Principle of ultra-low interfacial tension meter

The ultra-low interfacial tension meter mainly consists of two main components: the mechanical part with capillary tube, motor, and camera, and the electronic module part with power input, control electronic components, and temperature display. The video interface can be connected to a computer through the RS232 interface, and the speed can be controlled, measured, data can be stored, and calculation results can be obtained through software.

Principle of ultra-low interfacial tension meter:

The increase in free energy per unit interface area under constant temperature and pressure is called interfacial tension. This system originates from the different attractive forces of molecules on both sides of the interface towards the molecules on the interface. Different from typical interfacial tension testing, rotating droplets can achieve analysis of low interfacial tension, while conventional methods such as platinum plate method and platinum ring method cannot achieve such measurements.

Usually, we refer to the interfacial tension of 10-2-10-1mN/m as low interfacial tension, while the interfacial tension below 10-3mN/m is called ultra-low interfacial tension.

To determine ultra-low interfacial tension, it is necessary to artificially alter the balance between gravity and interfacial tension, making it easier to determine the shape of the droplet at equilibrium. This can be achieved by rotating the system and increasing the effect of the centrifugal force field. This is the principle of ultra-low interfacial tension testing.

Rotating droplet method

The rotating droplet method has been developed to measure surface tension as low as 0.000001mN/m! The measurement principle of this method is based on the fact that when a droplet rotates at high speed around its own longitudinal axis, the droplet attached to the symmetrical axis of the rotating capillary tube filled with thick liquid will form a cylindrical shape. When the volume and rotational speed of the droplet are appropriate, the diameter of the droplet is only related to the interfacial tension. The effect of gravitational acceleration on the shape of the droplet is negligible. Droplets exist stably on the rotating axis, while the surrounding liquid will be forced to move outward due to its high density.

interfacial tension

When two immiscible liquids, such as water and oil, come into contact, an interface will be formed. The magnitude of interfacial tension is directly proportional to the force required to increase the interfacial area. By adding surfactants and synergists that can disperse oil drops, oil drops in water can be stabilized to avoid coalescence of oil drops, so that oil and water are mutually soluble, that is, oil-water lotion is formed. The process of using household cleaning agents to remove grease from hard surfaces and the process of extracting petroleum from underground rock formations using Tertiary petroleum recovery technology both rely on reducing the surface tension between grease and water containing surfactants. The smaller the surface tension between the two, the higher the extraction efficiency.