FORMULATING Such behaviour aligns precisely with the
classical definition of an occlusive moisturizing agent, wherein physical impediment of water evaporation is achieved through the establishment of a durable hydrophobic layer, thereby preserving cutaneous hydration over extended periods. Concurrently, examination of the Kester Wax
K-70P molecule (as depicted in Figure 1) reveals structural features that confer intrinsic humectant properties independent of its primary plasticizing function. The presence of multiple electronegative oxygen atoms within the ester and ether linkages endows Kester Wax K-70P with strong hydrogen- bond acceptor capability. These electron-rich sites readily form
energetically favourable hydrogen bonds with water molecule, enabling the molecule to attract, immobilize, and retain water within the upper layers of the stratum corneum even under low relative humidity conditions.4
This water-binding
capacity operates via a classic humectant mechanism, distinct from mere occlusion, and contributes additively to overall skin hydration by establishing a hydrated microenvironment that counteracts desiccation stresses. Thus, Kester Wax K-70P exemplifies a rare
multifunctional excipient that simultaneously enhances film uniformity (superior occlusivity), reduces brittleness through plasticization (sustained emolliency), and actively sequesters water through hydrogen-bonding interactions (measurable humectancy), resulting in a tripartite moisturization profile that can be greater than the sum of its individual contributions.
Results and discussion Crystallization behaviour through PLM Close examination of Kester Wax K-72 (Behenyl Behenate) reveals a more segmented crystal structure with smaller crystal sizes when K-70 plasticizer is added, consistent with the suppression of crystal formation. With natural Waxes, such as Sunflower Wax and
Carnauba Wax as well as with the naturally derived, medium chain ester wax stearyl behenate (Kester Wax K-62) the plasticizing effect is manifested differently, i.e. large spaces between the crystals providing elasticity to the matrix and decreasing the cohesive forces between the crystals formed. This becomes more evident by rationalizing the rheometry studies discussed below.
Flow properties with Keser Wax K-70P plasticizer Rheology, being the study of flow and deformation properties of a wide range materials, is a convenient and valuable tool for determining the effect of plasticizers on these physical properties of wax matrices. We have compared the All Over Body Balm formulas (composition details can be found in the formula section below) containing both no plasticizer and 15 % Kester Wax K-70P in Dynamic Stress Sweep tests. At low stress amplitudes, both the elastic G´
and the viscous G´´ modulus formed a constant plateau region known as the linear viscoelastic range (LVR) of the materials. In the LVR, the stress induced in response to imposed strain
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TABLE 3: FORMULA 1: SQUEEZABLE LIP BALM - WITH 5% K-70P - MOST POPULAR FORMATS CONTAINING C18-38 ALKYL HYDROXYSTEAROYL STEARATE
Phase A
Trade Name Sunflower Wax
Kester Wax K-70P Coconut Oil Jojoba Oil
Jeechem CTG INCI
Helianthus Annuus (Sunflower) Seed Wax C18-38 Alkyl Hydroxystearoyl Strearate Coco Nucifera (Coconut) Oil
Simmondsia Chinensis (Jojoba) Seed Oil Caprylic/Capric Triglyceride
%
5.0 5.0
30.0 30.0 30.0
TABLE 4: FORMULA 2: ALL OVER BODY BALM - COMPARISON FORMULAS - MOST POPULAR FORMAT CONTAINING C18-38 ALKYL HYDROXYSTEAROYL STEARATE
Phase A
Trade Name
AR Cocoa Butter Sunflower Wax
*Plasticizer Kester Wax K-24 Lauryl Laurate
Extra Virgin Coconut Oil Cocos Nucifera (Coconut) Oil Jojoba Oil
Prunus Amygdalus Dulcis (Sweet Almond) Oil
Rice Bran Oil Vitamin E Acetate
Oryza Sativa (Rice Bran) Oil Tocopheryl Acetate
* Plasticizer used: Kester Wax K-60P, Kester Wax K-70P, Kester Wax K-82P
occurs in proportionality and, therefore, a linear range is found. For all studied body balms, G´ was observed to be higher than G´´ in the LVR, revealing a dominating elastic character of the products at low stress range. The greater the elastic nature of the products
leads to a substantial elongation of the structural network under continually increasing straining/ stress force before the structure is distorted into a state of viscoelastic liquid. When plasticizer is present, it becomes
evident how plasticizing waxes help to inhibit crystallization, which may not be essential for the product’s overall structure but instead plays a crucial role in enhancing thermal stability and overall formula integrity. The same All Over Body Balm formula with 15% added oils and no plasticizer also shows that the formula’s integrity is compromised at an earlier stage of stress, indicating that it may not maintain its structure at elevated stability temperatures due to the lack of appropriate crystal formation.
Conclusion In line with the objectives of this article we have investigated the efficiency of Kester Wax K-70P for changing the morphological and rheological properties of certain wax matrices. These properties, modification of these properties, are crucial for a plasticizer. The experimental results support the requirements described in the scientific literature. By modifying the crystallization and flow/
deformation properties of the wax matrices subjected to this research, Kester Wax K-70P, our assessment is that this material is a promising addition to the plasticizer market. Since it is
globally accepted and made from naturally sourced ingredients, it will greatly benefit the users, formulator in the personal care industry where improved workability and quality is desired.
9.4
40.0 15.9 10.6
1.2 8.0
49.0 13.5 9.0
1.0 INCI
Helianthus Annuus (Sunflower) Seed Wax
Helianthus Annuus (Sunflower) Seed Wax
Base 14.1
8.8 Oils
12.0 7.5
%
12.0 7.5
15.0 8.0
34.0 13.5 9.0
1.0
71
PCM
References 1. Hyatt JW. (1869). U.S. Patent No. 105,338. Improvement in the manufacture of celluloid
2. Idson B. Dry skin: moisturizing and emolliency. Cosmetics & Toiletries. 1992; 107(7), 69–78
3. Rawlings AV, Harding CR. Moisturization and skin barrier function. Dermatologic Therapy. 2004; 17(s1), 43–48
4. Lodén M. The role of topical humectants in the skin. American Journal of Clinical Dermatology. 2003; 4(11), 771–788.5. Wypych G. (2017). Handbook of Plasticizers (3rd ed.). ChemTec Publishing
6. Sears JK, Darby JR. (1982). The Technology of Plasticizers. Wiley-Interscience
7. Krause S, Roman N. Hydrogen bonding in plasticized polymer systems. Journal of Polymer Science Part A: General Papers. 1965; 3(5), 1631–1643
8. Ferry JD. (1980). Viscoelastic Properties of Polymers (3rd ed.). John Wiley & Sons
9. Mezger TG. (2020). The Rheology Handbook (5th ed.). Vincentz Network.
10. Fox TG, Flory PJ. Second-order transition temperatures and related properties of polystyrene. Journal of Applied Physics. 1950; 21(6), 581–591
11. Boyer RF. The relation of transition temperatures to chemical structure in high polymers. Rubber Chemistry and Technology. 1963; 36(5), 1303–1421
April 2026 PERSONAL CARE MAGAZINE
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