A Polyesters

If more than two functional groups are present in one of the monomers, the polymer chains can be linked to one another (cross-linked) to form a three-dimensional network. Such structures are usually more rigid than linear structures and are useful in making paints and coatings. They may be classified as thermosetting plastics. The polyester Glyptal is prepared as follows  

The reaction of phthalic anhydride with a diol (ethylene glycol) is described in the procedure. This linear polyester is compared with the cross-linked polyester (Glyptal) prepared from phthalic anhydride and a triol (glycerol). 

Place 1 g of phthalic anhydride and 0.05 g of sodium acetate in each of two test tubes. To one tube, add 0.4 mL of ethylene glycol and to the other, add 0.4 mL of glycerol. Clamp both tubes so that they can be heated simultaneously with a flame. Heat the tubes gently until the solutions appear to boil (water is eliminated during the esterification) then continue heating for 5 minutes. 

If you are performing the optional infrared analysis of the polymer, immediately save a sample of the polymer formed from ethylene glycol only. After removing a sample for infrared spectroscopy, allow the two test tubes to cool and compare the viscosity and brittleness of the two polymers. The test tubes cannot be cleaned. 

Lightly coat a watch glass with stopcock grease. Pour some of the hot polymer from the tube containing ethylene glycol use a wooden applicator stick to spread the polymer on the surface to create a thin film of the polymer. Remove the polymer from the watch glass and save it for Experiment 46D. 

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The speed of wetting has been measured by running a tape of material that is wetted either downward through the liquid-air interface, or upward through the interface. For a polyester tape and a glycerol-water mixture, a wetting speed of about 20 cm/sec and a dewetting speed of about 0.6 cm/sec has been reported [37]. Conversely, the time of rupture of thin films can be important (see Ref. 38). 

Polymerisation of a diol with a dicarboxybe acid is exemplified by the production of a polyester from ethylene glycol and terephthabc acid either by direct esterification or by a catalysed ester-interchange reaction. The resulting polyester (Terylene) is used for the manufacture of fibres and fabrics, and has high tensile strength and resibency its structure is probably ... 

Not all synthetic polymers are used as fibers Mylar for example is chemically the same as Dacron but IS prepared in the form of a thin film instead of a fiber Lexan is a polyester which because of its impact resistance is used as a shatterproof substitute for glass It IS a polycarbonate having the structure shown... 

Polycarbonate is a polyester in which dihydric (or polyhydric) phenols are joined through carbonate linkages. The general-purpose type of polycarbonate is based on 2,2-bis(4 -hydroxybenzene)propane (bisphenol A) and has the general structure ... 

The mechanistic aspect of these reactions is summarized by saying that the reactions occur in steps. Thus the formation of an ester linkage is not essentially different between two small molecules or in a polyester. 

Condensation polymers prepared with some monomer of functionality greater than 2, for example, a polyester formed with some glycerol or tricarboxylic acid. 

It is desired to prepare a polyester with = 5000 by reacting 1 mol of butane-... 

Fig. 7. Chemistiy of a diy-filin, negative-acting photoresist, (a) Polymerizable layer sandwiched between a polyolefin carrier sheet and a polyester cover...

Fig. 2. Scanning electron photomicrograph of a polyester nonwoven fabric.

Fig. 17. Distribution of U.S. synthetic fiber consumption A, acryUc I, olefin +, nylon and aramid A, polyester (71,72).

The Textile Eiber Product Identification Act (TEPIA) requires that the fiber content of textile articles be labeled (16). The Eederal Trade Commission estabhshed and periodically refines the generic fiber definitions. The current definition for a polyester fiber is "A manufactured fiber ia which the fiber-forming substance is any long-chain synthetic polymer composed of at least 85% by weight of an ester of a substituted aromatic carboxyUc acid, including but not restricted to terephthalate units, and para substituted hydroxyben2oate units."... 

Polyesters are also used in continuous filament spunbonded nonwovens (see Nonwoven fabrics). Reemay spunbonded fabric is composed of continuous filament PET with a polyester copolymer binder. These spunbonded fabrics are available in a wide range of thicknesses and basis weights and can be used for electrical insulation, coated fabric substrates, disposable apparel for clean rooms, hospitals, and geotextiles (qv). 

Alternative technology for modifying a poly(aLkylene terephthalate) by incorporation of a phosphinate stmcture has been developed by Enichem. Phosphinate units of the stmcture —P(CgH5) (0)CH20— are introduced into a polyester such as PET or PBT by transesterification with an oligomer comprised of the aforementioned units (136). 

In other areas, POD has been used to improve the wear resistance of a mbber latex binder by incorporation of 25% of Oksalon fibers. Heat-resistant laminate films, made by coating a polyester film with POD, have been used as electrical insulators and show good resistance to abrasion and are capable of 126% elongation. In some instances, thin sheets of PODs have been used as mold release agents. For this appHcation a resin is placed between the two sheets of POD, which is then pressed in a mold, and the sheets simply peel off from the object and mold after the resin has cured. POD-based membranes exhibit salt rejection properties and hence find potential as reverse osmosis membranes in the purification of seawater. PODs have also been used in the manufacturing of electrophotographic plates as binders between the toner and plate. These improved binders produce sharper images than were possible before. 

A polyester backbone with two HFIP groups (12F aromatic polyester of 12F-APE) was derived by the polycondensation of the diacid chloride of 6FDCA with bisphenol AF or bisphenol A under phase-transfer conditions (120). These polymers show complete solubkity in THF, chloroform, ben2ene, DMAC, DMF, and NMP, and form clear, colorless, tough films the inherent viscosity in chloroform at 25°C is 0.8 dL/g. A thermal stabkity of 501°C (10% weight loss in N2) was observed. 

A polyester-type fluorescent resin matrix (22) is made by heating trimellitic anhydride, propylene glycol, and phthaUc anhydride with catalytic amounts of sulfuric acid. Addition of Rhodamine BDC gives a bright bluish red fluorescent pigment soluble in DME and methanol. It has a softening point of 118°C. Exceptional heat resistance and color brilliance are claimed for products of this type, which are useful for coloring plastics. 

Lubrication oil additives represent another important market segment for maleic anhydride derivatives. The molecular stmctures of importance are adducts of polyalkenyl succinic anhydrides (see Lubrication and lubricants). These materials act as dispersants and corrosion inhibitors (see Dispersants Corrosion and corrosion control). One particularly important polyalkenyl succinic anhydride molecule in this market is polyisobutylene succinic anhydride (PIBSA) where the polyisobutylene group has a molecular weight of 900 to 1500. Other polyalkenes are also used. Polyalkenyl succinic anhydride is further derivatized with various amines to produce both dispersants and corrosion inhibitors. Another type of dispersant is a polyester produced from a polyalkenyl succinic anhydride and pentaerythritol [115-77-5]. 

Transesteramidation is a process similar to transamidation, except that a polyamide is mixed with a polyester rather than another polyamide (67). 

Fig. 3. Variation of moisture regain with rh at 20°C. Odon is an acryUc fiber Trevira, a polyester.

The polymer is then dried thoroughly and stored for subsequent processing. Whenever a polyester is made by melt polycondensation, a small amount of cycHc oligomer is formed which is in equiHbrium with the polymer. This can be extracted with solvents from soHd polymer but when the... 

In general, polymers are formed by two types of reactions condensation and addition. The formation of a polyester by polycondensation may be illustrated as follows. 

Quantum, by contrast, converted an ethylene—carbon monoxide polymer into a polyester-containing terpolymer by treatment with acidic hydrogen peroxide, the Baeyer-Villiger reaction (eq. 11). Depending on the degree of conversion to polyester, the polymer is totally or partially degraded by a biological mechanism. 

The concept of functionaUty and its relationship to polymer formation was first advanced by Carothers (15). Flory (16) gready expanded the theoretical consideration and mathematical treatment of polycondensation systems. Thus if a dibasic acid and a diol react to form a polyester, assumiag there is no possibihty of other side reactions to compHcate the issue, only linear polymer molecules are formed. When the reactants are present ia stoichiometric amouats, the average degree of polymerization, follows the equatioa ... 

Hand Lay-Up and Spray-Up. In hand lay-up, fiber reinforcements in mat or woven form are placed on the mold surface and then saturated with a Hquid polymer, typicaHy a polyester resin, that has been chemically activated to polymerize (cure) without the addition of heat. Multiple pHes of reinforcement and multiple cure steps aHow very heavy waH thicknesses to be achieved. 

Polyethylene terephthalate [25038-59-9] (8) is a polyester produced by the condensation polymerization of dimethyl terephthalate and ethylene glycol. Polyethylene terephthalate sutures are available white (undyed), or dyed green with D C Green No. 6, or blue with D C Blue No. 6. These may be coated with polybutylene adipate (polybutilate), polyydimethylsiloxane, or polytetrafiuoroethylene [9002-84-0]. The sutures are distributed under the trade names Ethibond Exel, Mersdene, Polydek, Silky II Polydek, Surgidac, Tevdek II, Polyester, and Tl.Cron. 

The principle of blending a conduction fiber with a static-prone fiber has been known for years. A mixture of a substantial quantity (30—40%) of a hydrophilic fiber such as cotton or rayon with a hydrophobic static-prone fiber such as a polyester can produce a static-free blend under ordinary conditions. However, blocking the hydrophilic groups by cross-linking of the cotton with biflinctional reagents such as dimethylolethylene urea or addition of a water-repellent finish such as a sUicone resin increases the static propensity of such a blend. 

Fig. 5. Interlaminar fracture toughness, for a number of thermosetting and thermoplastic composites (36,37). Open white bars represent glass-fiber composites shaded bars are for carbon fibers. The materials are A, polyester (unidirectional) B, vinyl ester (CSM = chopped strand mat) C, epoxy (R/BR1424) D, epoxy (T300/914) E, PPS F, PES and G, PEEK. To convert J/m to fdbf/in. multiply by 2100.

Polycarbonates. Polyarjiates are aromatic polyesters commonly prepared from aromatic dicarboxylic acids and diphenols. One of the most important polyarylates is polycarbonate, a polyester of carbonic acid. Polycarbonate composite is extensively used in the automotive industry because the resin is a tough, corrosion-resistant material. Polycarbonates (qv) can be prepared from aUphatic or aromatic materials by two routes reaction of a dihydroxy compound with phosgene accompanied by Hberation ofHCl(eq. 5) ... 

This anhydride can then be esterified with polyols yielding a polyester with a residual double bond available for further reaction. AppHcations for chlorendic anhydride derivatives are in polymers for building materials, paints, and other coatings. 

This process is based on the very high reactivity of the isocyanate group toward hydrogen present ia hydroxyl groups, amines, water, etc, so that the chain extension reaction can proceed to 90% yield or better. Thus when a linear polymer is formed by chain extension of a polyester or polyether of molecular weight 1000—3000, the final polyurethane may have a molecular weight of 100,000 or higher (see Urethane polymers). 

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