Longitudinal/transverse relaxation times polymers

In polymers one will often particularly be interested in very slow dynamic processes. The solid echo technique just described is still limited by the transverse relaxation time T being of the order of a few ps at most. The ultimate limitation in every NMR experiment however, is not T but the longitudinal relaxation time T, which for 2H in solid polymers typically is much longer, being in the range 10 ms to 10 s. The spin alignment technique (20) circumvents transverse relaxation and is limited by Tx only, thus ultraslow motions become accessible of experiment. 

To obtain information about the polymer, a material parameter imaging is used. Different properties can be utilized to provide image contrast without adding other substances. Such properties include the relaxation times Ti (relaxation time of longitudinal magnetization decay, spin-lattice relaxation) and T2 (relaxation time of transversal magnetization decay, spin-spin relaxation), as well as the chemical shift. Frequently, the decay of magnetization is measured. For liquids, a simple... 

Both longitudinal and transverse relaxation are stimulated by time-dependent perturbations acting on the nuclei, such as dipole-dipole coupling. Usually the time-dependence arises from molecular motion, and measurements of relaxation times are a powerful method of studying polymer motion in both solution and the solid state. Detailed discussions of such applications. 

As noted earlier in sections 2 and 3, LCPs are different from typical random coil polymers, in that the orientation that is produced in the die does not relax quickly. For this reason, the transverse stretch from internal air pressure and the longitudinal stretch from the take-up speed enhance the orientation from the die, and do so within a relatively short distance from the die lips. Typical blown film conditions would be 2 to 1 blow-up ratio, with the bubble reaching full diameter within a height equal to one to two times the die diameter. Typical LCP film thickness is 12 to 75 micrometers (0.0005 to 0.003 in.). 

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