Analysis of Key Properties and Main Indicators of Nano Calcium Carbonate
Nano calcium carbonate is a new type of ultrafine solid material developed in the 1980s, referring to calcium carbonate products with particle sizes ranging from 1 to 100 nm.
Key Properties of Nano Calcium Carbonate
Due to its unique particle size, nanoscale calcium carbonate exhibits superior properties, including surface effects, small size effects, and macroscopic quantum tunneling effects, making it a hot topic for research and development by various countries in recent years.
Nano calcium carbonate exhibits superior properties in magnetism, catalysis, photo thermal resistance, and melting point. It is an excellent white reinforcing material in the rubber and plastic industries, which can make the surface of products shiny, high in tension resistance, bending resistance, and good in crack resistance; As a filler in the coating industry and advanced ink industry, it can not only reduce costs but also improve product performance and play a role in thickening and anti settling; As a calcium supplement in the feed industry, it can increase the calcium content; In cosmetics, it can replace expensive titanium dioxide to meet the requirements of product purity, whiteness, and fineness.
Nano calcium carbonate is a universal material, and there are many aspects that affect its performance, including crystal form, morphology, particle size, etc. These factors can be effectively controlled by controlling key preparation conditions. Therefore, how to prepare nano calcium carbonate products with different morphological characteristics and special functions by regulating different process conditions and adding different crystal type control agents, in order to enhance their application performance and expand their value in the industry, is the focus of current research.
Analysis of Main Technical Indicators of Nano Calcium Carbonate
The Main Content of Nano Calcium Carbonate is Relatively Low
Due to the addition of a certain amount of crystal directing agent and surfactant during surface modification of calcium carbonate, the surface of calcium carbonate is coated with one or more layers of surfactant and dispersant, inevitably resulting in a decrease in the main content of calcium carbonate. Moreover, the smaller the particle size of calcium carbonate and the larger the specific surface area, the more dispersant and surfactant are applied, and the lower the main content of calcium carbonate. The relationship between the main content of calcium carbonate is: ordinary light calcium>active light calcium>specialized nano calcium. Therefore, the main content of some imported high-end nano calcium carbonate is below 95%.
The Relationship between Crystal Shape and Particle Size
When the particle size is generally larger than 200nm, the crystal form is mostly asymmetric, such as spindle shaped, rod-shaped, etc; When the particle size is between 50-120nm, it is generally symmetrical, such as cubic, spherical, etc; When the particle size is less than 30nm, it is mostly cubic and granular, and the crystals are easily linked into chains. The particle size of calcium carbonate is mainly related to the carbonization temperature, initial reaction rate during carbonization, and crystal directing agent.
Low temperature carbonization (0-30 ℃) is beneficial for the ultrafine refinement of particles, and carbonization temperature is the key to controlling particle size. As the carbonization temperature increases, the crystal particle size gradually increases and the particle size distribution becomes wider. The effect of reaction rate on the particle size of calcium carbonate crystals is very significant. With the increase of reaction rate, the primary particle size of calcium carbonate crystals decreases, especially by increasing the reaction rate in the early stage of carbonization reaction, which is very beneficial for the formation of calcium carbonate nuclei and the ultrafine refinement of calcium carbonate particles. This is the principle of low-temperature carbonization to produce nano calcium carbonate.
The addition of crystal directing agents plays a crucial role in the influence of crystal form and particle size, as well as the consistency of crystal form. Crystalline directing agents include soluble inorganic salts such as A13+, Zn2+, Mg2+, Na+, and some strong inorganic acids, as well as some organic dispersants such as lower fatty acids, resin acids, etc.
Comparison of Settlement Volume Size
The settling volume is the volume per unit mass of calcium carbonate product, which is obtained by shaking and standing for 3 hours in a sample containing 100 mL of water. The larger the settlement volume, the smaller the particle size, lighter the density, and higher the product grade. The settling volume of light calcium carbonate (2.4-2.8 mL/g) is larger than that of heavy calcium carbonate (1.1-1.4 mL/g), and the settling volume of nano calcium carbonate (3.0-4.0 mL/g) is also larger than that of light calcium carbonate. In addition to particle size, the factors affecting the settling volume of calcium carbonate are also the crystal form of calcium carbonate.
Oil Absorption Value and Application Performance
The oil absorption value of calcium carbonate is related to the gaps between its particles, their surface properties, and specific surface area. Products with uniform particle size distribution and smooth surface, small specific surface area, and low oil absorption value; On the contrary, if the particles are slightly large, the distribution of fine particles is uneven, the crystal structure is complex or defective, and the specific surface area is large, then the oil absorption value is high; For active calcium, its oil absorption value is much lower than that of ordinary calcium carbonate, and the oil absorption value decreases with the increase of the active content adsorbed on the surface of calcium carbonate. Nano calcium carbonate that has not been modified not only has static electricity on its surface, which makes it easy to agglomerate and not easily disperse during application, but also has a high oil absorption value, which will seriously affect its application performance.
The oil absorption value of nano calcium carbonate products varies greatly in different application fields. The oil absorption value of nano calcium carbonate used for plastics, coatings, and inks should be minimized as much as possible; The oil absorption value of nano calcium carbonate used in the fields of rubber and papermaking should be maximized while ensuring dispersibility.