as liquid paraffin. Plasticizers are oligomeric esters widely used to soften thermoplastics such as PVC. They may like the polycaprolactone diol (PCL) and the polyethylene adipate diol (PEA). They are then used as prepolymers.

Industry

Basics

Polyester is a synthetic polymer made of purified terephthalic acid Terephthalic acid is the organic compound with formula C6H42. This colourless solid is a commodity chemical, used principally as a precursor to the polyester PET, used to make clothing and plastic bottles. Several billion kilograms are produced annually. It is one of three isomeric phthalic acids (PTA) or its dimethyl ester dimethyl terephthalate Dimethyl terephthalate is an ester of terephthalic acid and methanol and is used in the production of polyesters, including polyethylene terephthalate and polytrimethylene terephthalate. It consists of benzene with methyl ester groups attached in the para position, or to the first and fourth carbon atoms (DMT) and monoethylene glycol (MEG). With 18% market share of all plastic materials produced, it ranges third after polyethylene (33.5%) and polypropylene (19.5%).

The main raw materials are described as follows:

• Purified Terephthalic Acid – PTA – CAS-No.: 100-21-0

Synonym: 1,4 Benzenedicarboxylic acid,

Sum formula; C6H4(COOH)2 , mol weight: 166,13

• Dimethylterephthalate – DMT- CAS-No: 120-61-6

Synonym: 1,4 Benzenedicarboxylic acid dimethyl ester

Sum formula C6H4(COOCH3)2 , mol weight: 194,19

• Mono Ethylene Glycol – MEG – CAS No.: 107-21-1

Synonym: 1,2 Ethanediol

Sum formula: C2H6O2 , mol weight: 62,07

More information about polyester raw materials can be found for PTA ^[2],DMT ^[3] and MEG ^[4], at the webpage INCHEM "Chemical Safety Information from Intergovernmental Organizations".

To make a polymer of high molecular weight a catalyst is needed. The most common catalyst is antimony trioxide (or antimony tri acetate):

Antimony trioxide – ATO – CAS-No.: 1309-64-4 Synonym: non, mol weight: 291,51 Sum formula: Sb2O3

In 2008 about 10 000 t Sb2O3 were used to produce around 49 Mio t polyethylene terephthalate.

Polyester is described as follows:

Polyethylene Terephthalate CAS-No.: 25038-59-9 Synonym / abbreviations: polyester, PET, PES Sum Formula: H-[C10H8O4]-n=60-120 OH, mol unit weight: 192,17

There are several reasons for the importance of Polyester:

• The relatively easy accessible raw materials PTA or DMT and MEG
• The very well understood and described simple chemical process of polyester synthesis
• The low toxicity level of all raw materials and side products during polyester production and processing
• The possibility to produce PET in a closed loop at low emissions to the environment
• The outstanding mechanical and chemical properties of polyester
• The recyclability
• The wide variety of intermediate and final products made of polyester.

In table 1 the estimated world polyester production is shown. Main applications are textile polyester, bottle polyester resin, film polyester mainly for packaging and specialty polyesters for engineering plastics. According to this table, the world's total polyester production might exceed 50 million tons per annum before the year 2010.

Table 1: World polyester production

Raw material producer

The raw materials PTA, DMT, and MEG are mainly produced by large chemical companies which are sometimes integrated down to the crude oil refinery where p-Xylene is the base material to produce PTA and liquefied petroleum gas (LPG) is the base material to produce MEG.

Large PTA producers are for instance BP, Reliance, Sinopec, SK-Chemicals, Mitsui, and Eastman Chemicals. MEG production is in the hand of about 10 global players which are headed by MEGlobal a JV of DOW and PIC Kuweit followed by Sabic.

Among the world's largest polyester producers are the following companies:

Artenius, Advansa, DAK, DuPont, Eastman, Hyosung, Huvis, Indorama, Invista, Jiangsu Hengli Chemical Fiber, Jiangsu Sanfangxian Industry, M&G Group, Mitsui, Mitsubishi, NanYa Plastics, Reichhold, Reliance, Rongsheng, Sabic, Teijin, Toray, Trevira, Tuntex, Wellman, Yizheng Sinopec, and Zhejiang Hengi Polymerization.

Polyester processing

After the first stage of polymer production in the melt phase, the product stream divides into two different application areas which are mainly textile applications and packaging applications. In figure 2 the main applications of textile and packaging polyester are listed.

Table 2: Textile and packaging polyester application list

Abbreviations: PSF = Polyester Staple Fiber; POY = Partially Oriented Yarn; DTY = Draw Textured Yarn; FDY = Fully Drawn Yarn; CSD = Carbonated Soft Drink; A-PET = Amorphous Polyester Film; BO-PET = Biaxial Oriented Polyester Film;

A comparable small market segment (<< 1 Million t/a) of polyester is used to produce engineering plastics and masterbatch.

In order to produce the polyester melt with a high efficiency, high-output processing steps like staple fiber (50–300 t/d per spinning line) or POY /FDY (up to 600 t/d split into about 10 spinning machines) are meanwhile more and more horizontal, integrated, direct processes. This means the polymer melt is directly converted into the textile fibers or filaments without the common step of pelletizing. We are talking about full horizontal integration when polyester is produced at one site starting from crude oil or distillation products in the chain oil -> benzene -> PX -> PTA -> PET melt -> fiber / filament or bottle-grade resin. Such integrated processes are meanwhile established in more or less interrupted processes at one production site. Eastman Chemicals introduced at first the idea to close the chain from PX to PET resin with their so-called INTEGREX process. The capacity of such horizontal, integrated productions sites is >1000 t/d and can easily reach 2500 t/d.

Besides the above mentioned large processing units to produce staple fiber or yarns, there are ten thousands of small and very small processing plants, so that one can estimate that polyester is processed and recycled in more than 10 000 plants around the globe. This is without counting all the companies involved in the supply industry, beginning with engineering and processing machines and ending with special additives, stabilizers and colors. This is a gigantic industry complex and it is still growing by 4–8% per annum, depending on the world region. Useful information about the polyester industry can be found under ^[5] where a “Who is Producing What in the Polyester Industry” is gradually being developed.

Synthesis

Synthesis of polyesters is generally achieved by a polycondensation reaction. See "condensation reactions in polymer chemistry". The General equation for the reaction of a diol with a diacid is : (n+1) R(OH)₂ + n R´(COOH)₂ ---> HO[ROOCR´COO]_nROH + 2n H₂O

Azeotrope esterification

In this classical method, an alcohol and a carboxylic acid react to form a carboxylic ester. To assemble a polymer, the water formed by the reaction must be continually removed by azeotrope distillation.

Alcoholic transesterification

O
\\
C - OCH3 + OH[Oligomer2]
/
[Oligomer1]

O
\\
C - O[Oligomer2] + CH3OH
/
[Oligomer1]

Acylation (HCl method)

The acid begins as an acid chloride, and thus the polycondensation proceeds with emission of hydrochloric acid (HCl) instead of water. This method can be carried out in solution or as an enamel.

Silyl method

In this variant of the HCl method, the carboxylic acid chloride is converted with the trimethyl silyl ether of the alcohol component and production of trimethyl silyl chloride is obtained

Acetate method (esterification)

Silyl acetate method

Ring-opening polymerization

Aliphatic polyesters can be assembled from lactones under very mild conditions, catalyzed anionically, cationically or metallorganically.

Cross-linking

Unsaturated polyesters are thermosetting resins. They are generally copolymers prepared by polymerizing one or more diol with saturated and unsaturated dicarboxylic acids (maleic acid, fumaric acid...) or their anhydrides. The double bond of unsaturated polyesters reacts with a vinyl monomer mainly the styrene, resulting in a 3-D cross-linked structure. This structure acts as a thermoset. The cross-linking is initiated through an exothermic reaction involving an organic peroxide, such as methyl ethyl ketone peroxide or benzoyl peroxide.

Health effects

A 1993 study found that polyester underwear reduced sperm count and sperm motility in male dogs.^[6]

Notes

1. ^ Rosato, Dominick V.; Rosato, Donald V.; Rosato, Matthew V. (2004), Plastic product material and process selection handbook, Elsevier, p. 85, ISBN 9781856174312, http://books.google.com/?id=Lqk5QgGoWFkC.
2. ^ PTA
3. ^ DMT
4. ^ MEG
5. ^ Chemical Engineering – Polyester Information Platform
6. ^ http://dx.doi.org/10.1007/BF00296839

References

• Textiles, by Sara Kadolph and Anna Langford. 8th Edition, 1998.

External links

• Polyester Market Polyester Market
• Chemical Engineering - Polyester Information Platform

Categories: Carboxylate esters | Packaging materials | Plastics | Polyesters | Synthetic resins | Synthetic fibers | Thermoplastics | Dielectrics | Airship technology | Recyclable materials | Thermosetting plastics

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• Polyester: Encyclopedia

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