Issues to note when using carbon black dispersants

Issues to note when using carbon black dispersants

1. Matching of dispersants and substrates

Polarity matching

The polarity of the dispersant needs to match the substrate, otherwise it will cause the dispersant to migrate or fail. For example:

Non-polar substrates (such as polyethylene, polypropylene) need to select low-polarity dispersants (such as fatty acids).

Polar substrates (such as water-based coatings, nylon) need to select hydrophilic dispersants (such as polyacrylates).

Solvent compatibility

In solvent-based systems, dispersants need to be miscible with solvents. For example:

Aromatic hydrocarbon solvents (such as toluene) need to select aromatic dispersants.

Alcohol ether solvents (such as ethylene glycol butyl ether) need to select alcohol ether type dispersants.

2. Dispersant dosage control

Critical micelle concentration (CMC)

The amount of dispersant should be close to but not exceed the CMC value. Excessive use will lead to:

Increased viscosity: dispersant molecules associate to form micelles, increasing the viscosity of the system.

Risk of precipitation: Free dispersant may migrate to the surface, causing frosting or foaming.

Dynamic adjustment

Adjust the dosage according to carbon black concentration, matrix type and processing conditions. For example:

High concentration of carbon black (>30%) requires increasing the amount of dispersant.

High temperature processing (such as rubber mixing) requires the selection of dispersants with good thermal stability.

3. Process parameter optimization

Shear force and time

High shear force (such as three-roll grinding) can promote carbon black depolymerization, but the time needs to be controlled to prevent excessive crushing.

Low shear force (such as stirring) requires extended dispersion time and combined with ultrasonic assisted dispersion.

Temperature management

Heating accelerates adsorption: The dispersant adsorbs faster at high temperatures, but matrix degradation needs to be avoided.

Cooling stabilizes dispersion: Cooling after dispersion can prevent carbon black from reaggregating.

4. Selection of dispersant type

Anchoring group

The anchoring group of the dispersant needs to match the surface functional group of carbon black. For example:

Carboxyl-containing carbon black (such as furnace carbon black) is suitable for reacting with amine-containing dispersants.

Hydroxy-containing carbon black (such as channel carbon black) is suitable for forming hydrogen bonds with ester-containing dispersants.

Steric hindrance and electrostatic repulsion

Polymer dispersants (such as polyurethanes) stabilize dispersion through steric hindrance.

Charged dispersants (such as phosphates) prevent agglomeration through electrostatic repulsion.

5. Common problems and solutions

Uneven dispersion

Reason: Insufficient amount of dispersant or mismatch of type.

Solution: Increase the amount of dispersant or replace it with a type with stronger anchoring ability.

System viscosity is too high

Reason: Excessive amount of dispersant or insufficient shear force.

Solution: Reduce the amount of dispersant or increase the shear force.

Dispersion effect attenuation

Reason: Poor thermal stability of dispersant or insufficient compatibility with the matrix.

Solution: Select a high temperature resistant dispersant or adjust the matrix formula.

Precipitation and foaming

Reason: Dispersant is incompatible with the matrix or the amount is too much.

Solution: Reduce the amount of dispersant or add a defoamer.

6. Safety and environmental protection

Toxicity control

Avoid using dispersants containing heavy metals (such as lead, cadmium) or carcinogens (such as aromatic amines).

Choose products that comply with REACH, RoHS and other regulations.

Environmental impact

Give priority to low VOC or solvent-free dispersants.

Ensure that the dispersant is biodegradable to reduce the burden of wastewater treatment.

7. Practical suggestions

Small-scale test verification

Before large-scale production, determine the best dispersant type, dosage and process parameters through experiments.

Long-term stability test

Evaluate the performance changes of the dispersion system during storage, transportation and use.

Synergistic effect utilization

Combining dispersants with other additives (such as antioxidants and plasticizers) to improve comprehensive performance.

Through the above measures, the role of carbon black dispersants can be maximized to improve product quality and production efficiency.