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Home / News / Industry News / Conductive Carbon Black Paste Has High Viscosity — The Problem May Be in the Dispersion Stage
Industry News
Graphene, carbon nanotubes, and conductive carbon black are increasingly used in conductive coatings, functional inks, and waterborne pastes. But these powders readily form agglomerates after entering liquid systems. If the wetting process is insufficient, subsequent dispersion is easily affected, further causing paste viscosity changes, non-ideal flow state, and re-coarsening after storage — particularly when increasing the carbon nanomaterial addition level, as inter-particle interaction strengthens further.
Powder Difficult to Wet Fully by Liquid
Graphene and carbon nanotubes have large specific surface areas and readily agglomerate in waterborne systems. If the powder surface is not fully wetted, the effect of mechanical dispersion is also easily limited.
Paste Viscosity Rises with Higher Solid Content
As carbon nanomaterial addition increases, inter-particle contact and interaction also increases — the paste readily develops thickening, which is a problem frequently faced when raising solid content in conductive pastes.
State Inconsistency Between Fresh and Stored Paste
Some pastes show a good state right after dispersion, but after standing for a period develop viscosity change, re-coarsening, or settling — indicating that although the powder was temporarily broken up, the subsequent stable state needs further adjustment.
Rheological State Affects Application
Conductive pastes need their flow state adjusted according to coating, spraying, or printing process requirements. Too high viscosity increases application difficulty; excessive flow may affect paste spreading on the substrate.
Why Increasing Shear Force Does Not Always Solve the Problem
For difficult-to-disperse powders such as graphene and carbon nanotubes, some formulations increase RPM or extend dispersion time to strengthen mechanical action. This approach can help agglomerates break down, but after the powder is separated, maintaining a relatively stable dispersed state is still needed. If particles readily re-agglomerate after coming back into contact, simply increasing mechanical dispersion time cannot fundamentally change the system state. Therefore, mechanical dispersion, powder wetting, and dispersion stabilisation need to be considered together.
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-area 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. Additionally, DH-6552W has good compatibility with acrylic resin, epoxy resin, and alkyd resin systems. In actual application: first allow the dispersant to fully mix with the water phase, then gradually add the carbon nanomaterial powder; observe viscosity changes during dispersion and adjust addition speed accordingly; also observe viscosity, fineness, settling, and re-coarsening after standing — not only the freshly prepared paste.
The difficulty in dispersing graphene, carbon nanotubes, and conductive carbon black is related to their powder characteristics and strong agglomeration tendency. Therefore, formulation adjustment for conductive paste cannot only rely on increasing shear force — it needs to simultaneously consider powder wetting, dispersion state, and paste rheology. 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
Does improving the dispersion of graphene affect its electrical conductivity in the cured film?
Yes — and the relationship is nuanced. Better individual graphene flake dispersion increases the available conductive surface area and reduces the percolation threshold (the minimum loading needed to achieve electrical conductivity). However, graphene's electrical conductivity depends on inter-flake contact forming a continuous conductive network — if dispersant coverage prevents direct flake-to-flake contact too effectively, conductivity may be lower than expected despite good dispersion. The optimal dispersion level for electrical performance is typically one that produces uniform distribution without excessive separation, balancing dispersion stability with the inter-particle contact needed for conductivity.
What is the difference in dispersion requirements between carbon nanotubes and graphene in waterborne systems?
Carbon nanotubes present a different dispersion challenge from graphene: their fibrous, high-aspect-ratio morphology creates strong entanglement between tubes, making complete de-bundling very difficult — and excessive high-shear processing can shorten the tubes, reducing their electrical conductivity benefit. Graphene flakes are more susceptible to stacking (re-aggregation in the face-to-face orientation), which requires steric stabilisation to prevent. Dispersants for carbon nanotubes typically need strong adsorption on the tube wall to prevent re-bundling; those for graphene need effective steric stabilisation between flake faces. DH-6552W is characterised for both types — the optimal dosage and process for each should be determined by evaluation.
