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 ep silon' and loss factor epsilon '', in keratin, were made in an electri c field, This was done in the frequency range 10(1)-10(5) Hz and at te mperatures 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 t o interfacial polarization. The temperature dependences of the dielect ric constants of horn keratin revealed the occurrence of two main mole cular processes. The first process corresponded to the removal of wate r in the temperature range 22-170 degrees C. The activation energy ass ociated with the release of loosely and strongly bound water, was abou t 35 and 7 kcal/mol, respectively. The second process, above 170 degre es C, was related to the denaturation of the alpha-helical phase in ke ratin. (C) 1997 Elsevier Science B.V.