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A Quaternized Diester to Protect Hair From UVA/UVB Damage
By: Regan Tillou, Croda Inc.
Posted: June 15, 2011
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 damage. To protect against both UVA and UVB damage and preserve hair strength, Croda has developed ChromAveil® (INCI: Quaternium-95 (and) Propanediol), a quaternized diester designed to provide broad-spectrum protection to hair in rinse-off systems. UV irradiation studies described here show that the product effectively protects hair from color fade and hair fiber damage as well as maintains hair strength.
As shown in Figure 1, the absorption spectrum of 20.0 mg/L ChromAveil® in SDA-40 ranges from the UVB region (280–320 nm) to the UVA region (320–400 nm), with an absorption peak at 310 nm. Thus, it was assumed that the product would provide efficacious, broad-spectrum color protection for dyed hair. The UVA and UVB assessments described here confirmed ChromAveil®’s capabilities; in addition, its stability after five days of UV exposure showed no change in absorbance or net weight.
UVA: To determine UVA protection, auburn-colored hair tresses were treated with a control (i.e., vehicle alone) and ChromAveil®-containing conditioner and were then exposed to 15 days’ equivalent UV exposure (see Figure 2). The treated tresses were visually compared to one another and to a dyed tress that was not exposed to UV irradiation. Results showed that the hair tresses treated with the conditioner containing ChromAveil® had significantly less color loss than the control.
UVB: To evaluate UVB protection, tryptophan damage to hair, which typically is caused by UVB exposure, was measured on the surface of hair fibers via fluorescence. Virgin brown hair tresses treated with either the same control or ChromAveil®-containing shampoos were tested after 15 days’ equivalent UV irradiation (see Figure 3) and compared with the fluorescence intensities of the hair before UV exposure.
The shampoo containing ChromAveil® showed 97.48% tryptophan protection while the control shampoo showed 91.42% tryptophan protection. The addition of the diester to the shampoo thus improved protection against the degradation of amino acids in the hair fiber. While the tryptophan degradation testing was not performed on a hair conditioner series, researchers anticipate similar results to the shampoo would be seen.
Hair 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. Therefore, a comparison was made between the tensile strength of virgin brown hair tresses treated with the same ChromAveil® and control shampoos previously described. While the disulfide bonds inside the cortex were broken in the tresses treated with the control shampoo, tresses treated with the ChromAveil® diester showed no disulfide bond breakage (see Figure 4). ChromAveil® therefore protected hair from UVB damage and preserved the hair’s natural strength.
The studies described here in brief show how the addition of ChromAveil® in wash-off systems provides protection against UVA-induced color fade as well as protects against UVB-induced disulfide bond breakage, which manifests as loss of hair strength. ChromAveil® 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 artificial hair color and fiber integrity.
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