Views: 5 Author: su Publish Time: 2018-11-14 Origin: Site
Nonionic surfactants are indispensable chemicals in people's daily life and industrial and agricultural production, and their application range is also expanding. In particular, nonionic surfactants are important in surfactants because of their convenient preparation, superior performance, compatibility with human body and environment, and their increasingly widespread use.
The molecular structure of the nonionic surfactant and its adsorption on the surface. According to the similar compatibility principle, when the surfactant is dissolved in water, the affinity of water for the hydrophilic group is relatively strong, and for the hydrophobic group in the surfactant molecule Repulsive force. This repulsion of water to the hydrophobic groups in the surfactant molecule causes the hydrophobic group to escape from the water, a tendency that enriches the surfactant molecules on the surface of the water, forming surfactant molecules in the water and Oriented monolayer adsorption at the air interface. This directional adsorption is characterized by a hydrophilic radical pointing to the water and a hydrophobic radical pointing to the air. Surfactants also form directional adsorption at the liquid-liquid interface as well as the liquid-solid interface, such as the water-oil interface, water and powder interfaces. The directional adsorption of surfactant molecules at the interface is the most important property of surfactants. It is closely related to the basic properties of surfactants such as critical micelle concentration and surface tension, and affects the wetting, emulsifying and dispersing of surfactants. , washing and foam properties. Effect of nonionic surfactant structure on surface tension Due to the directed adsorption of surfactant molecules on the surface of its aqueous solution, the chemical composition of the outermost layer of the liquid changes, the original water molecules are replaced by hydrophobic groups, and their contribution to surface energy Smaller, resulting in a decrease in the surface tension of the solution. Before the critical micelle concentration was reached, the amount of surfactant adsorbed on the surface of the solution increased significantly as the concentration increased, and the surface tension of the solution decreased significantly. After reaching the critical micelle concentration, increasing the amount of surfactant added to the solution does not significantly increase the amount of adsorption on the surface of the solution, and therefore, the surface tension of the solution does not continue to decrease significantly.
The relationship between the structure of the surfactant and its washing performance is related to the type of the soil, the nature of the substrate, the nature and concentration of the auxiliary in the washing liquid, the washing temperature, the hardness of the water, and the mechanism for removing the scale. It is only after the determination of these factors that the correlation between the structure of the surfactant and its washing performance makes sense. The effects of soil and matrix utilize nonionic surfactants to more effectively wash away non-polar soils on hydrophobic substrates than anionic surfactants. Therefore, research on such soil washing is now focused on the use of nonionic surfactants. Nonionic surfactants are a class of excellent surfactants. They are non-ionizing in water, do not exhibit ionic state, have good stability, and have excellent washing, penetrating, dispersing and emulsifying properties, especially hard water and biodegradation. Good performance, the non-ionic surfactant industry has developed rapidly in the past decade, widely used in textile, cleaning, paper, cosmetics and oil recovery industries; they have good compatibility with other types of surfactants, and are easy to use. . With the continuous advancement of science and technology, new requirements for the performance of nonionic surfactants are constantly being put forward, which requires continuous research and development of new functional surfactants based on the relationship between surfactant structure and properties.