A Diester to Protect Hair from Color Fade and Sun Damage

Timothy Gao, PhD, Jung-Mei Tien, Abhijit Bidaye, Scott Cardinali and Jena KinneyCroda Inc., Edison, N.J., USA

Like skin, hair is susceptible to damage from exposure to the sun. This damage affects its aesthetics and mechanical and physical properties, resulting in dull, flat hair. Research indicates that both UVA and UVB radiation are responsible for this dam-age. Hoting,1 for example, studied hair tresses dyed red by exposing them to UVA and UVB radiation, finding that the tresses underwent more fading after UVA irradiation. Artificial hair color based on pyrazole intermediates also has shown significant fading after shampoo washing and UV exposure.2 Hoting thus concluded that expo-sure to UVA radiation resulted in a significant and perceivable change in the dyed red hair color. Accord-ing to his research, the red pigment introduced into the hair fiber by the dyeing process acts as a photoreceptor, absorbing photons and photochemi-cally degrading after UVA and visible light irradiation.

The effects of UVB radiation on hair also can be severe, resulting in

the breakdown of disulfide bonds both inside the hair fiber and on the surface of the cuticle.3 Such disrup-tions to the disulfide linkages of the hair fiber can have a major impact on hairs mechanical properties, resulting in the loss of tensile strength and an increase in porosity and irregularities on the hair surface.

To protect hair from UV damage, UV filters deposited on the hair surface absorb incident UV light.

Key WorDS: diester, colorfade, tryptophan degradation, hair fiber integrity, broad-spectrum UV filter

ABSTrACT: A new broad-spectrum UV filter to protect hair from color fading and integrity damage, quaternium-95 (and) propanediol, has been developed for rinse-off formulations. Shampoos and conditioners containing this material protected dyed hair against surface tryptophan degradation and tensile strength reduction.

As noted, since both UVA and UVB radiation cause severe and perceiv-able damage, broad-spectrum UV absorbers provide the best protection from fading and sun damage. In addition to broad spectrum cover-age, deposition and absorption onto the hair surface are crucial factors to consider when designing materials for rinse-off systems.

In the present article, the authors introduce a quaternized diestera designed to provide broad-spectrum protection to hair in rinse-off systems. An absorption spectrum of the diester solution (20.0 mg/L active in SDA-40), shown in Figure 1, ranges from the UVB region (280320 nm) to the UVA region (320400 nm). The absorption peak, located at 310 nm, falls within the UVA region, thus researchers concluded the material should provide effica-cious color protection for dyed hair. Additional studies (data not shown) examined the materials stability after five days of UV exposure, showing no change in absorbance or net weight for the diester.

Thus, further studies were war-ranted to examine its ability to protect hair fibers from cuticle damage and reduced tensile strength resulting from degradation of tryptophan and proteins on the hair surface and inside

Artificial hair color based on pyrazole intermediates

has shown significant fading after shampoo

washing and UV exposure.

a ChromAveil (INCI: Quaternium-95 (and) Propanediol) is a product of Croda Inc.b The Atlas Ci300+ Xenon Weather-Ometer is a product of Atlas Material Testing Solutions, International Hair Importers

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the hair fiber. The ability of the diester to protect hair from colorfade in the presence of UV radiation also was examined.

Materials and MethodsVarious protocols were used to

evaluate the diesters ability to protect hair fibers from UV damage. Bleached European brown hair tresses were dyed with either a commercially

available medium brown hair color or medium auburn color for 30 min following the instructions provided in color kits. For testing of UVB damage, virgin dark brown hair was used. Some tresses were treated with control and diester-containing shampoos and conditioners (see Formulas 1 and 2). A subset of treated tresses were then irradiatedb for 3 hr on each side, totaling 6 hr- equivalent to one day of UV exposure4-with UV radiation (200400 nm) at 50 W/m1 using a quartz inner filter and type s borosilicate outer filter. At the start of the study and at intervals equivalent to every five days of UV exposure-e.g., after every 30 hrs-tresses were treated again with control and diester-containing shampoos and conditioners. Irradiated tresses were exposed to the total equivalent of 15 days of UV exposure. Test conditions were maintained at 40C and 65% relative humidity.

Different types of tresses were compared, including those that were dyed and not exposed to treatment or UV exposure; dyed and treated with the control shampoos and conditioners and exposed to UV; and dyed and treated with shampoos and conditioners containing the diester and exposed to UV. Comparative color loss was determined both objectively and subjectively. The total color loss (E) was calculated by assessing the changes in L*, a*, b* readings on the treated tresses using a spectrocolorimeterc. The equation used to calculate the total color loss was:

E = [(L)2 + (a)2 + (b)2]1/2

Figure 1. Absorption spectrum of the diester solution

c LabScan XE Spectrocolorimeter is a product of HunterLab.

d Spex FluoroLog-3 is a instrument manufactured by Horiba Jobin Yvon.e Miniature Tensile Tester (MTT) 670 is a product of Dia-Stron Ltd.

Formula 1. Shampoo test formulations

Ingredient Control Diester Shampoo

Sodium laureth sulfate 35.00% w/w 35.00% w/wCocamidopropyl betaine 10.00 10.00Quaternium-95 (and) propanediol, 75% active (ChromaVeil, Croda) --- 2.00PEG-150 pentaerythrityl tetrastearate (and) PEG-6 caprylic/capric glycerides (and) water (aqua) --- 2.80Water (aqua) 55.00 50.20 100.00 100.00

Table 2. Conditioner test formulations

Ingredient Control Diester Conditioner Conditioner

Quaternium-91 (and) cetrimonium methosulfate (and) cetearyl alcohol 2.14% w/w 2.14% w/wCetearyl alcohol 3.86 3.86Quaternium-95 (and) Propanediol, 75% active

(ChromaVeil, Croda) --- 2.00Phenoxyethanol (and) methylparaben (and) ethylparaben (and) butylparaben (and) propylparaben (and) isobutylparaben (Phenonip, Clariant) 1.00 1.00Water (aqua) 93.00 91.00 100.00 100.00

UVB can break down disulfide bonds inside

the hair fiber and on the surface of the cuticle.

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using a spectrofluorometerd. The excitation wavelength was set at 295 nm and the tryptophan emis-sion intensity was measured at

340 nm. The emission intensity was assumed to be directly proportional to the surface tryptophan concentration.

Using surface tryptophan intensities of the hair sample before UV exposure as the baseline, the tryptophan protec-tion factors of hair samples treated with diester shampoo or the control shampoo after UV exposure can be calculated using the equation:

F (Tr) = [If / Io] X 100%

In this equation, F(Tr) is the trypto-phan protection factor, calculated as a percentage; If is the surface tryptophan fluorescence intensity of the hair sample after UV exposure; and Io is the surface tryptophan fluorescence intensity of the same hair sample before UV exposure.

UVB rays not only decompose the sur-face tryptophan but also penetrate the hair cuticle and cause damage inside the cor-tex. This damage affects hairs mechanical properties and can be measured in terms of its tensile strength (stress-to-break). Using a tensile testere, the tensile strength of single fibers from the treated tresses was measured before and after UV exposure.

To test the ability of the diester to protect hair fibers in rinse-off systems, a shampoo and conditioner were formulated with and without the diester (see Formulas 1 and 2).

UV Protection with DiesterUVA protection in shampoo:

Auburn-colored tresses were treated with the control and diester shampoo and exposed to 15 equivalent days of UV exposure (see Figure 2). The treated tresses were visually compared

The changes in hair color indexes were calculated using the respective val-ues after the shampoo and conditioner treatments and before UV exposure; and after the equivalent of 15 days of UV exposure. The results of the instrumental evaluations were con-firmed via subjective testing. The swatches were photographed and com-pared to dyed but untreated swatches, which represent the initial dye color, to allow for visual comparisons. Panelists were also asked to rate the color protec-tion effects in simple comparisons of the control and the diester swatches to the

Figure 2. Effects of the diester vs. control shampoo on medium auburn hair

untreated control.To determine the amount of damage

on the hair fiber due to the UVB irradia-tion, several parameters of the hair fiber were measured. As noted, UV exposure to hair can break down the disulfide bonds in the hair fiber. Tryptophan is a key amino acid found on the hair surface and it decomposes under UVB irradiation.2

Surface tryptophan degradation is thus an indicator of damage to the disulfide bonds and it can be quantified through comparative fluo-rescence intensities of hair tresses

The addition of the diester into the shampoo improved the protection against degradation of amino acids in the hair

fiber.

Figure 3. Total color changes of medium auburn-colored hair treated with different shampoos after 15 days of UV exposure

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to one another and to a dyed tress that was not exposed to UV irradiation (Figure 2a). The tresses treated with the control shampoo (Figure 2b-c) lost a significant amount of color while the hair tresses washed with the shampoo containing the diester (Figure 2d-e) showed less color fade. The total color loss (E) of the tresses treated with the shampoos was also assessed after 15 days of UV exposure. Tresses that demonstrated better color protection had a smaller E. The quantitative color loss data confirms what the visual assessment illustratesthat the shampoo con-taining the diester had a significantly smaller E, and the diester-treated tress maintained more color. The diester thus demonstrates color

Figure 5. Total color change of medium brown-colored hair treated with different shampoos after 15 days of UV exposure

Figure 4. Effects of the diester vs. control shampoo on medium brown hair

Tryptophan is a key amino acid found

on the hair surface, and it decomposes

under UVB irradiation.

Figure 6. Effects of the diester vs. control conditioner for medium auburn color

protection with a E of 10.5, com-pared to the control shampoo with a E of 12.4, a difference of almost 2 units (see Figure 3).

To confirm the correlation between visual inspection of images, color index measurement and consumer perception, 17 panelists selected the tresses they thought had the most and least change in color after tresses were exposed to 15 days of UV. Subjective evaluation results indicated that 100% of the panelists perceived that the diester shampoo gave superior color protection on the medium auburn treated hair (data not shown).

A similar study was performed with the shampoos on hair dyed with medium brown color. The tresses shown in Figure

4 were treated with the control and diester shampoo. Hair tresses washed with the diester shampoo (Figure 4e-f) showed less colorfade than the control shampoo (Figure 4c-d). The left two tresses were dyed and not exposed to UV (Figure 4a-b), to serve as a reference.

Figure 5 shows the quantitative E total color changes of hair tresses col-ored medium brown that were treated with both shampoos and exposed to 15 days of UV exposure. Hair tresses treated with the diester shampoo showed less total color change, almost 3 units, than the control shampoo, indi-cating the diester shampoo provided better color protection.

Again, the panel evaluation dem-onstrated a strong correlation between the visual results and the instrumental results. On medium brown hair, 94.1% of panelists chose the tresses treated with the diester shampoo as having retained the most color.

UVA protection from a conditioner: Another set of auburn-colored tresses was treated with a rinse-off conditioner containing the diester

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(Formula 2) and the same conditioner without the UV filter to serve as a control. Figure 6 shows that hair tresses washed with the diester conditioner (Figure 6d-e)

showed less colorfade on auburn-colored hair than the control conditioner (Figure 6b-c). The left tress was dyed but not exposed to UV radiation (Figure 6a) to serve as a reference.

Although not as definitive as the shampoo studies, 64.7% of the panelists preferred the diester conditioner on auburn-colored hair.

UVB protection from a shampoo: To assess for surface tryptophan damage, the surface fluorescence intensities of virgin brown tresses treated with either the control or diester shampoo were deter-mined after 15 equivalent days of UV irradiation (see Figure 7) and compared to the fluorescence intensities of the hair before UV exposure.

The shampoo containing the diester showed 97.48% tryptophan protec-tion after the 15 equivalent days of exposure, while the control shampoo showed 91.42% tryptophan protec-tion. The addition of the diester to the shampoo improved the protection against degradation of amino acids in the hair fiber. The tryptophan degradation testing was not performed on the conditioner series; however, researchers anticipate similar results would be seen.

Testing UVB Protection with Tensile Strength

Fibers showing a decrease in stress-to-break forces after UV exposure have undergone a loss in mechanical strength primarily due to the breaking of disulfide bonds inside the hair cortex. A com-parison of the tensile strength of virgin brown hair treated with the diester sham-poo was made to hair similarly treated

Diester delivered from the conditioner also provided

protection against the damage to fiber integrity.

Figure 7. Change in tryptophan intensity after UV exposure and treatment with diester shampoo

Figure 8. Change in tensile strength after UV exposure and treatment with shampoos

Figure 9. Change in tensile strength after UV exposure and treatment with conditioners

With Croda products, you can reverse the damage from styling, perming, straightening or coloring as well as protect your tresses from further insult. Leave your bad hair days behind and always look like you just left the salon... Softer, more manageable hair CRODAZOSOFT SCQ, CRODAZOSOFT DBQ, INCROQUAT BEHENYL TMS-50 Strong, healthy tresses KERAVIS Moisture management CROPEPTIDE W Brilliant shine CRODAMOL STS Smooth surface with a no frizz finish CRODABOND CSA, LUSTREPLEX

Replenishment of essential lipids INCROQUAT 18-MEA-40, INCROQUAT BEHENYL 18-MEA

For samples, data and other hair enhancing ideas contect your Croda rep or visit crodausa.com

with CrodaInnovation you can build on

Every day is a great hair day

North America email:marketing@crodausa.com www.crodausa.com

Latin America email:marketing@croda.com.br www.croda.com/br

Europe, Middle East & Africa email:pc-europe@croda.com www.croda.com/europe

Asia Pacific email:sales@croda.com.sg www.croda.com/asia

Croda.5p_GCI_CondR.indd 1 7/1/09 4:19 PM

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with the control rinse-off product. Note that disulfide bonds inside the cortex have been broken in the tresses treated with the control shampoo, while tresses treated with the diester have no disulfide bond breakage (see Figure 8). The diester shampoo protected the hair from UVB damage and preserved the hairs natural strength.

Using the same methodology, virgin brown hair tresses were treated with the control and diester conditioner, respectively, for tensile strength mea-surements. The diester conditioner also provided protection against damage to the fiber (see Figure 9).

ConclusionsWhile protection of hair from the

sun is not a new concept, technology

continues to improve to offer consum-ers better protection as part of their daily regimen. As shown, the diester is substantive to the hair and offers broad-spectrum protection in rinse-off systems. Although the diester has not yet been tested in leave-in systems, the authors expect the diester to provide good hair protection.

The addition of the diester in wash-off systems provides protec-tion against UVA-induced colorfade as well as protection from UVB-induced disulfide bond breakage that manifests as a loss of hair strength. The diester also protects from the degradation of amino acids on the hair surface. This broad-spectrum protection gives consumers the freedom to enjoy the sun without

the concern for hair damage. In addition, it offers protection for arti-ficial hair color and fiber integrity.

Acknowledgments: The authors would like to acknowledge Marni Dexter, Sety Britton and Abel Pereira for their hard work and contributions to this project. references:Send e-mails to t.gao@crodausa.com

1. E Hoting, Sunlight-induced modifications in

bleached, permed, or dyed human hair, J Soc

Cosmet Chem, 48 7991 (Mar/Apr 1997)

2. B Locke and J Jachowicz, Fading of artificial

hair color and its prevention by photofilters,

J Cosmet Sci, 56 407425 (2005)

3. T Gao and A Bedell, UV damage on natural

gray hair and its photoprotection, J Soc Cos-

met Chem, 52 103118 (Mar/Apr 2001)

4. M Jeanmougin and J Civatte, Dosimetrtrie du

rayonnement UV solaire, Ann Dermatol Ven-

erol, 114 671676 (1987)

Reprinted from May 2009 Cosmetics & Toiletries magazine, Vol. 124, No. 5, p. 70-78. www.cosmeticsandtoiletries.com. Cosmetics & Toiletries magazine. All rights reserved. Foster Printing Service: 866-879-9144, www.marketingreprints.com.

With Croda products, you can reverse the damage from styling, perming, straightening or coloring as well as protect your tresses from further insult. Leave your bad hair days behind and always look like you just left the salon... Softer, more manageable hair CRODAZOSOFT SCQ, CRODAZOSOFT DBQ, INCROQUAT BEHENYL TMS-50 Strong, healthy tresses KERAVIS Moisture management CROPEPTIDE W Brilliant shine CRODAMOL STS Smooth surface with a no frizz finish CRODABOND CSA, LUSTREPLEX

Replenishment of essential lipids INCROQUAT 18-MEA-40, INCROQUAT BEHENYL 18-MEA

For samples, data and other hair enhancing ideas contect your Croda rep or visit crodausa.com

with CrodaInnovation you can build on

Every day is a great hair day

North America email:marketing@crodausa.com www.crodausa.com

Latin America email:marketing@croda.com.br www.croda.com/br

Europe, Middle East & Africa email:pc-europe@croda.com www.croda.com/europe

Asia Pacific email:sales@croda.com.sg www.croda.com/asia

Croda.5p_GCI_CondR.indd 1 7/1/09 4:19 PM

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