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Last Updated on November 21, 2025

Additives are important supplements that enhance the performance, processing, and longevity of adhesives, sealants, and coatings. While base polymers or resins give these materials their main properties, additives let them meet specific performance, processing and application requirements. For example, rheology modifiers manage flow, viscosity and application characteristics, ensuring consistent quality and reliable end-use performance.

By adding these additives, manufacturers can optimize formulations to achieve desired levels of performance, functionality, and durability.  Today, multifunctional coatings depend heavily on effective rheology modifiers to meet evolving industry demands for efficiency, durability and application versatility.

The Magic of Rheology Modifiers

Rheology modifiers are a specialized class of additives designed to control the flow, viscosity, stability and application performance of adhesives, sealants, paints and industrial coatings. In coating systems, they help achieve uniform film thickness and smooth surface finish.  In adhesives and sealants, they ensure proper bead formation and enhance the mechanical integrity of seals.

By influencing how a formulation behaves under different conditions, rheology modifiers play a critical role in enhancing key performance attributes such as:

• Thickness control
• Stickiness or tack
• Viscosity regulation
• Vertical spread (anti-sag)
• Storage stability
• Consistency and quality

Why Rheology Modifiers Matter

Viscosity Control

Viscosity measures a fluid’s resistance to flow. High viscosity makes the material flow slowly while low viscosity makes it thin and fast-flowing. Achieving the right viscosity in adhesives, coatings, sealants and inks prevents sagging, dripping, and splattering. Manufacturers must carefully maintain viscosity to balance ease of application and product stability

Rheology modifiers adjust viscosity to prevent products from becoming too liquid while maintaining optimal flow for application. They also prevent sagging, dripping and pigment settling, ensuring smooth, uniform coatings. Once shear forces from brushing or spraying stop, rheology modifiers help materials quickly regain structure and hold their shape, even on vertical surfaces,

Adhesion Support

Adhesion is the molecular attraction between a substrate and an adhesive, coating or sealant.  It ensures that the material remains securely bonded under mechanical, chemical or thermal stress. While rheology modifiers do not create chemical bonds, they support adhesion by ensuring complete wetting of the substrate, maintaining uniform film thickness and preventing sagging and drips.  By keeping pigments and fillers suspended for consistent contact, rheology modifiers allow adhesives and coatings to be applied more efficiently, a crucial factor in fast-paced production environments or on construction worksites.

Shelf Life Stability

Coatings, inks, paints and adhesives often change viscosity over time due to solvent loss, temperature fluctuations, or component interactions. Rheology modifiers extend shelf life by maintaining a consistent viscosity throughout storage.  They keep ingredients uniformly suspended, preventing settling and separation during transport. This ensures consistent film thickness, color, and performance as well as significantly reducing waste.

Thixotropy

Thixotropy describes a fluid whose viscosity decreases under shear (mixing, brushing, spraying) and recovers when shear stops. Thixotropic rheology modifiers allow products to remain thick and stable at rest, flow easily during application, and quickly return to a firm state. This prevents sagging and settling while enabling smooth, uniform coverage.

Value-Added Benefits of Rheology Modifiers

Offering a myriad of behavior benefits, rheology modifiers can improve adhesives, paints, laminates, tapes, and sealants by:

• Increasing shelf life by reducing settling
• Lowering time and energy needed for mixing
• Improving thickening efficiency
• Reducing raw material consumption
• Minimizing splattering during manufacture and application
• Boosting converting and production speeds
• Reducing penetration into porous substrates
• Increasing sag resistance
• Enabling higher coating build per application
• Reducing open/drying time
• Improving sprayability and brushability
• Enhancing printability and coating resolution

How Rheology Affects Adhesives

The table below outlines how rheology influences key processes in pressure-sensitive and laminating adhesives.

Rheology Modifiers Boost Performance and Cut Costs

In addition to enhancing product properties, rheology modifiers can reduce manufacturing costs, improve efficiency and minimize waste.

Optimized Manufacturing

• Improved mixing and pumping: Maintaining lower viscosity during handling allows faster mixing and reduced energy consumption.
• Consistent quality: Rheology modifiers prevent pigment and filler settling, phase separation, and sedimentation for consistent product performance.
• Formulation flexibility: Adjusting rheology modifier type/level allows fine-tuning without reformulating the entire system.
• Increased production speed: Enhances application efficiency in high-speed tape, label and laminate manufacturing.

Enhanced Product Performance

• Improved film build: Rheology modifiers produce formulations with less shear thinning, providing thicker wet films in a single coat.
• Excellent sag resistance: Coatings and adhesives stay in place, even on vertical or overhead surfaces.
• Uniform dispersion: Suspends pigments and fillers evenly for consistent color, opacity and performance.

Reduced Waste

• Minimized splattering and sagging reduces material waste and clean-up time.
• Extended storage life prevents degraded and unusable product disposal.
• Controlled absorption into porous containers such as corrugated boxes to reduce waste.
• Consistent application quality prevents costly defects.

Rheology Modifiers Chemistries

Rheology modifiers are classified into organic and inorganic types.

Organic rheology modifiers are generally polymeric and interact with formulations via entanglement, swelling or associative networks.  Common types include:

• Cellulosic derivations
• Associative thickeners
• Carbomers/polyacrylates
• Natural polymers

Inorganic modifiers are typically particulate materials that form physical networks to control viscosity.  Common types include:

• Clays/layered silicates
• Silicas
• Metal oxides/hydroxides

Each type offers unique performance properties. For instance, cellulose-based organic modifiers provide excellent shear-thinning behavior and good compatibility with colorants, making them ideal for water-borne architectural paints.

On the other hand, inorganic modifiers such as clays offer superior resistance to settling and heat, making them ideal for industrial, automotive, and protective coatings. The choice of rheology modifier depends on performance goals, application method and environmental conditions.

Formulating with Rheology Modifiers

Rheology modifiers can be added into water-borne, solvent-based or solvent-less formations, depending on formulation requirements. The table below summarizes common inorganic and organic rheology modifiers and their suitability for different types of formulations:

Selecting the Ideal Rheology Modifier

Different rheology modifiers are designed to address specific formulation challenges, and each category includes multiple grades tailored to performance needs. For example, HM Royal offers grades of  DuPont pulp fibers, Shiraishi precipitated calcium carbonates, as well as KaMin kaolin & Tokuyama fumed silica, all of which function as effective rheology modifiers in paints, inks, sealants, PVC resins and coatings.

• DuPont Kevlar pulp fibers offer unmatched thixotropy and reinforcement due to their high aspect ration and specific tensile strength and are recommended for use in adhesives, sealants, mastics and composites.
• Shiraishi’s precipitated calcium carbonates offer dimensional stability, uniform dispersion and reliable consistency to give optimum rheology in adhesives, sealants and coatings.
• KaMin kaolins allow manufacturers to fine-tune rheology and viscosity properties for enhanced performance and a better finished product.
• Tokuyama fumed silica consists of very fine, amorphous silicon dioxide particles that increase viscosity and thixotropy, improving the stability and application properties of resins, paints and adhesives.

Selecting rheology modifiers isn’t just about properties. Users should also consider how easy it can integrate into a formulation, costs, regulatory compliance, and long-term durability. With extensive expertise in rheology modifiers and industrial formulation challenges, HM Royal can help identify the ideal additive for your specific needs. Contact us today, or visit hmroyal.com to find out more about the products we represent.