Investigations of cosmetic treatments on high-pressure differential scanning calorimetry.
High Pressure Differential Scanning Calorimetry (HPDSC) can be used to gain information on both the degree of crystallinity in the intermediate filaments (IFs) and the structural rigidity of the surrounding matrix or intermediate filament associated proteins (IFAP) of the hair cortex. We have used HPDSC to measure changes in denaturation temperature (T(D)) and enthalpy (deltaH(D)) of the crystalline components after treatment with bleach products. Literature reports suggest that a decrease in peak denaturation temperature is indicative of permanent damage to the hair. However, changing the rigidity of the matrix surrounding the IFs, by temporarily changing electrostatic interactions, should also result in a similar decrease in peak temperature. The complex nature of bleach formulations including oxidants, alkalizers and salts suggests that several of the components could have a non-permanent affect on salt bridges and hydrogen bonds and hence rigidity or viscosity of the matrix. We have compared the denaturation temperature with levels of lightening (dL) and tensile properties of the fiber after treatment both before and after removal of actives from the fiber. It is evident that the HPDSC results are strongly influenced by formulation components and that these changes are reversible with extensive washing or dialysis. Combined with tensile data, it is proposed that a decrease in T(D) and deltaH(D) following treatment with bleach products can be due to both permanent and reversible changes to either the intermediate filaments or intermediate filament associated proteins of the hair fiber.
Marsh
J M
JM
Procter & Gamble Technical Centres, Rusham Park, Egham Surrey, UK.
Clarke
C J
CJ
Meinert
K
K
Dahlgren
R M
RM
D002152:Calorimetry, Differential Scanning; D006197:Hair / Q000737:chemistry*; D006203:Hair Preparations / Q000737:chemistry*; D006801:Humans; D011489:Protein Denaturation / Q000187:drug effects*; D013718:Tensile Strength
D006203:Hair Preparations