Melt-quenched samples

Fig. 5 Difference intensity SAXS curves of PET after subtraction of the intensity of the melt-quench sample crystallized from the glassy state at 80 C for 3-122 min (a) and 157-313 min (b) [7]...

Fig. 2 WAXD profiles (a) and the distance distribution functions P(R) (b) of PET as a function of annealing time at 115 °C. M.Q. Melt-quenched sample [6]...

It is known that polyoxymethylene in the crystalline phase takes the all gauche conformation with a 9/5 helix [21]. However, the amorphous phase has a distribution of gauche and frans-conformations. Figures 7.10 and 7.11 show the CPMAS NMR spectra and powder pattern spectra of polyoxymethylene, respectively [22]. Sample A is a polyoxymethylene single crystal. To produce Sample B, Sample A is heated to 200°C and then quenched in ice water. Sample C is a melt-quenched sample of bulk polyoxymethylene and sample D is a bulk polyoxymethylene heated and cooled at a rate of... 

Figure 12.3(a, b) shows expanded CP/MAS and PST/MAS NMR spectra as functions of the CH2 carbons in the nylon 4 melt-quenched sample, which contains a larger noncrystalline fraction compared with the single crystal samples. In the CP/MAS spectra, the noncrystalline jS-CH2 and W-CH2 peaks are observed with a weak intensity, but in the PST/MAS spectra their peak intensities increased drastically. This leads to the correct... 

CP/MAS and PST/MAS NMR spectra of nylon 6 single crystals sample, melt quenched sample, and drawn sample at room temperature (the carbonyl peak is not shown because a single sharp line appears without significant change for all samples). The lineshapes of the CHa peaks depend on the crystallization conditions, and, furthermore, those for the same sample obtained by CP/MAS and PST/MAS are markedly different. It is noted that the PST/MAS method, in contrast to the CP/MAS method, enhances the peak intensity for CHa carbons, such as those in the noncrystalline state, which undergo relatively rapid reorientation. Therefore, a comparison of C CP/MAS and PST/MAS spectra leads to a discussion of the structure and dynamics of the crystalline and noncrystalline states in nylon 6 sample crystallized under various conditions. The C chemical shifts are listed in Table... 

Fig. 12.5. CP/MAS and PST/MAS NMR spectra of nylon 6 sample at room temperature (a) single crystal (b) melt-quenched sample and (c) drawn sample.

Figure 12.5(b) shows expanded PST/MAS NMR spectra of the CH2 carbons in nylon 66 melt-quenched sample as a function of temperature. The aN(n)CH2 peak is more intense than the nCH2 peak, which appears as a small shoulder on the aN(n)CH2 in the CP/MAS spectrum. At 20°C, a peak appears between the, yiM)CH2 and )8cCH2 peaks. This peak moves to low frequency as the temperature is increased and overlaps with the i3cCH2 peak. This peak is assigned to the noncrystalline 7nCH2 carbon. Figure 12.5(c) shows the expanded LD/MAS NMR spectra of the nylon 66 sample at 20, 60 and 100°C. In the spectrum no peak is observed at 20°C, and very broad peaks appear at 60°C. At 100°C, five CH2 peaks and a carbonyl peak appear clearly due to fast molecular motion (T = 50°C). The chemical shifts are listed in Table 12.3. The carbonyl chemical shift... 

The central part of the spherulites and spherulitic impinging lines is degraded first, followed by the other parts of the spherulites (Fig. 16). It was also found that a sample isothermally crystallized at 60°C, which had a spherulite composed of less densely packed fibrils, had a higher degradation rate compared with a melt-quenched sample, in spite of similar crystallinity. This result indicates that the internal stmcture of the spherulite also played an important role in hydrolytic degradation. 

Figure 4.2 DSC traces of as-received samples of poly(propylene alkylene dicarboxylatejs recorded at a heating rate of 20°Cmin (a) and of the melt-quenched samples, recorded at a heating rate of 2.5 °C min" (b) [9].

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