changing the internal properties of hair

Changing the Internal Properties of Hair by Non-Reactive Means

Traditional daily-use hair care products likely act solely on fiber surfaces to produce their benefits. However, other hair attributes are dictated by the fibers’ inner structure and will not be influenced by the larger molecules (surfactant, polymers, oils) traditionally used in such formulations. Indeed, penetration would seem to necessitate considerably smaller molecules – which then have the potential to change properties of hair in ways that are not currently possible. In short, there may be a whole new class of hair care product waiting to be developed – ones that act to change the internal properties of hair. At present, such treatments involve reactive molecules that also induce considerable damage – yet there are also seemingly non-reactive routes. By means of illustration, it is difficult to think of any molecule that has a bigger effect on the properties of hair than water. Water readily penetrates, hair where is causes plasticization and swelling – and accordingly suggests routes to non-reactive alteration of hair’s internal properties. Other small, hydrogen bonding molecules would be expected to induce comparable effects – as would an ability to manipulate the water content of hair. The historical scientific literature teaches of the ability for phenols and carboxylic acids to lower the water content of hair. We have been following up on this work though the combination of Dynamic Vapor Sorption (DVS) studies to monitor technical water content and mechanical measurements to assess property changes. Results indicate the ability for a variety of small molecules to have an effect on such properties – but penetration rates of even small species tend to be rather slow.  

Hair-Water Adsorption Isotherms

Adsorption isotherms illustrating the ability for a 5% citric acid solution to lower the watercontent of hair.

Reduction in Water Content of Hair after Treatment with Phenols

Adsorption and desorption isotherms illustrating the ability for chloro‐resorcinol to lower the
water content of hair by approximately 40%.

A reduction in fiber moisture content produces a concomitant increase in fiber stiffness.

Results illustrating how soaking in carboxylic acid and phenolic solutions increases the
dimensions of hair fibers.

Reduction in Water Content for Virgin Caucasian Hair after Soaking
in a 5% Citric Acid Solution as a Function of Time and Temperature

Ability for a 5% citric acid to lower hair’s water content as a function of soak time.

Adsorption Isotherm for Hair and Water

The water content of hair is overwhelmingly dictated by the relative humidity of the
surrounding environment and is mostly unaffected by conventional cosmetic treatments.

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