IOTA 704 and 705 have excellent thermal stability and oxidation resistance at very low saturated vapor pressure. Mainly used in vacuum smelting industry, electron tube industry, bulb, high vacuum coating (film), atomic accelerator and electron microscope, display and so on. Lubricating oil is widely used in the operation of machinery. In the process of oil use, due to temperature rise or flow and other reasons, it is easy to produce bubbles, which has a great impact on the lubrication system. It will produce gas resistance, flow interruption and other phenomena, increasing the wear of machinery and increasing the loss of oil. In addition to improving the performance of the oil itself, a more economical and effective method is to add antifoam agent.


Mechanism of action of antifoam agent


Oil foam can be divided into two aspects, one is surface foaming, usually can be controlled by antifoaming agent; The other is the internal foam of the oil, the internal foam is not easy to improve by antifoaming agent, and the effective antifoaming agent on the surface of the foam may make the internal foam of the oil more stable. For the oil that needs excellent defoaming performance, it is necessary to choose the base oil and additives to be deployed.


1.1 local surface tension reducing lead to bubble foam this mechanism is implemented by lowering the surface tension, by higher alcohols or vegetable oil etc on the surface of a bubble, in order to reduce the tension on the surface of the bubble, but the mechanism is limited to local position, because this kind of material does not dissolve in water, so the diffusion force is poorer, Doesn't do much for the surrounding bubbles. When the local tension of the foam surface is reduced, under the action of this force, it slowly diffuses around and finally forms a rupture.


1.2 Defoaming agent can destroy the elasticity of the film and cause bubbles to burst. Sprinkle defoaming agent on the surface of the oil, and the foam on the surface can be eliminated. Foam is produced on the surface of oil because there is a layer of surfactant floating, which has a strong support force for the formation of surface foam. When defoaming agent is added, it can effectively inhibit the diffusion of active agent, making it difficult to play the elastic ability, so as to eliminate the surface foam.


1.3 Defoaming agent can promote liquid film drainage, resulting in bubble burst and foam elimination speed is related to its drainage speed, and the injection of defoaming agent can accelerate the rate of foam drainage, so as to quickly eliminate foam.


1.4 Adding hydrophobic solid particles can cause bubbles to burst. The hydrophobic solid particles on the surface of bubbles will attract the hydrophobic end of surfactants, making hydrophobic particles produce hydrophilicity and enter the water phase, thus playing the role of defoaming.


It has been mentioned in the second point that the generation of foam has a great relationship with the surfactant on the oil surface. If the surfactant can be dissolved quickly or its tightness can be reduced, the stability of the foam can be reduced. Therefore, low molecular substance can be added to it, which has very strong solubility and can be fully fused with the solution to adsorb on the surface, thus reducing the tightness of the surfactant and achieving the function of quickly eliminating the foam.


1.6 Electrolytes collapse of the double electric layer of surfactants resulting in bubble burst For the surfactant double electric layer with the help of foam interaction, produce stable foaming liquid, adding ordinary electrolytes can collapse the double electric layer of surfactants play a role in defoaming.


2.1 Selection of antifoam agents Antifoam agents are divided into silicon and non-silicon two types. Silicon antifoam agent, excellent antifoam performance, but poor oil solubility, great impact on air release, mainly use foam part of the reduced surface tension to break bubbles, reduce the formation of bubbles; For dispersed bubbles, it reduces the surface tension and makes the bubble diameter smaller, difficult to float, resulting in poor air release. The bubbles generated by non-silicon antifoam agents are large in diameter, easy to release, and have little impact on air release, but the antifoam effect is poor, and the compatibility of alkaline additives such as T705 is also poor. In order to give consideration to both properties, compound antifoam agents are mostly used at present.