Jf. Mano et al., THE MOLECULAR RELAXATION MECHANISMS IN CORK AS STUDIED BY THERMALLY STIMULATED DISCHARGE CURRENTS, Journal of Materials Science, 30(8), 1995, pp. 2035-2041
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.