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Yuan Lei tells you about the common surface modifier and process of ultrafine barium sulfate.

Release time:

2024-01-29 09:35

 

Yuan Lei tells you about the common surface modifier and process of ultrafine barium sulfate.

 

As a high-quality barium sulfate product, ultrafine barium sulfate has the advantages of non-toxic, tasteless, and small particle size, which is widely used in various fields. However, there are two key problems with ultrafine barium sulfate products:

 

  • On the one hand, the ultrafine barium sulfate particles have small particle size, large specific surface area, high surface energy, and are prone to agglomeration between particles, so that the particle size becomes larger and the morphology is not regular.

  • On the other hand, the surface polarity of ultrafine barium sulfate is strong, the particles are hydrophilic and oleophobic, and the organic compatibility is poor, and the affinity with organic polymers is poor, which affects the performance of composite materials and limits its application.

 

In order to inhibit the agglomeration of particles, stabilize the dispersion system, improve the organic compatibility of barium sulfate, and improve the performance of composite materials, it is necessary to modify the surface of ultrafine barium sulfate to make its surface lipophilic and hydrophobic, and broaden its application.

 

1, barium sulfate commonly used surface modifiers

 

The surface polarity of ultrafine barium sulfate particles is strong, and it is easy to dissociate the water adsorbed on the surface of barium sulfate particles to generate hydroxyl groups, which provides the possibility for the surface modification of barium sulfate. The surface modifier should first have a hydrophilic polar group and a lipophilic non-polar group, which can be adsorbed on the surface of barium sulfate particles to form a firm adsorption layer; secondly, it can also change the electrostatic force on the surface of the particles or produce steric hindrance effect to stabilize the dispersion of ultrafine barium sulfate particles and inhibit their aggregation; at the same time, it should also have acid resistance, alkali resistance and weather resistance.

 

(1) Coupling agent

 

The process of surface coating of ultrafine barium sulfate with coupling agent is simple, but it is widely used. The surface modified ultrafine barium sulfate with coupling agent can improve the mechanical properties of composite coatings, such as shock resistance, impact resistance, strength and stiffness.

 

Various interfacial coupling agents such as titanium (aluminum) acid esters, stearic acids, and silanes may be preferred according to different base materials.

 

(2) Superdispersant

 

Hyperdispersant is a new type of water-soluble polymer dispersant, which can combine with the surface hydroxyl of barium sulfate particles to form an adsorption layer or physically wrap the surface of barium sulfate particles through hydrogen bonding, reduce the surface tension and surface energy of particles, thereby changing the electrostatic force on the surface of particles or producing steric hindrance effect to stabilize the dispersion system, inhibit the interaction between particles and improve the agglomeration between particles. Commonly used hyperdispersant: polyester dispersant, low molecular soap dispersant, water-soluble polymer dispersant, etc.

 

(3) Silicone

 

Polymeric organic silicon is a kind of polymer with silicon oxygen bond chain (Si-O-Si) as the skeleton and organic functional groups connected to silicon atoms. The inorganic skeleton of polymer organic silicon molecules has high structural stability, and the organic functional groups outside the inorganic skeleton determine the surface properties of polymer organic silicon molecules.

 

The ultrafine barium sulfate modified by silicone can be widely used in the coating industry. It can react with some components in the coating material to improve the fluidity of the composite material and solve the problems of agglomeration and dust. Common silicone modifiers: silane coupling agent, silicon surfactant, liquid silicone rubber, silicone resin, etc.

 

2. Barium sulfate surface modification process

 

(1) Dry modification

 

Dry modification is through the grinding process of modifier and barium sulfate particles dispersed friction to achieve the purpose of modification. A certain proportion of the modifier and the product will be taken, and the modifier will be wrapped on the surface of the barium sulfate particles during the stirring or grinding process to achieve the modification effect. This method is simple, easy to operate, and low in cost, but the modifier coverage is uneven, the binding force is weak, and the modification effect is not good. In the actual industrial production, it can be used as an auxiliary modification method.

 

(2) In-situ modification

 

In-situ modification refers to the two processes of particle synthesis and modification, which are completed simultaneously in the reaction, that is, the in-situ modification of barium sulfate, which not only completes the synthesis of barium sulfate, but also includes the modification process of barium sulfate. Because of its in situ modification characteristics, the modifier is not only combined with barium sulfate particles, but also with the free Ba in the solution.2 The modifier is not only wrapped on the surface of barium sulfate particles, but also exists between particles, which inhibits the agglomeration and growth of particles, and improves the dispersibility and hydrophobicity of ultrafine particles.
 

Barium sulfate, particle, surface, modification, modifier, dispersant, silicone, coupling agent, improve

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