Aramids reaction conditions

Use of diiodinated aromatics allowed the formation of a variety of aramids (Table I). The optimum stoichiometry for achieving maximum molecular weight in the reaction of m-dihalobenzene and 4,4 -diaminodiphenylether was to use a slight excess of the diamine. Model studies indicated that this decreased the likelihood of reduction of the aryl-halide bond that would effectively terminate the polymer chain (6). The other aramid reactions were not optimized but used conditions found optimal for equation 1 (X = I). 

Properties of an aramid fiber are shown in Table 13.2. Extensive tables of chemical stability are given in the literature. Nomex can be chlorinated without any significant decomposition, however, Kevlar decomposes under the same conditions of chlorination. Experiments with model compounds revealed that the p-diaminophenylene moiety is oxidized to a quin-one intermediate when treated with h)q)ochlorous acid, that is not stable. In contrast, with Nomex such a reaction mechanism is not possible. ... 

As mentioned in Section 3, typical aramid-6-polyether elastomers are synthesized by the polycondensation reaction of polyether diol with the aramid compound I in the presence of transesterification catalysts. Under these conditions, the synthesis of aramid-6-polyester elastomers gave only low molecular weight elastomers with a broad segment length distribution due to transesterification reactions of the polyester segments. This result inidicated that in the obtaining of aramid-6-polyester elastomers, transesterification catalysts should be avoided. Later, a method for the obtaing of this type of elastomers was developed, which consisted in the copolymerization of an activated acyl lactam-terminated aramid compound II with polyester diols in the molten state, in the absence of transesterification catalysts [40,42]. Compound II was obtained by the reaction of N-(p-aminobenzoyl) caprolactam with terephthaloyl chloride, as shown in Scheme 8 [61]. 

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