MECHANICAL PROPERTIES OF VIRGIN AND TREATED HUMAN HAIR FIBRES 409 Effectively, the S.D.S. could be forming a quasi-salt bridge which is stronger than those present in the untreated fibre, and as a result of its hydrophobic interaction it drives water from the structure leading to lower moisture regains at given r.h. compared with the untreated fibres. Both these effects will increase E'. There is some evidence to support this point of view from low angle X-ray diffraction studies on wool (19). This indicated that the detergent molecules were lying perpendicularly to the fibre axis with the head portion close to cystine cross links. The marked increase in the loss modulus is ascribed to a disruption of the matrix by the non-polar parts of the S.D.S. molecule. This would be in accord with the X-ray studies previously referred to and also to the work of Weigmann and Chen (20) who showed that at high pH ( 6) there is a considerable increase in entropy accompanying the diffusion of S.D.S. into wool. In conclusion it may be stated that although the action of the S.D.S. is not clearly determinable, the absence of the cuticle does allow increased access to the cortex with a corresponding marked effect on the mechanical properties of the fibre (compare control data Table II). A waving lotion (Pin-up©) and setting aid (Textra©) It was of interest to examine changes in the mechanical properties of single hair fibres after application of these commercial treatments. Neither produced significant changes in E' or E". This result for Textra can be explained simply by the fact that the setting aid provides a surface coating to the fibre which is too thin to be mechan- ically important and its set properties probably derive from enhancement of interfibre friction. In the case of hair fully treated with Pin-Up waving lotion, which involves a reduction followed by a reoxidation, the system has returned to its original mechanical state even though its internal and external con- figuration may have changed. Thus the 'no change' result indicates that internal fibre damage is at a minimum which confirms the earlier work of Hamburger and Morgan (6). CONCLUSION The measurement of the elastic and loss moduli in human hair keratin fibres by the oscillating beam technique has been shown to be reliable,

410 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS inexpensive and relatively quick. In this context it can be of particular use in assessing various hair treatments. The data appear to indicate that the value of the elastic modulus, E', is dependent on the more crystalline components in keratin and also on the degree of cross-linking. The loss modulus, E', however, seems to vary with the extra degree of disorder which is superimposed on the cortex by some of the reactive materials introduced into the hair. ACKNOWLEDGEMENT We thank Miss T. A. Howard for her invaluable assistance in obtaining some of the experimental results. (Received: oe1st December 1970) (1) (2) (3) (4) (S) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) REFERENCES Speakman, J. B. Mechano-chemical methods for use with animal fibres. J. Textile Inst. Trans. 118 102-26 (1947). Mitchell, T. W. and Feughelman, M. The bending of wool fibres. Textile Res. J. 11õ 311-14 (1965). Guthrie, J. C., Morton, D. H. and Oliver, P. H. An investigation into bending and torsional rigidities of some fibres. J. Textile Inst., Trans. 45 912-929 (1954). Beyak, R., Meyer, C. F. and Kass, G. S. Elasticity and tensile properties of human hair. I. Single Fibre Test Method. J. Soc. Cosmet. Che,n. 20 615-626 (1969). Rebenfeld, L., Weigmann, H. D. and Dansizer, C. Temperature dependence of the mechanical properties of human hair in relation to structure. ibid 17 525-538 (1966). Hamburger, W. J. and Morgan, H. M. Some effects of waving lotions on the mechanical properties of hair. Proc. Sci. Sect. Toilet Goods Assoc. 18 44-8 (1952). Feughelman, M. and Reis, P. J. The longitudinal mechanical properties of wool fibres and their relationship to the low sulphur keratin fraction. Textile Res. J. 87 334-6 (1967). Feughelman, M. and x•Vatt, I. C. Wool fibres treated with ninhydrin or formaldehyde: mechanical properties. Textile Res. J. 34 643-4 (1964). Deam, D. E. and Rieger, M. M. Mechanical hysteresis of chemically modified hair. J. Soc. Cosmet. Chem. 19 395-410 (1968). Feughelman, M. and Robinson, M. S. The relationship between some mechanical pro- perties of single wool fibres and relative humidity. Textile Res. J. 117 441-6 (1967). Tokita, N. The effects of crystallization and drawing on the visco-elastic properties of fibres. J. Polymer Sci. 9.0 515-536 (1956). Khayatt, R. M. and Chamberlain, N.H. The bending modulus of animal fibres. J. Textile Inst., Trans. 119 185-197. Alexander, P., Fox, M. and Hudson, R. F. The reaction of oxidizing agents with wool. Blochem. J. 129-138 (1951). Ripa, O. and Speakman, J. B. The plasticity of wool. Textile Res. J. 9.1 215-22 (1951). Breuer, M. M. The binding of phenols to hair IV. The binding of 1,3 dihydroxynaphthalene (DHN) to hair. J. Colloid Interface Sci. 9.4 577-583 (1967). Wolfram, L. J. Modifications of hair by internal deposition of polymer. J. Soc. Cosmet. them. 20 539-553 (1969). Simpson, W. S. Int. Wool Text. Res. Conf., 3rd, Paris 359-375 (1965). Zahn, H., Stein, W. and Blankenburg, G. The influence of surfactants on the physical properties of keratin fibres. l•'ette, Seifen, Anstrichm 70 (10) 757-760 (1968). Spei, M. Influence of anionic detergents on low angle X-ray diffraction patterns of a-keratin. Int. Wool Text. Res. Conf. •tth, Berkeley, Calif. 125-6 (1970). Weigmann, H. D. and Chen, J. C. Chemisorption of an alkyl sulphate by wool. Int. Wool Text. Res. Conf., 4th, Berkeley, Calif. 126 (1970).