1972•Journal of the Chemical Society Faraday Transactions 2 Molecular and Chemical PhysicsRequires access
Nuclear magnetic relaxation in polypropylene
Vincent J. McBrierty, Dean C. Douglass, D. R. Falcone
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Abstract
Nuclear magnetic resonance T1, T1ρ, and T2 relaxation results are reported for drawn polypropylene. The results indicate that three relaxation processes are operative: a low-temperature methyl relaxation process, a higher temperature β relaxation, and a high temperature α relaxation process. The data presented here are consistent with previous interpretations of the first two relaxations. Little anisotropy was observed in the relaxation times when recorded as a function of the applied magnetic field direction. A theoretical expression for the rotating-frame relaxation time, T1ρ, is derived which is appropriate to a rotation of the methyl group about its threefold axis. The effects of a distribution of relaxation times which result from a random orientation of methyl groups in the polymer are included as also are the effects of spin diffusion. The agreement between theory and experiment is satisfactory.