2006 ANNUAL SCIENTIFIC MEETING
(2) Radical Scavengers
The purpose of an effective radical scavenger is not to prevent the radical formation but to trap a highly
reactive radical rapidly converting it into a much less reactive species. This species has reduced potential to
indiscriminately react with and destroy protein and other materials in the hair fiber. The less reactive radical
species thus does much less damage to the fiber. We have demonstrated the effectiveness of adding a range of
radical scavengers to hair colorants, particularly formulations based on the combination of ammonium carbonate
and hydrogen peroxide. We have shown that when formulated to provide equivalent levels of bleaching (dL),
the addition of a radical scavenger such as glycine, glutamine, glucosamine, arginine or proline can reduce the
fiber damage significantly as measured by tensile strength as shown in Chart 2 below.
Chart 2 -Tensile Strength data for range of radical scavengers
Treatment 15% Extension Force Force To Break Fibre Lightening
(gmf) (gmf) (dL)
Untreated virgin Hair 20.3 72.7 -
Reference composition 12.5 S 46.1 S 15
(Ammonium Carbonate +
Hydrogen Peroxide)
+Sodium Glycinate 18.1 s 72.6 15
+Glutamine 18.9 77.2 15
+Anrinine 17.0 s 67.8 15
s =significant versus untreated hair to 95% confidence, S =sigmficant versus untreated hatr to 99% confidence.
The suggested mechanism is the conversion of either the reactive hydroxyl or carbonate radical to the less
reactive superoxide radical.
89

90 JOURNAL OF COSMETIC SCIENCE
UNDERSTANDING THE EFFECT ON HAIR FIBERS OF COLORING AND BLEACHING
FORMULATIONS USING HIGH PRESSURE DIFFERENTIAL SCANNING CALORIMETRY
(HPDSCJ
Christopher Gummer1, Ph.D., Jennifer Marsh1, Ph.D., R. Marc Dahlgren 1 ,Ph.D.
and Knut Meinhert2, Ph.D.
1 The Procter &Gamble Company, Rusham Park Technical Centre,
Whitehall Lane, Surrey, United Kingdom, TW20 9NW
2 Wella, Darmstadt Innovation Center, D-6427 4, Darmstadt, Germany
High Pressure Differential Scanning Calorimetry (HPDSC) can be used to gain information on both the
degree of crystalinity in the intermediate filaments (IF's) and the structural rigidity of the surrounding matrix or
intermediate filament associated proteins (IF AP) of the hair cortex. A decrease in the peak denaturation
temperature may result from either a change in crystalline material amount or integrity, or changes in viscosity
of the matrix (IFAP's), particularly in the wet state.
We have used HPDSC to measure changes in denaturation temperature (Td) of the crystalline components
after treatment with retail colorant and bleach products. We also attempted to correlate these changes with the
degree of lightening from these products (dL) and their tensile strength.
We have demonstrated that a decrease in the HPDSC peak temperature after treatment from a hair colorant or
bleach is due to a combination of two effects:
(1) Oxidative breakdown of the keratin protein matrix covalent bonds. This change is permanent.
(2) Addition to the hair of formulation components such as salts, surfactants or alkalisers that change the
electrostatic environment in the matrix proteins. This change is to some extent reversible either by repeat
washing cycles or dialysis in deionised water.
Results
Our preliminary studies were unable to establish a significant correlation between increasing lightening (dL),
tensile strength, and HPDSC denaturation temperature (Td )for typical retail bleach or color treatments. Chart 1
shows a good correlation between the lightening of the bleach products and their tensile strength but there is no
correlation between either lightening or tensile strength and the HPDSC peak temperature data.
Chart 1 -The effect of different retail colorant and bleach formulations containing different oxidant and
alkaliser technologies on peak temperature Td 0 C:-
Product No. of Lightening HPSDC Tensile Streneth Data
treatments dL Peak temp Plateau load Load@25% Break load
Td °C Gmf/sq.micron Gmf/sq.micron Gmf/sq.micron
Virgin Hair Na na 148.3 0.0064 0.0075 0.0209
Retail Color 1 3 12 145 0.0051 (s) 0.0057 (s) 0.0190 (s)
Retail Color 2 3 12 137 0.0054 0.0065 0.0199 (s)
Retail Bleach 1 3 25 143.8 0.0040 (s) 0.0044 (s) 0.0172 (s)
Retail Bleach 2 3 26.8 138.7 0.0039 (s) 0.0044 (s) 0.0164 (s)
To test our hypothesis that the HPDSC peak temperature is influenced by both permanent changes and
reversible changes we first investigated the effect of an alkaliser alone on the HPDSC peak temperature, i.e. no
oxidant present. Virgin hair was soaked in an alkaliser solution (0.8M) buffered at pH 10 for 30 minutes, rinsed
for 1 minute and then shan1pooed and rinsed for 2 cycles. The samples were then dialysed in deionised water.
Chart 2 shows the results for ammonia and ethanolamine as the alkaliser. The results show that the effect of the
alkaliser is to reduce the HPDSC peak temperature significantly but that the result can be reversed on dialysis
with deionised water.