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6 types of powder surface modification methods

Source:nclirik Posted:2021-09-14
The surface modification of inorganic powder is the corresponding surface modification according to the performance of the powder required by the industry to meet the development needs of modern new materials, processes and technologies, and to improve the performance characteristics of the original products. Increasing the corresponding production capacity and production efficiency has also received more and more attention in the powder processing industry. At present, there are six main types of inorganic powder surface modification methods.

Method 1: Physical coating

Principle of the method: The surface of the powder is treated with polymer or resin, generally including cold method and thermal method.

Powder modifier: polymer, phenolic resin, furan resin, etc.

Influencing factors: particle shape, specific surface area, porosity, type and amount of coating agent, coating treatment process, etc.

Applicable powder: foundry sand, quartz sand, etc.

Method 2: Chemical coating

Principle of the method: Use the adsorption or chemical reaction of the functional groups in the organic molecules on the surface of the inorganic powder to coat the surface of the particles, generally including dry and wet methods. In addition to surface functional group modification, the method also includes surface coating modification using radical reaction, chelation reaction, sol adsorption and the like.

Powder modifier: various coupling agents such as silane, titanate, aluminate, zirconium aluminate, organic chromium, higher fatty acid and its salt, organic ammonium salt and various other types of surfactants, phosphoric acid Esters, unsaturated organic acids, water-soluble organic polymers, etc.

Influencing factors: the surface properties of the powder, the type, dosage and use method of the powder modifier, modification process, modification equipment, etc.

Applicable powder: quartz sand, silica powder, calcium carbonate, kaolin, talc, bentonite, barite, wollastonite, mica, diatomaceous earth, brucite, barium sulfate, dolomite, titanium dioxide, aluminum hydroxide, Various powders such as magnesium hydroxide and alumina.

Method 3: Precipitation reaction

Method principle: Through the precipitation reaction of inorganic compounds on the surface of the particles, one or more layers of "coating" are formed on the surface of the particles to improve the surface properties of the powder, such as gloss, tinting power, hiding power, color retention, and weather resistance , Electrical, magnetic, thermal and bulk properties.

Powder modifier: various inorganic compounds such as metal oxides, hydroxides and their salts.

Influencing factors: the nature of the raw materials (particle size and shape, surface functional groups), the variety of inorganic surface modifiers, the pH value, concentration of the slurry, reaction temperature and reaction time, washing, dehydration, drying or roasting and other subsequent treatment processes.

Applicable powder: titanium dioxide, pearl mica, alumina and other inorganic pigments.

Method 4: Mechanochemistry

Principle of the method: Use ultrafine pulverization and other strong mechanical effects to purposefully activate the surface of the powder, and to a certain extent change the crystal structure, solubility (amorphization of the surface), chemical adsorption and reaction activity (increase Surface active sites or active groups) etc.

Modification equipment and agents: ball mills, jet mills, high-speed mechanical impact mills, etc., grinding aids, dispersants, modifiers, etc.

Influencing factors: type of crushing equipment, mode of mechanical action, crushing environment (dry, wet, atmosphere, etc.), type and amount of grinding aid or dispersant, time of action of mechanical force, crystal structure and chemical composition of powder materials , Particle size and particle size distribution, etc.

Applicable powders: kaolin, talc, mica, wollastonite, titanium dioxide and other powders.

Method 5: Intercalation modification

Method principle: using layered structure of mineral powder particles with weak bonding force (such as molecular bonds or van der Waals forces) or the existence of exchangeable cations, through ion exchange reaction or chemical reaction to change the interface properties of the powder and Other properties of modification methods.

Powder modifiers: organic intercalating agents such as quaternary ammonium salts, polymers, organic monomers, and amino acids, and inorganic intercalating agents such as carboxyl titanium, metal oxides, and inorganic salts.

Influencing factors: the nature of the raw material, the reaction environment, the type and amount of intercalation agent, etc.

Applicable powder: kaolin, graphite, mica, hydrotalcite, vermiculite, rectorite, metal oxide and layered silicate, etc.

Method 6: High-energy surface modification

Method principle: It refers to the method of surface modification of powder by using ultraviolet, infrared, corona discharge, plasma irradiation and electron beam radiation. E.g:

Treating calcium carbonate with ArC3H6 low temperature plasma can improve the adhesion between calcium carbonate and PP.

Using infrared radiation to graft polystyrene and other polymers on the surface of carbon black can significantly improve the dispersibility of carbon black in the medium.

Microwave radiation and air plasma treatment have an activating effect on the surface of porous silica, which can increase the surface hydroxyl content and enhance the hydration effect.

With the development of science and technology, the surface technology and operation technology of inorganic powder will also be improved so that industrial production can be realized, and there will be a qualitative improvement in terminal products.



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