Permanent wave

Keratin is the protein of hair and wool. These proteins are insoluble because of the disulfide cross-linking between cystine units. Permanent waving of... 

Manufacturing. The highly reactive nature of the active components of the permanent waving products requires rigorous control at every... 

The most successful of these products contain high ratios of VP to DMAEMA and are partially quatemized with diethyl sulfate (Polyquaternium 11) (142—144). They afford very hard, clear, lustrous, nonflaking films on the hair that are easily removed by shampooing. More recendy, copolymers with methyl vinyl imidazoliiim chloride (Polyquaternium 16) (145) or MAPTAC (methacrylamidopropyltrimethyl ammonium chloride) (Polyquaternium 28) have been introduced. Replacement of the ester group in DMAEMA with an amide analog as in Polyquaternium 28 results in a resin resistant to alkaline hydrolysis and hence greater utility in alkaline permanent-wave and bleach formulations (see Quaternary ammonium compounds). 

The loss of structure by a protein is called denaturation. This structural change may be a loss of quaternary, tertiary, or secondary structure it may also be degradation of the primary structure by cleavage of the peptide bonds. Even mild heating can cause irreversible denaturation. When we cook an egg, the protein called albumen denatures into a white mass. The permanent waving of hair, which consists primarily of long a helices of the protein keratin, is a result of partial denaturation. 

A permanent wave changes the shape of a person s hair by changing the tertiary structure of hair protein. A solution that breaks the disulfide bridges between the protein chains is applied to the hair. The hair is then set in curlers to give the desired shape. A second solution that recreates S—S bonds is applied to the hair. When the curlers are removed, the new disulfide bridges hold the hair in its new configuration. 

Normal hair is slightly acidic. In fact, the pH of hair is between 4.5 and 5.5. Hair that becomes too alkaline dries out, tangles easily, becomes dull, and generally looks damaged. Chemical processes, such as permanent waves, hair coloring, and bleaching, as well as a person s natural body chemistry, can all raise the hair s pH. 

Uses. In the formulations of permanent wave solutions and depilatories in pharmaceutical manufacture as a stabilizer in vinyl plastics... 

If the misfit strain is less than a critical value, the undulations cannot mount cracktips, as demonstrated in Fig. 4, where a periodic length is equal to 100 a and film thickness is 30 ML. With the same physical parameters employed for Fig. 3, no islands are created if the misfit strain is less than 0.006. When the misfit strain is less than but close to the critical value, a permanent wave structure sets in the film as in the case ofs = 0.005. If the misfit strain is further reduced, coherency-induced undulations are swept away by thermal fluctuations. 

A permanent wave breaks and reforms disulfide bonds in hair. 

Hair dyeing includes the use of permanent, semipermanent, and temporary dyes. A permanent dye lasts through any number of washings as well as permanent waving. A semipermanent dye is removed after two to ten washings, and a temporary dye is largely eliminated after one washing. 

In permanent-wave neutralization, bleaching, or oxidation dyeing, metal salts catalyze the decomposition of hydrogen peroxide used as oxidant. When the temperature rises, the liberated oxygen can make the hair brittle. 

Sulfur (S) Sulfur is a yellow solid. Iron-sulfur clusters are found in cytochrome enzymes. The sulfur-containing amino acid cysteine is common in hair. Cysteine residues can connect to each other via disulfide bridges, giving hair a natural curl. Permanent waves are achieved by artificially removing and then re-forming these disulfide bridges. 

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