Advanced Crystallization Control In Personal Care Formulations

What Is A Plasticizer?

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Plasticizers are solid form chemistries designed to reduce crystallization, manage consistency, texture and stability in both anhydrous and emulsion formulations.

Products

Kester Wax K-82P

Kester Wax K-60P

Kester Wax K-70P

Formulas

Formulas

The Benefits Of Using A Plasticizer In Personal Care

• Suppress Crystallization
• Creates Creamy Texture
• Supports Thermal Stability
• Inhibits Migration
• Enhances Dispersions
• Stops Bloom and Syneresis

Objectives

The objective of this article is to summarize the benefits of Kester Wax K-70P, a new plasticizer from Koster Keunen, Inc. In particular, the crystallization and rheological properties were investigated and correlated with the desired properties of an efficient plasticizer.

Introduction

Plasticizers are additives for increasing the flexibility and ease of processing. The presence of a plasticizer typically causes a reduction in the cohesive intermolecular forces along the wax molecules, enabling these chains to move more freely relative to one another, resulting in the reduction of stiffness of the wax matrix¹.

Polyesters are among the commonly used plasticizers due to their favorable physical interactions with high molecular weight molecules that are typical constituents of waxes. This physical interaction between the wax and plasticizer molecules causes these materials to form a homogenous physical unit, meaning they do not separate.

The two main categories of plasticizers are primary and secondary. The former interacts with the wax molecules, while the latter increases the effectiveness of a primary plasticizer2. There are two types of plasticization with primary plasticizers: internal and external. Internal plasticization involves the chemical alteration of the wax molecule or its building blocks (prior to synthesizing the wax molecule). The second type of plasticization is external. External plasticization is the focus of this study. It is important to note that the plasticizer interacts with the wax physically, although hydrogen bonding and Van der Waals forces often play a role. Polyester plasticizers are favored across various industries and applications due to their exceptional flexibility.

Materials, Methods, and Instrumentation

Wax samples were prepared from Koster Keunen, Inc. commercial grade wax products with 5% w/w of plasticizer unless listed otherwise. Crystallization studies were carried out using an Olympus CH microscope using polarized light. Images were captured using a Moticam 3 3.0 MP camera integrated with the microscope. Microscope slides and cover glasses were purchased from Fisher Scientific and were electrically heated before cooling to ambient temperature for inspecting the crystallization process and the resulting crystalline particles.

Dynamic stress sweep rheology studies were conducted at the University of Connecticut, Institute of Materials Science Laboratory³. A Discovery HR20 rheometer (DHR20, TA) was employed utilizing a serrated Peltier plate fixture. The test configuration featured a modified cross-hatched 40 mm cone plate. Samples were loaded and zero gap determination was performed at the designated test temperature. A Peltier temperature control system connected to a recirculating water bath maintained the system at the required temperature throughout the tests. Yield stress measurements were performed […]

Mastering Oleogels: From Gel Formation to Formulation Efficiency

Gels are remarkable semi-solid materials that balance solid and liquid components in a unique harmony. Their solid component, known as the gelator, creates a network of aggregates that immobilizes the liquid, resulting in a soft, solid-like texture. For cosmetic scientists, oleogels—gels where the liquid medium is oil-based—are particularly compelling. They combine wax, oil, and specific processing techniques to create a diverse range of textures and consistencies.

What Makes a Successful Oleogel?

Formulating a stable, effective oleogel hinges on three critical factors:

1. Wax Concentration: The proportion of gelator to liquid.
2. Type of Wax: Different waxes create different gel structures.
3. Liquid Medium: The oil or liquid must be compatible with the wax for effective gelation.

Compatibility between these elements is vital to achieving the desired gel structure.

The Role of Gel Charts in Oleogel Formulation

To streamline the formulation process, Koster Keunen scientists developed a gel chart—a visual guide for predicting gel properties based on wax type and concentration. This chart allows formulators to select their ingredients more efficiently, reducing trial-and-error in the lab.

How to Read a Gel Chart

The y-axis of the gel chart measures penetration value, a key indicator of the gel’s hardness or flowability. Penetration values are reported in decimillimeters (dmm), with higher values indicating softer, more fluid gels. Here’s a breakdown:

• 15-40 dmm: Firm, waxy structures (e.g., sticks or hard balms).
• 40-70 dmm: Moderately hard, semi-solid products (e.g., push-up tubes or harder pot products).
• 70-150 dmm: Soft, flowable gels (e.g., lotions or light creams).
• 150+ dmm: Highly fluid, pourable gels (e.g., oil serums).

Why Use a Gel Chart?

By referencing a gel chart, you can:

• Save Time: Skip extensive lab testing by narrowing down the ideal wax concentration for your target gel structure.
• Optimize Performance: Achieve consistent product properties by selecting the right wax and oil combination.
• Enhance Understanding: Gain insights into the relationship between wax concentration and gel firmness.

For example, if you’re formulating a push-up deodorant, you can consult the chart to find the wax concentration that produces penetration values in the 40-70 dmm range. This ensures the product holds its shape while remaining easy to apply.

Empowering Cosmetic Scientists

Oleogels offer unmatched versatility in the world of cosmetics, from firm balms to silky serums. With tools like gel charts, cosmetic scientists can harness the science of gels to innovate more effectively. Whether you’re aiming for a luxuriously soft feel or a firm, functional structure, gel charts bring clarity to the complex world of oleogel formulation, helping you get it right the first time.

Gel Charts

Natural Waxes

Beeswax

Candelilla Wax

Rice Bran Wax x #224P

Rice Bran Wax #849P

Sunflower Wax

Kester Waxes

Kester Wax K-48

Kester Wax K-56

Kester Wax K-59

Kester Wax K-62

Kester Wax K-72

Other Waxes

Cera Bellina

Synkos O-1070

Synthetic […]

What Is A Water-In-Oleogel Emulsion?

A water-in-oleogel emulsion is a moderately complex system, with properties dictated by both water-in-oil emulsion theory, as well as oleogel theory.

Products

Sunflower Wax

Beeswax

Rice Bran Wax

Ozokerite

Synkos

Formulas

Formulas

What are the benefits of a water-in-oleogel emulsion in personal care?

• Incorporation of both water and oil soluble actives.
• Increased emulsion stability.
• Flexibility: multiple levels of structure are possible.
• Innovative, interesting textures.
• Benefits of oil based formulas without the greasy feel.
• Possible cooling effects on skin.
• Sticks and other “on-the-go” formats.

What are the sensory benefits of a water-in-oleogel emulsion?

Because of this hybrid nature, w/og emulsions can offer both the positive sensory benefits of w/o emulsions as well as of anhydrous formulations. In a sensory panel, participants were presented with a trio of skin care formulations: a standard w/o emulsion, a structured w/o emulsion and an anhydrous balm, all based on the same formula backbone. Panelists were asked to rate and describe the sensory properties.

The sensory panel results show an overwhelming preference towards the structured w/o format, as well as a wider range of sensory/texture descriptors when compared to the corresponding w/o emulsion and anhydrous balm.

Overall format performance

initial observations and hypothesis

The addition of waxes in increasing levels to the oil phase of w/o emulsions (external phase) show very different results than those observed when adding waxes to the oil phase of o/w emulsions (internal phase). Those results are consistent with our observations when working with oleogels. Our theory is that if there is a direct correlation between the structural properties of w/og systems and their og counterparts, all tools and techniques chemists use when working with anhydrous systems can be applied to working with structures w/o systems.

objectives

1. Create oleogel (og) charts showcasing the structuring properties of different waxes in different oil mediums.
2. Create water-in-oleogel (w/og) charts: Replicate #1, but with 50% water phase dispersed internally using an appropriate w/o emulsifier.
3. Compare charts from #1 and #2 and determine any relationships. If they exist, test our theory on complex formulas and provide formulators with the tools and guidance to create their own systems.

oleogels theory and gel charts

Oleogels (og) are viscoelastic materials comprising a nonpolar liquid phase (the oil) and a gelator or mix of gelators, very typically waxes. Waxes immobilize the lipid phase through the formation of three-dimensional networks, resulting in systems of varying consistencies and firmnesses, largely dependent on the amount of wax used.

This oleogel firmness or strength can be measured with a penetrometer and recorded on a gel chart, a tool that can organize gel strength data in a meaningful way and save a lot of trial-and-error time. Gel charts published here were built by plotting penetration distance on the y-axis vs. % wax on the x-axis for each individual gel following the simple formula: