Behind the black rubber layer of rubber tires, the dark outer shell of plastic products, and the uniform blackness
of paints and inks, a key additive silently plays a role—polyester carbon black viscosity reducer and dispersant.
It solves the problem of carbon black's tendency to agglomerate through physicochemical means, becoming
an "invisible hero" in improving the performance of industrial materials.
I. Why is a Dispersant Needed? The "Inherent Defects" of Carbon Black
As the most widely used black pigment and reinforcing filler in the industrial field, carbon black has extremely
high surface energy. Particles easily aggregate through electrostatic or van der Waals forces, forming
agglomerates with diameters reaching micrometers. This characteristic leads to:
Processing difficulties: Agglomerates cause the Mooney viscosity of rubber compounds to soar, and the melt
flowability of plastics to decrease;
Performance degradation: Uneven dispersion of carbon black reduces the abrasion resistance of rubber, the
conductivity of plastics, and the hiding power of coatings;
Storage hazards: After long-term standing, carbon black settles and separates, affecting product stability.
II. The "Dual-Effect Mechanism" of Polyester Dispersants
Polyester dispersants achieve viscosity reduction and dispersion through a dual effect of "physical isolation
+ chemical adsorption":
Stereohindrance Effect: Polyester molecular chains unfold on the carbon black surface, forming a "protective layer"
several nanometers thick. When particles approach each other, the molecular chains collide, generating physical
repulsion and preventing agglomeration. For example, in rubber compounding, polyester dispersants can reduce
the carbon black particle size from 10 micrometers to less than 1 micrometer.
Chemical Anchoring Effect: The carboxyl and ester functional groups in polyester molecules form hydrogen bonds
or chemical bonds with oxygen-containing groups (such as hydroxyl and carboxyl groups) on the carbon black
surface, forming a stable adsorption layer. This effect is particularly significant in polar solvents (such as water-based
coatings), improving dispersion stability by more than 90%.
III. Application Scenarios: Full-Chain Penetration from Laboratory to Production Line
Rubber Industry: Adding polyester dispersants to tire tread rubber can reduce the Mooney viscosity of the compound
by 20%-30%, while simultaneously improving the carbon black dispersion grade (from grade 5 to grade 2). This directly
results in a 15% increase in tire wear resistance and an 8% reduction in rolling resistance.
Plastics Processing: Introducing polyester dispersants into polypropylene (PP) allows for an increase in carbon black filling
content from 30% to 50% without significant thickening, while maintaining stable melt flow rate (MFR), making it suitable
for the production of highly conductive plastic films.
Coatings and Inks: In water-based coatings, polyester dispersants can control the viscosity of the carbon black dispersion
system within the range of 50-100 KU, preventing storage sedimentation. In UV inks, it can improve the dispersion stability
of carbon black, reducing the blackness (L value) of printed materials to below 25.
IV. Usage Guidelines: Precise Control is Key
Dosage Optimization: Determine the optimal addition amount using the "viscosity-dosage curve method." For example, in
rubber compounding, 2-5 parts dispersant should be added per 100 parts carbon black; excessive amounts will lead to
"over-dispersion," which will actually reduce performance.
Process Adaptation: High-shear equipment (such as three-roll mills) can reduce dispersant usage by 10%-15%; Temperature
control at 60-80℃ accelerates adsorption equilibrium and avoids high-temperature decomposition; Adjusting the pH to
6-8 enhances the interaction between polyester molecules and carbon black.
Compatibility Testing: The compatibility between the dispersant and the matrix resin needs to be verified. For example,
in polyester (PET) systems, polyester dispersants with a molecular weight below 5000 should be selected to avoid
phase separation.
V. Future Trends: Green and Intelligent Development
With increasing environmental protection requirements, water-based polyester dispersants are gradually replacing
solvent-based products, reducing their VOC content to below 50g/L. Simultaneously, intelligent responsive
dispersants (such as pH/temperature dual-sensitive types) are emerging, enabling dynamic control of dispersion
effects. For example, in 3D printing resins, the dispersant can automatically adjust the carbon black dispersion state
during printing, improving product precision.
From tires to electronic devices, from architectural coatings to packaging materials, polyester carbon black viscosity
reducers and dispersants are driving the evolution of industrial materials towards high performance and green
manufacturing through "microscopic regulation." Their core value lies in using the wisdom of chemistry to allow
black particles to "breathe freely" within the matrix, ultimately resulting in a superior product experience.
