What are Rheology Modifiers and How Do They Work?
The cosmetics and personal care products we all use every day are complex formulations containing numerous active ingredients. The average consumer may not understand the purpose of all those ingredients, but each one has been carefully selected to fulfill a specific role.
In today’s post, we will take a close look at one category of personal care ingredients: rheology modifiers. What are they, how do they work, and how do they enhance the performance of the products in which they are used?
What is Rheology?
Before we can dive into the purposes of rheology modifiers, it is important to understand what rheology actually is. In short, it is a branch of physics that pertains to the deformation and flow of materials (solids, liquids, and gasses). When enough force or stress is applied to a material, it eventually begins to flow in response.
Therefore, when we refer to the rheological properties of a material, we are referring to several key areas including its yield stress (the stress point at which the material begins to flow), relaxation time (the time taken for the material to return to its pre-stress equilibrium), viscosity (the material’s resistance to flow), and compliance (how tolerant the material is to undergoing deformation).
Rheology has applications in numerous different fields including engineering, physiology, biology, pharmaceuticals, and, of course, the personal care and cosmetics industry. Viscosity is a particularly important rheological property in the context of cosmetics.
What Are Rheology Modifiers?
Rheology modifiers, therefore, are substances that alter the rheological properties of a material. They are added to formulations to increase viscosity and to control the finished product’s properties and characteristics in a desired manner.
In the cosmetics world, you may hear certain ingredients referred to as “thickeners”. This is another, more commonplace term for rheology modifiers and essentially means the same thing. Thickeners provide increased consistency and improve the appearance and sensory properties (how the formulation feels on the skin) of the finished product. They can also improve stability and enhance performance.
Different Types of Rheology Modifiers
There are many kinds of rheology modifiers available, and different ingredients will be appropriate for different applications.
For example, rheology modifiers may be hydrophilic (attract water), hydrophobic (repel water), or ambiphilic (able to perform in either manner). Hydrophilic modifiers act as humectants, keeping the product moist by attracting and retaining water, which makes them ideal for use in skin and hair moisturizers.
Broadly speaking, thickeners can be grouped into three categories:
Natural polymers are the most common rheology modifiers and are long chain polysaccharides from natural sources such as trees, plants, and algae. Common examples include xanthan gum, carrageenan, guar gum, and alginates.
Natural polymers have the advantage of meeting the environmentally-friendly “green” credentials that more and more manufacturers are striving towards as consumers become more eco-conscious. However, they do not always boast the same levels of functionality as their synthetic counterparts. They can also result in the end product having a sticky or tacky consistency.
Synthetic polymers come in two major classes: Polyethylene glycol derivatives (PEGs) and acrylic polymers. PEG thickeners are hydrophilic and thicken by uncoiling and taking up a large volume. Acrylic polymers swell in water-based systems and open to fill the space.
The advantage of synthetic polymers, particularly acrylic polymers, is that they are more functionally efficient in thickening and provide improved, more shear-thinning sensory. They are also less prone to bacteria growth than their natural counterparts. That said, some are also non-renewable and therefore less environmentally friendly.
Inorganic materials are those not derived from living material. In other words, those that contain no or very small amounts of carbon. Common inorganic rheology modifiers include clays, which are hydrophilic and thicken by volume exclusion, and silica, which thickens oils by forming inter-particle hydrogen bonds.
Inorganic rheology modifiers tend to have a high yield stress point, good thixotropy (the property of being viscous under normal circumstances but flowing under stress), and good stability.
Our Rheology Modifiers
We offer a number of high quality rheology modifiers to our clients in the cosmetics and personal care industries.
Our Sensogel series consists of light, pre-neutralized, acrylamide-free liquid thickeners with soft, skin-friendly sensory properties. Sensogel is highly versatile, suitable for products ranging from thin sprays to thick butters. It is suitable for use through a wide pH range and particularly well suited to low-pH applications.
OleoFLEX is our hybrid rheology modifier, making use of both natural oils and premium synthetic components. OleoFLEX Elastomer Gel (EG) 200 is typically used in skincare and “stick” applications and provides a soft and cushioned feel, while the OleoFLEX Flowing Gel (FG) 100 series is most suited to haircare and lip care products.
Sorbithix L-100 is the most powerful non-ionic surfactant thickener currently on the market and is suitable for use in all kinds of surfactant formulations including soaps, shower gels, and shampoos. Unlike its competitors, Sorbithix L-100 boosts and sustains viscosity in products containing high amounts of fragrance, without compromising on the foaming properties valued by consumers.
G-Gel is a series of bentonite clay master gels and provides an extremely stable thickener which will not separate over time. Highly versatile, G-Gel is used to improve thixotropic viscosity in a wide array of cosmetic and personal care products and can be used to thicken any class of oil. Our unique formulation offers almost twice the suspension and thickening efficacy as other bentonite gels in the same class.
Do you have additional questions about rheology modifiers? Are you interested in samples to find out whether any of our thickeners and rheology modifiers are right for your products? If so, please get in touch.
We believe in providing samples generously and offering best in class customer service. Therefore, when you reach out to us, you will receive a rapid response from a member of our friendly, highly knowledgeable team.
We look forward to working with you.