Waxes are known to give shampoos a milky or pearlescent appearance and due to their affinity to hair, they interact with it during the shampooing process. These factors led to the development of a micro-wax compound that enhances the appearance of shampoos while also providing benefits to hair, such as anti-hair breakage properties. In addition, since benchmark shampoos on the market claiming anti-hair breakage properties typically contain high amounts of silicones, the described micro-wax compound provides a naturally derived and renewable alternative. Here, the authors demonstrate how a specifically designed micro-wax dispersiona can impart a marble, dense-white appearance to shampoos as well as provide conditioning and anti-breakage properties that are equal to or better than benchmarks utilizing silicones.
The present micro-wax compound first was developed by dispersing several ethers into sodium laureth sulfate. The ether chemistry was chosen to ensure stability over a broad pH range to allow for the use of the compound in acidic, neutral and alkaline formulations. Sodium laureth sulfate was selected since it is used as a standard surfactant in shampoos and body washes. In addition, PEG-4 distearyl, distearyl and dicaprylyl ethers were chosen as lipid components for their conditioning performance. Test shampoos were then developed containing varying amounts of the micro-wax dispersion (see Formula 1).
Shampoos typically contain cationic polymers to enhance the deposition efficacy of conditioning additives;1 these cationic polymers can also enhance the deposition of waxes in shampoos. In Formula 1, a cationic guar derivative was used but other cationic polymers such as polyquaternium-10 or polyquaternium-67 could be substituted for, or added to, the cationic guar derivative.
As an added formulating benefit, shampoos that contain silicone dispersions such as dimethicone require a polymer for stabilization whereas those containing waxes do not. With regard to thickening, a combination of micellar thickeners such as fatty alcohol ethoxylates and salts is recommended. Salt as a single thickener will cause large differences in density between the formulation and the wax, and according to Stokes’ law, large differences in density will result in creaming of the waxes. Therefore, laureth-2 was used for thickening in addition to salt.
Having developed the test formulations, the authors then compared the conditioning and anti-breakage performance of shampoo formulations containing 0–4% of the micro-wax dispersion with two commercial anti-hair breakage benchmark shampoos, as described below. Additionally the amount of silicone oil in the benchmarks was determined by extraction and induced coupled plasma-optical emission spectroscopy (ICP-OES) analytics. The silicone oil concentrations of benchmarks 1 and 2 were found to be 3% and 1.4%, respectively. According to the INCI declarations, both benchmarks also contained a cationic guar derivative.
Combability measurements: The wet- and dry-combing performance of the tested shampoos were determined using an automated system.2 Ten dark brown European hair strands per shampoo formula were bleached with hydrogen peroxide and the baseline combing forces for each were recorded in the system. From force-displacement curves, the combing work was calculated by integration.
Then, the hair strands were treated twice with 0.25 g/L g hair of a test shampoo formulation and rinsed after the first and the second treatment. Afterwards, the combing force and work were determined for the treated hair strands. For each strand, the residual combing work was calculated according to the following equation:
Anti-breakage performance: The performance of the shampoos to reduce hair breakage was determined using a repeated combing device
(see Figure 1).3 Briefly, 10 bleached hair strands per formulation were repeatedly combed. The broken hair was collected in drawers separately for each strand. The content of each drawer was weighed and related to the weight of the whole strand before combing, resulting in the percentage of hair breakage. The mean and standard deviation for the hair breakage for all 10 strands were calculated.
Half-head testing: To demonstrate the conditioning effects of the shampoos containing the micro-wax dispersion in vivo, a half-head test was performed with 10 panelists, where one side of an individual’s hair was treated with a 3% micro-wax dispersion shampoo, and the other with the placebo. All relevant hair properties after shampoo application such as foam, combability and feel were assessed by a trained hair dresser.
The placebo test shampoo (see Formula 1) did not alter the wet-combing work of the treated hair strands. In contrast, a dose-dependency was confirmed for shampoos containing the micro-wax dispersion (see Figure 2).
With an increasing amount of the micro-wax dispersion—from 2% to 3% and 4%—the researchers reported a reduction in hair breakage. This can be seen in Figure 3 where, from the left, the strands were treated with shampoos containing 0% (placebo), 1%, 2%, 3% and 4% micro-wax dispersion. Statistical analysis showed that the shampoo containing 2% of the micro-wax dispersion reached the wet-combability level of benchmark 2, and the shampoo with 4% micro-wax dispersion met the wet-combability level of benchmark 1.
In addition, for treated and dried hair strands, a dosage-dependency was again confirmed (see Figure 4). While the placebo shampoo did not alter the combability, the addition of 1% of the micro-wax compound to the shampoo reduced the dry combing work to nearly 57%. The residual combing work could be further decreased to a level of 40% with the addition of 4% of the micro-wax dispersion to the shampoo. This result is somewhat exceeded by the two benchmark shampoos.
The amount of broken hair collected after combing (Figure 1) for all tested shampoo formulations is shown in Figure 5. Similar to the conditioning performance, hair breakage prevention was found to be dependent on the concentration of the micro-wax dispersion. Interestingly, the test formulas reached the same protection level as the two benchmark shampoos with 2% of the micro-wax dispersion. With micro-wax concentrations of 3% and 4%, the performance of the benchmark shampoos was exceeded.
Further examination of the commercial products confirmed a 1.4% reduction in hair breakage when the hair was treated with the benchmark shampoos together with the corresponding conditioner formulations. Comparing these findings with results from the combing tests, the researchers noted the anti-breakage properties mostly depended on conditioning the dry hair.
Formulations containing 0.75% and 1.0% of the micro-wax dispersion also exhibited deposition with a higher level of durability than those containing 1.4% and 3% dimethicone.
In vivo Tests
To examine whether the conditioning effects found in vitro could be confirmed under real application conditions, the formulations were applied to human hair in a simultaneous hair washing test comparing a formulation containing 3% of the micro-wax dispersion with a placebo formulation (see Figure 6). For all four conditioning parameters-combability and feel for both dry and wet hair, significant advantages were observed with the micro-wax dispersion in the 10 panelists. These results confirm the findings of the physical lab tests, where the parameters of wet and dry hair were improved.
This article describes a micro-wax dispersion that provides conditioning and anti-hair breakage properties in shampoos. By testing formulations containing varying amounts of the micro-wax dispersion, researchers confirmed a dose-dependent effect. Shampoos containing 3% and 4% of the dispersion reached the conditioning performance level of two commercial anti-breakage benchmarks. In addition, the micro-wax formulations outperformed the silicone-containing benchmarks in hair protection properties.
The described micro-wax dispersion enables formulators to develop conditioning shampoos with proven anti-hair breakage claims, as well as offers an alternative to silicone-containing shampoos. Since the described micro-wax dispersion is of a plant-based origin, it serves the trend for green and renewable ingredients without compromising performance. Additionally, formulas incorporating the material do not require a polymer stabilizer and they are cold processable, thus saving formulation and energy costs.
1. RY Lochhead and L R Huisinga, A brief review of polymer/surfactant interactions, Cosm & Toil 119 37-45 (2004)
2. M Hloucha, H-M Haake and G Pellon, “Green” microemulsion for improved hair conditioning performance of shampoos, Cosm & Toil (2009)
3. H-M Haake, S Marten, W Seipel and W Eisfeld, Hair breakage-How to measure and how to counteract, J Cosm Sci 60 143–151 (2009)