African Hair

The biophysical properties of African hair are more closely related to wool fibers than to the other hair types. African hair shows some special properties as a result of its very curly structure [9-11]. These properties are listed in Figure 2. African hair is treated with hair relaxers, perms, or straighteners in order to get a straight to light curled style. This

© Rough hair surface 9 Increased amount of negative charges ® Reduced mechanical solidity

■4 Increased combing forces

Increased eiectrostatical loading ^ Higher breaking behavior, split ends

Figure 1 Properties of damaged hair.

Table 2 Objective Measuring Methods

Term

Objective measuring methods

Measurement parameter

Combability, detangling Strength

Charging capacity

Splitting

Gloss

Resistance to combing

Resonance frequency Tensile strength measurement Breaking strength of single hair Breaking strength of hair tress Faraday cage

Electron-scanning microscope Goniophotometer

Wet combing work

Dry combing work

Modulus of elasticity

Elastic range (range of Hooke's law)

Breaking force

Breaking force

Charge difference

Reflection has an influence on the hair structure. We measured the wet tensile strength of hair tresses after the application of typical hair relaxers. As expected, straighteners and relaxers have a strong influence in decreasing the tensile strength. Relative to untreated hair we found a residual tensile strength of only 60% depending upon the relaxing agent. Thioglycolate (7.5% active at pH 9.3) is milder than sodium hydroxide (2.0% at pH 13.5) and this is better than calcium hydroxide (0.6% active at pH 13.5). A more detailed description of the physical properties and differences of African hair relative to Caucasian hair is reported in the literature [9-11].

Influence of Surfactants and Protein Hydrolysates on African Hair

The use of mild surfactants in shampoos is necessary and avoids additional damage. Applying 2% sodium hydroxide (pH 13.5) to kinky hair resulted in a residual strength of about 73%. Shampooing this hair with a 12% active solution of sodium laureth sulfate (SLES) gave a further decrease of the tensile strength to 64%. If we choose decyl glucoside as surfactant, there is no further damage and a significantly higher wet tensile strength relative to the SLES result.

Adding protein hydrolysates to relaxers or straighteners strongly increases tensile strength. Using 2% active hydrolysed collagen in a 0.6%-containing calcium hydroxide straightener at pH 13.5 resulted in an increase of the wet tensile strength up to 142% relative to the same straightener without hydrolyzed collagen. This is important for the formulation not only for these products, but for shampoos and conditioners in general. The addition of protein hydrolysates to restructure the hair is strongly recommended.

»4 dry hair (less sebum along hair shaft)

o High dry combing forces Figure 2 Characteristics of African hair.

Figure 3 Dry and wet tensile strength of single fibers.

Asian, dry Wet Caucasian, dry

Figure 3 Dry and wet tensile strength of single fibers.

11 Habits To Make or Break For Soft Flawless Skin

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Habits to Break and Habits to Maintain for Dazzling Skin. As you all know, our skin is the obvious appearance of who or what we are, or perhaps would like to be. However, it is more than just a simple mask.

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