Abstract
The changes in morphological structure and physical properties of human hair by the three types of solvent extraction have been investigated in detail. The transmission electron microscopy revealed the following features. The hair fibers treated with formic acid and acetic acid were characterized by the extended unstained band in cell membrane complex(CMC)between cuticle cells, indicating the severe structure damage to CMC. The hair fibers treated with ethanol/chloroform were characterized by lack of β-layers in the CMC of both cuticle and cortex. In the fibers treated by boiling water, the density distribution of staining in the β-layer of the CMC between cuticles appears to be intermittent and the boundary between β-layer and δ-layer in the CMC of cortex was markedly obscured. Differential scanning calorimetry indicated that the enthalpy of the endothermic peak for extracted specimens decreased compared with that of untreated one, suggesting the reduced structural rigidity of the macrofibril in the cortex cells. The rigidity of hair treated with formic acid and acetic acid was clearly lower than that of other samples. On the basis of these findings, we discussed again about the effects of the constituent components of hair fiber on the mechanism of the permanent wave formation.
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