Effect of Crystallization of Polymers on Dielectric Loss

Abstract

Abstract The values of ε′ and tan 5 in the range of dielectric losses of relaxation character decrease on crystallization of polymers. In the case of medium frequency relaxation losses tan δ sometimes decreases 2 to 4 fold and ε′ by 20 to 30%. This is mainly connected with transition of polar portions of macromoleules into crystallites, on the one hand, and on the other hand with an increase in the breadth of the relaxation spectrum for the polar groups remaining in the amorphous phase. The relaxation time for the medium frequency relaxation dielectric losses, connected with the thermal motion of segments of maeromolecules, in the amorphous phase, increases on crystallization, while for high frequency relaxation losses, reflecting the thermal motion of separate groups or links, does not change or indeed even decreases. The dielectric method may be used for the investigation of the kinetics of crystallization and melting of polymers and, in the case of polar polymers, also for the determination of the degree of crystallinity.