PPTA

Factor (synonym) CAS Registry Number Protein type Molecular weight, daltons Isoelectric point PPTA, %... 

PPTA = degree of saturation of (NH 2S04 solution necessary for precipitation of factor. Synthesis is vitamin K-dependent. 

See also 3,4 -Diaminodiphenyl ether (3,4 ODA) ODA/PPTA fibers Polyfp-phenylene terephthalamide) (PPTA) commercial process for, 19 721-723 wet spinning of, 19 725 Copolyfp-phenylene sulfide sulfone/ ketone) s, 23 710... 

Diaminodiphenyl ether (3,4 ODA), 19 715. See also Copoly(p-phenylene/ 3,4 -diphenyl ether terephthalamide) (ODA/PPTA)... 

Octynoic acid, 5 34t Ocular drug delivery, 9 50 Ocular infections, sulfonamides for, 23 499 ODA/PPTA fibers, uses for, 19 734-735 Oddy test, in fine art examination/ conservation, 11 409 O-dealkylation, 9 441 Odometric titration method, 14 59 Odontalag, molecular formula and structure, 5 9 It Odor... 

Recording media, PPTA film in, 19 735 Record keeping, for market research, 15 635... 

Effect of surface modification on pull-out force of PPTA silicone rubber composite ... 

As a consequence of this almost perfect alignment of molecule structures, such polyamides are able to orientate in solution and to form liquid crystalline phases (see Sect. 1.3.4). Out of these solutions one obtains fibers of poly(p-phenylene terephthalamide) (PPTA) having 5-10-fold higher values for stiffness and strength as the all-mefa linked polymers. In addition, PPTA crystallizes, whereupon the fibers achieve an extraordinary temperature resistance in a nitrogen atmosphere they decompose at temperatures above 550 °C without melting. 

The extreme insolubility of PPTA in common organic solvents is a serious disadvantage for the production and processing of this type of polymer. The solu-... 

Perhaps the most widely utilized (and studied) lyotropic LCP is poly j -phenylene terephthalamide (PPTA), more commonly known as Kevlar (see Figure 1.70). Kevlar belongs to the class of aramids that are well known for their LCP properties. Because these polymers are crystalline in solution, they are often spun into filaments, from which the solvent is subsequently removed in order to retain the aligned polymer structure. The result is a highly oriented, strong filament that can be used for a wide variety of structural applications. Most thermotropic LCPs are polyesters or copolymers that can be melted and molded into strong, durable objects. 

In concluding this section, we should touch upon phase boundary concentration data for poly(p-benzamide) dimethylacetamide + 4% LiCl [89], poly(p-phenylene terephthalamide) (PPTA Kevlar)-sulfuric acid [90], and (hydroxy-propyl)cellulose-dichloroacetic acid solutions [91]. Although not included in Figs. 7 and 8, they show appreciable downward deviations from the prediction by the scaled particle theory for the wormlike hard spherocylinder. Arpin and Strazielle [30] found a negative concentration dependence of the reduced viscosity for PPTA in dilute Solution of sulfuric acid, as often reported on polyelectrolyte systems. Therefore, the deviation of the Ci data for PPTA in sulfuric acid from the scaled particle theory may be attributed to the electrostatic interaction. For the other two systems too, the low C] values may be due to the protonation of the polymer, because the solvents of these systems are very polar. 

The zero-shear viscosity r 0 has been measured for isotropic solutions of various liquid-crystalline polymers over wide ranges of polymer concentration and molecular weight [70,128,132-139]. This quantity is convenient for studying the stiff-chain dynamics in concentrated solution, because its measurement is relatively easy and it is less sensitive to the molecular weight distribution (see below). Here we deal with four stiff-chain polymers well characterized molecu-larly schizophyllan (a triple-helical polysaccharide), xanthan (double-helical ionic polysaccharide), PBLG, and poly (p-phenylene terephthalamide) (PPTA Kevlar). The wormlike chain parameters of these polymers are listed in Tables... 

We compare Eq. (74) with the experimental results for two more stiff-chain polymers, PBLG and poly(p-phenylene terephthalamide) (PPTA). Since avail-... 

In most of the previous work with polyimide fibers, the fibers were spun from poly(amic acid) precursors, which were thermally imidized in the fiber form. However, high degrees of imidization were not achieved. Thus, tensile properties of these polymers were not as good as those of high-performance fibers. Work in our laboratories has shown that when the fibers are spun directly from preimidized polymers, it is possible to achieve tensile properties that are as good or even better than those of poly(p-phenyleneterephthalamide) (PPTA or Kevlar ) fibers. For example, fibers have been prepared from m-cresol solutions of BPDA-PFMB using a dry-jet wet-spinning method. The as-spun fibers were then extensively drawn and annealed above 400°C to achieve excellent mechanical properties. 

A PFMB-based polyimide (BPDA-PFMB) can be used to prepare fibers with mechanical properties comparable to those of commercial PPTA fibers. However, owing to superior thermooxidative stability, the fibers retain their properties for much longer periods of time when subjected to isothermal aging in air at elevated temperatures. In fact, BPDA-PFMB fibers retain their properties under these conditions better than any other available high-performance fiber. 

PdCI . deposited on poly(p-phenylenc terephthalamide) (PPTA)... 

A theoretical analysis of the possible conformations of polylp-phenylene terephthalate) (PPTA) and polylp-phenylene isophthalate) (PPIA) is performed on the basis of molecular mechanics and molecular dynamics trajectories. The dependence of the persistence length on the fluctuations of the torsional angle around the ester bond is discussed for PPTA in the frame of the RIS model. Realistic parameters like bond length and bond angles are provided by computer simulations using MD. 

Sometimes in practice, we may have no choice of solvent for a given polymer. For example, poly(l,4-phenyleneterephthalamide) (PPTA or Kevlar) is only soluble in very strong acids which are viscous. In such cases, ultracentrifugation instead of filtration has to be used to remove dust particles from the solution [14-16,25]. As for copolymers, the selection of proper solvents is even more difficult, because at least two solvents which satisfy the above mentioned three criteria are needed. For this reason, reported characterization of copolymers is quite limited [26-29]. 

Silver Chlorite, AgC102, yel crysts, detonates on heating was ppta when an acidified soln of alk chlorite was treated withAg nitrate Refs l)Mellor 2(1922), 283 2)G.R. Levi,... 

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