Performance and selection of optical grease

The quality of optical grease is directly related to the main properties of the lubricant used. Lubricating oil directly plays a role in lubrication and friction reduction. Its viscosity, viscosity-temperature characteristics, freezing point, flash point, acid value, etc. have a great influence on the properties of grease. The viscosity can directly reflect the magnitude of the friction within the lubricating oil molecules; lubricating oil with good viscosity-temperature characteristics has a large viscosity-temperature index, and its viscosity changes little when the temperature rises or falls. The freezing point can reflect the low-temperature resistance of the oil; the flash point shows the high-temperature resistance of the lubricant; the acid value can be used to measure the corrosion of the lubricant to metals. Generally, the larger the acid value, the more low-molecular-weight organic acids it contains, and the more serious the corrosion to metals. You should choose a small or neutral oil to make optical grease.

Optical grease refers to a plastic paste-like substance that is specially used to lubricate the friction parts of optical instruments, or to prevent dust from falling on the inner surface of the cavity of optical instruments and to absorb dust. Its quality is closely related to its composition. The main properties for evaluating the quality include needle penetration, dropping point, low temperature resistance, chemical stability, colloid stability, corrosion resistance, volatility, oil layer retention capacity, diffusivity and mildew resistance.

The development direction of optical grease in China In view of the vigorous development of the domestic optoelectronic industry and the special role of optical grease in optical instruments, it is very important to develop highly targeted special grease, especially for some precision optical instruments, such as biological microscopes, camera lenses, military optical instruments, etc. The serialization of these highly targeted optical greases can ensure the correct selection by domestic optical manufacturers. Since the output of these greases is small and the targeting is strong, it is not practical for larger grease manufacturers to develop and produce these greases, but it does provide very convenient testing and production conditions for the auxiliary material production units attached to some large optical factories (companies).

Requirements for the performance of optical grease a. Appropriate adhesion and damping requirements Optical grease is different from other industrial greases. It requires *its own adhesion to be fixed at the lubrication part, and will not be squeezed out of the range of action due to the rotation and stretching of the friction part; the damping effect is more important in optical instruments. It can not only maintain the working state of the optical instrument in use, but also bring a very comfortable feel to the user. Adhesion and damping complement each other in the design of optical grease formula. Adjusting the relationship between the two can bring very ideal use effects to optical instruments. b. Optical grease should have good anti-dispersion performance The so-called anti-dispersion performance refers to the adsorption capacity of grease to base oil. Optical grease with good anti-dispersion performance can ensure that the base oil will not diffuse to non-lubricated parts due to capillary action (the so-called oil climbing phenomenon), pollute other optical systems and affect the normal use of optical instruments. This phenomenon has been found in some domestic optical greases. c. Low volatility and good mildew resistance The low volatility of optical grease can ensure that the instrument is not contaminated by oil mist during use; and good mildew resistance is mainly to prevent mildew from growing in optical instruments. d. Optical grease should have a certain operating temperature range. In principle, optical grease is required to meet the use requirements of -40 to 80°C, but for some general civilian optical instruments, the low temperature can be appropriately adjusted according to the actual working environment. For medium and low damping optical grease, the low temperature performance can basically meet the requirements below -40°C after using low-condensing mineral oil or some low-condensing synthetic oil; and for some high-damping optical grease, due to the high content of thickener in the formula, the low-temperature torque of the optical grease is greatly affected. In the formulation design, damping and low temperature performance are often difficult to take into account at the same time. For example, optical lubricating (damping) grease used in the adjustment, hinges and other parts of optical telescopes. In addition, for optical grease, its long life, corrosion resistance, extreme pressure of grease in certain parts and other requirements should also be fully met.

Selection principles for optical grease
a. Select grease with appropriate damping according to the structure of the friction part and the needs of the product. For the rotating part, the size of its torque directly affects its performance. b. Fully examine the comprehensive quality of the grease The quality standards for measuring optical grease include anti-dispersion, anti-oxidation, high and low temperature performance, shear resistance, volatility, corrosion resistance, mildew resistance, etc. However, it is very difficult for most non-professional manufacturers to conduct a comprehensive investigation on them. This requires an investigation of the manufacturers of optical grease to see whether they have professional production technology. Otherwise, inappropriate selection often buries a large quality risk for optical instruments, causing optical instruments to fog, mold, oil seepage, low-temperature freezing or stuck rotating parts and other quality accidents. C. Fully consider the cost-effectiveness of optical grease At present, the domestic optical industry is very competitive. It is very important to select optical grease products with appropriate prices according to the grade and requirements of optical products. For example, in the domestic telescope industry, telescopes of various grades also have different needs for grease.