Perm-waved human hair: a thermorheologically complex shape memory composite

Wortmann, Franz; Jones, Celina; Davies, Thomas; Wortmann, G

doi:10.1016/j.bpj.2021.03.044

Cited by 4 publications

(4 citation statements)

References 59 publications

(141 reference statements)

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“…While chemical shaping involves the opening of disulphide bonds and reforming them in new positions, corresponding to the desired new shape of the hair, thermal shaping creates new bonds between protein chains for attaining the new shape. Independently of the way to shape, hair fibres, like any keratin material, possess a shape memory [8] and, assisted by environmental relative humidity and temperature, tends towards recovering the original shape once the shaping process ends.…”

Section: Resultsmentioning

confidence: 99%

“…As has been described elsewhere [8] recovery arises from a combination of chemical re‐formation of disulphide bonds between the protein chains, and a physical relaxation process, facilitated by the ‘flow’ within the material. The scope of the present work is to examine how the recovery process proceeds following the two different ways of shaping, namely thermal and chemical.…”

Section: Resultsmentioning

confidence: 99%

“…As discussed elsewhere [8], the setting/shaping and relaxation processes occur at the level of the matrix of the hair, relating to its viscoelastic behaviour, a property well reflected by torsional measurements [21]. Investigating the torsional modulus of wool fibres in water, at temperatures between 7°C and 44°C, Feughelman and Mitchell calculated the activation energy of the relaxation after a torsional process as being E A = 16 ± 2.2 kJ·mol −1 and modelled the matrix as a cross‐linked polymer stabilized by a network of hydrogen bonds [22].…”

Section: Resultsmentioning

confidence: 99%

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Hair relaxation after shaping – A kinetic approach

Breakspear,

Noecker,

Popescu

2023

Intern J of Cosmetic Sci

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OBJECTIVEHair fibres have been shaped via either a thermal route or via a chemical route. The time‐relaxation transients of the shaped hairs in air, and in water, respectively, were evaluated. The collected data were kinetically modelled in order to reveal information about the rate controlling mechanism of the recovery process.METHODSHair fibres were thermally shaped at different temperatures between heated plates and left to relax in an environment of controlled humidity and temperature. Different hair fibres were chemically shaped and left to relax in water of different controlled temperatures. Relaxation data were used for modelling the kinetics of the recovery processes by using exponential and logarithmic kinetic laws. The fitting of the models to the two sets of data has been checked by using the residual sum of squares for matching the proper model to each set of data.RESULTSThe processes of shaping and recovery were assimilated with a sequence of two successive quasi‐chemical reactions, occurring at the used temperatures. Based on chemical and physical assumptions, the two groups of experiments were modelled by two different laws: an exponential law, suggesting a first‐order process as the rate‐determining step of the relaxation of thermally shaped fibers, and a logarithmic law, suggesting a slow relaxation, based on percolation theory, for the chemically shaped fibers. This allowed use of chemical kinetics tools for calculating the values of the activation energy in each case. The evaluated values of activation energy of the relaxation processes for both thermal and chemical shaping were found to be close to each other, in spite of the different methods of shaping.CONCLUSIONThe kinetic analysis suggests that, despite different reaction sequences occurring during the different shaping‐relaxation processes, the rate‐controlling mechanism that manages the recovery process is the same in all cases, and this process is proposed to be the thiol‐disulfide reformation of intra‐protein bonds inside hair.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Hair relaxation after shaping – A kinetic approach

Breakspear,

Noecker,

Popescu

2023

Intern J of Cosmetic Sci

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“…While the cross-sectional shape of a hair follicle dictates how curly or straight a natural strand is, it is disulfide and hydrogen bonds that maintain the shape of the hair. 6,7 Permanent styling leads to potential hair damage and loss due to denaturing of disulfide bonds and changing the integrity of covalent bonds on the hair surface, altering the hydrophobic property to hydrophilic. 8 Permanent styling formulations rely on high alkaline chemicals, such as sodium hydroxide ("lye") or guanidine, lithium, or potassium hydroxide ("no-lye"), to disrupt the natural disulfide bonds of the hair.…”

Section: Cosmetic Practices That Damage Hair Permanent Styling Practicesmentioning

confidence: 99%

How to Put Your Patients on a “Hair Diet”

Yousefian

Krejci

2023

Hair Transplant Forum International

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The integrity of hair is determined by the intricate building blocks of the many layers of the hair follicle, but it also relies on proper nutrition. Weak hair can result from external factors such as physical trauma, heat manipulation, and chemicals, as well as internal factors such as inadequate nutrition. A "hair diet" addresses both internal and external factors that lead to fragile or damaged hair and provides the basis for a conversation with patients to improve the health of their hair.

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Aesthetics and Perception: Dynamic Facade Design with Programmable Materials

Clifford

2022

Advanced Materials in Smart Building Skins for Sustainability

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Perm-waved human hair: a thermorheologically complex shape memory composite

Cited by 4 publications

References 59 publications

Hair relaxation after shaping – A kinetic approach

Hair relaxation after shaping – A kinetic approach

How to Put Your Patients on a “Hair Diet”

Aesthetics and Perception: Dynamic Facade Design with Programmable Materials

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