Aromatic Polyamides Polyaramides

Research on polyaramides began at DuPont after 1950, and a first patent appeared in 1958 [24]. The hrst technical product was the m-polyaramide , which was commercialized as a fiber in 1967 under the name Nomex . Due to a Tm of 290-295 °C, combined with high thermostability, Nomex allows for faster sewing and weaving than Nylon-6,6, and it has a higher form stability. Particular important for most applications is its low flammability (see below) Mainly responsible for this success was Wilfred Sweeney (1926-2011), who earned in 2002 the Lavoisier Medal for his life work as researcher [25, 26]. Sweeney had worked at DuPont for 38 years, and he had also contributed to the development of the Dacron polyester fiber. The Lavoisier medal is the highest honor of science excellence awarded by DuPont. 

In 1976, the Teijin Co. began with production of a copoly(p-aramide) containing a smaller amount of 4,4 -diamono diphenyl ether in addition to p-pheny-lene diamine. The incorporation of the second diamine slightly reduced the strength of the fiber, but it also had two benefits, first, only one solvent was needed for the synthesis (see below) and second, a patent war with DuPont was avoided. Later Teijin also acquired the Twaron production from the Dutch AKZO. Twaron is the trademark of a Kevlar - like poly(p-aramide) developed by AKZO in the years 1968-1978 [35, 36]. It was commercialized in 1978 under the name Arenka and later renamed. 

Regardless of chemical stmcture, the synthetic method is, in principle, the same for all polyaramides [37-39]. The diamine is reacted with isophthaloyl- or te-rephthaloyl chloride in dry N-methylpyrrohdone (NMP) at —10 °C in the presence of CaCU, LiCl, or mixtures of both salts. The solvent plays the role of HCl acceptor and it strongly solvates the cations, thereby enhancing the basicity of the chloride anions. The Cl anions react, in turn, as acceptors of H-bonds and prevent association and precipitation of the polyaramide chains. The resulting viscous 

The poly(p-aramide)s possess the following additional advantages  

Since important properties of the poly(p-aramide)s are quite different from those of Nomex , most apphcations are also different. Characteristic are applications as bullet-proof body armor, cut-fast gloves, substitute of asbestos, and as reinforcing component in concrete. They are also used as fibers in high performance tires for airplanes and racing cars, or as laminates for the constmction of boat hulls. Furthermore, poly(p-aramide)s are used for the production of sports articles, drum heads, brake pads, turbo hoses, optical fiber cables, or electrical-mechanical cables. Their fabrics serve as hot air filters and in combination with Nomex for the production of protective clothing and helmets. The total production of polyaramides amounts in 2008 to 60,000 tons. 

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Palladium- or nickel-catalysed carbonylation polycondensation of dibromoar-enes with bifunctional nucleophilic monomers such as aromatic diamines and bisphenols in the presence of carbon monoxide appeared to be a new promising method for the synthesis of aromatic polyamides [scheme (15)] and polyesters [scheme (16)] respectively [162-170], The first successful example was the synthesis of high molecular weight polyaramide according to scheme (15) (Ar1 = m-C6H4-, Ar2 = p-C6H4 O C6H4 ) [162],... 

The composite systems studied by Takayanagi et al. (1980) used the polyaramides poly(p-phenylene terephthamide), PPDT, or pol.y-p-benzamide (PBA) as the reinforcing component with nylon 6 or nylon 66 as the ductile matrix polymer. Block copolymers of one of the aromatic polyamides with one of the nylon polymers were also evaluated. The blends were prepared by extruding the sulfuric acid solutions of polymers into a... 

For example, there is a dramatic improvement in modulus, tensile strength, and thermal stability when the aliphatic components in polyamides (nylons) are replaced by aromatic components, resulting in polyaramides such as Kevlar (29). Likewise, poly(ether ether ketone) (PEEK), one of the mechanically strongest condensation... 

The most extensive research on furanic polyamides is recent (33) and deals essentially with furanic-aromatic structures, although an important effort was also devoted to all-fiiranic compositions. The reaction of the diacid 11a with various aromatic diamines leads to high-molecular weight polymers with good thermal stability and ciystallinity. Structure 23, obtained with p-phenylenediamine, exhibited features resembling closely those of polyaramides ... 

Polyaramid is a term applied to polyamides containing aromatic groups. These polymers were originally made for use as tire cords but have since found many other uses, a. Kevlar is used in bulletproof vests and many high-strength composites. The structure of Kevlar is... 

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