Bending relaxation properties of human hair and permwaving performance

between the change of the bending stiffness and that of the extensional stress during reduction suggests that a non-uniform Young's modulus distribution is induced in the fiber during the reducing step. The evaluation of two simple types of distributions (linear and quadratic) leads to results that are consistent with the experimental data, giving sensible estimates for the local moduli of the reduced fiber at the fiber core and at the surface. The results show that only for severe reducing conditions does the reductant reach the fiber core in a sufficient concentration to substantially reduce the local modulus.