How to determine the shear stability of lubricating oil

How to determine the shear stability of the lubricating oil - 2019 02 - The shear stability of 20 lubricating oil/shear stability: ( 剪切稳定性) Represents the lubricant under mechanical shear, the nature of the RCC can keep stable viscosity, also known as mechanical stability, 机械稳定性) 。 Good shear stability, lubricating oil can keep stable in the mechanical shear viscosity, otherwise will be due to shear viscosity lubricating oil ( Oil is thinning) 。 Temperature affects the viscosity of liquid, high viscosity index of lubricating oil, viscosity-temperature properties to temperature change can maintain a stable viscosity, in order to improve the viscosity index of lubricating oil, lubricating oil viscosity index improver ( Also known as reinforced adhesion agent, viscosity - 指数改进剂) 。 Viscosity index improver is sensitive to the temperature of the polymer, the temperature rises, its molecular chain stretching, friction increase of the base oil, the oil liquid blocking effect, namely viscosity increase, lubricant viscosity decreased to some extent. Has its drawbacks as well as viscosity index additive under high shear rate, the viscosity index of the molecular chain of additives easily because of the shear is cut off, to reduce or even completely lose viscosity improvement ability, shear including not only shear in the cause of the mechanical components, including high temperature shear, under the condition of high temperature, open the molecule is more likely to be mechanical shear, therefore to pay attention to the hot shear stability of viscosity index improver, generally speaking, high relative molecular mass of polymer reinforced adhesion effect is better, but the shear resistance is poor. Small molecular weight polymer is more resistant to shear, but increases the adhesion effect is limited, so use relatively more. Some lubricating oil in use, sudden drop, the oil viscosity is thinning because of viscosity index improver molecules are cut, lose reinforced adhesion effect. Viscosity index improver used to multistage oil ( Automobile engine oil) , hydraulic oil, gear oil, high viscosity, therefore, it is important to pay special attention to the shear stability of these oil. Although all will get a shear viscosity index improver, but viscosity index improver in shear viscosity stability but there are differences. This needs us through professional inspection, judging on the shear stability of the product: the shear stability of the lubricating oil by shear stability test to measure, under certain conditions, the lubricating oil is cut, and then testing viscosity changes as a result, the shear stability there are three main testing standard: 1. DIN 51382: Bosch injector test ( 博世喷油器测试) Three detection methods, this one is the requirement of minimum standards, in this experiment, oil in 2550 psi pressure state run 250 times, then detect lubricating oil viscosity variation. 2. ASTM D5621: acoustic shear method ( 声波剪切方法) Is put oil in the sound wave oscillators, after the sound wave shear, record loss caused by the shear viscosity. The testing standard is commonly used equipment manufacturers in the United States, however, is gradually by the CEC - below 给- - - - - - A - Replace 99 KRL tapered roller bearing experiments. 3. CEC - 给- - - - - - A - 99: tapered roller bearing experiment ( KRL圆锥滚子轴承测试) Is the worldwide, the more popular a kind of test, as is generally believed that it requires the most strict, and the reality of lubricating oil in use most strongly linked to shearing condition. Lubricating oil is used for bearing, bearing in the load stress under the condition of continuous running 20 hours, and then record after test before and after the experiment of lubricant viscosity, viscosity loss rate calculation. In shear test, the lubricating oil viscosity change rate of shear stability index (remember Shear stability index, shorthand for SSI) , the values of shear stability index is lower, that lubricating oil after subjected to shear viscosity change is smaller, the shear stability of the oil, the better, the better the viscosity index improver shear resistance. Performance good multistage oil use excellent viscosity index improver, high quality stick refers to smaller values of the SSI agent, molecular chain is not easy to be cut off, such as polyolefin ( OCP） Polymers. In general, the oil of SSI shear index should be below 25.