The NMR spectra of polyamide 46/polyamide 6I copolymers, which were obtained by reaction in the molten sate, are studied. Using 13 C NMR, a physical blend of polyamide 46 and polyamide 6I and a polyamide 46/polyamide 6I copolymer could be discriminated. Four kinds of diad sequences are observed in the carbonyl resonance signals of the polyamide 46/polyamide 6I copolymer, and an assignment has been made. From the relative peak areas of the diad sequences and using a statistical method for a four-component polyamide system, the degree of transamidation, the degree of randomness, and the number-average block length have been calculated.

The structure of polyamide 46/polyamide 6I copolymers obtained by reaction in the molten state is analyzed as a function of the extrusion time, the extrusion temperature, and the overall blend composition by 13 C NMR. The degree of transamidation, the degree of randomness, and the numberaverage block length of the copolymers are calculated using the method for a four-component polyamide system. It is shown that the transamidation processes are occurring very fast during the first period of melt-mixing but are slowing down at longer extrusion times. High extrusion temperatures affect the transamidation processes in an increasing way. From 13 C NMR experiments on PA 46/PA 6I copolymers with different compositions, differences in reactivities are observed. The change of the molecular structure of the copolyamides as a function of the processing conditions and the overall blend composition strongly affects their crystallization behavior.

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Melt-mixing of blends of polyamide 46 (PA 46) and polyamide 6I (PA 6I) gives rise to the formation of copolymers on account of the occurrence of transamidation reactions. The degree of transamidation as obtained during the first minutes of melt-mixing is often too low to permit characterization by NMR or FTIR. To solve this problem, gradient elution chromatography (GEC) has been used. It is visualized using this technique to what extent transamidation is occurring during the first 10 min of melt-mixing. Also, the dependence of the reaction rate on the extrusion temperature has been studied using GEC. Melt-blending of PA 46 having varying end-group concentrations and end-group ratios with PA 6I does not seem to alter the elution behavior of the copolyamides formed; this indicates a transamidation mechanism of hydrolysis and recombination. Finally, it has been proved that degradation processes occurring during the residence time of the melt in the extruder do not influence the retention time of the polyamides in the column.