Dielectric relaxation of air-dried horn keratin.

Dielectric measurements as a function of temperature and frequency are reported for horn keratin. The measurements of dielectric constant epsilon' and loss factor epsilon", in keratin, were made in an electric field. This was done in the frequency range 10(1)-10(5) Hz and at temperatures from 22 to 220 degrees C. The samples contained 8% water by mass at room temperature at a relative humidity of 40%. A remarkable dispersion observed in the range of lower frequencies was attributed to interfacial polarization. The temperature dependences of the dielectric constants of horn keratin revealed the occurrence of two main molecular processes. The first process corresponded to the removal of water in the temperature range 22-170 degrees C. The activation energy associated with the release of loosely and strongly bound water, was about 35 and 7 kcal/mol, respectively. The second process, above 170 degrees C, was related to the denaturation of the alpha-helical phase in keratin.