EXTENSION OF PERMED HAIR 139 would lead to a reduction of the experimentally determined fiber bending recovery compared to the prediction from extensional properties. This mechanism is in qualitative accordance with the observations by Wickett (22) who showed that, for conditions where the reaction is slow compared to diffusion, e.g., for thioglycolate below pH 10, the diffusion sets up a diffuse reaction front while the reaction averaged for the whole fiber follows pseudo first-order kinetics. On the basis of this concept, the data in Figure 7 indicate that the reduction in 0.3 M TA, a highly effective agent at a low concentration, is strongly influenced by this mechanism. The effect is less pronounced for the reducing agents at higher concentra- tions, so that 0.3 M TA achieves the same value of Ri as 1 M Cys-HCI, though R o is significantly higher for 0.3 M TA compared to 1 M Cys-HC1. ACKNOWLEDGEMENT The authors gratefully acknowledge the financial support of this project by the Lawrence M. Gelb Foundation. REFERENCES (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (1) J. A. Maclaren and B. Milligan, WoolScience.' The ChemicalReactivity of the WoolFiber (Science Press, Sydney, 1981). (2) S. D. Gershon, M. A. Goldberg, and M. M. Rieger, "Permanent Waving," in Cosmetic Science and Technology, M. S. Balsam and E. Sagafin, Eds. (Wiley Interscience, New York, 1972), Vol. II, pp. 167-250. C. R. Robbins, Chemical and Physical Behaviour of Human Hair (Van Nostrand Reinhold Co., New York, London, 1979). A. V. Tobolsky, Mechanische Eigenschaften und Struktur von Polymeren (Berliner Union, Stuttgart, 1967). G. A. Eriemann, Die modernen Dauerwellsysteme, Parfiimerie und Kosmetik, 64, 541- 544 (1983). S. DeJong, Linear viscoelasticity applied to wool setting treatments, Text. Res. J., 55, 647-653 (1985). B. M. Chapman, Linear superposition of time-variant viscoelastic responses, J. Phys. D. Appl. Phys, 7, L185-L188 (1974). E. F. Denby, A note on the interconversion of creep, relaxation and recovery, Rheol. Acta. 14, 591-593 (1975). M. Feughelman and M. S. Robinson, Some mechanical properties of wool fibers in the "Hookean" region from zero to 100% relative humidity, Text. Res. J., 41, 469-474 (1971). F.-J. Wortmann and S. DeJong, Analysis of the humidity-time superposition for wool fibers, Text. Res. J., 55, 750-756 (1985). M. Feughelman and T. W. Mitchell, Set in bending of single wool fibers, Text. Res. J., 35, 88-89 (1965). C. R. Robbins, Load elongation of single hair coils, J. Soc. Cosm. Chem., 34, 227-239 (1983). S. DeJong and N. A. Michie, A model for predicting set in helices, Text. Res. J., 56, 219-227 (1986). H. Munakata, The stress relaxation and set of wool fibers with particular reference to their structure and mechanical properties, Text. Res. J., 34, 97-109 (1964). A. StriiBmann and H. Zahn, Alterations caused by cosmetic treatments on human hair--The impor- tance of the degree of reduction in permanent waving, Proc. 7, Into Wool Text. Res. Conf. Tokyo, IV, 173-182 (1985). (16) M. Feughelman, A two-phase structure for keratin fibers, Text. Res. J., 29, 223-228 (1959).

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