Viscoelastic indentation on iodine-treated coal tar pitch

The viscoelastic behavior of iodine-treated coal tar pitch is examined by t he use of a Vickers indenter as an efficient micro probe. The charge-transf er complexes formed by the iodine treatment of a coal tar pitch significant ly alter the rheological behavior. Five different iodine-treated pitches ar e prescribed at 100 degreesC by controlling the soaking time in saturated i odine vapor. Two different types of time-dependent indentation tests, tests for a constant rate of indentation penetration and creep tests with a cons tant indentation load, are conducted. The softening and the creeping are pr ogressively and significantly suppressed by increasing the soaking time. Th e effects of iodine treatment on these rheological behaviors are quantitati vely discussed and related to the molecular/ionic structures in terms of th e stress relaxation modulus E(t), instantaneous creep compliance D(0), stea dy-state creep compliance D-s, creep compliance function D(t), retardation time spectrum L(tau), steady-state shear viscosity eta (s), etc. (C) 2001 E lsevier Science Ltd. All rights reserved.