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 cosmetics and personal care range from oils
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
www.personalcaremagazine.com
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
(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 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,
% w/w q.s.
0.1 1.0
4.0 0.4
5.0
5.0 3.0
0-6 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
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
If the human lipid layer becomes
compromised, waxes can provide a temporary barrier,8
cetyl palmitate functions as an emollient, and also contributes a specific body and texture to cream and lotion products.9
which is why waxes are a staple in skin
care formulations. According to the Cosmetic Ingredient Review,
Mintel classifies it as
a skin conditioning and masking agent, with its main uses in Q4 2021 being in skin care (70% of launches), followed by hair care (15%).10 After multiple experiments, we found that cetyl palmitate had something else to offer
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
45
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