毛髪のガラス転移に伴うエンタルピー緩和と水の作用

抄録

Glass transition and enthalpy relaxation behavior of human hair and their dependent on water content and aging time were investigated by means of differential scanning calorimetry (DSC). The obtained values of heat capacity change (dCp) and of execs enthalpy (dH) determined by DSC were used for analyzing the glass transition and the enthalpy relaxation process, respectively. In the relationship between the value of dCp and dH and the water content of hair samples aged for 4 days at various relative humidity, the value of dCp and dH increased to a maximum around 10%-15% water content, and then decreased. when the water content was over 15%. However, in the case of the long storage under the conditions of the constant temperature and humidity, the different relationship was found from that mentioned above. This indicates that dCp and dH at glass transition of hair depend on both the water content and the aging time. So, for the hair samples aged under three storage conditions with the different humidity, the values of dCp and dH for all aged samples was found to change periodically during isothermal aging, and their changes tended to be opposite phase, indicating that the increase of polymer chain mobility increased the extent of the enthalpy relaxation but decreased the extent of heat capacity change. These results suggest that the polymer chain network of glassy state repeated periodically a stable <-> unstable structural transformation through plasticization by water, and that the mobility of the macromolecular chain occurred mainly in a lower cross-linked and higher hydrophilic region of the amorphous components, such as endocuticle, cell membrane complex, intermacrofibril material and nuclear remnants, in hair fiber.