PPTA Poly para-phenylene

The para-aramids are typified by Kevlar (DuPont) and Twaron (Teijin) and are based on poly (para-phenylene terephthalamide) or PPTA. While having enhanced tensile strengths and moduli as a consequence of the extreme symmetry of their polymer chains and hence order or crystallinity, they also have improved thermal performance with a second order transition... 

When the diamine and the dicarboxylic acid are attached to aromatic rings, the generic term for the polymers produced is aramide. The reaction of 1,4-diaminobenzene with tere-phthaloyl chloride gives poly(para-phenylene terephthalamide) (PPTA) marketed as Kevlar (Figure 21.23). Because of the extensive hydrogen bonding network between the chains (Figure 21.24), this is an extremely stiff material and has found wide applications in body armor and safety equipment. 

There are three types of major commercial aramid fibres in the market para-aramid (or p-aramid, poly-(p-phenylene terephthalamide), PPTA), meta-aramid (or m-aramid, poly-(meta-phenylene isophthalamides), MPIA) and co-polyamides fibres. 

Aramid yarns (Kevlar of DuPont, Twaron of Teijin-Twaron) are produced from poly(p-phenylene terephthalamide), PPTA (2), which is specially developed for fiber spinning and not used in any other application. DuPont had experience with poly(m-phenylene isophthalamide) in a fiber product called Nomex for high-temperature applications. The polymer is produced in dimethylacetamide and the solution is dry-spun. This cannot be done with the stiff-chain para-para analogue PPTA. The polymer does not dissolve in organic solvents. A special polymerization route had to be developed, and the discovery of lyotropic behavior of concentrated solutions in sulfuric acid then led the way to the production of a magnificent new fiber material. 

In poly (p-phenylene terephthalamide), there are very stiff polymer chains and this is due to the bonding of rigid phenylene rings in the para position. The other advantage of PPTA is the presence of... 

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