Permanent waving tensile properties

One purpose of these studies was to try to achieve essentially complete reduction of a smaller cross section of the hber and to determine if effective permanent-waving could still be achieved. A potential advantage to this type of process is to lessen cortical reduction and thereby to lessen cortical damage to the hair (the region primarily responsible for tensile properties) during the permanent-wave process. 

The wet tensile properties (through 30% extension) of hair are decreased by permanent waving. However, the dry tensile properties remain virtually... 

The chemistry of the reactions of permanent waves with human hair involves reduction of disulfide cross-links and molecular shifting by stressing the hair on rollers followed by reoxidation. These reactions produce extensive changes to the tensile properties of the fibers, both during reduction and even after reoxidation. 

Data by Crawford [33] (see Table 8-4), using hair waved in the laboratory with a commercial home permanent at a 4 1 solution-to-hair ratio, show a decrease in the tensile properties of approximately 5 to 20%. Beyak et al. [23] confirms this finding for the wet tensile properties of permed hair. 

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