Measurements of the alternating-current conductivity and direct-current conductivity before and after irradiation were studied for matrices composed of toluene diisocyanate mixed in four different ratios with dehydrated caster oil fatty acids. Different irradiation doses were investigated for all the samples. The alternating-current conductivity in the frequency range of 500-10000 Hz was found to obey the very well-known law sigma(ac)(omega,T) = A omega(S) where sigma(ac)(omega,T) is the alternating-current conductivity at angular frequency co and temperature T and S is an exponent. The exponent decreased with increasing temperature for all compositions. A strong temperature dependence of the alternating-current conductivity and the exponent in the entire ranges of the temperatures and frequencies was reasonably interpreted with the correlated barrier-hopping model. (c) 2007 Wiley Periodicals, Inc.