engleski

Depolarization current of novolac phenol-formaldehyde resins doped with 1,4-diazabicyclo [2.2.2] octane

Mixtures of novolac phenol-formaldehyde (NPF) resins and 1, 4-diazabicyclo [2.2.2] octane (DABCO) were polarized at different temperatures applying different d. c. electric fields. Thermally stimulated depolarization current (TSDC) measurements performed from 298 to 373 K showed a dipolar α peak and a space charge α peak as in pure NPF. The addition of DABCO decreases the magnitude of the α peak and the activation energy of the dipolar relaxation but increases the background current and the magnitude of the α peak significantly. The maximum of the α peak is only slightly shifted towards higher temperatures. New aspects in the analysis of the background current by consecutive heating and cooling experiments are considered. The results obtained show an increase in concentration of trapping sites due to the heterogeneity of the mixed systems. The proposed interactions between nitrogen from DABCO and hydroxy groups from NPF are discussed.

thermally stimulated current ; phenol-formaldehyde resins

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