NATURALS


Opacity, viscosity, structure or body


Belén M. Lemieux, Joelle Lamontagne, Alexandra McMahon, Steven L. Puleo - Koster Keunen


Wax esters, like most lipidic materials, have a long history of use in personal care and cosmetics. For example, in 2nd century BCE China, it was common practice to apply naturally occurring animal fats and vegetable oils onto human skin to soothe or heal wounds.1 Although there was no formal knowledge about the composition of these natural fats, early users reasoned they must be similar to the composition of human skin, thus making them key ingredients in early ointments, liniments and salves. Aside from being efficient, these early formulations were relatively resistant to microbiological contamination and stable over time.2


Their shortcomings, like oxidation and


rancidity, were eventually overcome with the introduction of antioxidants and replacement with synthetic ingredients.3 Today’s chemists are evolving with the


global demand for functional, sustainable and renewable plant derived materials. In this paper, we study three alkyl esters that meet these current needs.


Functionality & sustainability In organic chemistry, esters are the reaction product of an organic acid with an organic alcohol, represented by the following general reaction:


RCOOH + R’OH --> RCOOR’ + H2 O


where R and R’ are alkyl chains of varying lengths, degrees of saturation and degrees of branching. There can be considerable combinations of the two initial components to form alkyl esters, yet the ones used in


TABLE 2: FORMULATION OF BASE 1 Phase A


Ingredients


Deionised Water Pemulen TR-2 Optiphen


Glycerin NaOH 10% B Kostol NatureMuls


Kester Wax K-24 Jeechem CTG


Test wax/control wax


INCI Aqua


Acrylates/C10-30 Alkyl Acrylate Crosspolymer


Phenoxyethanol, Caprylyl Glycol Glycerin


Sodium Hydroxide


Candelilla/Jojoba/Rice Bran Polyglyceryl-3 Esters, Glyceryl Stearate, Cetearyl Alcohol, Sodium Stearoyl Lactylate


Lauryl Laurate


Caprylyc/Capric Triglyceride TBD


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TABLE 1: PROPERTIES OF KESTER WAXES INCI Name


Trade name Feedstock #1 Feedstock #2 # Carbons


Melt point (°C) Molecular weight Cetyl Palmitate


Kester Wax K-48 Cetyl Alcohol Palmetic Acid 32


45 – 53 480.08


cosmetics and personal care range from oils (lower molecular weights) to waxy solids (higher molecular weights).4


The differences


in composition will affect the product form, its properties, its behaviour in finished formulations and the properties of those finished formulations. Alkyl esters are classified in cosmetics as emollients and skin-conditioning agents. Cosmetic emollients can soften the skin by replacing lost lipids in the stratum corneum, keeping it flexible and reducing trans-epidermal water loss (TEWL).5 The wax esters highlighted in this study are


produced with sustainability as a factor. The starting materials come from natural, traceable feedstocks and standard esterification methods do not consume water in the manufacturing process or produce wasteful by-products.


Definitions & properties In this study we will focus on three chemically similar esters to determine the individual traits of each one. The products studied are Kester


% w/w q.s.


0.1 1.0


4.0 0.4


5.0


5.0 3.0


0-6 Reprinted from March 2022 PERSONAL CARE B Ingredients Cetyl Stearate Kester Wax K-56


Cetyl Alcohol Stearic Acid 34


54 -58 508.91


Stearyl Stearate


Kester Wax K-59 Stearyl Alcohol Stearic Acid 36


57 -61 536.96


Wax K-48 (INCI: Cetyl Palmitate), K-56 (INCI: Cetyl Stearate and K-59 (INCI: Stearyl Stearate). Although they are close in carbon chain length and thus in physicochemical properties, previous lab work has shown they can have surprisingly different performances in finished personal care products (Table 1). The starting materials that make up plant-


derived waxes are biopolymers. Like naturally occurring plant waxes, they are biosynthesised by specialised cells to become the outermost boundary of the plant. The purpose is to provide protection from environmental stresses, while still allowing a suitable exchange with the atmosphere.6 These natural barriers are not unlike the lipid


layer that covers the surface of human skin, being partially made up of triglycerides, wax esters and squalene.7


staple in skin care formulations. According to the Cosmetic Ingredient Review, cetyl palmitate functions as an


TABLE 3: FORMULATION OF BASE 2 Phase A


INCI


Deionised Water Glycerin


Keltrol CG-SFT Optiphen KOH


Stearic Acid


AR Cocoa Butter Jeechem CTG


Test wax/control wax


Aqua Glycerin Xanthan Gum


Phenoxyethanol, Caprylyl Glycol Potassium Hydroxide Stearic Acid


Theobroma Cacao (Cocoa) Seed Butter


Caprylyc/Capric Triglyceride TBD


% w/w q.s. 5.0 0.5 1.0


0.4 4.0


6.0


15.0 0-6


becomes compromised, waxes can provide a temporary barrier,8


If the human lipid layer which is why waxes are a


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