Oil AbsorptionValue (OAV) is a key physical property parameter that is widely used to evaluate the performance of fillers, pigments and additives. It not only affects the dispersion and processing performance of powder materials, but also plays an important role in the quality and application effect of terminal products. For magnesium oxide fillers, the oil absorption value is an index that indirectly reflects the specific surface area and porosity of the powder. The specific surface area is determined by the particle size of the magnesium oxide, and the porosity is related to the agglomeration state between the powders. Different oil absorption values will directly affect the performance of magnesium oxide fillers in various applications, such as thermally conductive materials, coatings, plastics and other industries.
What is oil absorption value?
The oil absorption value indicates the amount of oil that the powder can absorb per unit mass, usually expressed in g/100g. For example, the oil absorption value of a certain filler is 30g/100g, which means that 100g of the filler can absorb 30g of oil.
High oil absorption value (>50g/100g): The particles are fine, the specific surface area is large, the surface is porous or irregular, and the adsorption capacity is strong.
Low oil absorption value (<30g/100g): The particles are large, the surface is smooth or tightly packed, and the adsorption ability is weak.
At present, the determination of oil absorption value of powder materials in China is mostly concentrated in pigments and paints. The oil absorption value is generally determined by the linseed oil absorption method: add oil (such as linseed oil, DOP, etc.) drop by drop to a powder sample of a certain mass; stir continuously until a uniform paste is formed and no more oil can be absorbed; calculate the amount of oil absorbed by the powder unit mass, that is, its oil absorption value.
Effect of oil absorption value on the application of magnesium oxide fillers
Generally speaking, magnesium oxide fillers with higher oil absorption values usually have a larger specific surface area and strong adsorption capacity, but at the same time may increase the viscosity of the system and affect processing fluidity. Magnesium oxide fillers with lower oil absorption value are easier to disperse, which can increase the filling amount and reduce the viscosity of the system, thereby optimizing production efficiency. Therefore, the size of the oil absorption value directly determines the application characteristics of magnesium oxide fillers in different industries. Some application occasions are as follows:
① Thermal conductive materials (thermal conductive glue, thermal grease, thermal gasket, etc.)
High oil absorption value: High oil absorption value usually means that the specific surface area of the magnesium oxide filler is larger or has more pores, which will increase the contact area with the oily medium and thus improve the oil absorption capacity. However, high oil absorption values may lead to an increase in the consumption of resin/silicon oil, thereby increasing costs. In addition, high oil absorption values may increase colloid viscosity and affect the construction performance of the material.
Low oil absorption value: Low oil absorption value can reduce the consumption of resin/silicon oil by fillers, allowing higher filling amounts, making the heat transfer path more dense, and directly improving thermal conductivity. At the same time, low oil absorption value can also reduce the viscosity of the system, improve fluidity, make the material easier to be coated, potted or press-synthesised, and improve processing performance.
②Coating and ink industry
High oil absorption value: Magnesium oxide fillers with high oil absorption value will adsorb more resins or solvents, resulting in an increase in system viscosity. This will directly affect the leveling and construction performance of the coating. In addition, during the coating process, the resin not only needs to completely coat the surface of the powder, but also fill the gaps between the particles. When the powder oil absorption value is high, more resin is needed to complete these functions.
Low oil absorption value: Low oil absorption value filler adsorbs less resin and solvent, which can effectively reduce system viscosity and improve the fluidity and leveling of the coating. At the same time, higher filler filling volume is allowed to improve the mechanical properties of the paint (such as hardness, wear resistance).
How to reduce oil absorption?
It can be seen that magnesium oxide fillers are expected to have a lower oil absorption value in many applications. This optimization is usually achieved through surface treatment during production.
Surface modification can improve the dispersion of magnesium oxide powder, reduce the gaps formed by agglomeration between powder particles, and thus reduce oil absorption value. In addition, surface treatment agents such as coupling agents can wet and cover part of the surface of particles, reduce the adsorption of the powder on the resin or solvent, and reduce the overall viscosity of the system. Therefore, magnesium oxide fillers that have been properly surface-treated not only have better filling performance in applications, but also improve processing fluidity and dispersion stability.
A thermal filler magnesium oxide suitable for potting glue was developed using a specific coupling agent modification method. The coupling agent can significantly reduce the oil absorption value of the filler magnesium oxide. Compared with the unsurface-treated filler magnesium oxide, the oil absorption value of the filler magnesium oxide after the coupling agent surface treatment can be reduced by 10%-30%. The filler magnesium oxide powder after surface treatment has good dispersion, no obvious agglomeration of particles, and the edges and angles of the powder can be reduced, which can improve the performance of the composite material, enhance the interfacial interaction of the system, and improve the mechanical properties of the composite material.
Messi Biology stated that oil absorption value, as an important indicator of powder materials, can reflect its specific surface area, porosity and other characteristics, and has important application value in many industries. For enterprises, rational choice of fillers with suitable oil absorption values can optimize product performance, improve production efficiency, and reduce overall costs.