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ON THE RELAXATION MECHANISMS OF SOME RADIATION INDUCED FREE RADICALS IN POLYMERS

M. Velter-Stefanescu1,* , O. G. Duliu2, N. Preda1

Affiliation

  1. National Institute of Materials Physics, Magurele, P.O. Box MG-7, RO-077125 Bucharest, Romania
  2. University of Bucharest, Department of Atomic and Nuclear Physics, Magurele, P.O. Box MG-11, RO-077125 Bucharest, Romania

Abstract

Electronic spin-lattice relaxation measurements performed in X and Q bands on electrons irradiated polyethylene, polycarbonate and polymethylmethacrylate have shown that at liquid helium temperatures and higher, up to 12K, the spin-lattice relaxation time of radiation induced free radicals does not depend on the magnetic field but varies inverse proportionally with the square of absolute temperature and free radicals concentration. These peculiarities have been well explained by admitting that below 77 K there is a considerable amount of stable free radicals coupled in pairs that mediate the spin-lattice relaxation process of single radicals. Consequently, we have proposed an analytical equation that, within this hypothesis, quantitatively describes all these particularities..

Keywords

Relaxation mechanism, Free radicals, Polymers, Irradiated polyethylene, PMMA.

Submitted at: Dec. 20, 2004
Accepted at: March 23, 2005

Citation

M. Velter-Stefanescu, O. G. Duliu, N. Preda, ON THE RELAXATION MECHANISMS OF SOME RADIATION INDUCED FREE RADICALS IN POLYMERS, Journal of Optoelectronics and Advanced Materials Vol. 7, Iss. 2, pp. 985-989 (2005)