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Home / News / Industry News / Conductive Carbon Black Poorly Dispersed — Why Does the Paste Keep Getting More Viscous?
Industry News
Conductive carbon black, graphene, and carbon nanotubes are increasingly used in coatings, inks, and functional pastes. Compared to ordinary pigments, these powders typically have larger specific surface areas and special particle structures. During paste preparation, whether the powder can be fully wetted by the liquid, and whether particles can maintain a good dispersed state, directly affects paste viscosity, flow state, and behaviour after storage — especially high-surface carbon black and carbon nanotubes, which easily form strong aggregate structures between particles.
Common Problems in Carbon Nanomaterial Paste Preparation
Powder Difficult to Fully Wet by Liquid
Conductive carbon black, graphene, and similar powders need to first complete wetting before the liquid can gradually enter the aggregate structure. If wetting is insufficient, aggregation and rough paste state easily result during subsequent dispersion.
Increased Dispersion Time Causes Higher Paste Viscosity
As larger aggregates are progressively opened under high-shear conditions, if the dispersant is not well-matched to the powder surface, particles may re-form network structures after coming back into contact — and system viscosity may still rise. Dispersion time is not always better when longer.
Concentrated Paste Solid Content Difficult to Increase
As powder proportion rises, inter-particle interaction strengthens, paste may gradually thicken, and even affect normal application and subsequent paint mixing. High-solid paste preparation requires attention not only to powder addition but also to whether the dispersion system can accommodate higher powder concentration.
Paste State Changes After Standing
Carbon nanomaterial dispersed paste is not necessarily stable. If particles still have strong mutual interaction, viscosity change, thixotropy change, or re-formation of aggregate structure may develop after standing. Evaluation of the dispersion effect must also observe paste state after storage, not only the freshly prepared state.
DH-6552W: Dispersant for Waterborne Carbon Nanomaterial Systems
DH-6552W is a waterborne system dispersant that can be used for graphene, carbon nanotubes, conductive carbon black, and high-surface carbon black powders. For waterborne carbon nanomaterial pastes, the powder first needs to be well wetted before it can be further dispersed through mechanical action. DH-6552W can participate in this process, making powder dispersion in waterborne media easier to carry out.
In terms of paste state, the product can also help the system form a certain thixotropic character — which is a useful reference for formulations that need to balance static stability with application flowability. The product has good compatibility with acrylic resin, epoxy resin, and alkyd resin systems. Reference addition: 50%–80% of powder weight. Actual application can be adjusted based on carbon nanomaterial type, target solid content, resin system, and paste viscosity requirements.
Recommended Development Sequence
1
Confirm Powder Type
Select conductive carbon black, high-surface carbon black, graphene, or carbon nanotubes separately — observe matching of different powders with the dispersion system.
2
Set Addition Level Gradient
Set multiple addition ratios near the recommended range, comparing paste viscosity, appearance, and dispersion state.
3
Test Concentrated Paste
Progressively increase powder proportion, observing flow state and thixotropy changes at different solid contents.
4
Conduct Storage Observation
After completing dispersion, carry out standing, comparing viscosity, flow state, and paste appearance at different time points.
5
Combine Resin System Testing
Select acrylic, epoxy, alkyd, and other resin systems based on the final application, further observing compatibility and post-let-down state.
Graphene, carbon nanotubes, conductive carbon black, and high-surface carbon black are easily influenced by powder structure, wetting state, inter-particle interaction, and paste concentration during paste preparation. When paste viscosity is too high, dispersion time is long, or concentrated paste solid content cannot be further increased, in addition to adjusting equipment process, the bonding state between dispersant and powder is also worth analysing. DH-6552W can be used in waterborne carbon nanomaterial paste systems, improving powder wetting and dispersion state while balancing thixotropy and storage performance.
Frequently Asked Questions
Why can excessive dispersion time for graphene and carbon nanotubes actually reduce their functional performance?
Both graphene and carbon nanotubes have aspect ratio-dependent functional properties — longer, larger-dimension structures give better electrical conductivity and mechanical reinforcement per unit mass. Prolonged high-shear dispersion progressively shortens carbon nanotube length and reduces graphene platelet lateral dimension through mechanical scission. The resulting smaller structures have lower functional efficiency per unit mass, meaning more material is needed to achieve the same functional target. Finding the minimum dispersion energy input that achieves the target degree of de-agglomeration — rather than maximising dispersion intensity — preserves more of the aspect ratio that makes these materials valuable.
Is 50%–80% of powder weight a very large addition amount compared to conventional pigment dispersants — is this a printing error?
No — the large dosage is correct and reflects the extreme specific surface area of carbon nanomaterials. Conventional pigment dispersants are dosed at 1%–20% of pigment weight because typical inorganic pigments have specific surface areas of 5–30 m²/g. High-surface carbon blacks and carbon nanotubes have specific surface areas of 100–1,500 m²/g, meaning there is 10–100 times more surface area to cover per unit of powder mass. Far more dispersant is therefore needed per unit mass to achieve adequate surface coverage and steric stabilisation — the 50%–80% figure correctly reflects this physical requirement, not a misprint.
