Spin-lattice relaxation Nylon

Figure 26 Crystallization time dependence of the spin-lattice relaxation time for nylon 46. (A) The crystalline phase (B) the amorphous phase.

The improved sensitivity of 15N enriched nylon-12 samples allows the clear identification of a shoulder appearing at 122.8 ppm (see Fig. 6C ). Although the exact identity is unclear, this peak is assigned on the basis of spin-lattice relaxation data to material epitaxially crystallized on the surface of 7 crystallites or to an ordered interphase region. The spectra of quenched samples (Fig. 6B, 6B ) are very similar in shape. However, the broader base of natural abundance sample indicates that the residual monomer (lauryllactam) may be acting as a plasticizer and increasing the size of conformational mobility of the amorphous region. The residual monomer is probably responsible for the difference in the relative intensities between natural abundance and 15N enriched samples (Fig. 6A, 6A ) [50]. 

Spin-lattice relaxation times, nTj, for different phases of various nylon samples are listed in Table 6. The a crystal form of both nylon-6 and nylon-11 exhibit a single exponential decay function in a plot of signal intensity vs delay x, with corresponding nTt values in the 103 s range. The sample prepared in situ has the shortest Tj relaxation time which indicates more rapid motions due either to plasticization by residual caprolactam or differences in the crystalline regions. 

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