Polyethylene terephthalate chemical structure

The effect of incorporating p-hydroxybenzoic acid (I) into the structures of various unsaturated polyesters synthesised from polyethylene terephthalate (PET) waste depolymerised by glycolysis at three different diethylene glycol (DEG) ratios with Mn acetate as transesterification catalyst, was studied. Copolyesters of PET modified using various I mole ratios showed excellent mechanical and chemical properties because of their liquid crystalline behaviour. The oligoesters obtained from the twelve modified unsaturated polyesters (MUP) were reacted with I and maleic anhydride, with variation of the I ratio with a view to determining the effect on mechanical... 

Polyesters form via a condensation reaction between a dicarboxylic acid and a dialcohol to create an ester linkage, as shown in Fig. 24.1. By far, the two most common polyesters are polyethylene terephthalate and polybutylene terephthalate, the chemical structures of which are shown in Fig. 24.2. These two polymers differ from one another by the length... 

In 1953, E. F. Izard of du Pont was awarded the Schoellkopf Medal of the American Chemical Society. The report [36] of this award states that work on the development of a hydrolytically stable polyester was started by Dr Izard in 1944, and it led in a comparatively short time to the discovery of polyethylene terephthalate . The report recognises that polyethylene terephthalate was earlier discovered independently in England by J. R. Whinfield . Izard himself says [37] that the duPont research programme led immediately to the discovery of poly(ethylene terephthalate) (PET), which suggests that detailed information from ICI about the structure of the new fibre had not yet reached him by that time. 

Poro-xylene is an industrially important petrochemical. It is the precursor chemical for polyester and polyethylene terephthalate. It usually is found in mixtures containing all three isomers of xylene (ortho-, meta-, para-) as well as ethylbenzene. The isomers are very difficult to separate from each other by conventional distillation because the boiling points are very close. Certain zeoHtes or mol sieves can be used to preferentially adsorb one isomer from a mixture. Suitable desorbents exist which have boiling points much higher or lower than the xylene and displace the adsorbed species. The boihng point difference then allows easy recovery of the xylene isomer from the desorbent by distillation. Because of the basic electronic structure of the benzene ring, adsorptive separations can be used to separate the isomers of famihes of substituted aromatics as weU as substituted naphthalenes. 

Chemically, Dacron and Mylar are polymers made from a ring structure called dimethyl terephthalate and ethylene glycol (HO-CH2CH2-OH). The polymer unit is called polyethylene terephthalate, or PET. Dacron fiber is used in tires and fabrics, and is even used to repair blood vessels. Mylar is used in magnetic recording tape. In the 1960s, it was used in huge balloons that were sent into orbit around Earth. Plastic soda containers are made of PET. 

FIGURE 43.7 Examples of porous structures produced in thin polymeric films using various methods of irradiation and chemical treatment. (Reprinted from Apel, P., Radial. Meas., 34, 559, 2001. With permission from Elsevier.) (A) Cross section of a polycarbonate membrane with cylindrical nonparallel pore channels (B) polypropylene membrane with slightly conical parallel pores (C) polyethylene terephthalate membrane with cigar-like pores and (D) polyethylene terephthalate membrane with bow-tie pores. 

Figure 10.6 General chemical structure of polyethylene terephthalate (PET).

Polyethylene terephthalate (PET), known by the trade names Mylar, Dacron, and Terylene, has good mechanical strength up to 150-175°C as well as good chemical and solvent resistance. PET can be blended with cotton fiber to give better crease resistance, and it can also be used as tire cord, magnetic tape, and x-ray and photographic film, to name only a few applications. The structure is... 

A brief introduction to commonly used polyesters would be in order here. The most well-known and daily used man-made polyester is polyethylene terephtha-late (PET)(more often written as poly(ethylene terephthalate), whose chemical structure is shown in Figure 1.3). PET is a thermoplastic polymer resin of the polyester family and is used in the form of synthetic fibers. This polyester is generally nonbiodegradable. Whinfield synthesized PET in 1941 and called it terylene [16] and Hardy [17] characterized teryleneusing a couple of methods (Figure 1.3). 

Shabana H. M. (2004). Refractive index-structure correlation in chemically treated polyethylene terephthalate fibers. Polymer Testing, Vol. 23, pp. 291-297, ISSN 0142-9418... 

One of the most useful applications of FITR is the determination of the conformation of polymer chains. This is a result of the high sensitivity of the IR spectra to rotations around chemical groups. This is illustrated in Fig. 6.2, which shows the IR spectrum of the trans and gauche structures for the ethylene glycol portion of the polyethylene terephthalate (PET) chain. From these spectra, it is possible to determine the conformational composition for PET as a function of crystallization, annealing, and processing conditions. 

Polyethylene terephthalate polyester is the leading man-made fiber in production volume and owes its popularity to its versatility alone or as a blended fiber in textile structures. When the term "polyester" is used, it refers to this generic type. It is used extensively in woven and knitted apparel, home furnishings, and industrial appl ications. Modification of the molecular structure of the fiber through texturizing and or chemical finishing extends its usefulness in various applications. Polyester is expected to surpass cotton as the major commodity fiber in the future. 

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