THE MOLECULAR RELAXATION MECHANISMS IN CORK AS STUDIED BY THERMALLY STIMULATED DISCHARGE CURRENTS

The dielectric relaxation mechanisms present in cork have been investi gated in the temperature range - 100 to 100 degrees C using the techni que of thermally stimulated discharge currents. A relaxation mechanism was detected which showed a compensation behaviour as observed for th e alpha-relaxation (or glass transition relaxation) of synthetic polym ers and which lead us to attribute to cork a glass transition-like tem perature of 18 degrees C. One lower temperature mechanism was also obs erved, with low activation enthalpy and entropy, which is presumably o riginated by local motions (internal rotations) of polar molecular gro ups. An upper T-g relaxation of higher intensity was also detected whi ch was attributed to large-scale non-cooperative motions of polymeric segments.