NATURALS


However, our three waxes have very similar chemistries and early work pointed to the possibility of building multiple robust emulsions and making variations for data collection without compromising stability and integrity. Koster Keunen conducted a comprehensive to evaluate the impact


series of experiments1


of adding them in increasing concentrations to different O/W emulsions. Three very different formula bases were designed based on previous formulation work. Base 1 is a leave-on chassis that can be used in skin care formulations with a neutral emulsifier and the oil phase range of 13-16%. Base 2 is another leave-on skin care chassis using an anionic emulsifier and the oil phase is 25-31%. Base 3 is a chassis for any hair conditioner, the emulsifier is cationic and the oil phase is 16-22%. Tables 1-3 show their compositions and the


modifications made to them for testing. Each emulsion base was modified by adding five different ingredients at 3% and again at 6%, then observing the different results. The ingredients were our three waxes, along with two widely used oil phase components - caprylic/capric triglycerides (CCT) and cetyl alcohol - as controls. For each of the eleven modifications per base, we recorded the following properties: ■ Emulsion viscosity (cP): Measured at one week, with a Haake Mars rheometer at constant shear ■ Emulsion complex modulus (Pa): Measured at one week, with a Haake Mars rheometer at increasing oscillation stress values ■ Sensory emulsion properties: Evaluated with human panel testing, rated on a scale of 1=least to 5=most


Results The viscosity of Formulas 1-33 at one week are grouped by base and plotted on graphs, where the y-axis is viscosity (in cP) and the x-axis is the percentage wax added to each base. Figures 1, 2 and 3 correspond to Bases 1, 2 and 3 respectively. The complex modulus (G’) of Formulas


1-33 was also measured at one week. Results are grouped by base and plotted on graphs, where the y-axis is G’ (in Pa) and the x-axis is the percentage wax added to each base. Figures 4,5 and 6 correspond to Bases 1, 2 and 3 respectively. Formulas 1-22 were evaluated (via human panel, n=10) for sensory and performance parameters pertaining to skin care (Tables 5 & 6). Formulas 23-33 were evaluated on mannequin heads for sensory and performance parameters pertaining to hair care (Table 7). All formulas were evaluated, but only relevant results are shown (controls without wax, additions of 6% of each of our waxes). Each of the three wax esters reviewed


showed improvements in the overall appearance of the emulsions studied. Specifically, they can impact O/W emulsions by increasing opacity, gloss and overall brightness, making formulas look more expensive and luxurious. Each also creates differences beyond these first attributes. The study shows that both cetyl palmitate


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TABLE 5: SENSORY & PERFORMANCE EVALUATION OF SELECTED BASE 1 FORMULAS Formula 1 (0%, control)


Formula 3 (6% K-48)


Before application Shape integrity Whiteness Opacity Gloss


During application (skin) Bounce


Firmness


Slip/Spreadability Absorption Soaping


After application (skin) Hydrated look Hydrated feel


2 4 3 4


1 1


5 5 2


4 4


4 5 5 4


4 4 5 4 2


4 4


Formula 14 (6% K-48)


4 5 4 3


Firmness


Slip/Spreadability Absorption Soaping


After application (skin) Hydrated look Hydrated feel


4 4 2 4 1


3 2


Formula 5 (6% K-56)


5 5 5 5


4 4 4 4 2


4 4


TABLE 6: SENSORY & PERFORMANCE EVALUATION OF SELECTED BASE 2 FORMULAS Formula 12 (0%, control)


Formula 16 (6% K-56)


Before application Shape integrity Whiteness Opacity Gloss


During application (skin) Bounce


3 3 3 3


2 2 4 5 1


3 2


4 5 4 2


3 3 4 5 1


3 2


TABLE 7: SENSORY & PERFORMANCE EVALUATION OF SELECTED BASE 3 FORMULAS Formula 23 (0%, control) Formula 25 (6% K-48)


Formula 27 (6% K-56)


Before application Shape integrity Whiteness Opacity Gloss


During application (skin) Bounce


Firmness


Slip/Spreadability Absorption Soaping


After application (skin) Hydrated look Hydrated feel


3 3 3 3


2 2 4 5 1


3 2


and stearyl stearate have a pronounced effect on the visual and textural properties of an emulsion, without affecting the formula viscosity. Adding cetyl stearate to emulsions also improves the above visual and textural properties, with the added function of being a highly effective viscosity builder. Cetyl stearate is comparable in this sense to cetyl alcohol, a well-known emulsion viscosity builder. The waxes did not show any immediate impacts on the formula performance, be it skin or hair care. From a functional standpoint, they are natural opacifiers, texture modifiers and viscosity modifiers. Future work includes more


4 5 4 3


4 4 2 4 1


3 2


4 5 4 2


3 3 4 5 1


3 2


3


Formula 7 (6% K-59)


4 5 4 5


3 2 5 4 2


4 4


Formula 18(6% K-59)


4 5 4 5


3 3 2 4 1


3 2


Formula 29 (6% K-59)


4 5 4 5


3 3 2 4 1


3 2


comprehensive sensory testing, gathering TEWL data, and increasing the number of alkyl esters studied.


Formulating anhydrous systems Cosmetic chemists who formulate anhydrous products, such as sticks, bars or balms, are generally familiar with waxes as structurants. Many waxes thicken organic liquid media by building a three-dimensional network (called a gel) that keeps them entrapped and immobilised. Not all waxes thicken and the ones that do, do not always behave the same, which is why the ability to measure, record and


Reprinted from March 2022 PERSONAL CARE


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