Polyesters: Characteristics and Applications

Polyesters Characteristics and ApplicationsScrunch it, wash it without any wear and wrinkles. Thats what polyester became famous for. Polyester was the veridical of pickaxe in a changing economy of speed, efficiency and convenience. If the food industry produced fries and coke, the cloth industry supplemented it with Polyester quick, cheap and easy.It was W.H. Car separates who discovered that alcohols and carboxyl acids could be success to the full mixed to create characters. Carothers was take a craping for duPont at the time and unfortunately when he discovered Nylon, polyester took a back seat.PET TeryleneCarothers incomplete research had not groundbreaking to investigating the polyester soma from mixing ethylene glycol and terephthalic acid. It was British scientists Whinfield and Dickson who patented PET or PETE in 1941. Polyethylene terephthalate forms the stern for synthetic fibers interchangeable Dacron, Terylene and polyester.Later that year, the first polye ster fiber Terylene was created by Whinfield and Dickson along with Birtwhistle and Ritchiethey. Terylene was first construct by Imperial Chemical Industries or ICI.DuPonts RoleIt was in 1946 that duPont bought completely legal rights from ICI. In 1950, the Dealw ar property of duPont make another polyester fiber, which they named Dacron. Mylar was introduced in 1952. Polyester was first introduced to the Ameri eject public in 1951 as the magical fabric that compulsory no ironing PET and PEN be duPont apportionmarks that have sullen the part and consumption of Polyester around.Polyester Becomes popSubsequent to the development of Terylene and Dacron, Kodel was developed by Eastman Chemical Products, Inc in 1958.The polyester market underwent rapid expansion and textile mills emerged e precisewhere. Many of the mills were located at excellent gas stations and produced cheap polyester app atomic number 18l. The garish and durable fiber became very(prenominal) popular an d the industry expanded rapidly till the 1970s. Unfortunately, the infamous double-knit polyester ensure hit the industry and polyester soon came to be k straightawayn as the uncomfortable fabric.The Phoenix RisesToday, polyester is largely regarded as a cheap fabric that is rather uncomfortable for sensitive human skin to wear.However, the emergence of lavishness fibers like polyester microfiber and various polyester blends the industry is experiencing resurgence. The Tennessee Eastman Company and the Man-Made persona Producers Associations (MMFPA) Polyester Fashion Council played a remarkable role in the revival of polyester. The Tennessee Eastman Company started a YES campaign for polYESter and popularized it via radio and television. The idea was to focus on the wash and go properties of polyester rather than sell it as a cheap fabric.Hoechst Fibers Industries besides played a part. They conducted various studies from 1981 to 1983 and found that 89% of people could not dis tinguish between polyester and other natural fibers like cotton, wool and silk. Also, it was found that people were more interested in the appearance of the app bel than the fabric it was make of.Today, the biggest contri scarcelyor to the appeal of polyester is the discovery of microfibers. Microfibers give polyester the feel of silk and argon rapidly becoming the choice of fabric. With an dearly-won tag to match, the cheap image of polyester seems to be on its way out. Heres to heralding a immature era in the history of polyesterPolyester is a term often de bewitchingd as long-chain polymers chemically composed of at to the lowest degree 85% by cornerstonet of an ester and a dihydric alcohol and a terephthalic acid. In other words, it means the linking of some(prenominal) esters within the fibers. Reaction of alcohol with carboxylic acid results in the constitution of esters.Polyester likewise refers to the various polymers in which the backbones be make by the esterific ation condensation of polyfunctional alcohols and acids.Polyester can also be split upified as double-dyed(a) and unsaturated polyesters.Saturated polyesters refer to that family of polyesters in which the polyester backbones atomic number 18 saturated. They are thus not as reactive as unsaturated polyesters. They consist of low molecular tip liquids utilize as plasticizers and as reactants in forming urethane polymers, and linear, senior high molecular weight thermoplastics such as polyethylene terephthalate (Dacron and Mylar). Usual reactants for the saturated polyesters are a glycol and an acid or anhydride.Unsaturated polyesters refer to that family of polyesters in which the backbone consists of alkyl thermosetting resins characterized by vinyl unsaturation. They are nearlyly used in rein forced plastics. These are the most widely used and economical family of resins.Characteristics of polyesterPolyester fabrics and fibers are exceedingly strong.Polyester is very dura ble resistant to most chemicals, stretching and shrinking, wrinkle resistant, mould and abrasion resistant.Polyester is hydrophobic in nature and quick drying. It can be used for insulation by manufacturing kettle of fish fibers.Polyester retains its shape and hence is good for making outdoor clothing for harsh climates.It is slowly wash and dried.Uses of PolyesterThe most popular and one of the earliest uses of polyester was to make polyester suits all the rage in the 70s. Polyester clothes were very popular. Due to its dominance and tenacity polyester was also used to make ropes in industries. PET bottles are straight off one of the most popular uses of polyester.Polyester care tipsTaking care of polyester clothing is really easy and very time efficient.Polyester clothing can be machine washed and dried. Adding a fabric break uper generally helps. change the fabric at low temperatures to get maximum usage from the clothing.Though polyester does not require oftentimes ir oning, if you must then iron warm.Polyester can be dry-cleaned with no hassles.Polyester is the choice of fiber and fabric for umpteen industries. It can be applied to a wide variety of useful purposes.Use of polyester in garmentsPolyester is used in the manufacturing of all strains of clothes and home furnishings like bedspreads, sheets, pillows, furniture, carpets and even curtains. The disco clothing of the 70s with all its jazz and flash was do of polyester.Hydrophobic nature High tenacity and good durability makes polyester the choice of fabric for high stress outdoors use. Polyester is also a strong fiber that is hydrophobic in nature. It is thus ideal for clothing to be used in wet and damp environments. The fabric is also coated with a water-resistant finish and get ahead intensifies the hydrophobic nature.Being the most heavily recycled polymer worldwide, it is also used by climbers. Climbing suits, parkas, sleeping bags and other outdoor gear are using the new insulati ng polyester fiberfill produces. One can also do winter windsurfing wearing dry suits lined with polyester fleece.Creating insulation By creating hollow fibers it is also possible to build insulation into the polyester fiber. Air is trapped inside the fiber, which is then warm up by the heat of the body. This keeps the body warm in cold weather. Another regularity to build insulation is to use crimped polyester in a fiberfill. The crimp helps keep the warm air in. Polyester is an ideal fabric for this kind of insulation because it retains its shape. Cotton and wool tend to flatten over a period of time and candid the warming effect.Wrinkle resistant Polyester is also wrinkle resistant and is used very often in everyday clothing like pants, shirts, tops, skirts and suits. Used either by itself or as a blend, it is also stain resistant and hence very popular.Industrial uses of polyesterWhile clothing used to be the most popular use of polyester and which made it a household name w orldwide, there are many other uses polyester is put to.PET The most common use of polyester today is to make the plastic bottles that store our often beloved beverages. Shatterproof and cheap these bottles are an absolute boon to the beverages industry.Mylar An unusual and little known use of polyester is in the manufacturing of balloons. Not the rubber kind that you use for water balloons but the really pretty adorned ones that are gifted on special occasions. These are made of Mylar a kind of polyester film compeld by DuPont. The balloons are made of a composite of Mylar and aluminum f inunct.Miscellaneous Polyester is also used to manufacture high authorization ropes, thread, hoses, sails, floppy disk liners, power belting and much more in industries.Thus, polyester has many uses for homes and industries as well.The process of manufacturing polyester is fascinating. It is an artificial man-made fiber. Polyesters are generally manufactured from petroleum from which the consti tuent acids and alcohols are derived. at that vest are three steps in the synthesizing of polyester.Condensation Polymerization When acid and alcohol are reacted in a vacuum at high temperatures it results in condensation polymerization. Once the polymerization has occurred the material is extruded onto a casting trough in the form of a ribbon. Once cool, the ribbon hardens and is cut into chips.Melt-spun Fiber The chips are dried completely. Hopper reservoirs are then used to ladder the chips. A unique frisk of polyester is that it is melt-spun fiber. The chips are heated, extruded through and through spinnerets and cools upon hitting the air. It is then loosely wound around cylinders.Drawing The fibers consequently organize are hot stretched to about five times their original length. This helps to reduce the fiber width. This fiber is now ready and would into cones as filaments. It can also be crimped and cut into staple lengths as per requirements.Different Types Of Polyest erThere are several processes that can be carried out on the base polyester fiber. These processes add dimension to the polyester fiber as required for various end uses.Polyester is a bright fiber by nature. However, it can be made dull or semi-dull by adding a delusterant. By changing the shape of the spinneret also, the hand and the strength of the fiber can be changed. Most spinnerets are circular. However, square, oval and bean-shaped fibers are also produced sometimes. Hollow fibers can also be created.Polyester fiber is generally drawn to about five times its original length. However, brief it out further makes it thinner. This is how the latest microfibers are being manufactured. Dyeing can give desired colors of polyester fiber. Normal polyester fiber is long and smooth. Crimping it can give the fiber more bulk and texture and development its insulation capabilities.Using PolyesterOnce the polyester fiber is ready it is used to make filament and spun yarns. The yarns can b e blended with other fibers to make various blended fabrics.Polyester and cotton are a popular combination. wool and rayon are also blended with polyester to make fabrics.Polyesters are long chain synthetic polymers that have ester linkages. Polyester materials are used as fibers, plastics, and films in composites and elastomers and as coatings. They are truly versatile materials.In the late twenties American chemist Wallace Carothers and his research group at DuPont began to investigate the formation of polymers from the reaction of aliphatic di acids (having devil acid groups) with diols (having two alcohol groups), in search of materials that would give them fibers. At first they were able to form only syrupy mixtures. But the Carothers group did make polyester fibers. They investigated a wide array of dialcohols, diacids, and w-hydroxy acids for use as starting points. Some of the polyesters that they achieved were solids, but they had rather low melting points and thus were n ot useful as fiber materials. The lack of success was due to the fact that the researchers had used only aliphatic diacids. In lay to form long polymer chains, the reactive groups of the reactants must be present in approximately equal amounts. This is easily achieved via the use of amines and the subsequent formation of amine table salts. (Diols do not easily form salts.) Carotherss group understand the principle of driving an equilibrium reaction and so sought to remove water from their amine salt mixtures, thus forcing the reaction toward ester formation. For this they developed a so-called molecular still, which involved heating the mixture and applying a vacuum coupled with a cold-finger that allowed evacuated water to condense and be removed from the reaction system. Even with this instinct and lots of hard work, they achieved polymer chains with fewer than 100 repeat units. (See get a line 2.)The DuPont research team turned from the synthesis of polyesters to tackle, mor e successfully, the synthesis of polyamides. The experience with polyesters was put to use in the making of polyamides.Initial polyester formation actually occurred much earlier and is attributed to Gay Lussac and Thophile-Jules Pelouze in 1833 and Jns Jakob Berzelius in 1847. They did not take up what they had discovered, however, and so moved on to other work.Glyptal polyesters were first produced in 1901 by heating glycerol and phthalic anhydride. (See Figure 3.) Because the secondary hydroxyl is little active than the terminal, primary hydroxyl in glycerol, the initial product make is a linear polyester. A cross-linked product is produced by further heating through reaction the third gear alcohol.Related compounds, alkyds, were synthesized by Kienle in the 1920s from trifunctional alcohols and dicarboxylic acids. Unsaturated oils (alcohols and anhydrides containing double bonds) were also reacted with phthalic anhydride, yielding polyesters that contained a double bond, whic h could be further reacted to produce cross-linked products. The extent of cross-linking or drying depends on the amount of unsaturated oil present.Today, the term alkyd is often used to describe all polyesters produced from the reaction of a diacid or anhydride and a diol or triol resulting in a product that contains a double bond that can be further reacted, giving a cross-linked product. (See Figure 4.) These polyesters are called unsaturated polyesters. They are mainly used in the intersection of reinforced plastics (composites) and nonreinforced filled products for the marine, automotive, and other industries.These glyptal and alkyd polyesters are useful as coating materials but not for fiber or plastic labor. The first commercially available polyesters were made by GE in the 1920s. Called Glyptals , they were used as sealing waxes. Out of the Glyptal research came alkyd paints. Although these reactions had low fractional conversions, they organise high molecular weight mat erials because they had functionalities (i.e., a number of reactive groups on a single reactant) greater than 2, resulting in cross-linking.The heat resistance of Carotherss polyesters was not sufficient to withstand the temperature of the hot ironing process. Expanding on the work of Carothers and his coworkers on polyesters, Whinfield and Dickson, in England, overcame the problems of the Carothers group by using aromatic acids, especially terephthalic. This classic reaction, which produces plastics and fibers that are change under a variety of tradenames, including Dacron, Fortrel, Trevira, and Terylene, and films sold under a variety of trade names that includes Mylar, is shown in Figure 5. All new plants now use pure acid for this reaction.Methyl alcohol, or methanol, is subvert boiling than water (65 C compared with 100 C) and is thus more easily removed, allowing the reaction to be forced toward polymer formation more easily. Although this poly(aryl ester), produced by Whi nfield and Dickson, poly(ethylene terephthalate) or PET, met the specifications for a useful synthetic fiber, because of inferior cast machines and understaffed plastic technology, it was not possible to use it in injection molds. Until more recently PET was not a widely used plastic or film material.Although aromatic polyesters had been successfully synthesized from the reaction of ethylene glycol with various aromatic diacids (almost always terephthalic acid or its ester), commercialization of polyester synthesis awaited an chinchy source of aromatic diacids. In 1953 an inexpensive process for the separation of the various xylene isomers by watch crystal was discovered. The availability of inexpensive xylene isomers enabled the formation of terephthalic acid through the air oxidation of the p-xylene isomer. Du Pont, in 1953, produced polyester fibers from melt spinning, but it was not until the 1970s that these polyester fibers became commercially available.John Travolta and K aren Lynn Gorney in the 1970s hit film Saturday night Fever. Polyester was a popular fabric used in clothing in the 1970s.In 2000 about 3,900 jillion pounds of polyester fiber were used in the United States, making it the largest single fiber group material. As with nylon, polyester fibers are comparable to and/or surpass common natural fibers such as cotton and wool in heat stability, wash-and-wear properties, and wrinkle resistance. Textiles blended from polyester, cotton, and wool (in varying combinations) can also be made to be permanent press and wrinkle resistant. The fibers are typically formed from melt or response spinning. Chemical and physical modification can generate fibers of differing fiber appearances from the same basic fiber material. Self-crimping textiles are made by combining materials that have differing shrinkage properties. Different shaped dyes produce materials with varying contours and properties, including hollow fibers.Along with the famous polyester suits and slacks, polyester fibers are widely used in undergarments, permanent press shirts, tire cord, and felts.Because the simple(a)ness of processing and fabricating polyesters is related to the number of methylene groups (-CH 2 -) in the repeat units, scientists turned to the use of diols with additive methylene units. Whereas PET is difficult to mold because of its high melting point, Tm 240 C, poly(butylene terephthalate), or PBT, because of its two excess methylene units in the diol-derived portion, is press down melting with a Tg of about 170 C. PET also crystallizes relatively slowly, so extra care must be exercised to insure that PET molded products become fully crystallized. Otherwise, the partially crystallized portions will be preferred sites for cracking, crazing, shrinkage, and so on.By comparison, PBT melts at a lower temperature (as noted above), crystallizes more rapidly, and is often employed as a molding compound. PBT has properties that represent a counte rpoise between those of nylons and acetals. It is characterized by low moisture absorption, good fatigue resistance, good solvent resistance, exceedingly good self-lubrication, and good maintenance of its physical properties even at relatively high use temperatures. Fiber-reinforced PBT molding compound is sold under the trade-name Celanex. Another PBT molding compound was first sold under the trade name Valox. Today, there are many PBT molding compounds available.In 2000 worldwide production of PET was 30 million tons. The manufacture of PET textiles is increasing at 5 percent a year, of PET bottles at 10 percent a year. China produces the most polyesters. PET is now used extensively as bottling material for soft drinks instead of glass because it is shatterproof and lightweight. Carbon dioxide permeability decreases with increasing film onerousness and crystalline. Glass has better CO 2 impermeability than PET in these respects. Therefore, to achieve optimal crystalline, partial ly crystalline PET is employed in the stretch blow molding process, carried out to promote further crystalline formation. It is also used for molded automobile parts. Over 500,000 tons of polyester engineering plastics are produced annually in the United States.Polymers are the origin of polyestersClassification of polymers-Based on characterstics ,intended use and performances of the finished product, polyesters are divided into three main categories-Plastics, eccentrics, elastomers.Plastics are widely variety of polymers-based composite materials which possess appreciable me chanical strength (they have stiff chains at room temperature) and are characterised by plasticity,they can be formed or moulded into useful shapes by application of heat andpressure. Materials which possess plasticity at some peg during their formation are also included in this category.Based on their thermal behaviour, plastics have been subdivided into thermoplatics (that soften and meld on heating) an d thermosetting or thermohardening plastics (that set or harden on heating)A fibre is any material whose minimum length is 100 times its average diameter which should be less then .25 mm. fibres are natural (cotton, silk, wool) or artficially prepared long chain polymers with average molecular weight of 15000 or more. Fibre forming materials are characterised by high softening or melting points, a high degree of resistence to chemicals and solvents, high tensile strength and very hight rigidityThey however undergo irreversible deformation.Elastomers or rubbrs are polyesters characterised by a very high degree of reversible or rubberlike deformation. They can be stretched to several times their original length but regain their previous shape or dimensions when the streching force is removed. The molecular chains of elastomers can exist in randomly coiled state and their elastic behaviour can be can be compared to that of the spring of a chest expander which uncoils and recoils on ap plication and removal respectively, of an elongated force. The glass-transition temperatures of elastomers are very much below their use temperature.Preparation of polymers-Bulk polymerization- a free radical catalyst or initiator is dissolved in the monomer which is then heated and stirred in a suitable vessel. The polymerization n is exothermic and dissipation of heat through cooling ma y be required. As the reaction progresses, the suystem becomes vicious making brainchild difficult. The method is economical and the product is of high purity. The technique is used for preapring polyvinyl chloride (PVC) polystyrene (PS) polymethymethacrylate (PMMA).Solution polymerization- the monomer and catalyst (free radical, cationic and anionic) are dissolved in a suitable inert solvent.The resulting solution is heated and stirred.The presence of solvent helps in heat dissipation and in attendling viscosity. The solvent may interact and reduce the molecular wieght of the product whose isol ation from the solution is uneconomical unles it is in alcohol-soluble. The technique is employes where the polymer is to be used in solution form such that as in case of adhesives and surface coatings. Polyacrylonitrile, polyisobutylene and certain block copolymers are produced by this method.Suspension polymerization- a solution of the catalyst in the monomer is disperse as fine droplets in a n inertsolvent,usually water. To stabilize the suspension, water soluble protective colloids such as polyvinyl alcohol, methyl cellulose or scratch are added and the mixture is kept stirring continuously. The problems of heat dissipation and viscosity increase are absent. The method gives a fairly high molecular weight product in the form of easily separable form that can be filtered or centrifuged and water washed to remove the protective colloids. The technique is employed for the production of pvc,ps and styrene divinylbenzene copolymer(used for making ion-exchange resins)Emulsion polymer isation- the particle size of the monomer is reduced to colloidal dimensions by more vigrous stirring and use of synthetic surfactants(aninoic,cationic or non-ionic)in place of protective colloids used in suspension polymerisation.usually water soluble catalysts such as persulphate, hydrogen peroxide are used.thermal dissipaton and viscosity problems are absent. Both the rate of polymerisation and the molecular weight of the product formed are very high. The product which is in the form of fine particles dispersed in water (called latex) can be used directly as adhesive or an emulsion paint, or it can be isolated by coagulating with an electrolyte. The technique is employed for the industrial production of PVC, PCP, polybutadiene, polyacrylates, polymetyl methacrylate.Melt polycondensation-The reactants are heated together in exact stochiometry above the melting point of the product, at which temperature the starting materials and product must be thermally stable. Oxygen has to be e xcluded form the reaction sleeping room to avoid oxidation at high temperature. Increase in viscosity makes removal of the by-product extremely difficult towards the end (unless high vacuum is applied) which may prevent formation of high molecular weight product. The molten polymer is usually sent directly forspinning, extrision etc. The technique is usually applied for the preparation of polyesters and polyamides.interfacial polymerization-The reaction takes place at the user interface of between solutions of the recatants in immiscible solvents. increasing the interface by thorough agitation of two solutions substantially the rate of polymerisation. Exact stochiometry is not necessary and a high molecular weight product can be easily formed. Being very simple the method is widely used for the production of polyamides, polyesters, polyurethanes, polysulphonamides. Difference in the reactivity of materials can be utilised to prepare ordered copolymers which otherwise are very diff icult to produce. The technique is however limited to reactants having passing reactive functional groups that can readily react at the ambient temperatures. interrogation and characterization of polymers-Testing and characterization of polymeric materials is essential for determining their suitability for a Particular application. The manufactures and processors and need it for quality control such as maintaining product uniformity and for accessing the performance of new material in relation to the alive ones. processors and users wanting to better understand the polymeric behaviors. Under various conditions are naturally interested in knowing their chemical nature.Polymeric materials are very complex in nature. their high molecular weights in homogeneity and their chemical inertness often present difficulties in their identification which therefore requires specific techniques and the use of advanced methods of analysis. The problem of characterstic is further complicated by t he market availability of an extermely wide range of materials and the presence of heighten materials such as plastic stablizers and filers (which change the physical propeties of the product) and thusComplete identification of polymeric materials may not always be possible. It is howevere possible to make a positive identification as to the class of polymers (polyeolefine, polyesters, polyamine) to which a given sample belongs. By carrying out some simple test and correlating their resultsApplication of these tests to the identification of to common polymeric materials is described as-Physical test-Physical examination of polymeric materials includes the ceremony of their color,,solubility,density etcFloatation test-The test is based on Archimedes principal from which it follows that a material will flow in liquid of same or high density .Combustion test-holding the pair of tweezers or tongs insert a small piece of the sample into flame of Bunsen burner and ob coiffure the ease of ignition, flammability of the sample in and out of flamePh paper test-take a small amount of powdered sample in a paralysis or ignition tube-shaped structure and place at its open end a piece of moist ph paper holding tube with a clip heat it with Bunsen burner at low heat.