Anti-flocculation Dispersants: The "Invisible Guardians" of the Coatings Industry
In coatings production, uniform dispersion of pigments and fillers is a critical factor in determining coating performance.
However, solid particles in liquids easily aggregate due to van der Waals forces or chemical bonds, forming
difficult-to-disperse flocs. This can lead to coating settling, floating color, and poor leveling. Anti-flocculation dispersants,
a special class of chemical additives, act as the "invisible guardian" that addresses this challenge through the dual effects
of physical barrier and charge repulsion.
I. The Core Mechanism of Action of Anti-flocculation Dispersants
Charge Repulsion: Building an "Electric Field Shield"
Dispersant molecules are mostly anionic or nonionic surfactants, containing both hydrophilic and hydrophobic groups in
their molecular structure. When a dispersant adsorbs onto the pigment surface, the hydrophilic groups extend toward the
aqueous phase, forming a negatively charged double layer. According to the DLVO theory, when two charged particles
approach, the electrostatic repulsion generated by the overlapping double layers effectively prevents particle aggregation.
For example, in water-based coatings, anionic dispersants ionize to form negative ions. These adsorb onto the surface of
titanium dioxide, generating a zeta potential of up to 30-50 mV between particles and forming a stable dispersion.
Steric Hindrance: Building a "Physical Barrier"
Polymer dispersants (such as polyurethanes and acrylates) adsorb onto the pigment surface via anchoring groups. Their
long molecular chains extend in solution, forming an adsorption layer up to 8-9 nm thick. When particles approach, the
entropic repulsion of the polymer chains and the solvation layer create a physical barrier. Even if charge repulsion fails,
steric hindrance maintains dispersion stability. Experiments have shown that dispersants prepared using controlled
free radical polymerization techniques (such as RAFT polymerization) have a more concentrated molecular weight
distribution and a steric hindrance efficiency that is over 40% higher than traditional products.
II. The Core Application Value of Anti-Flocculation Dispersants
Preventing Settling and Delamination
In heavy-duty anti-corrosion coatings, metallic fillers such as zinc powder are prone to settling due to their high density.
By adding a multifunctional polymer dispersant, a three-dimensional protective layer is formed on the zinc powder surface,
reducing the settling rate to below 0.02 mm/h, significantly extending the coating's shelf life. A marine coatings company,
after implementing this technology, saw its product's storage stability extended from 3 months to 18 months.
Inhibiting Flooding and Floating
Dark coatings (such as carbon black and phthalocyanine blue) often delaminate with titanium dioxide due to density
differences, resulting in discoloration after application. Dispersants control the surface wettability of the pigment, ensuring
uniform distribution of particles of varying densities. For example, adding a modified polysiloxane dispersant to automotive
topcoat can reduce the difference in settling rates between carbon black and titanium dioxide from 0.8 mm/h to 0.05 mm/h,
completely eliminating flooding.
Improving Tinting Strength and Hiding Power
Dispersants can reduce pigment particle size to submicron levels (<0.5 μm), significantly increasing the specific surface area.
Experimental data shows that red color paste treated with dispersants exhibits a 65% increase in tinting strength and a 20%
increase in hiding power compared to untreated samples. This has significant economic benefits in high-end industrial
coatings, reducing pigment usage by 15%-20%.
Optimizing Leveling and Gloss
In wood coatings, dispersants reduce the system's thixotropy, reducing the surface tension difference of the coating film from
8mN/m to 3mN/m and shortening leveling time by 50%. Furthermore, the refined pigment particles reduce light scattering,
increasing the 60° gloss from 75 to 92, achieving a mirror-like effect.
III. Typical Application Scenarios
Solvent-Based Coating Systems
In polyurethane coatings, polyamine amide-based polycarboxylate dispersants (such as JT-224) achieve a balance between
anti-sagging and anti-settling properties through a controlled flocculation mechanism. When used in PCB inks, this product
can reduce filler settling volume from 45% to 5% while maintaining a thixotropic index >3.5, meeting precision printing
requirements.
Water-Based Industrial Coatings
For water-based epoxy primers, the use of phosphate-based polymer dispersants can simultaneously address zinc dust
corrosion protection and dispersion challenges. Its unique anchoring groups form chemical bonds with metal surfaces,
achieving an adsorption strength of 50 mN/m, three times greater than conventional products. It also remains stable in
alkaline systems with a pH of 8-10.
High-Solid Coatings
In ultra-high-solid coatings with solids contents up to 80%, dispersants achieve high filler content by reducing system viscosity.
Experimental results show that adding 2% of an acrylate dispersant can reduce the slurry viscosity from 12,000 mPa·s to
3,500 mPa·s, increasing the pigment and filler content to 75% while maintaining application fluidity.
IV. Technological Development Trends
Green Transformation
With tightening VOC limits, the development of water-based dispersants is accelerating. Dispersants synthesized from
bio-based raw materials (such as cardanol) achieve biodegradability exceeding 90% while maintaining performance, complying
with EU EC 648/2004.
Intelligent Design
Optimizing the dispersant structure through molecular simulation technology enables "multiple effects with one dose."
For example, a new zwitterionic dispersant combines wetting, dispersing, and anti-settling properties, replacing three traditional
additives in architectural coatings and reducing costs by 25%.
Nanoscale Control
To address the dispersion challenges of nanopigments (such as TiO₂ nanotubes), a core-shell dispersant has been developed.
Its core provides strong adsorption, while its shell imparts steric hindrance, ensuring nanoparticle dispersion stability for
over six months, meeting the demands of cutting-edge applications such as quantum dot coatings.
Anti-flocculation dispersants, the "molecular engineers" of the coatings industry, are driving the industry toward
high-performance and environmentally friendly coatings through continuous technological innovation. From traditional
architectural coatings to high-end aerospace coatings, their applications continue to expand, providing critical support for
surface protection and decoration in modern manufacturing.
