Het verbeteren van de hydrofiliteit van carbon zwart powder particles is key to improving their dispersion stability in water and increasing compatibility with polar media. This is crucial in fields such as coatings, inks, and rubber composites.
Surface Chemical Wijziging
Oxidation Modification
- Gas-phase oxidation: Ozone, oxygen, or plasma treatment is used to introduce oxygen-containing functional groups (such as carboxyl and hydroxyl groups) onto the carbon zwart surface. For example, oxygen plasma treatment significantly increases the oxygen content on the surface, reduces the contact angle to below 40°, and improves dispersion stability.
- Liquid-phase oxidation: Oxidizing agents like nitric acid and hydrogen peroxide are used. Nitric acid oxidation (10% concentration at 70°C for 3 hours) effectively removes organic substances on the surface and enhances hydrophilicity.
- Anodic oxidation/Plasma oxidation: Accelerates oxidation reactions in an electric field, increasing efficiency by more than 30% compared to traditional methods. However, temperature control is necessary to prevent excessive oxidation and decomposition of oxygen-containing groups.
Entmodificatie
- Polyacrylic acid grafting: At pH=3, using 0.5% ammonium persulfate initiator for 2 hours, the dispersion stability of carbon black in water improves by 50%.
- Copolymers with sulfonic acid groups (such as sodium 2-acrylamido-2-methylpropanesulfonate): Introduces strong hydrophilic groups to enhance dispersion through electrostatic repulsion.
- Free-radical polymerization grafting: Under ultrasonic radiation, hydrophilic polymers (such as polyacrylic acid and sodium polystyrene sulfonate) are grafted onto the carbon black surface.
- Comb-like copolymer grafting: Uses sodium polyethenesulfonate (PSS) to adsorb onto the carbon black surface through π-π conjugation, followed by 12-hour ball milling. The resulting carbon black dispersion is stable and suitable for rubber wet blending.
Physical Coating and Dispersant Wijziging
Polymer Coating
- Microemulsion polymerization coating: For example, polyethylene glycol derivatives or anionic surfactants (such as AKN-2290) are used to coat the carbon black powder. The mass ratio of carbon black to surfactant is 1:0.05–1, and high-speed shearing forms a hydrophilic shell.
- Phase separation coating: Hydrophobic carbon black is coated with hydrophilic polymers (like polyvinyl alcohol) through interface self-assembly, forming a core-shell structure with >95% activation efficiency.
Dispersant Application
- Anionic/Non-ionic surfactants: Examples include sodium dodecyl sulfate and the O-series (O-10 to O-35). These reduce the surface tension of carbon black, improving wettability.
- Silane coupling agents: Examples like Si-69 (TESPT), typically used for wit roet, modify the carbon black powder by combining hydrophobic groups with the carbon black and exposing hydrophilic groups, though this process is more costly.
Process Optimization and Auxiliary Techniques
Mechanical-Chemisch Treatment
- Kogelmalen activation: Ball milling carbon black with sodium polystyrene sulfonate (PSS) for 12 hours. The mechanical force breaks down aggregates while PSS enhances hydrophilicity through π-π adsorption. This method is ideal for natural rubber composites.
- Ultrasonic irradiation: Reduces grafting reaction time by 50%, lowers energy consumption, and prevents group decomposition due to excessive heat.
Plasma Treatment
- Oxygen plasma treatment under vacuum conditions increases surface oxygen functional groups within 5 minutes, enhancing dispersion (D value) by 30%, with no pollutant generation.
Salt-Induced Assembly
- Adding trace cations (such as Li⁺ or Na⁺) enhances the interface affinity between carbon black and water through cation-π interactions. The contact angle hysteresis effect is significant, making it suitable for water-based systems.
Application Verification and Performance Optimization
- Rubber Composites: Hydrophilic carbon black, when used in latex mixing, improves tear strength by 40% and greatly enhances filler dispersion uniformity.
- Water-based Inks/Coatings: Carbon black grafted with polyacrylic acid improves deeltjesgrootte stability, reducing clogging during inkjet printing.
- Environmental Considerations: Closed granulation systems combined with exhaust gas recovery reduce dust emissions by over 90%.
Conclusie
The core of improving the hydrophilicity of carbon black powder lies in introducing polar functional groups and enhancing steric hindrance. For low-cost scenarios, oxidation modification (liquid-phase nitric acid oxidation) or surfactant coating is preferred. For high-performance requirements, ultrasonic-assisted grafting with polyacrylic acid or comb-like copolymers, along with ball milling, is ideal. For green processes, oxygen plasma treatment combined with Si-69 coupling agents provides both efficiency and environmental benefits.