Poly-p-phenylene terephthalate

The moduli of polymers cover a wider range than those of other materials (from 105 N/m2 for rubber to 1010 N/m2 = 10 GPa for rigid polymers), which is one of the reasons why polymers are so versatile in application. Absolute stiffness and strength of polymers are much lower than those of metals, but on the basis of equal weight polymers compare favourably due to their much lower density. The specific moduli, defined as the moduli divided by the density, of isotropic polymers are of the order of one tenth of those of the stronger metals. The hyper-strong and hyper-stiff polymeric fibres such as fully extended polyethylene, stretched poly-(p-phenylene terephthalic amide) and carbon,... 

Launne, T., Neelov, I., and Sundholm, F., Molecular dynamics simulations of polymers of unsubstituted and substituted poly(p-phenylene terephthalate)s in the bulk state, Macromol. Theor. Simul., 10, 137, 2001. 

Aromatic polyesters undoubtedly represent the most important class of thermotropic nematics. Fully aromatic rod-hke homopolymers such as poly(p-oxybenzoate) or poly (p-phenylene terephthalate) melt at temperatures which are too high to form a stable nematic mesophase. However if the regular chemical structure of the homopolymer is disrupted, the melting temperature is reduced and it is possible to obtain thermotropic nematics. ... 

In addition to the higher Nylons (610 and 11) there are aromatic polyamides named aramids. One of them is poly (p-phenylene terephthalate) commonly known as Kevlar , made by DuPont. This material can be made into fibers. The specific strength of such fibers is five times that of steel, therefore, it is most suitable for making composites. 

Figure 3. Monomers and polymer structures of the unsubstituted para-linked aromatic polyesters, poly-(p-phenylene terephthalate) [poly(TA/HQ)] and poly-(p-hydroxybenzoic acid) [poly(HBA)].

Table 1. Glass transition temperatures, melting temperatures, and clearing temperatures of selected mono- and disubstituted poly-(p-phenylene terephthalate) esters with flexible substituents.

A selection of monosubstituted and disub-stituted poly-(/ -phenylene-terephthalate)s is compared in Table 2. Poly(p-phenylene-terephthalate)s with methyl, methoxy, chlo-ro, or bromo substituents on either the hy-droquinone or the terephthalic acid moiety exhibit melting temperatures of 350 °C or higher. Thermotropic liquid crystalline behavior is observed in these samples, although it is in the range of thermal decomposition. A comparison of the mono- and diphenyl substituted polyesters reveals an important trend. The monosubstituted poly-(p-phenylene-terephthalate) with the phenyl substituent in the hydroquinone moiety melts at 346 °C, also forming a nematic melt up to a clearing temperature of... 

Already in 1965, the formation of lyotropic liquid crystalline solutions of poly-(p-aminobenzoic acid) in concentrated sulfuric acid was observed. This work was the basis for the commercialization of high strength, high modulus, and heat-resistant poly-(p-phenylene terephthalate) (PPDT) fibers under the trade name Kevlar (Dupont) and Twaron (Akzo) (Fig. 15) [31]. PPDT is typically prepared by the polycondensation of terephthaloyl chloride and 1,4-pheny-lenediamine in tertiary amidic solvents such as A-methylpyrrolidinone or dimethylacet-... 

A polymer composite with a low glass transition temperature has been described as based on layered photoconductive polymers, namely, poly(p-phenylene terephthalate carbazole)s. " These polymers consist of a rigid backbone of poly(pentylene terephthalate) with pendant oxyalkyl carbazole groups. When the host polymers are mixed with various dopants, the layers are preserved and their layer distance increases, indicating that all the guest molecules are confined to the nanoscale interlayer space. 

Quite early solution blend work by Takayanagi et al. [83] of rigid aromatic polyamides (poly(p-phenylene terephthalate)) (PPTA) and flexible aliphatic polyamides, nylon 66 and nylon 6 (the latter will be discussed here) has been instrumental in developing the concept of molecular composites and although this lies more in the realm of lyotropic blends, it is often cited in the literature with regard to the effect of the PLC on the crystallization of other components in blends. PPTA has the structure... 

Experimental results show that the reinforcement depends primarily on the EP -f PLC miscibility, PLC concentration, and sizes and shapes of the islands. A method of miscibility improvement was developed by Schleeh, Kossmehl, and Hinrichsen [86-88] who synthesized poly(p-phenylene terephthalates) with pentoxy groups as flexible side chains. Needless to say, such side chains mix well with EPs. 

W. Hatke, H.-T. Land, H.-W. Schmidt, and W. Heitz, Influence of aryl substimtes on the thermal and solubiUty behavior of poly(p-phenylene terephthalate) and poly(p-phenylene terephthala-tmAe), Makromol. Chem., Rapid Commun., 12, 235 (1991). 

Polyesters such as poly(p-phenylene terephthalate), which would be expected to form liquid crystalline phases, decompose at temperatures below the melting point. Three principal methods have been used for lowering the melting... 

Ballauff M (1989) Networks composed of rigid rod polymers, Angew Chem Int Ed 28 1130-1131. Krigbaum W R, Hakemi H and Kotek R (1985) Nematogenic poljmers having rigid chains. 1. Substituted poly(p-phenylene terephthalates), Macromolecules 18 965-973. 

Various workers have discussed aspects other than those mentioned above in studies of the viscoelastic properties of polymers. These include PVOH [62], hydroxy-terminated polybutadiene [63], styrene-butadiene and neoprene-type blends [64], and polyamidoimides [65]. Other aspects of viscoelasticity that have been studied include relaxation phenomena in PP [66] and methylmethacrylate-N-methyl glutarimide copolymers [67], shear flow of high-density polyethylene [68], Tg of PMMA and its copolymers with N-substituted maleimide [69] and ethylene-vinyl acetate copolymers [70], and creep behaviour of poly(p-phenylene terephthalate) [71] and PE [72]. 

Two examples of aromatic polyesters poly(4-oxybenzoyl) 1 and poly(p-phenylene terephthalate) 2 are shown below ... 

Poly-p-phenylene terephthalate (PPT) and poly-p-hydroxybenzoate (PHB) are the simplest and most accessible representatives of the aromatic polymers ... 

The first totally aromatic polyester was poly p-phenylene terephthalate (Ekonol) prepared by the following route. 

Chen C. Wen, Sauer A. John, and Kara Masanori. Melt processable blends of ionic poly(p-phenylene terephthalate) and poly(4-vinylpyridine) Relaxation behavior. J. Polym. Sci. Pol. Phys. 41 no. 13 (2003) 1468-1475. 

Damman, S.B. and Buijs J.A.H.M. (1994) Liquid-crystalline main-chain polymers with a poly(p-phenylene terephthalate) backbone. 5. Dynamic-mechanical behavior of the polyester with dodecyloxy side-chains. Polymer, 35, 2359. 

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