Crystalline polyethylene terephthalate

Elenga, R., Seguela, R. and Rietsch, F., Thermal and mechanical behaviour of crystalline polyethylene terephthalate) effects of high temperature annealing and tensile drawing, Polymer, 32, 11, 1975-1981 (1991). 

ABA ABS ABS-PC ABS-PVC ACM ACS AES AMMA AN APET APP ASA BR BS CA CAB CAP CN CP CPE CPET CPP CPVC CR CTA DAM DAP DMT ECTFE EEA EMA EMAA EMAC EMPP EnBA EP EPM ESI EVA(C) EVOH FEP HDI HDPE HIPS HMDI IPI LDPE LLDPE MBS Acrylonitrile-butadiene-acrylate Acrylonitrile-butadiene-styrene copolymer Acrylonitrile-butadiene-styrene-polycarbonate alloy Acrylonitrile-butadiene-styrene-poly(vinyl chloride) alloy Acrylic acid ester rubber Acrylonitrile-chlorinated pe-styrene Acrylonitrile-ethylene-propylene-styrene Acrylonitrile-methyl methacrylate Acrylonitrile Amorphous polyethylene terephthalate Atactic polypropylene Acrylic-styrene-acrylonitrile Butadiene rubber Butadiene styrene rubber Cellulose acetate Cellulose acetate-butyrate Cellulose acetate-propionate Cellulose nitrate Cellulose propionate Chlorinated polyethylene Crystalline polyethylene terephthalate Cast polypropylene Chlorinated polyvinyl chloride Chloroprene rubber Cellulose triacetate Diallyl maleate Diallyl phthalate Terephthalic acid, dimethyl ester Ethylene-chlorotrifluoroethylene copolymer Ethylene-ethyl acrylate Ethylene-methyl acrylate Ethylene methacrylic acid Ethylene-methyl acrylate copolymer Elastomer modified polypropylene Ethylene normal butyl acrylate Epoxy resin, also ethylene-propylene Ethylene-propylene rubber Ethylene-styrene copolymers Polyethylene-vinyl acetate Polyethylene-vinyl alcohol copolymers Fluorinated ethylene-propylene copolymers Hexamethylene diisocyanate High-density polyethylene High-impact polystyrene Diisocyanato dicyclohexylmethane Isophorone diisocyanate Low-density polyethylene Linear low-density polyethylene Methacrylate-butadiene-styrene... 

CLTE coefficient of linear thermal expansion CPET crystalline polyethylene terephthalate... 

Nucleating agents are typically added postreactor and are used primarily in injection molding application. However, they can also be used in other thermoplastic processing applications. They are generally incorporated into materials such as nylon, polypropylene, crystalline polyethylene terephthalate (PET), and other thermoplastic PET molding compounds at use levels typically below 1 percent. Incorporation is done in several ways including powder mixtures, suspensions, solutions, or in the form of a masterbatch. 

Figure 6.6 Tensile modulus and loss factor tand for unoriented amorphous polyethylene terephthalate (a) and unoriented crystalline polyethylene terephthalate (b) as a function of temperature at 1.2 Hz (x) modulus ( ) land. (Reproduced with permission from Thompson and Woods, Trans. Faraday Soc., 52, 1383 (1956))...

It is somewhat arbitrary to select the compliances rather than the moduli for decomposition, without more knowledge of the origin of the viscoelasticity. In fact, a similar analysis on the basis of the moduli E and E" has been performed on data for crystalline polyethylene terephthalate by Kawai and associates. The two procedures correspond to assuming that the stress or the strain, respectively, is homogeneous throughout the sample. Actually, depending on the structure and microscopic features of the viscoelastic response, neither may be strictly homogeneous cf. Chapter 14, Section F). 

Polyamide-6 Polyamide-66 (crystalline) Polyethylene terephthalate (crystalline) Pb3(P04)2 NaHjPO NayPsOig Ti02 [77]... 

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... 

All of these intermolecular forces influence several properties of polymers. Dispersion forces contribute to the factors that result in increased viscosity as molecular weight increases. Crystalline domains arise in polyethylene because of dispersion forces. As you will learn later in the text, there are other things that influence both viscosity and crystallization, but intermolecular forces play an important role. In polar polymers, such as polymethylmethacrylate, polyethylene terephthalate and nylon 6, the presence of the polar groups influences crystallization. The polar groups increase the intensity of the interactions, thereby increasing the rate at which crystalline domains form and their thermal stability. Polar interactions increase the viscosity of such polymers compared to polymers of similar length and molecular weight that exhibit low levels of interaction. 

In addition to the desired polymerization reaction, the dialcohol reactants can participate in deleterious side reactions. Ethylene glycol, used in the manufacture of polyethylene terephthalate, can react with itself to form a dialcohol ether and water as shown in Fig. 24.4a). This dialcohol ether can incorporate into the growing polymer chain because it contains terminal alcohol units. Unfortunately, this incorporation lowers the crystallinity of the polyester on cooling which alters the polymer s physical properties. 1,4 butanediol, the dialcohol used to manufacture polybutylene terephthalate, can form tetrahydrofuran and water as shown in Fig. 24.4b). Both the tetrahydrofuran and water can be easily removed from the melt but this reaction reduces the efficiency of the process since reactants are lost. 

Both polyethylene terephthalate and polybutylene terephthalate exhibit partial crystallinity in the solid state. The molecular weight of the polymer and the time permitted for cooling define the degree of crystallinity of the polymer. Very slow cooling results in high crystallinity and opacity, while fast quenching creates low crystallinity, high clarity material. 

Polyethylene terephthalate crystallizes very slowly into only one stable crystalline form, containing monoclinic unit cells. To maximize its physical strength, high crystallinities must... 

Because polyethylene terephthalate crystallizes slowly, it can readily be produced in its amorphous state. This is especially true when it is used in packaging materials, such as thin films and carbonated drink bottles. The final products exhibit high clarity and directionally balanced properties because they lack crystalline regions. 

Semicrystalline polyalkyl terephthalates are opaque due to diffraction of light as it crosses the interface between crystalline and amorphous regions. Amorphous polyethylene terephthalate has a low refractive index, making it appear glass-like in quenched parts. 

Polyethylene terephthalate is most often extruded into films or fibers, or blow molded into bottles. Polybutylene terephthalate is primarily found in injection molded parts. Such parts are highly crystalline, which makes them opaque. Polybutylene terephthalate is often modified with glass fibers or impact modifiers. Table 24.1 contains applications by processing method and resin. 

Why does the incorporation of ethylene glycol in polyethylene terephthalate reduce the crystallinity of the final polymer ... 

Polyethylene terephthalate is the dominant material for the manufacture of carbonated beverage bottles Why are the bottles clear despite the tendency for this polymer to form crystalline domains ... 

For semicrystalline isotropic materials a qualitative measure of crystallinity is directly obtained from the respective WAXS curve. Figure 8.2 demonstrates the phenomenon for polyethylene terephthalate) (PET). The curve in bold, solid line shows a WAXS curve with many reflections. The material is a PET with high crystallinity. The thin solid line at the bottom shows a compressed image of the corresponding scattering curve from a completely amorphous sample. Compared to the semicrystalline material it only shows two very broad peaks - the so-called first and second order of the amorphous halo. 

Polyethylene terephthalate (9.94 mg) gave a peak of area 116.3 cm2 on melting on a DSC, whereas 5.89 mg of pure indium (AHtus = 28.45 J g 1) gave a peak of 40.0 cm2. Calculate the latent heat of fusion of this polyethylene terephthalate, and compare with the pure crystalline value AHtus = 117.57 J g. Comment on the answers. 

In fibres of some polymers, made under certain conditions, the crystalline regions are found to be tilted with respect to the fibre axis in a well-defined crystallographic direction. This is a very valuable feature, because the diffraction patterns of specimens in which this type of orientation occurs are of precisely the same form as tilted crystal diffraction patterns of single crystals rotated round a direction inclined to a principal axis. The unit cell cannot be obtained directly, for 90° oscillation tilted crystal photographs are required for direct interpretation, but unit cells obtained by trial can be checked by the displacements of diffraction spots from the layer lines this is a severe check, and consistent displacements would leave no doubt of the correctness of a unit cell. This procedure played an effective part in the determination of the unit cell of polyethylene terephthalate (Daubeny, Bunn, and Brown, 1954). 

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