Aromatic polyamide fiber

The primary driving forces behind investigation of new solvents include environmental concerns and the abiUty to form Hquid crystals in the new solvent systems. By analogy with Kevlar, a synthetic aromatic polyamide fiber, spinning from a Hquid crystalline solution should yield cellulose fibers with improved strength, as has been demonstrated in laboratory experiments. 

Aramid Fibers. Aromatic polyamide fibers exhibiting a range of mechanical properties are available from several manufacturers, perhaps the best known being Du Pont s proprietary fiber Kevlar. These fibers possess many unique properties, such as high specific tensile strength and modulus (see Fig. 4). Aramid fibers have good chemical resistance to water, hydrocarbons, and solvents. They also show excellent flame retardant characteristics (see High PERFORMANCE fibers Polyamdes). 

Aromatic nitrations, 17 160-161 by-products of, 17 161 kinetics of, 17 162 Aromatic nitriles, 17 243 Aromatic nucleophilic displacement, polyimide synthesis via, 20 273 Aromatic phosphines, 19 60, 62 Aromatic poly(monosulfide ketone)s, 23 709 Aromatic poly(monosulfide)s, 23 706 Aromatic polyamide copolymers, laboratory synthesis of, 19 720 Aromatic polyamide fibers, 24 614 Aromatic polyamides, 10 210-212 19 713-738. See also Aliphatic polyamides (PA)... 

High performance polymer fibers (HPPF) have excellent mechanical properties compared to traditional textile fibers such as nylon. The typical HPPFs are aramid and polyethylene fibers (6). Aramid is a generic name for a class of aromatic polyamide fibers, most of which are varieties of poly(p-pheny-lene terephthalamide). Kevlar is the trade name of the varieties of aramid polymers introduced conunercially by Dupont. The molecules in the fibers of these materials are oriented in the axial direction. Poly(p-phenylene terephthalamide) is a rigid molecule with the following structure ... 

Most micromechanical theories treat composites where the thermoelastic properties of the matrix and of each filler particle are assumed to be homogeneous and isotropic within each phase domain. Under this simplifying assumption, the elastic properties of the matrix phase and of the filler particles are each described by two independent quantities, usually the Young s modulus E and Poisson s ratio v. The thermal expansion behavior of each constituent of the composite is described by its linear thermal expansion coefficient (3. It is far more complicated to treat composites where the properties of some of the individual components (such as high-modulus aromatic polyamide fibers) are themselves inhomogeneous and/or anisotropic within the individual phase domains, at a level of theory that accounts for the internal inhomogeneities and/or anisotropies of these phase domains. Consequently, there are very few analytical models that can treat such very complicated but not uncommon systems truly adequately. 

Aniline is the second largest petrochemical use of gaseous hydrogen. About half as much hydrogen is used for aniline as for cyclohexane production. Approximately 80% of the aniline produced worldwide is used in the manufacture of MDI for polyurethanes. The balance is used for rubber processing chemicals, agricultural chemicals, dyes, pigments, pharmaceuticals, and specialty polymers. DuPont s aromatic polyamide fiber Kevlar is also derived from aniline [1). 

Aramid fiber is the generic name for aromatic polyamide fibers. As defined by the U.S. Federal Trade Commission, an aramid fiber is a manufactured fiber in which the fiber forming substance is a long chain synthetic polyamide in which at least 85% of the amide linkages are attached directly to two aromatic rings ... 

The fiber may be spun from a solution of the polymer in dimethylformamide containing lithium chloride. In 1973, Du Pont commenced production of another aromatic polyamide fiber, a poly(p-phenylene terephthalamide) marketed as Kevlar. It is produced by the reaction of p-phenylenediamine with terephthaloyl chloride in a mixture of hexametylphosphoramide and N-methyl pyrrolidone (2 1) at -10 C. 

Erickson, R.H. 1985. Creep of the aromatic polyamide fibers. Polymer, 26 733-746. 

Glass fibers Carbon fibers Carbon black Aromatic polyamide fibers Fabric chips... 

Definition Generic name for class of highly aromatic polyamide fibers which are characterized by flame retardant properties Uses Flame retardant protective clothing for military pilots, firefighters, etc. dust-filter bags tire cord bullet-resistant structures business machine components belts hoses ... 

Schmitt TE, Sarzotti DM. Rame resistant yarns and fabrics including partially aromatic polyamide fiber and other flame resistant fibers. WO Patent 2013074181 assigned to Invista Technologies S.A R.L. 2013. 

Fibers are identified here by their chemical names. In this respect it is useful to know that Twaron and Kevlar are the trade names for PpPTA fibers, and that PRD-49 is a fiber made from PpBA. The para-aromatic polyamide fibers PpPTA, PpBAT and PpBA are often called aramid fibers. 

Table 2. Observed refractive indices of para-aromatic polyamide fibers and a PBO fiber, radially lateral, n, tangentially lateral, Hji lateral, n longitudinal. The results of Weeda were obtained by matching immersion liquids under the interference microscope, or from measuring the retardation [139]. For PBO fiber ii was estimated from a birefringence determination...

Fig. 16a-c. Models for the structure of aromatic polyamide fibers, a) Northolt, b) Morgan and c) Panar... 

This mechanical model is depicted in Fig. 21. The Eqs. (15) and (17) have been confirmed for aromatic polyamide fibers by a variety of experiments. Figure 22 shows the dynamic compliance versus the orientation parameter measured during extension of medium and high-modulus PpPTA fibers. It confirms the linear relation (15) and yields e = 240 G Nm and go = 2 G Nm . It has been shown that the tensile curves of the second and higher extensions of an aramid fiber are well described by Eq. (17) [143]. A relation between the strain and the dynamic... 

As discussed previously para-aromatic polyamide fibers show a pleated sheet, which can also be described as a sinusoidal undulation of the fibrils. The effective orientation parameter determining the modulus of the fiber may then be approximated by... 

PBT fibers show a very small strength loss of only 2% after an exposure of 65 h in air at 300 °C. This indicates a thermal stability of the mechanical properties which is even better than that of the aromatic polyamide fibers [31, 170].. 

Most polyamides, such as Nylon 6 (mp 200°C), tend to melt before achieving complete thermal stability. Nylon 6,6 (mp 260°C) is better [302], but best results are obtained with an aromatic polyamide fiber, NOMEX (mp > 400°C) which can be oxidized at 300°C and can be carbonized... 

Interest, academic and Industrial, In Liquid Crystal Polymers (LCP s) was sparked by the commercialization of Kevlar aromatic polyamide fiber In the early 1970 s. [1,2] This fiber can be made almost as stiff and as strong as steel, at one fifth of the density of steel. In addition. It has good resistance to chemical attack and outstanding resistance to heat. From a scientific point of view, LCP s are Interesting because they. In addition to displaying a variety of phenomena and properties seen with conventional Isotropic polymers, also exhibit many of the complex physical properties of small molecule liquid crystals.[3]... 

Lastly, aromatic polyamide fibers have been used as stable thixotropes for epoxy compositions, demonstrating that useful thixotropy can be achieved with organic materials. ... 

The properties of aromatic polyamide fibers and films are sufficiently different from those of the products that preceded them that many new uses and... 

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