Nylons, temperature dependence

Nakajima, T., and K. Torii Temperature dependence of the electrical conductivity of nylon. Rep. Prog. Polymer Phys., Japan 5, 209 (1962). 

Figure 24.7 Temperature dependence of surface configuration change rate of nylon 6 in air and in water.

The brittle-ductile transition temperature depends on the characteristics of the sample such as thickness, surface defects, and the presence of flaws or notches. Increasing the thickness of the sample favors brittle fracture a typical example is polycarbonate at room temperature. The presence of surface defects (scratches) or the introduction of flaws and notches in the sample increases Tg. A polymer that displays ductile behavior at a particular temperature can break in the brittle mode if a notch is made in it examples are PVC and nylon. This type of behavior is explained by analyzing the distribution of stresses in the zone of the notch. When a sample is subjected to a uniaxial tension, a complex state of stresses is created at the tip of the notch and the yield stress brittle behavior known as notch brittleness. Brittle behavior is favored by sharp notches and thick samples where plane strain deformation prevails over plane stress deformation. 

Figure 7 shows the temperature dependence of tan 8 of nylon 6 films the melt-pressed and quenched, the melt-pressed and slowly-cooled, and the balance-type (two axis expanded) commercial films. The packaging of molecule becomes tight in that order. The tan 5 curves of these specimens show different behaviors, but these curves include at least two relaxation peaks. One is near 40°C, and the other near 90"C the former corresponds to the Tg, and the latter corresponds to the relaxation of the crystalline region. ... 

Figure 7 Temperature dependence of the viscoelastic propcitics( tan ) of nylon 6 films (Ihnsile mode, iOHz).

Fig. 4.12. (a) Temperature dependence of azimuthal Wtp dots) and zenithal Wo (squares) anchoring coefficients for nematic 5CB on rubbed Nylon with Tni being the transition temperature into the isotropic phase (b) A comparison of the ratios of the two anchoring coefficients W jW p (circles) with the ratio of the corresponding Frank elastic constants KijK2 [Q5](solid line) [64]. 

Fig. 23. Temperature dependence of the spectral amplitude of nylon 6 for signal (II) in Fig 22...

Hydrogen bonding plays a fundamental role in the structural and physical properties of nylons and is the most significant type of intermolecular interaction that influences the infrared spectrum of this polymer. The temperature dependence of the infrared spectra of nylons was investigated and the infrared spectra of nylon 6 at 25 and 235°C are shown... 

Nylon-6, thermal degradation of n. When exposed to elevated temperatures, immod-ified nylons undergo molecular weight degradation, which results in loss of mechanical properties. The degradation process is highly time-temperature dependent. 

More realistic interpretation of DBT, based on an idea of mechanical nature of this transition, was proposed based on studies of PC, PMMA, PE, rubber-toughened PP, and nylons (77). The concept of mixed mode of fracture has been used to analyze experimental data on temperature dependence of G/. 

The temperature dependence of intrinsic viscosity of nylon 6 and 6,6 along with our own and literature data were used in the determination of the tenqjerature coefficient of the characteristic ratio dlnCoo/dr. The values of this coefficient for the two nylons in m-aesol and 90 wt.-% HCOOH are very sinular and vary between —3xl0 and —4xl0 The fact that the amide bond has a partial double bond character implies the possibility of the cis-trans isomerism. 

It is probable that the equilibrium between the two forms is displaced in favor of ffie cis form with increasing temperature, which has as a consequence shortening of the nylon chain. The negative value of the temperature coefficient is in accordance with such a view. On the other hand, no temperature dependence of unperturbed dimensions was observed in a solution of njdon 6.6 in 85 wt.-% HCOOH by other authors... 

Figure 3.6. A. Temperature-dependent FT-NIR spectra obtained from 30 to 150°C in the 6000 to 5500-cm region of nylon 12. B. Mean centering of the spectra shown in A. [Reproduced from Ref. 29 with permission. Copyright (1997) American Chemical Society].

Generalized 2D NIR correlation spectroscopy has been appUed to study, for example, temperature-dependent spectral variations of various compounds such as A-methylacetamide (NMA) (34) and nylon 12 (29), concentration-dependent spectral changes in milk (18) and protein solntions at various temperatures (35, 36), composition-dependent spectral changes in polymer blends (37), and depth-dependent spectral variations of a polymer film (38). Examples of heterospectral correlation are 2D NlR-mid IR heterospectral correlation analysis of nylon 11 (39) and 2D NIR-Raman correlation analysis of polymer blends (40). 

Figure 10. Temperature dependence of the d.c. conductivity behavior of PANI-0.5-HMSA / (a) nylon 6 and (b) nylon 12 blends against T ".

In blends containing polyaniline doped with HDBSA, no significant variation in the temperature dependence behavior between PANI-0.5-HDBSA / nylon 6 and PANI-0.5-HDBSA / nylon 12 is observed, although a weaker temperature dependence is expected for tiie latter blend. In this case, a larger fraction of the doping acid is expected to remain in the nylon 12 matrix rather than in nylon 6. This would result in lower carrier concentration for the PANI-0.5-HDBSA in the nylon 12 host and a stronger than expected temperature dependence of conductivity. 

Transport in conducting polyaniline / nylon blends is observed to be independent on the composition, dopant anion, host matrix and structure of the conducting phase. The microscopic transport in all salt networks remains unchanged by the dilution of the salt in the nylon matrix. The conductivity follows a temperature dependence characteristic of generalized variable r e hopping mechanism with % = -1/4. The slope of the temperature dependence increases with dilution, indicating increased disorder in the polyaniline salt. 

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