AbstractCaprolactam was copolymerized withm‐xylylenediammonium isophthalate (MXD‐I) to form a series of partially aromatic, thermoplastic copolyamides. The MXD‐I mole‐ in these systems varied between 91 and 31. Using differential scanning calorimetry (DSC), the glass transition temperature of these copolyamides was shown to decrease with decrease in their aromatic content. TheTgof a typical copolyamide with an MXD‐I mole fraction of 0.34 is about 50°C higher than that of nylon 6. The DSC thermograms of MXD‐I homopolymer and all the reported copolymers revealed no distinct melting endotherms or crystallization exotherms, and these polymers were considered to be essentially amorphous. Most of these copolyamides were shown by thermogravimetric analysis to be more thermally stable than nylon 6. Compression‐molded films of several copolymers were prepared and were shown to be less hydrophilic than nylon 6, regardless of their suggested amorphous nature. Tensile properties of several copolyamides were measured and were shown to depend on their MDX‐I content, degree of polymerization, and chain sequential arrangement. A few of the reported copolyamides exhibited some unusual solution, thermal, and tensile properties. This was ascribed to the presence of block structures and/or branching
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