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    Home > Coatings News > Coating Technologies > [Science Popularization of the Coating Society] Five surface modification methods and characteristics of nano-barium sulfate

    [Science Popularization of the Coating Society] Five surface modification methods and characteristics of nano-barium sulfate

    • Last Update: 2021-04-23
    • Source: Internet
    • Author: User
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    As a new type of inorganic material, nano-barium sulfate is widely used in many fields because of its high specific surface area, high activity, and good dispersibility.

     However, on the one hand, nano-barium sulfate has hydrophilic and oleophobic properties, and there is a great difference in polarity with the polymer matrix, so it is easy to agglomerate in the polymer, and its dispersibility is poor, which reduces its mechanical properties; on the other hand, due to the nanometer Barium sulfate has high surface activity, and it is easy to agglomerate or agglomerate between adjacent particles, which affects its application in production.

    Therefore, in order to improve the dispersibility of barium sulfate in polymers and improve the comprehensive performance of nano-barium sulfate in composite materials, surface modification of nano-barium sulfate is needed to expand its application range.

    1.
    Coupling agent modification Coupling agent is a kind of substance with an amphoteric structure.
    It can connect the inorganic and organophilic groups, that is, the coupling agent acts as a molecular bridge to make the inorganic The interface with organic matter is enhanced.

    Typical coupling agents include silanes, aluminates, and titanates.

    Silanes are currently the most widely used coupling agents in larger dosages.
    They are very effective for inorganic nanoparticles with hydroxyl groups on the surface, but the general silane coupling agents have a weak surface bonding force with barium sulfate.

    The more effective is the multi-component coupling agent, which can silanize the surface of nano-barium sulfate, which is costly and complicated to use.

    The titanate coupling agent has a good modification effect on most inorganic particles.
    The reason is that titanate can form chemical bonds with free protons on the surface of nano-barium sulfate, thereby forming an organic film on the surface, resulting in surface properties changes happened.

    However, due to its relatively high price and the existence of ingredients harmful to human health, its application is becoming less and less.

    Aluminate coupling agent is a new type of coupling agent.
    The easily hydrolyzed alkoxy group in the molecule reacts with free protons on the surface of barium sulfate to produce a monomolecular film to form an irreversible Al-O bond.
    Thereby improving product performance, and its performance is better than other coupling agents.

    2.
    Surfactant modified surfactants have a long-chain alkyl group at one end of the molecule, which can be uniformly dispersed in the polymer matrix; the other end is a polar hydrophilic group, which can physically adsorb or chemically react with the surface of barium sulfate.
    Wrapped on the surface of barium sulfate to achieve the purpose of modification.

    Commonly used surfactants include higher fatty acids and their salts, alcohols, amines, and phosphate esters.

    Surfactants are low in cost, diverse in variety, and large in output.
    Different types of surfactants can be used to synthesize products with different properties.
    The modification technology is more mature, so its applications are increasing.

    Fatty acid (salt) is a commonly used and very inexpensive surface modifier for barium sulfate.
    The modified nano-barium sulfate has better dispersibility and affinity in the polymer.

    The modified nano barium sulfate is not easy to precipitate in water due to its surface tension, so the activation degree can be used to reflect the surface modification effect.

    3.
    Compound modifier Modified compound modifier is a compound formula composed of two or more single modifiers, such as sodium palmitate/sodium stearate, sodium stearate/zinc sulfate, Sodium stearate/sodium dodecyl sulfonate/allyl alcohol polyoxyethylene ether and other composite modifiers.

    Choosing a composite modifier when modifying nano barium sulfate can give full play to the advantages of each modifier, making the modification effect better than a single modification effect, and meeting the needs of specialization and functionalization.

    Zhang Beibei and others used sodium stearate to modify the surface of ultrafine barium sulfate.

    The study found that the temperature and mass fraction were reduced, energy consumption was saved, and the activation degree reached 99.
    90%.

    After modified with sodium palmitate/sodium stearate composite modifier, the heat resistance of the product is improved compared with the effect of a single modifier, the particle size distribution is narrowed, and the average particle size is from 0.
    89μm (unmodified) ) Reduce to 0.
    78μm.

    This is because the polar groups of the modifier react with the barium sulfate particles, and the non-polar groups are coated on the outside.
    After the composite modification, the long carbon chains are entangled with each other to form a network structure, which enhances its hydrophobicity.

    The use of this modification method will be one of the future development trends.

    4.
    Precipitation reaction modification The precipitation reaction modification method is a method in which a modifier is added to the reaction through a chemical precipitation reaction to form a coating film on the surface of barium sulfate.

    This modification method has low production cost, simple operation, easy control of precipitation conditions, and is one of the commonly used methods for modifying the surface of particles.

    The particle size and morphology of different modifiers and precipitation agents are also different.

    5.
    Inorganic coating modification Inorganic coating modification is to form a coating film on the surface of the particle through physical action or van der Waals force, without other reactions with the surface.

    Metal oxides such as titanium dioxide (TiO2), silicon dioxide (SiO2), and zinc oxide are usually used as modifiers.

    In recent years, there have been more and more researches on the modification of nano-particles, because barium sulfate surface coating can prevent nano-particles from oxidation, crystal growth, corrosion and agglomeration, and can improve the surface properties of nano-barium sulfate and improve its surface.
    Active point, expand its application range.

    This method improves the dispersibility of inorganic particles in different media, but it is difficult to control the uniformity and strength of the coating, which is a problem to be solved in actual operation.

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