Wetting and dispersion are important processes in the preparation of coatings. Due to the wide variety of coatings, the related dispersing agents used are diverse. The selection of wetting and dispersing agents is simply a choice of two aspects: the type and amount of dispersants. Among them, the former is the difficulty in the selection of dispersants. The selection of dispersant varieties must meet two basic requirements:
The dispersant is compatible with the system to which it is applied and the dispersant has the ability to disperse the pigment varieties dispersed. The variety of dispersants should be able to meet specific performance requirements. What factors should be considered when selecting wetting and dispersing agents? We should pay attention to the following principles:
- Coating system
Coatings are divided into several major systems such as water-based, solvent-based, and powder according to different media. In general, the wetting and dispersing agents used are not universal.
- Pigments
The pigments needed in coatings are also divided into many types, such as organic and inorganic, as well as alkaline and acidic. Different pigments also have different characteristics, and each pigment requires different wetting and dispersing agents. Inorganic pigments such as calcium carbonate, talcum powder, titanium dioxide, iron red, iron yellow, etc. generally use anionic types such as carboxylates, phosphates, sulfonates, etc. For organic pigments, aromatic groups are very effective. Dispersants containing aromatic groups (such as phenyl and naphthyl) are particularly helpful for the long-term stability of the dispersion.
- Base material (i.e. resin)
Different resin systems have different wettability to pigments, so there are some restrictions on the selection of wetting dispersants.
- System compatibility
In a coating system, the additives used are generally not only wetting dispersants, but may also include leveling agents, defoamers, etc., so compatibility is important. Some wetting dispersants have strong emulsifying properties, which may cause the defoamer to emulsify and lose its defoaming ability. Paying attention to compatibility is conducive to formula balance, so that the comprehensive performance of the product can be taken into account.
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