Study On Oxidation Of Carbon Black And Grafting Of Water-soluble Polymer Containing Sulfonic Groups Under Ultrasonic Wave

Carbon black has excellent properties, such as heat- and corrosion- resistance, surroundings change adaptability, good electric conduction and low thermal expansion coefficient, and is widely used in the fields including rubbers, plastics, batteries, pigments, etc. With stricter environmental protection laws being carried out, more and more carbon black requires using in water. Due to small size, high specific surface area and high surface free energy, carbon black particles seriously aggregate together and thus produce poor dispersion stability in water and solvents, which undermine the applications of carbon black.In this thesis, liquid oxidants were adopted to oxidize carbon blacks and polymerization grafting of acrylic acid monomer onto carbon blacks was firstly achieved by initiator under ultrasonic effect. Sulfonic group with strong water-adsorption also was firstly introduced into grafted polymers. It has been found that grafting reaction can occur at room temperature and come to end in a short of time under the effect of ultrasonic wave. The grafting ratio has been also increased to some degrees. The dispersion stability of carbon black after modification was increased significantly.By comparison of the surface properties of carbon black before and after oxidation, it has been found that the higher oxidative capacity and concentration of oxidants are, the more functional groups containing oxygen exist and the stronger their acidity is. Oxidation of carbon black is closely correlated with the physical properties of its surface. The carbon blacks with low structuredness and high specific surface area tend to be oxidized by liquid oxidizer. After oxidation, pH value of the surface of carbon black has a specific relation with the volatile content. Oxidation of carbon black can facilitate hydroxymethylation on its surface and is also favor of the free radical polymerization grafting of acrylic acid monomer.Water-wetting, electric double layer and steric resistance are the three main factors to influence the dispersion stability of carbon blacks in water. The strong water-adsorption of sulfonic group can enhance the force between carbon black and water and its strong ionization can increase the potential of electric double layer. The flexibility of polymer chains in water can be increased by the polarity and large volume of side chains containing sulfonic groups, which consequently increases thesteric resistance of particles. In a word, due to the introduction of sulfonic group, the carbon black with low grafting ration can has excellent dispersion stability in water.Research results show that different surroundings of water will influence, to a large degree, the dispersion stability of the oxidized carbon blacks and grafted ones by poly-acrylic acid. For the surfaces of oxidized and grafted carbon blacks are mostly covered by carboxylic groups, the influence of water surroundings on the both kinds of carbon blacks is similar. They have best dispersion stability in alkaline solutions and relatively poorer dispersion stability in neutral water solutions. In acid and saline water solutions the dispersion stability of modified carbon blacks is the worst.Some analysis methods, such as X-ray photoelectron spectroscopy (XPS), infrared analysis (IR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) and etc., are used to characterize the obtained modified carbon blacks.