Nylon 11, relaxation dynamics

S.2. Polyamides Extensive scientific research in the area of polyamides has been devoted to the exploration of the relaxation dynamics of Nylon 11,... 

Cold drawn specimens of nylon 6 have recently been investigated by Owen and Ward who measured static moduli between — 110 C and -t-20°C, and dynamic tan d between — 70°C and -l- 110 C in a vibrating reed instrument. As can be seen from Fig. 15 the pattern of anisotropy changes with temperature, there being a minimum in o and 90, near room temperature, around the draw ratios at which X-ray diffraction indicates a transformation from an form to a more stable y form. These structural changes, and the changes responsible for the rise in the temperature of the a relaxation with orientation, prevented a detailed understanding of the mechanical deformation processes. 

Dynamic-mechanical and dielectric data have been widely reported for most aliphatic polyamides, especially poly(g-caprolactam) (nylon-6 or PA-6 rg 313K) and poly(hexamethylene adipamide) (nylon-6,6 or PA-6,6 Tg 323 K). Results of dynamic-mechanical and dielectric measurements of PA-6 and PA-6,6 (Table 13.8) provide evidence for three relaxations (/3, y, and 8) in these polymers at temperatures below their crystalline-melting temperature Tni (487-506 K for PA-6 and 523-545 K for PA-6,6) [8]. The /3 relaxation (located at above 310-347 K for PA-6,6 and 357-370 K for PA-6,6) is associated with high... 

The dependence of the relaxation temperatures on the level of absorbed water in Nylon 6-6 is known from dynamic mechanical studies (Starkweather 1980,1973a Prevorsek et al. 1971) as well as dielectric studies (Starkweather and Barkley 1981). The temperature variations with sorbed moisture of the loss modulus peaks for the three relaxations are shown in Fig. 5.29 (Starkweather 1980). The test frequency for the three relaxations varies slightly but is around 1 Hz. The data indicate that the temperature of the a relaxation at a given frequency decreases by about 100 °C (to below ambient) between dryness and saturation. The P relaxation is also shifted to lower temperatures and higher frequencies by absorbed water, while the temperature of the y relaxation is only slightly affected, shifting to somewhat lower temperatures and higher frequencies. 

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