The oil absorption value of calcium carbonate is very important!
In the process of using fillers, the oil absorption value is often used to predict the required amount of resin for the filler. In other words, the oil absorption value affects the selection of fillers.
For example, when discussing the heavy calcium carbonate (HCC) powder produced by different grinding equipment, some people may mention that the vertical mill produces HCC powder with high fine powder content, wide particle size distribution, and low oil absorption value, making it suitable for plastic filling; while the ring roller mill produces HCC powder with low fine powder content, good control of large particles, and narrow particle size distribution, making it suitable for coatings.
This involves the secrets of oil absorption value and filler selection.
What is oil absorption value?
The oil absorption value, also known as resin adsorption capacity, represents an index of the resin absorption capacity of a filler. The magnitude of the oil absorption value not only determines the chemical composition and purity of the powder material, but also relates to its surface chemical properties. Different oil absorption values correspond to varying powder particle sizes, specific surface areas, and adsorption properties. The oil absorption value can alter the compatibility of calcium carbonate with polymers, exerting a certain influence on material quality, performance, and application.
The value of oil absorption value
Cost control
The oil absorption value reflects the absorption capacity of calcium carbonate for liquids such as resins and plasticizers. A lower oil absorption value indicates that, under the same formulation, the amount of resin or plasticizer required is less, thereby directly reducing production costs. This effect is particularly significant in high-filling fields such as plastics and rubber.
Optimization of processing performance
The oil absorption value affects the rheological properties of materials. Calcium carbonate with an excessively high oil absorption value can significantly increase the viscosity of the resin, making mixing, extrusion, injection molding, and other processing processes difficult, and even affecting the molding quality of the products. Calcium carbonate with a low oil absorption value helps improve the fluidity of the material, making processing smoother and reducing equipment wear and energy consumption.
Product performance improvement
Mechanical properties: Calcium carbonate with low oil absorption value exhibits better dispersibility in resin, allowing it to distribute more uniformly in the matrix, reducing stress concentration, and thereby enhancing the mechanical properties of the product, such as tensile strength, impact strength, and bending strength.
Surface quality: Good dispersibility helps improve the surface finish of the product, reduce surface defects caused by particle agglomeration, and enhance the appearance quality.
Dimensional stability: Calcium carbonate with low oil absorption value exhibits better compatibility with resin, effectively inhibiting resin shrinkage and deformation, thereby enhancing the dimensional stability of the product.
Formula design and optimization
The oil absorption value serves as a crucial basis for selecting calcium carbonate types. It assists engineers in choosing suitable calcium carbonate varieties and specifications according to specific application needs, optimizing the proportions of various components in the formula, and achieving the optimal balance between performance and cost. In summary, the oil absorption value of calcium carbonate is not only an important indicator for measuring its physicochemical properties, but also a key factor affecting product cost, processing efficiency, and final performance. It holds extensive application value in industries such as plastics, rubber, coatings, paper making, and inks.
Comparison of oil absorption values between light calcium carbonate and heavy calcium carbonate
The oil absorption value of light calcium carbonate is 60-90mL/100mg, significantly higher than that of heavy calcium carbonate, which ranges from 40-60mL/100mg. The performance of both in absorbing liquids and resins differs greatly. Simply put, a high oil absorption value can lead to a significant "waste" of resin, diminishing the effectiveness of using calcium carbonate as a filler to reduce production costs.
In addition, if the formula contains liquid additives, heavy carbonic acid with low oil absorption and inorganic powder with high oil absorption should be selected, and the required coupling agent will also increase.
Ways to reduce the oil absorption value of calcium carbonate
1. Control particle morphology
The oil absorption value of light calcium carbonate or nano-calcium carbonate is closely related to its production process. In cases where there are no specific requirements for particle morphology, crystal form control agents can be used to regulate the crystal form and specific surface area, thereby reducing its oil absorption value.
2. Control fineness and particle size distribution
In the application of calcium carbonate products in general fields, where the requirements for fineness and particle size distribution are not stringent, it is appropriate to choose blended products with a significant variation in particle size distribution. This way, small particles will enter the gaps between larger particles, increasing the packing density and reducing the overall oil absorption of the product.
For high-quality product applications, calcium carbonate with high fineness and narrow particle size distribution helps improve product performance. At this point, surface modification is needed to address the issue 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 surface modification of calcium carbonate, the number of aggregated particles decreases, the dispersibility improves, and the interparticle voids reduce. In addition, the modifying molecules weaken the surface polarity of calcium carbonate, reduce the interparticle friction, improve the lubricity, make the powder pile up more tightly, increase the packing density, and naturally reduce the oil absorption value.