Stearic acid is a common saturated fatty acid with long carbon chains, which has both the lipophilic end of the long carbon chain and the hydrophilic end of the carboxyl group. However, the surface of nano calcium carbonate is hydrophilic. Therefore, coating stearic acid on the surface of nano calcium carbonate can greatly improve its lipophilicity, making it suitable for filling in rubber, plastics, advanced inks, and coatings, Its large specific surface area and high specific surface energy are conducive to the strong bonding between calcium carbonate particles and organic polymer molecules, which can make the surface of the product shiny and have excellent reinforcement performance.
1. Mechanism of Stearic Acid Coated Modified Nano Calcium Carbonate
Using commercial stearic acid, the precipitated calcium carbonate is coated under aqueous conditions, and the content of stearic acid in the coated calcium carbonate is 3%~13.5%. Fourier transform infrared (FTIR), thermogravimetry (TG) and differential scanning calorimetry (DSC) analysis showed that there was no free stearic acid on the surface of calcium carbonate, but only calcium stearate. It was found that the formed calcium stearate exhibits partial chemical adsorption and partial physical adsorption on the surface of the coating layer, and can solve the problem of calcium carbonate not being fully coated on the surface under aqueous conditions, with a large coating amount of 3.25%.
2. The Effect of Long Chain Fatty Acids on Calcium Carbonate
The addition of long-chain fatty acids does not affect the crystal form of calcium carbonate, but it affects the morphology of the generated calcium carbonate particles. When lauric acid is added, the dispersity of calcium carbonate particles is greatly improved; When a large amount of palmitic acid and stearic acid is added, a micro rod like structure and a spindle like structure are formed. The author proposes that during the carbonization reaction between calcium hydroxide and carbon dioxide, on the one hand, the length of the carbon chain affects the shape of the micelles formed by the calcium hydroxide suspension, and on the other hand, the contact mode between the micelles determines the morphology of the resulting calcium carbonate.
3. Application characteristics of active nano calcium carbonate
After surface modification, nano calcium carbonate can significantly improve the tensile strength, elongation, wear resistance, and flame retardancy of composite materials compared to unmodified nano calcium carbonate and commercial calcium carbonate. Surface modification can also generate strong adhesion, which makes the polymer chain stronger and improves the thermal stability of the polymer. Based on the high strength and toughness of these nanocomposites, they can be used for cable connectors, electrical and lighting switchgear, and also have important value in the aerospace field.
Stearic acid, as a common long-chain fatty acid, is cheap and widely used, and can effectively modify nano calcium carbonate. As a cheap and easily available filler, the active nano calcium carbonate modified with stearic acid can be well dispersed in numerous organisms, and can improve the mechanical and thermodynamic properties such as tensile strength, elongation, wear resistance, and flame retardancy of the organism. Therefore, choosing stearic acid to modify nano calcium carbonate has great research and application value. For more related matters, come to our website http://www.tmgwork.com Consult!