Polyester is a category of polymers A polymer is a large molecule (macromolecule) 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 variety of properties which contain the ester Esters are chemical compounds derived formally from an oxoacid , and a hydroxyl compound such as an alcohol or phenol. Esters consist of an inorganic acid or organic acid in which at least one -OH (hydroxyl) group is replaced by an -O-alkyl (alkoxy) group. They are analogous to salts, using organic alcohols instead of metallic hydroxides 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, which is much more readily preserved in the fossil record, is cutan. 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 polymerizations in which bi-functional or multifunctional monomers react to form dimers, trimers, longer oligomers and eventually long chain polymers. Many naturally occurring and some synthetic polymers are produced by step-growth polymerization. It requires a high extent of reaction to achieve high molecular 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. Their plastic identification code is 7 and polybutyrate. Natural polyesters and a few synthetic ones are biodegradable, but most synthetic polyesters are not.

Polyesters may be produced in numerous forms such as sheets and three-dimensional shapes. Polyesters as thermoplastics A thermoplastic 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 even stacking of aromatic rings ( 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 fibers have high tenacity and E-modulus as well as low water absorption and minimal shrinkage in comparison with other industrial fibers.

Woven polyester fabrics are used in apparel and home furnishings such as bed sheets, beds, table sheets, curtains and draperies. Similarly, industrial polyesters are used in tyre reinforcements, ropes, fabrics for conveyor belts, safety belts, coated fabrics and plastic reinforcements with high energy absorption. Polyester fibers are also used to stuff pillows, comforters and cushion padding.

Polyester fabrics are claimed to have a "less natural" feel when compared to similarly-woven fabrics made from natural fibers (i.e. cotton Cotton is a soft, staple fiber that grows in a form known as a boll around the seeds of the cotton plant, a shrub native to tropical and subtropical regions around the world, including the Americas, 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 used natural- in textile uses). However, polyester fabrics may exhibit other advantages over natural fabrics, such as improved wrinkle resistance. As a result, polyester fibers are sometimes spun together with natural fibers to produce a cloth with blended properties.

Polyesters are also used to make bottles, films, tarpaulin A tarpaulin or tarp is a large sheet of strong, flexible, water resistant or waterproof material, often cloth such as canvas or polyester coated with plastics such as latex or PVC. In some places such as Australia, and in military slang, a tarp may be known as a hootchie. Tarps often have reinforced grommets at the corners and along the sides to, 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 block certain objects or substances while letting others through. Filters are often used to remove harmful substances from air or water, for example to remove air pollution, to make water drinkable, to prepare coffee. In domestic food and drink preparation where bulk solids, dielectric A dielectric is a nonconducting substance, i.e. an insulator. The term was coined by William Whewell in response to a request from Michael Faraday. Although "dielectric" and "insulator" are generally considered synonymous, the term "dielectric" is more often used to describe materials where the dielectric polarization film for capacitors A capacitor or condenser is a passive electronic component consisting of a pair of conductors separated by a dielectric. When a voltage potential difference exists between the conductors, an electric field is present in the dielectric. This field stores energy and produces a mechanical force between the plates. The effect is greatest between wide,, 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, elongated 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 and insulating tapes.

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

Thermosetting Thermosetting plastics are polymer materials that irreversibly cure. The cure may be done through heat (generally above 200 degrees Celsius), through a chemical reaction (two-part epoxy, for example), or irradiation such as electron beam processing polyesters 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, and chemosetting polyester resins Polyester resins are unsaturated resins formed by the reaction of dibasic organic acids and polyhydric alcohols. Among other uses, it is the basic component of sheet moulding compound and bulk moulding compound are used as 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. Fiberglass-reinforced unsaturated polyesters find wide application in bodies of yachts and as body parts of cars.

Polyesters are also widely used as a finish on high-quality wood products such as guitars The guitar is a musical instrument with ancient roots that is used in a wide variety of musical styles. It typically has six strings, but four-, seven-, eight-, ten-, eleven-, twelve-, thirteen- and eighteen-string guitars also exist, pianos The piano is a musical instrument which is played by means of a keyboard. Widely used in Western music for solo performance, 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, the piano's versatility and ubiquity have made it one of the 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 some non-Newtonian pseudoplastic fluids to show a time-dependent change in viscosity; the longer the fluid undergoes shear stress, the lower is its viscosity. A thixotropic fluid is a fluid which takes a finite time to attain equilibrium viscosity when introduced to a step change in shear rate. However, this is not a 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.

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 Ethylene glycol (monoethylene glycol , 1,2-ethanediol, IUPAC name: ethane-1,2-diol) is an alcohol with two -OH groups (a diol), a chemical compound widely used as an automotive antifreeze. In its pure form, it is an odorless, colorless, syrupy, sweet tasting, toxic liquid (MEG). With 18% market share of all plastic materials produced, it ranges third after polyethylene Polyethylene or polythene (IUPAC name polyethene or poly) is a thermoplastic commodity heavily used in consumer products (notably the plastic shopping bag). Over 60 million tons of the material are produced worldwide every year (33.5%) and polypropylene Polypropylene or polypropene is a thermoplastic polymer, made by the chemical industry and used in a wide variety of applications, including packaging, textiles (e.g. ropes, thermal underwear and carpets), stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer (19,5%).

The main raw materials are described as follows:

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

Synonym: 1,4 Dibenzenedicarboxylic acid,

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

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

Synonym: 1,4 Dibenzenedicarboxylic 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 ^[1],DMT ^[2] and MEG ^[3], at the webpage INCHEM "Chemical Safety Information from Intergovernmental Organizations".

To make a polymer of high molecular weight The molecular mass of a substance, frequently referred by the older term molecular weight and abbreviated as MW, is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one isotope of carbon-12). This is distinct from the relative molecular mass of a molecule, which is the ratio of the a catalyst is needed. The most common catalyst is antimony trioxide Antimony trioxide is the chemical compound with the formula Sb2O3. It is the most important commercial compound of antimony. It is found in nature as the minerals valentinite and senarmontite (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 PTA:

• 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 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 recycle ability
• The wide variety of intermediate and final products made of polyester

In table 1 the estimated world polyester production for textile A textile is a flexible material consisting of a network of natural or artificial fibres often referred to as thread or yarn. Yarn is produced by spinning raw wool fibres, linen, cotton, or other material on a spinning wheel to produce long strands known as yarn. Textiles are formed by weaving, knitting, crocheting, knotting, or pressing fibres polyester, bottle polyester resin, film polyester mainly for packaging Packaging is the science, art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of design, evaluation, and production of packages. Packaging can be described as a coordinated system of preparing goods for transport, warehousing, logistics, sale, and end use. Packaging and specialty polyesters for engineering plastics, which are the main fields of application, can be seen. 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 p-Xylene is an aromatic hydrocarbon, based on benzene with two methyl substituents. The “p” stands for para, identifying the location of the methyl groups as across from one another is the base material to produce PTA and liquefied petroleum gas Liquefied petroleum gas is a mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles, and increasingly replacing chlorofluorocarbons as an aerosol propellant and a refrigerant to reduce damage to the ozone layer (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/Voridian, 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, Zhejiang Hengi Polymerization.

With more than 500 plants in China, about half of the world production originates in that country. More information about polyester in China can be found under the web site of China Chemical Fiber Economic Information Network ^[4].

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 A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride, methanol, or acetic acid. The word "condensation& 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 In chemistry, an alcohol is any organic compound in which a hydroxyl group (-O and a carboxylic acid Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the formula -COH, usually written -COOH or -CO2H. Carboxylic acids are Brønsted-Lowry acids — they are proton donors. Salts and anions of carboxylic acids are called carboxylates react to form a carboxylic ester. To assemble a polymer, the water formed by the reaction must be continually removed by azeotrope An azeotrope is a mixture of two or more liquids (chemicals) in such a ratio that its composition cannot be changed by simple distillation. This occurs because, when an azeotrope is boiled, the resulting vapor has the same ratio of constituents as the original mixture 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 Hydrochloric acid is the solution of hydrogen chloride (H (HCl) instead of water. This method can be carried out in solution or as an enamel In a discussion of material science, enamel is the colorful result of fusing powdered glass to a substrate by firing, usually between 750 and 850 degrees Celsius. The powder melts and flows and hardens to a smooth, durable vitreous coating on metal, glass or ceramic. According to some sources, the word enamel comes from the High German word.

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 In organic chemistry, compounds composed of carbon and hydrogen are divided into two classes: aromatic compounds, which contain benzene rings or similar rings of atoms, and aliphatic compounds , which do not contain aromatic rings polyesters can be assembled from lactones A lactone is a cyclic ester in organic chemistry . It is the condensation product of an alcohol group and a carboxylic acid group in the same molecule. The most stable structure for lactones are the 5-membered lactones and 6-membered lactones (delta-lactone), because of the minimal angle strain in the compounds' structure. Gamma-lactones are so under very mild conditions, catalyzed anionically In chemistry, an anionic species is one that contains a full negative charge. These types of compounds can range in reactivity, but most are fairly reactive, cationically or metallorganically.

Thermosetting resins are generally copolymers of unsaturated polyesters with styrene. Polyester saturation is governed through the use of maleic acid or fumaric acid. In vinyl esters, saturation (or lack thereof) is found in the alcohol group of the polyester. The double bond of unsaturated polyester reacts with 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.

Footnotes

1. ^ PTA
2. ^ DMT
3. ^ MEG
4. ^ China Chemical Fiber Economic Information Network
5. ^ Chemical Engineering – Polyester Information Platform

References

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

External links

• Polyester manufacturing process
• Chemical Engineering - Polyester Information Platform

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

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• Polyester

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