The present invention relates to a method for evaluating the crosslink degree
of a vulcanized sample in real time during a vulcanization process or diagnosing
the electrical properties of the sample after the completion of the vulcanization
process, and then determining an optimal vulcanization time and an optimal content
of each constituent gradient of a composition for vulcanization that optimize the
properties of the composition according to the vulcanization conditions, for the
sake of improving the properties of the vulcanized sample prepared from a polymer
by vulcanization at a high temperature.
The method for determining an optimal vulcanization time and an optimal content
of each constituent gradient of a composition for vulcanization that optimize the
properties of the composition according to the vulcanization conditions includes:
(a) measuring an impedance spectrum in a specific frequency range in the individual
vulcanization condition; (b) approximating the measured impedance spectrum to an
equivalent circuit model consisting of resistance and capacitance components; (c)
determining a polymer resistance Rp (i.e., a value obtained by subtracting a real
part of the impedance measurement at a maximum frequency from a real part of the
impedance measurement at a minimum frequency, or the magnitude of a real part of
the semicircle in a Nyquist diagram) from the determined parameters; (d) determining,
as an optimal end point of vulcanization, a time point at which the increasing
rate of the polymer resistance Rp rapidly slows down; and (e) determining the optimal
content of each constituent ingredient of the composition for vulcanization when
the polymer resistance Rp of the sample completely vulcanized is at its minimum.
