Fundamental properties of Afro-American hair as related to their straightening relaxing behaviour

The aim of this thesis is to improve the current understanding of straightening processes in Afro hair by alkaline treatment. It is therefore fundamentally important to gain a more detailed insight into the properties of Afro-American hair. The geometry of Afro-American hair has been initially investigated by cross-sections of hair. The apparent diameter of Afro-American hair is dependent on gender. Furthermore, differences between Caucasian, Asian and Afro hair, with respect to their morphology, chemical composition, and thermal properties, have been evaluated after various treatments such as perming and relaxing, and combination of these treatments. Amino acid analysis of treated hair leads to the conclusion that dehydroalanine residues, which are generated upon alkaline relaxing of hair, are quite stable. They are converted with cysteine residues to form lanthionine cross-links. Lanthionine residues occur with a higher frequency after perming treatment of relaxed hair. The thermal properties of hair show that the keratin associated proteins of the matrix are strongly affected by relaxing treatments In addition, a detailed study to properties of "simulated" Afro hair has been made. Simulated hair is actually Asian hair, which has been crimped using steam. Part of this work evaluates the extent to which the properties of this modified Asian hair resemble those of natural Afro hair, so that the results obtained may be realistically transferred. As a result, the cosmetic research companies are advised against using simulated Afro hair as a model for natural Afro hair. Besides these topics, the straightening efficacy of modified relaxer creams (pure creams and creams containing added thioles) on Afro hair has been investigated. The time-depending straightening effect can be described by a pseudo first-order kinetics function. Addition of thioles to the relaxer creams (1 % w/w TGA or cysteine) straightens hair considerably faster than pure relaxer creams do. A further chapter deals with the chemical and thermal properties of modified relaxed hair. The data of amino acid analysis show that the straightening effect is mainly based on the cleavage of disulfide bridges, and that formation of lanthionine is not primary requirement for permanent hair straightening. The possibility to perm hair after relaxing, and the chemical and thermal changes caused upon perming have been investigated. In summary, besides a more rapid straightening of hair, the presence of thioles during the relaxing process leads subsequently to a better waveability of hair. This effect is more significant for TGA compared with cystine as the additional thiole. The last chapter contains results about the swelling of hair at high pH, and diffusion of alkaline solution and thioles (TGA or cysteine) into iodid-dyed hair fiber, which is recorded as a result of the visible color change. Swelling of hair follows pseudo-first order kinetics at pH 12.4 and 12.8, and is related to the proportion of broken disulfide bridges. Thiole containing solutions at pH 12.8, and the solution at pH 13.4, do not show a first-order relationship. This is associated with the additional cleavage of disulfide bridges by thioles, and increasing hydrolysis of protein chains by alkali, respectively. A sharp front between the colorless outer area and the colored inner area of the fiber was observed, and is attributed to the penetration of alkali. Thiole containing solutions showed two penetration fronts, the first front representing the penetration of alkali and the second front the penetration of thiole.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2003

Author dc:creator

• Quadflieg, Jutta Maria

Contributors dc:contributor

• Höcker, Hartwig

• info:eu-repo/classification/ddc/660
• Schwarze
• Haar
• Physikalisch-chemische Eigenschaft
• Haarbehandlung
• Haarglättungsmittel
• Deformationsverhalten
• Dauerwelle
• Technische Chemie
• Ethnic hair
• Afro hair
• relaxing
• straightening
• swelling
• diffusion
• waveability

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-121220%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:59435