Several series of nylon 66 copolyamides were prepared with up to 30 mole‐% substitution of ringed comonomers of the type X‐(CH2)n‐R‐(CH2)n‐X, where n = 0, 1, or 2; X = −NH2 or CO2H; and R = phenylene, cyclohexylene, or naphthyle. The ring structure was correlated with glass transition temperature and melting point. The important features of ring structure fall into the following categories: ring isomerism, aromaticity, diamine vs. diacid substitution, chain length, and ring substitution. Proper “fit” (isomorphism) of the comonomer into the nylon 66 chain appears to be the main criterion for ringed copolymers of high Tg and high melting point.

Polyamides were prepared from linear, aliphatic dicarboxylic acids of six to twelve carbon atoms with 1,4‐cyclohexanebis(methylamine), 1,4‐cyclohexanebis (ethylamine), p‐xylylenediamine, and p‐phenylenebis(ethylamine). Melting points, glass transition temperatures, densities, and moisture regains were compared for the polymers to determine the relative effect of the cyclohexylene and phenylene linkages. While polyamides containing the trans‐cyclohexylene group possessed higher glass transition temperatures than their aromatic counterparts, melting behavior was not as consistent. The odd‐even rule, which states that polyamides with an even number of methylene linkages between the ring and the functional group melt higher than those with an odd number of such linkages, was violated in the cycloaliphatic systems. The Tg of ring‐containing polyamide fibers was not dependent solely upon ring concentration, but was influenced by the molecular fit of the ringed intermediate in the polymer chains. Molecular fit appears to affect the Tg and melting point of alicyclic polyamides to a greater extent than the aromatic analogs. Differences in Tg, both within and among the polymer series, was not explained by either density or the degree of crystallinity.

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synopsisA homologous polyamide series of 1,4cyclohexanebis(ethylamine) (CBEA) was prepared with Cg to Clz linear, aliphatic dicarboxylic acids. Polymer and fiber properties were found to be quite dependent upon the cis and trans structure of the cycloaliphatic ring. Polyamides based on trans-l,.Q-CBEA had higher melting and higher glass transition temperatures than their cis analogs. In addition, trans polyamides were quite crystalline, whereas the cis polymers were almost completely amorphous. The boiling water shrinkage, tenacity, and moisture regain of the fibers reflected the differences in molecular fit between the cis and trans polyamides. INTRODUCTIONPolyamides containing cyclohexylene linkages have not been studied as extensively as those with phenylene linkages. Moreover, the influence of the cyclohexane ring upon polymer and fiber properties is complicated by the existence of cis and trans isomers. Interconversion of these isomeric forms can occur during melt polymerization, which dictates careful selection of intermediate materials and analysis of polymeric products. Isomerization of cis to trans structure during thermal polymerization has been reported to occur where the carboxyl group is joined directly to the cyclohexane ring.''2 Carboxyl groups separated from the ring by a methylene linkage do not cause isomerization under thermal polyc~ndensation,~ nor do amino groups, whether attached to the ring4 or separated by a methylene link.5Investigations of the cyclohexylene linkage have been concentrated primarily upon the development of heat-resistant, fibers, most of which employed cyclohexane amino acids as the starting monomer. Polyamides prepared from simple cycloaliphatic diacids and diamines have been limited primarily to diaminocy~lohexane,~~~ hexahydrophthalic acids, 1*7 and 1,4-cyclohexanebis(methylamine) .5 Unfortunately, many polyamides based on these materials are unsuitable for melt polymerization because the polymer melting points are too high.Most studies of cyclohexylene polyamide properties have been limited to melting point, solubility, or thermal stability. While such data are quite valuable, a broader investigation of structure-property relationships would be helpful.

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