Relaxation amorphous

Dynamic mechanical measurements were made on PTEE samples saturated with various halocarbons (88). The peaks in loss modulus associated with the amorphous relaxation near —90°C and the crystalline relaxation near room temperature were not affected by these additives. An additional loss peak appeared near —30° C, and the modulus was reduced at all higher temperatures. The amorphous relaxation that appears as a peak in the loss compliance at 134°C is shifted to 45—70°C in the swollen samples. 

PVF displays several transitions below the melting temperature. The measured transition temperatures vary with the technique used for measurement. T (L) (lower) occurs at —15 to —20 " C and is ascribed to relaxation free from restraint by crystallites. T (U) (upper) is in the 40 to 50°C range and is associated with amorphous regions under restraint by crystallites (63). Another transition at —80° C has been ascribed to short-chain amorphous relaxation and one at 150°C associated with premelting intracrystalline relaxation. 

Generally, to fit the observed FID, a series of exponential functions (Equation (1)) are used because the distribution of dipole interaction is expressed by Lorentzian function. This is true for the solution, melt and amorphous phases of the polymers. Actually, a PE melt with low MW exhibits a single exponential curve.14-17 The shape of the relaxation curve of amorphous molecular motion still retains the combined exponential types on cooling. On the other hand, Weibullian functions (Equation (2))6 18 are also applicable for the phase with partially restricted motion such as the interfacial phase.19 Therefore, it is reasonable to introduce the exponential and Weibullian functions as the amorphous relaxation ... 

Figure 2 A series of FID resolution procedures into several component decays. The longest relaxation decay, showing a simple exponential function at the longer timescale, was subtracted from the observed FID (A). The other exponential component at the middle timescale was also fitted as amorphous relaxation (B).

Figure 5 Temperature dependencies of integral widths during heating for solution-crystallized, melt-crystallized and nascent powder samples of UHMW-PE. Changes in both values for crystalline and amorphous relaxations were plotted for each sample.

Changes in the amorphous relaxation behaviour with rising temperature exhibited a monotonous reduction of the integral width, independent of sample morphology, while a crystalline relaxation change is unique for each sample. Thus, the complete analysis of XH FID allows us to discuss chain mobility of amorphous and crystalline phase independently. 

Figure 11 Separated H NMR characteristics for crystalline and amorphous relaxations as a function of prior polymer concentration.

Figure 8.8 Schematic representations of change in modulus E with temperature on the Takayanagi model for (a) the and (h) the L situations corresponding to Eo and 90, respectively. Calculations assume amorphous relaxation at temperature r(aa) and crystalline relaxation at temperature r( c) and (c) shows combined results. C, crystalline phase A, amorphous phase. (Reproduced with permission from Takayanagi, Imada and Kajiyama, J. Polym. Sci. C, 15, 263 (1966).

FIG. 2 The double glass transition, T g(L) and Tg(JJ), and the Ty amorphous relaxation in linear polyethylene. The size of the circles indicate the intensity of the two Tg. Intensity of the Ty transition increases continuously with decreasing crystallinity. (Reproduced from the review paper of Boyer [2] with the permission of ACS Publication Division.)... 

Polyvinyl fluoride has a number of transitions below the melting temperature, the values of which depend on the measurement techniques. The lower glass transition occurs at -15 to -20°C and is believed to relate to relaxation free from restraint by crystallites. The upper glass transition ranges from 40 to 50°C, apparently due to amorphous regions under restraint by crystalhtes.1 1 Yet another transition occurs at -80°C because of short-chain amorphous relaxation and another at 150°C associated with premelting intracrystalline relaxation. 

Fatigue Susceptibility to failure due to cyclic loading Glass transition Amorphous relaxation... 

From the fitting of these FlDs, the integral width and component ratios for the relaxation in the crystalline and amorphous phases were plotted in Figure 8.10. The crystallinity lies around 86%, independent of prior polymer concentration, which is well coincident with the WAXD result. Although the integral width for the crystalline component is a constant value around 67 kHz, that for the amorphous decreased gradually with increasing prior polymer concentration. This trend of the amorphous relaxation exhibits the restricted molecular motion in the amorphous phase for a lower prior polymer concentration system. 

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