Magnesium hydroxide is an important inorganic chemical material, but the surface polarity is very strong, easy to agglomerate, bringing great difficulties to the preparation and preservation; at the same time, the surface of particles with positive charge, also easy to electrostatic agglomeration due to the difficulty of uniform dispersion in polymer materials; in addition, as inorganic filler magnesium hydroxide, its surface hydrophilicity is good, and lipophilic polymer materials are extremely poor bonding ability, easy to cause interface defects, resulting in Therefore, reasonable surface modification is extremely important to improve the performance of magnesium hydroxide.
Surfactant treatment is under the action of van der Waals force, the use of surfactant molecules unique “amphiphilic structure”, that is, one end of the molecule for the non-polar hydrophobic group (long chain alkyl), the other end of the polar hydrophilic group (-COOH, -NH2, etc.), to the magnesium hydroxide surface modification method.
Since magnesium oxide has a high positive charge on the surface, it is suitable to use anionic surfactants and to adopt a wet process where some kind of solvent is used to disperse the magnesium hydroxide first, and then the modifier is added and mixed. Stearic acid, sodium stearate, sodium oleate, sodium dodecyl sulfonate and other surfactants are more commonly used.
Hebei Messi Biology Co., Ltd. has used sodium stearate and sodium dodecyl sulfate to modify industrial magnesium hydroxide, and the agglomeration of magnesium hydroxide particles was significantly reduced after modification, and the activation rate of magnesium hydroxide was 89.4% and 90.5% respectively, and the dispersibility was improved.
2, coupling agent treatment
Coupling agent refers to organic compounds with reaction functional groups and organic long chain amphoteric structure, can produce chemical bonding with the surface of magnesium hydroxide, covering the surface of magnesium hydroxide particles, thus making the surface of magnesium hydroxide particles organic, from hydrophilic to hydrophobic. Silane coupling agent, titanate coupling agent and aluminate coupling agent are more commonly used.
Most of the coupling agents have poor water resistance and can be dissolved and diluted in inert organic solvents, so the coupling agent treatment of magnesium hydroxide is mostly used in a dry process. That is, the coupling agent with the appropriate amount of inert solvent dilution, sprayed on the magnesium hydroxide powder, so as to ensure that the coupling agent in the magnesium hydroxide powder surface uniform dispersion. The amount of solvent needs to be strictly controlled, the amount of too little coating effect is poor, the amount is too much need to remove the excess solvent, the modification cost increases. So recently, researchers do not use solvent dilution, but directly mix the coupling agent with magnesium hydroxide powder for coating.
Microencapsulation technology is a polymer continuous film as a wall material will be completely coated with magnesium hydroxide, forming tiny particles, that is, microencapsulated flame retardant, thus playing a role in improving thermal stability, improve compatibility with polymer matrix. The advantage of microcapsule coating technology is that when microcapsules are formed, the flame retardant is wrapped to retain its own properties and isolated from the outside world, and under appropriate conditions, the wall material is destroyed to release the flame retardant to play a role. The disadvantage is that the coating is difficult and can form an incomplete coating, which requires strict control of the experimental conditions to form a complete coating. Commonly used cladding wall materials are phenolic resin, mylar resin, urea-formaldehyde resin, etc.
4、Polymerization grafting cladding
Polymerization graft coating is the use of polymeric active monomer in the initiator under the action of polymerization reaction and thus graft coating on the surface of magnesium hydroxide a method. Polymer grafting makes the surface of magnesium hydroxide organic, reducing the agglomeration between the particles, while grafting on the polymer and the matrix material has a better physical compatibility, filling to the polymer material can obtain better dispersion and processing properties. In order to enhance the grafting effect, it is sometimes necessary to pretreat the surface of inorganic particles before initiating grafting polymerization.
5, modifier compounding use
Messi Biology use compound modifier to modify magnesium hydroxide, is expected to achieve a better modification effect. Modifier compounding use in practice has shown a good flame retardant effect, different types of modifier compounding use, can give full play to the advantages of each type of modifier itself, to form a complementary, with good prospects for development.
Messi Biology used silane coupling agent and titanate to modify magnesium hydroxide, to obtain a good viscosity, high dispersion of magnesium hydroxide flame retardant; by comparing with its single component on the surface modification of magnesium hydroxide, the modified activity index, specific surface area, smoke suppression effect are higher than the single component modified degree, the existence of synergistic effect of the compound modifier itself to enhance the modification effect of magnesium hydroxide. The modification effect of magnesium hydroxide was enhanced by the synergistic effect of the compound modifier itself.