What are rheology modifiers and how do they work?


rheology modifiers

When we look at creating the perfect formulation, there has to be an element of tweaking and refining to get it to the desired consistency. In order to achieve this, we’ll often look to incorporate rheology modifiers.

Rheology modifiers are a common additive used in nearly every industry to alter the flow behaviour, rheology and mechanical properties of materials to meet specific requirements. 

The introduction of rheology modifiers can have transformative effects on material performance in end-use applications and is therefore a crucial piece of the puzzle when it comes to perfecting your formulations.

The RBH Group specialises in supporting businesses to enhance their product performance, through a diverse portfolio of materials which includes a range of high-quality rheology modifiers. In this article, we’ll share our knowledge and insights into this process and how modifiers can help to meet the needs of the most unique manufacturing requirements.

Understanding rheology modification

To understand how these powerful additives work, we first need to understand the science behind rheology modification.

Rheology is a fundamental concept in the field of materials science and is the act of studying the behaviour of materials. It’s centred around understanding how they flow, deform, or change shape when a force is applied to them.

If we take a ball of dough, for example, when you squeeze it, push or pull it, it will change shape. The same scenario can be applied to liquids such as water or honey. A glass of water is thin and fast-moving when poured, but honey is thick and slower-moving when drizzled. 

Rheology is all about understanding and controlling these kinds of behaviours in materials like liquids, gels, and even solids. Once we have this understanding, we can then manipulate their flow properties for different purposes with the use of rheology modifiers.

rheology

What is a rheology modifier?

Rheology modifiers are often referred to as thickening agents, but they offer far more than simply altering the thickness of a formulation. 

Reliable rheology modifiers can be thickeners, stabilisers, or other additives and allow formulators to bring structure to a formulation whilst controlling factors such as viscosity, thixotropy, sag resistance, and film formation.

The main goal here is to improve the end product and ensure it performs as it should in specific conditions when used by the consumer. For example in skincare, rheology modifiers will affect how a cosmetic product feels, how easy it is to pour, how it sinks into the skin and how long its shelf-life is. 

With the right modifier in place, these factors can all be controlled to ensure a high-quality end product that consumers are likely to re-purchase.

Why we use rheology modifiers in polymers

When it comes to the development of polymer-based products such as paints, adhesives, coatings and personal care products, rheology is a key consideration.

Polymers naturally have diverse structures and properties with complex rheological behaviour influenced by factors such as molecular weight, chain architecture, temperature, and processing conditions. Understanding the rheological properties of polymers is essential for predicting how they will behave under different processing and application scenarios. 

Performing rheological studies on polymers typically involves measuring parameters such as viscosity, elasticity, shear stress, shear rate and viscoelastic properties. Through this, we can gain insights into flow behaviour and mechanical performance under different conditions to inform the ideal rheological modification solution required to improve and stabilise a formulation.

How rheology modifiers work

As we mentioned earlier, rheology modifiers don’t just thicken a formulation. They can significantly change the entire formulation of a product, essentially dictating how it looks, feels, performs, and how long it lasts.

Some key advantages of using rheology modifiers include having the ability to:

  • Modify viscosity: Does the formulation need to be thicker or thinner for the application? Depending on the purpose it will be used for, rheology modifiers can dictate the fluid’s resistance to flow.
  • Alter thickness: Once the viscosity is set the formulation’s thickness can be fine-tuned to ensure it flows smoothly and has the desired texture or spreadability.
  • Control flow behaviour: Rheology modifiers can also control how a product flows to ensure easy pumping or pouring in applications. For example, they may be used to prevent paint dripping or enhance the sprayability of coatings to ensure even coverage. 
  • Prevent settling: If a formulation has solid pigments or particles, rheology modifiers can help to suspend these evenly throughout the product to prevent any settling or sedimentation.
  • Enhance texture: They can help to create smoother, creamier textures where the look and feel of a product is a priority, for example in cosmetic formulations.
  • Improve stability: Rheology modifiers help products remain stable by preventing the separation of particles and ensuring longevity.
rheology modification for automotive coating

Types of rheology modifiers

The types of rheology modifiers available are as diverse as the applications and industries in which they can be used. 

There’s no one-size-fits-all solution, from proprietary additives and reactive compounds to naturally occurring minerals, each modifier has unique benefits and functionalities for controlling the rheological behaviour of materials in various applications. 

Below are some of the rheology modifiers that RBH can supply.

Acti-Gel®

Acti-gel 208® is a highly purified form of magnesium aluminium silicate. It serves as a multifunctional additive which can be used in various applications including paints, coatings and construction materials, and can also be used as a reinforcing filler.

In water-based products, Acti-Gel® forms a three-dimensional network structure through hydrogen bonding and electrostatic interactions, leading to fast viscosity enhancement. It can improve stability, sag resistance, and suspension properties, and is particularly effective in controlling rheology at low to moderate shear rates.

Min-U-Gel®

Min-U-Gel® is a range of specially processed colloidal gelling agents in powdered form, derived from attapulgite clay. At their core, they are rheology modifiers with thixotropic thickening suitable for a vast array of applications. 

They can function as thickeners, stabilisers, and viscosifiers, with the ability to increase viscosity and enhance adhesion properties amongst many other benefits. Applications range from paints, coatings and adhesives to mortars, seed coatings and many more.

Organic peroxide

Organic peroxides are a class of compounds often used as crosslinking agents in polymerisation reactions to create crosslinked polymer networks. 

Whilst they’re not typically considered traditional rheology modifiers, they can indirectly influence the rheological properties of materials by affecting the polymerisation and curing processes.

For example, if a formulation contains reactive polymers or resins, organic peroxides can initiate crosslinking reactions which can lead to changes in viscosity and mechanical properties.

We supply the Luperox® brand of organic peroxides from Arkema, a unique range that helps to increase mechanical strength and resistance to chemicals or weather.

Rheology modifier selection

Rheology modification plays a critical role in the development of advanced materials, allowing formulators to develop products with specific functionalities. In order to achieve these desired properties, choosing the right rheology modifier and striking the perfect balance is essential.

At RBH, we offer a diverse range of rheology modifiers that equip our clients with the ability to control viscosity in both aqueous and non-aqueous systems. Our expert team of market managers specialise in offering technical support and guidance on the right product for your application.

To find out more about how our range of modifiers can improve your product performance, get in touch with us.

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