Hebei Messi Biology Co., Ltd. stated that magnesium hydroxide, as an inorganic filler, has been widely used in many industries such as rubber, plastics, coatings, inks, medicine, and food. Among the indicators related to magnesium hydroxide product quality, oil absorption value has a very important impact on product application.
The oil absorption value is also called the resin adsorption capacity, which is an index indicating the amount of resin absorbed by the filler. In addition to determining the chemical composition and purity of the powder material, the oil absorption value is also related to its surface chemical properties. Different oil absorption values will lead to different powder particle size, specific surface area, and adsorption performance. The oil absorption value can change the compatibility of magnesium hydroxide and polymers, which has a certain impact on the quality, performance and use of the material.
Simply put, if the oil absorption value is large, a large amount of resin will be “wasted”, and the effect of filling magnesium hydroxide to reduce production costs will be weakened. In addition, if the formula contains liquid additives, magnesium hydroxide with a small oil absorption value should be used. Inorganic powders with a large oil absorption value will also require more coupling agents.
Ways to reduce the oil absorption value of magnesium hydroxide
1. Control particle morphology
The oil absorption value of magnesium hydroxide has a great relationship with the production process. When there are no special requirements for particle morphology, crystal form control agents can be used to control the crystal form and specific surface area, thereby reducing its oil absorption value.
2. Control fineness and particle size distribution
The application of magnesium hydroxide products in general fields does not have high requirements on fineness and particle size distribution. Compound products with large particle size distribution differences can be appropriately selected. In this way, small particles will enter the gaps of large particles, the stacking density will increase, and the product will absorb oil as a whole. The amount will decrease.
For high-quality product applications, magnesium hydroxide with high fineness and narrow particle size distribution can help improve product performance. At this time, surface modification is needed to solve the problem of oil absorption value.
3. Surface modification
Surface modification is one of the important means to effectively reduce the oil absorption value of powder. After the surface modification of magnesium hydroxide, the aggregated particles are reduced, the dispersion is improved, and the gaps between particles are reduced. In addition, the modified molecules weaken the polarity of the surface of magnesium hydroxide, reduce the friction between particles, improve the lubricity, and cause powder accumulation. Tighter, the packing density increases, and the oil absorption value naturally decreases.
Effect of magnesium hydroxide production process variables on oil absorption value
1. Influence of secondary carbonization time
2. Influence of the dosage of crystal form control agent
The carbonization reaction includes the generation of magnesium hydroxide crystal nuclei and the growth of crystals. In the early stage of the carbonization reaction, as the amount of crystal form control agent increases, the nucleation rate is greater than the growth rate, and the particle size of the prepared nano-magnesium hydroxide is smaller than that of The larger the surface area, the higher the yield value, but the oil absorption value also increases accordingly.
3. Influence of surfactant dosage
As the amount of surface treatment agent increases, the oil absorption value of magnesium hydroxide continues to decrease. However, when the dosage of treatment agent increases to a certain level, the oil absorption value almost no longer decreases, and the excess treatment agent in the system causes the yield value to decrease.
Conclusion
From a microscopic perspective, the oil absorption value is related to the gaps between powder particles, the surface properties of the particles and the specific surface area of the powder. When the nanoparticles are not modified, they are in an aggregated state, and the gaps between the particles are large. At this time, the oil absorption value of the powder will increase.
The hydrophilic and lipophilic properties of the particle surface have a great influence on the oil absorption value. After the powder is modified, the lipophilicity increases, the surface energy decreases, the oil absorption value decreases, and the dispersion is better. From another perspective, obtaining magnesium hydroxide with a smaller oil absorption value can greatly improve the dispersion and lipophilicity of the particles.
In addition, in the process of producing magnesium hydroxide, of course, particle size and dispersion performance are first considered. On this basis, consider how to reduce its oil absorption value. Only in this way will it have practical significance.