NUMBER FRACTION (a) 020 0.18 0.16 0.14 0.12 0.10 0.06• 0.04 0.02 0 2 6 I0 14 18 22 26 $0:54:58 42 46 EXTENSION-TO-BREAK (%) NUMBER FRACTION 0.20 - 0.18 - 0.16 0.14 0.12 - 0.10 - 0.0•- 0.06- 0 2 6 (b) F'• N IO 14 I• 22 26 30 34 38 42 46 50 EXTENSION-TO- BREAK (%) NUMBER FRACTION ø'2ø t (c) 0.18 0.16 - 0.14 0.12 0.10 - 0.08- 0.04 I I 0 2 6 I0 14 18 22 26:30 34 38 42 46 50 EXTENSION-TO-BREAK (%} NUMBER FRACTION 0.20 0.18 0.16 0.14 0.12 O. lO 0.08 0.06 0.04 0.02 0 (d) 6 IO 14 18 22 26 30'34 38 42 46 50 EXTENSION-TO-BREAK (%) N U M BER FRACTION (e) 0.25 - 0.2- 0.t5 0.05 0 4 8 12 16 20 24 28 32 36 40 44 46 EXTENSION-TO-BREAK (%) Figure 20. Distribution of breaking extensions for untreated Negroid hair. a) Not fatigued. b) Fatigued 11 kc with 10-g load. c) Fatigued 11 kc with 20-g load. d) Fatigued 11 kc with 30-g load. e) Fatigued 11 kc with 40-g load.

BEHAVIOR OF NEGROID HAIR 43 fracture have been identified. These modes involve smooth, step, angled, fibrillated, and split fracture ends. In contrast to Caucasian hair, there are very few smooth fractures the step fracture pattern is the predominant mode, although a relatively high percentage of fibrillated fracture ends is also observed. In water, an increase in axial splitting is observed, whereas smooth fracture surfaces are the predominant mode of failure for Caucasian hair. This suggests that Negroid hair fibers have weak intercellular cohesion between cortical cells. Fatiguing, in an experiment designed to simulate the impact loading experienced during grooming, produces fractured ends in which fibrillation is the predominant mode of failure. Fatiguing at higher load levels appears to produce damage in the fiber structure which leads to premature failure. This observation suggests that damage produced during grooming procedures such as combing and picking may contribute significantly to premature failure. While realizing that the hair was taken from one person only, the authors consider this sample typical for Negroid hair and feel that the conclusions have general validity. ACKNOWLEDGEMENTS These studies were part of the work on the Textile Research Institute project "Properties of Negroid Hair," supported by Nicholas Laboratories, Inc. REFERENCES (1) Y. K. Kamath and H.-D. Weigmann, Fractography of human hair, J. Appl. Poly. Sci., 27, 3809-3833 (1982). (2) J. W. s. Hearle andJ. T. Sparrow, The fractography of cotton fibers, Textile Res. J, 736-749 (1971). (3) B.C. Goswami andJ. W. S. Hearle, A comparative study of nylon fiber fracture, Textile ResearchJ., 46, 55-70 (1976).