Polyfethylene terephthalate

The successful development of polyfethylene terephthalate) fibres such as Dacron and Terylene stimulated extensive research into other polymers containing p-phenylene groups in the main chain. This led to not only the now well-established polycarbonates (see Chapter 20) but also to a wide range of other materials. These include the aromatic polyamides (already considered in Chapter 18), the polyphenylene ethers, the polyphenylene sulphides, the polysulphones and a range of linear aromatic polyesters. 

Linear polyesters were studied by Carothers during his classieal researches into the development of the nylons but it was left to Whinfield and Dickson to discover polyfethylene terephthalate) (BP 578079), now of great importance in the manufacture of fibres (e.g. Terylene, Dacron) and films (e.g. Melinex, Mylar). The fibres were first announced in 1941. 

With the expiry of the basic ICI patents on poly(ethylene terephthalate) there was considerable development in terephthalate polymers in the early 1970s. More than a dozen companies introduced poly(butylene terephthalate) as an engineering plastics material whilst a polyether-ester thermoplastic rubber was introduced by Du Pont as Hytrel. Polyfethylene terephthalate) was also the basis of the glass-filled engineering polymer (Rynite) introduced by Du Pont in the late 1970s. Towards the end of the 1970s poly(ethylene terephthalate) was used for the manufacture of biaxially oriented bottles for beer, colas and other carbonated drinks, and this application has since become of major importance. Similar processes are now used for making wide-neck Jars. 

Some typical properties of commercial polyfethylene terephthalate) film, e.g. Melinex (ICI), Mylar (Du Pont), are given in Table 25.6. 

The principal uses of polyfethylene terephthalate) film are electrical, particularly in capacitors, as slot liners for motors and for recording tape. Its high strength and dimensional stability have led to a number of drawing office applications. The film is also a useful packaging material whilst metallised products have a number of uses as a decorative material. 

Allyl resins Polyester Moulding Compositions Fibre-forming and Film-forming Polyesters Polyfethylene terephthalate) Moulding Materials... 

Problem 31.8 I Polyfethylene terephthalate), or PET, is a polyester used to make soft-drink bottles. 

Ashida, M., Composites of polychloroprene rubber with short fibres of polyfethylene terephthalate) and nylon, in Short Fiber-Polymer Composites, De, S.K. and White, J.R. (Eds.), Woodhead Publishing, Cambridge, 1996, Chapter 5. 

Figure 9. Uncorrected fluorescence spectra of polyfethylene terephthalate yarn ...

Both vibrational spectroscopies are valuable tools in the characterization of crystalline polymers. The degree of crystallinity is calculated from the ratio of isolated vibrational modes, specific to the crystalline regions, and a mode whose intensity is not influenced by degree of crystallinity and serves as internal standard. A significant number of studies have used both types of spectroscopy for quantitative crystallinity determination in the polyethylenes [38,74-82] and other semi-crystalline polymers such as polyfethylene terephthalate) [83-85], isotactic poly(propylene) [86,87], polyfaryl ether ether ketone) [88], polyftetra-fluoroethylene) [89,90] and bisphenol A polycarbonate [91]. 

Identification of individual film layers was performed using ATR-FTIR. The outside layer labeled "1" was optically clear and was identified as an aromatic polyester most likely polyfethylene terephthalate) (PET) or an ethylene terephthalate/isophthalate copolymer. 

Figure 4. Particle size histograms of dust collected while processing cotton and polyfethylene terephthalate) (PET). Key 100% PET VE, 577 gg/nP N,...

Table 9. Mechanochemical polycondensation of polyfethylene terephthalate) with Polymer-...

Shortening the flexible spacer must ultimately lead to rigid chain macromolecules. Many examples of such macromolecules have been reviewed by Preston99. An interesting example is the series of polyfethylene terephthalate-co-oxybenzoate)s... 

Yeh JT, Hsieh SH, Cheng YC, Yang MJ, Chen KN. Combustion and smoke emission properties of polyfethylene terephthalate) filled with phosphorous and metallic oxides. Polym. Degrad. Stab. 1998 61 399 107. 

Figure 7. The C-Is ESCA spectra of polyfethylene terephthalate) (top), poly-(ethylene oxide) fcenterj, and antraqui-none (T)ottoinJ. All spectra charge-referenced to alkyl-like C-ls at 284.0 eV.

This distinction is primarily useful when the main chain of the macromolecule consists of carbon-carbon bonds. There is little point in labeling polyfethylene terephthalate), 1-5, a copolymer, since this repeating unit obviously contains the residues of two monomers and the polymer is made commercially only by reaction (1-1) or (1-7). Some polyesters are, however, made by substituting about 2 mol % of sodium-2,5-di(carboxymethyl) sulfonate (1-24) for the 3,5 isomer for the dimethyl terephthalate in reaction (1-7) ... 

The only practical means for ensuring the desired polymer quality is to use scrupulously pure monomers. Purification of a polymer after it is synthesized would be prohibitively expensive, because these materials are sparingly soluble and are often difficult or impossible to crystallize or free of solvent. The overall least expensive route to good quality polyfethylene terephthalate) was therefore through the dimethyl ester of terephthalic acid as shown in reaction (b). The byproduct methanol was recovered to generate more diester from the acid. In more recent years, methods have been developed to produce the diacid with satisfactory purity, and reaction (a) is now the preferred route to this polymer because the esterification step with methanol can be eliminated. Reactions (d), (e), and others, which the reader may be able to write, will be more expensive in the final analysis for the various reasons mentioned above. 

Suzuki F, Onozato K, and Takahashi N. Pervaporation of thermal mixture of benzene/toluene by polyfethylene terephthalate) membrane and synergetic effect on concentration dependence of diffusion rate. J Appl Polym Sci 1982 27 2179-2188. 

To the diacid and did type polyester belongs, for example, polyfethylene terephthalate), CAS 25038-59-9, which can be viewed (and synthesized) from terephthalic acid and ethylene glycol by water elimination, as shown below ... 

Figure 10.1.11. Result for a Py GC/MS analysis of polyfethylene terephthalate) sample Mm = 18,000. Pyrolysis done on 0 4 mg material at 60(f C in He, with the separation on a Carbowax type column.

Table 10.1.7. Compounds identified in the pyrogram of polyfethylene terephthalate) shown in Figure 10.1.11.

Figure 1.20 Spectra measured by raising the level of a polymer laminate sample consisting of a lOOpm-thick layer of polyfethylene terephthalate) (PET) under a 20pm-thick layer of poly(ethylene) (PE). The strongest bands in the Raman spectra of PE and PET are marked with arrows. Illustration courtesy of Dr Neil Everall, Measurement Science Croup, Intertek Corporation.

Crystallization can take place whenever the polymer is at a T above T. At 25° C, polycaprolactone is above Tg and so it may crystallize. On the other hand, polyfethylene terephthalate) can be quenched to 25°C at various rates resulting in various degrees of crystallinity which will not change as long as the temperature does not exceed Tg. So this polymer will be more suitable for the biodegradabOity study. 

Jackson and Kuhfuss from Tennessee Eastman demonstrated that liquid crystalline behavior existed in copolymers based on polyfethylene terephthalate) (PET) and para-hydroxy benzoic acid (ABA). However, intricate details pertaining to the polyesterification kinetics have remained imexamined. 

Copolymers, Block Polymers, and Graft Polymers. When more than one monomer is involved, monomer-based names are more complex. Some common polymers have been given names based on an apparent structure, as with polyfethylene terephthalate) A better system has been approved by the lUPAC. With this method, the arrangement of the monomeric units is introduced through use of an italicized connective placed between the names of the monomers. For monomer names represented by A, B, and C, the various types of arrangements are shown in Table 1. 

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