A comprehensive and precise dispersant selection and implementation solution covering all water-based application scenarios
I. First Step: Determine 4 Core Judgment Prerequisites, Directly Deciding the Overall Direction of Dispersant Selection
1. The core judgment criterion for dispersant selection is the type of powder and pigment, which is the most critical selection factor in the entire process.
1) Covering a wide range of functional inorganic powder materials, including calcium carbonate, talc, titanium dioxide, zirconium oxide, silicon nitride, silicon powder, and alumina; Prioritizing polycarboxylate, ammonium acrylate, and phosphate dispersants as core suitable selection categories; their core function is to achieve anti-settling, reduce system viscosity, and possess excellent hard water resistance through electrostatic repulsion.
2) Covering two highly reactive metallic functional powder materials, aluminum powder and zinc powder; Acidic dispersants are strictly prohibited (they will cause gas generation and powder corrosion problems); neutral/weakly anionic, corrosion-inhibiting polycarboxylate dispersants without free acid should be selected.
3) For organic pigments and carbon black-based coloring powders with high specific surface area and poor wetting properties, modified polyacrylic acid and graft copolymer dispersants with strong anchoring group adsorption are preferred. Small molecule dispersants are prone to causing flocculation and coarsening problems in the system. HR-4031 and HR-4061EF are recommended.
2. Base solvent carrier media as the core component of the continuous phase of the dispersion system
1) For pure deionized water systems, anionic, ammonium polyacrylate, and maleic anhydride copolymer dispersants are the core selection categories;
2) For waterborne epoxy and waterborne PU curing systems, special dispersants that are acid and alkali resistant, do not interfere with the curing reaction, and have low free acid content must be selected;
3) For aqueous alcohol ether cosolvent systems (propylene glycol methyl ether, ethanol), neutral wetting and dispersing agents and modified polycarboxylic acid products are suitable.
3. System pH Value
In most water-based coating systems with a pH value between 7 and 10, ammonium polyacrylate is the most suitable dispersant category;
In acidic dispersion systems with a pH value below 6, modified nonionic and neutral high-molecular-weight dispersants are preferred as suitable options;
In strongly alkaline systems with a pH greater than 11, specialized polyphosphates for strong alkali stability and high-molecular-weight sodium salt dispersants are selected as appropriate options.
4. Downstream terminal application scenarios
- The compatibility of adhesives and water-based ink systems with resins is the primary priority, and they must not negatively impact coating adhesion; - For water-based coatings and dip coating systems, dispersants must balance dispersion and anti-settling properties, avoid interfering with leveling effects, and possess low-foaming characteristics;
The electronic ceramic slurry system requires dispersants to possess core compatibility characteristics such as low impurities, low sodium and potassium ions, no residual carbon, and complete decomposition at high temperatures;
- The requirements for digital inkjet scenarios necessitate that dispersants possess core compatibility characteristics such as low viscosity, no precipitation, electrolyte resistance, and nozzle non-clogging.
II. Analyzing the Core Advantages, Disadvantages, and Precision Applicable Scenarios of Three Major Mainstream Water-Based Dispersants
1. The commonly available anionic polycarboxylate dispersant category on the market, with ammonium and sodium salt acrylates as core components
The advantages of this type of dispersant include outstanding cost performance, excellent dispersion effect on inorganic powders, superior anti-settling properties, and compatibility with the vast majority of water-based system applications;
The limitation of this type of dispersant lies in its mediocre dispersing effect on carbon black and organic pigments, while some sodium salt-based products may enhance the overall conductivity of the system.
Suitable for titanium dioxide, silica powder, zirconia, calcium carbonate powder, as well as water-based dipping and industrial water-based primer applications.
2. The category of inorganic small-molecule dispersants represented by sodium hexametaphosphate and sodium trimetaphosphate as core components
The advantages of this type of dispersant are low cost and excellent viscosity reduction, while its shortcomings include poor water resistance, susceptibility to failure in the presence of electrolytes, and a tendency to revert to coarse particles during long-term storage.
Suitable for interior wall putty and ordinary filler paste scenarios; strictly prohibited for use in electronic pastes, weather-resistant coatings, and inkjet systems.
3. Product categories of polymer-based multifunctional wetting and dispersing agents prepared through grafting modification processes
By firmly adsorbing pigment particles through anchoring groups, it achieves dual stabilization via steric hindrance and electrostatic effects, featuring electrolyte resistance and long-term storage stability, suitable for dispersing scenarios involving carbon black, organic pigments, and nanomaterials.
The core drawback of this class of dispersants is the relatively high overall procurement cost of the products.
Suitable for high-end topcoats, inkjet inks, nano-ceramic slurries, and high-durability coatings in downstream application scenarios.
III、 The rigid and rigid rules for avoiding pitfalls that must be strictly followed in the selection process of dispersants
1. Cross linked water-based resin systems (epoxy, PU) need to avoid high acid value dispersants to prevent the adverse problems of gel advance and slow curing speed;
2. The inkjet system should eliminate silicon containing components and high surfactant dispersants to prevent defects such as nozzle corrosion, coating pinholes, and shrinkage.
3. Nano zirconia, silicon nitride, nano silicon powder and other nano powders are strictly prohibited to use small molecule phosphates. Long term storage will inevitably lead to agglomeration, and polymer polycarboxylic acid dispersants must be used;
IV、 Simple practical selection steps
1.determine the three core basic parameters of the powder to be dispersed, the supporting resin, and the pH value of the dispersion system;
2. During the pilot stage, the amount of dispersant added should be fixed (controlled at 0.3% to 2% of the total powder content, with inorganic powder in the lower range and carbon black in the higher range);
3. In the small-scale trial stage, it is necessary to lock in the amount of dispersant added (based on 0.3% to 2% of the total powder mass, with inorganic powder selected in the lower range and carbon black selected in the higher range).
