CN114576537A - A capillary with excellent lubricating oil droplet desorption performance and its processing technology - Google Patents

Abstract

The invention discloses a capillary tube with excellent desorption performance of lubricating oil droplets and a processing technology thereof, wherein the outlet end of the capillary tube is provided with an inner conical surface, and the included angle between the inner conical surface and the end surface is 15-60 degrees; the inner wall, the outer wall and the inner conical surface of the outlet end of the capillary tube are coated with oleophobic polymer coatings. The inner conical surface opening is used for stabilizing the main flow field at the outlet end and inducing stable growth and smooth desorption of liquid drops. The oleophobic polymer coating is used for preventing lubricating oil from climbing upwards and overgrowing along the outer wall surface of the capillary, and promotes micro-droplets to realize desorption under a smaller particle size.

Description

A capillary with excellent lubricating oil droplet desorption performance and its processing technology

technical field

The invention relates to the technical field of mechanical engineering surface treatment, in particular to a capillary tube with excellent lubricating oil droplet desorption performance and a processing technology thereof.

Background technique

Long-life, high-reliability satellite platforms are my country's growing space strategic needs. Momentum flywheel is an important component of space actuator. At present, limited by the technical bottleneck of lubricating bearing components under space conditions, bearing components that have been in service for a long time often have problems such as decreased friction performance and unstable friction torque after the lubrication state deteriorates, making the design life distance of the momentum flywheel to meet the long-term requirements of the satellite. There is still a gap in life expectancy. The lubrication of the momentum flywheel has become a key factor restricting the technological advancement of satellite platforms.

The space precision bearing assembly is the core component of the momentum flywheel, and its long-life lubrication technology is one of the important research contents to be carried out in the field of space tribology. Carry out research on active trace oil supply technology to achieve continuous trace supply of lubricating oil, so that bearing components can be lubricated in a timely and effective manner, improve tribological performance during service, and meet the application requirements of high precision and long life of products. Development is of great value.

One of the key links of micro oil supply is to realize the smooth desorption of micro lubricating oil droplets at the outlet end of the oil supply capillary. The short growth period and small desorption particle size of lubricating oil droplets at the outlet end of the oil supply microchannel are very important for the long-term MQL and long-life operation of the bearing.

At present, limited by the surface characteristics and geometric characteristics of the oil supply capillary, the growth period of lubricating oil droplets at the outlet end is relatively long and the desorption particle size is relatively large. The bearing assembly waits for the lubricating surface to be depleted of oil for a considerable period of time before desorption of the lubricating oil droplets, resulting in increased wear. However, after desorption of lubricating oil droplets with larger particle size, it is difficult to achieve the fluid lubrication effect due to the inability to spread and infiltrate in time, resulting in excess lubricating oil. Bearing components that have been in service for a long time often have problems such as decreased friction performance and unstable friction torque after the lubrication state deteriorates, which seriously affects the long-life operation of on-orbit products.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a capillary with excellent lubricating oil droplet desorption performance, to solve the problems of long growth period, large desorption particle size and poor desorption performance of existing lubricating oil droplets at the outlet end of the micro oil supply capillary. question.

Another object of the present invention is to provide a process for manufacturing a capillary tube with excellent lubricating oil droplet desorption performance.

For achieving the above object, the technical scheme adopted in the present invention is as follows:

A capillary tube with excellent lubricating oil droplet desorption performance, the outlet end of the capillary tube is provided with an inner cone surface, and the angle between the inner cone surface and the end surface is 15°-60°; the inner wall, outer wall and inner cone surface of the outlet end of the capillary tube are all coated With oleophobic polymer coating.

Further, the dry film thickness of the oleophobic polymer coating is 15-50 μm. The oleophobic polymer coating is applied to the surface of the capillary substrate by dip coating, so the dry film thickness of the coating is closely related to the viscosity of the oleophobic polymer coating: increasing the content of organic solvents, reducing the viscosity of the coating, and the thickness of the coating film Reduce; reduce the amount of organic solvent, increase the viscosity of the coating, and increase the thickness of the coating film. The wet film thickness after dip coating is usually 20-80 μm. After the solvent is volatilized and cured, the thickness of the coating film will decrease.

Further, the oleophobic polymer coating is composed of polydimethylsiloxane, polyhexamethylene diisocyanate, fluorocarbon resin, benzoyl peroxide, nano-silica and xylene. Fluorocarbon resins are the main film-forming substances for the preparation of oleophobic polymer coatings. Polydimethylsiloxane is a low surface energy adjuvant used to increase the surface tension gradient during coating film formation and further reduce the surface energy of the coating. Polyhexamethylene diisocyanate is a cross-linking curing agent, which is used for cross-linking and curing of coatings to form films; benzoyl peroxide is used as an initiator and catalyst for resin cross-linking and curing. Nano-silica is an inorganic filler, used to adjust the rheological properties of the coating during curing and film formation. After the coating is cured and formed into a film, a micro-nano structure is formed, which is used to improve the oleophobic properties of the polymer coating and increase the oil contact angle. . Xylene is an organic solvent used to dilute and disperse the components in the paint and adjust the viscosity of the paint.

Further, the oleophobic polymer coating comprises the following components in parts by mass:

The processing technology of the above-mentioned capillary tube with excellent lubricating oil droplet desorption performance includes the following steps:

S1: Process the inner cone surface at the outlet end of the capillary, and the angle between the inner cone surface and the outlet plane of the outlet end is 15°～60°;

S2: Formulating oleophobic polymer coatings;

S3: Coat the oleophobic polymer coating in step S2 on the inner and outer walls of the capillary, and after the solvent contained in the oleophobic polymer coating is volatilized, the capillary is cured at 100° C. for 2 hours, so that the oleophobic polymer coating is cured For oleophobic polymer coating.

Further, in step S2, oleophobic polymer coating is made up of each material of following mass percentage:

Further, the preparation method of the oleophobic polymer coating in step S2 is as follows: take the polydimethylsiloxane and polyhexamethylene diisocyanate of the formula amount, stir evenly, and obtain the silicone rubber coating; then take the formula amount of fluorine The carbon resin and benzoyl peroxide are stirred evenly to obtain the fluorocarbon resin coating; finally, the silicone rubber coating, the fluorocarbon resin coating and the formula amount of nano-silica and xylene are taken, and the mixture is uniformly stirred.

Further, the stirring is performed by a planetary mixer.

Further, when the oleophobic polymer coating is applied to the inner wall surface and the outer wall surface of the capillary, the coating is carried out by dipping.

The capillary with excellent lubricating oil droplet desorption performance of the present invention has the following advantages:

Figure 2 is a micrograph of the growth and desorption process of lubricating oil droplets at the exit end of an existing conventional capillary. It can be seen that in the gravity environment, the growth and desorption process of lubricating oil at the outlet end of the conventional oil supply capillary can be divided into five stages: expansion, creep, slide, necking and desorption. In the initial stage, the lubricating oil is slowly injected under the pressure and expands at the end of the capillary to form a hemispherical convex droplet. With the continuous injection of lubricating oil, the diameter of the hemispherical droplet gradually increases. When it reaches the outer wall of the capillary, the lubricating oil starts to climb up along the outer wall of the capillary under the action of capillary force. As the creeping height of the lubricating oil increases, the droplet volume gradually increases, and the gravity increases accordingly, and gradually exceeds the capillary force limit, and the lubricating oil will gradually slide along the outer wall to the outlet end face. As the lubricating oil continued to be injected, the volume and weight of the droplets further increased, the gravity effect began to highlight, and the phenomenon of droplet necking appeared. With the continuous increase of the volume and weight of the droplet, the gravity of the droplet is gradually greater than the viscous force and surface tension, and the necking line becomes longer and thinner until it breaks and desorbs from the outlet end of the capillary. As the lubricating oil is continuously injected, the residual liquid at the end of the capillary shrinks into a hemisphere, and then enters the next cycle. From the above-mentioned different stages of expansion, creeping, sliding, necking, and desorption, it can be seen that the growth and desorption process of lubricating oil at the outlet end of the capillary is the joint action of wall capillary force, oil viscous force, surface tension and gravity. the result of.

From the growth and desorption process of the above-mentioned lubricating oil droplets at the outlet end of the conventional oil supply capillary, it can be seen that the existence of wall capillary force is the main factor that produces wall creep and affects the desorption of microdroplets. The schematic diagram of its action principle is shown in the figure. 3 shown.

The invention exerts influence on the capillary force on the wall surface by modifying the surface of the capillary, thereby breaking the original stress state, and finally achieving the purpose of optimizing the growth and desorption performance of the lubricating oil at the outlet end of the capillary. Figure 4 is a micrograph of the growth and desorption process of lubricating oil droplets at the outlet end of the capillary of the present invention. It can be seen that after the inner cone surface design and surface oleophobic modification treatment, the growth and desorption process of lubricating oil droplets have changed significantly, the two stages of creeping and sliding disappear, and the entire growth and desorption process has evolved. For the three stages of expansion, necking and desorption, the growth period and desorption particle size of droplets at the outlet end of the capillary decreased significantly.

To sum up, the inner cone surface is processed at the outlet end of the capillary, and the opening of the inner cone surface is used to stabilize the main flow field at the outlet end and induce the stable growth and smooth desorption of droplets; It is used to prevent the oil from creeping up and overgrowing along the outer wall of the capillary, so that the microdroplets can be desorbed at a smaller particle size. Under the combined action of the inner cone surface and the oleophobic polymer coating, the capillary effect of the outer wall of the capillary on the lubricating oil is weakened, the wall creeping behavior gradually weakens and finally disappears, and the lubricating oil droplets are stable under the guidance of the inner cone surface. grow and achieve smooth desorption at a smaller particle size, as shown in Figure 4.

Description of drawings

1 is a schematic diagram of a capillary structure with excellent desorption performance of lubricating oil droplets in Example 1;

Figure 2 is a micrograph of the growth and desorption process of lubricating oil droplets at the outlet end of the capillary of Comparative Example 1;

3 is a schematic diagram of the creeping behavior of lubricating oil droplets at the outlet end of the capillary of Comparative Example 1;

4 is a photomicrograph of the growth and desorption process of lubricating oil droplets at the outlet end of the capillary of Example 1;

The scanning electron microscope picture of the oleophobic polymer coating of the capillary of Fig. 5 embodiment 1;

Figure 6(a) is a micrograph of static contact angle of lubricating oil droplets on the capillary surface of Comparative Example 1;

FIG. 6( b ) is a micrograph of static contact angle of lubricating oil droplets on the capillary surface of Example 1. FIG.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments, but those skilled in the art should understand that the embodiments described below are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples can be obtained through commercial channels unless otherwise specified.

Example 1

In the capillary tube with excellent lubricating oil droplet desorption performance in this embodiment, the outlet end is provided with an inner tapered surface, and the angle between the inner tapered surface and the end face of the outlet end is 15°. The inner wall, outer wall and inner cone surface of the outlet end of the capillary are all coated with an oleophobic polymer coating. The thickness of the oleophobic polymer coating was 15 μm. The oleophobic polymer coating includes each of the following parts by mass:

The processing technology of the capillary tube with excellent lubricating oil droplet desorption performance of the present embodiment includes the following steps:

S1: Select a 304 stainless steel metal capillary with a geometric size of Φ1.2×0.1, and use the precision milling method to machine an inner tapered surface at the outlet end of the capillary. The angle between the inner tapered surface and the end face of the outlet end is α=15°.

S2: Weigh each component raw material according to the following mass percentage ratio:

According to the above-mentioned proportions, polydimethylsiloxane and polyhexamethylene diisocyanate are first weighed into a measuring cup, and the measuring cup is put into a planetary mixer and stirred for 2 minutes to obtain a silicone rubber coating. Then, weigh the fluorocarbon resin and benzoyl peroxide into a measuring cup, and stir with a planetary mixer for 2 minutes to obtain a fluorocarbon resin coating. Finally, put the silicone rubber coating, fluorocarbon resin coating, nano-silica and xylene into a measuring cup, and use a planetary mixer to stir for 2 minutes to prepare an oleophobic polymer coating.

S3: Under the condition of room temperature, apply the oleophobic polymer coating in step S2 to the inner and outer walls of the capillary by dip coating, and then leave it in a ventilated place to wait for the surface solvent to evaporate, and then place the capillary at 100 After curing in a constant temperature oven for 2 h, an oleophobic polymer coating was finally prepared on the surface of the capillary, and the dry film thickness of the oleophobic polymer coating was 15 μm.

Example 2

In the capillary tube with excellent lubricating oil droplet desorption performance in this embodiment, the outlet end is provided with an inner tapered surface, and the angle between the inner tapered surface and the end face of the outlet end is 60°. The inner wall, outer wall and inner cone surface of the outlet end of the capillary are all coated with an oleophobic polymer coating. The thickness of the oleophobic polymer coating is 50 μm. The oleophobic polymer coating includes each of the following parts by mass:

The processing technology of the capillary tube with excellent lubricating oil droplet desorption performance of the present embodiment includes the following steps:

S1: Select a 316 stainless steel metal capillary with a geometric size of Φ1.0×0.1, and use the precision milling method to machine an inner tapered surface at the outlet end of the capillary. The angle between the inner tapered surface and the end face of the outlet end is α=60°.

S2: Weigh each component raw material according to the following mass percentage ratio:

According to the above-mentioned proportions, polydimethylsiloxane and polyhexamethylene diisocyanate are first weighed into a measuring cup, and the measuring cup is put into a planetary mixer and stirred for 2 minutes to obtain a silicone rubber coating. Then, weigh the fluorocarbon resin and benzoyl peroxide into a measuring cup, and stir with a planetary mixer for 2 minutes to obtain a fluorocarbon resin coating. Finally, put the silicone rubber coating, fluorocarbon resin coating, nano-silica and xylene into a measuring cup, and use a planetary mixer to stir for 2 minutes to prepare an oleophobic polymer coating.

S3: Under the condition of room temperature, apply the oleophobic polymer coating in step S2 to the inner and outer walls of the capillary by dip coating, and then leave it in a ventilated place to wait for the surface solvent to evaporate, and then place the capillary at 100 After curing in a constant temperature oven for 2 h, an oleophobic polymer coating was finally prepared on the surface of the capillary, and the dry film thickness of the oleophobic polymer coating was 50 μm.

Example 3

In the capillary tube with excellent lubricating oil droplet desorption performance in this embodiment, the outlet end is provided with an inner tapered surface, and the angle between the inner tapered surface and the end face of the outlet end is 45°. The inner wall, outer wall and inner cone surface of the outlet end of the capillary are all coated with an oleophobic polymer coating. The thickness of the oleophobic polymer coating was 33 μm. The oleophobic polymer coating includes each of the following parts by mass:

The processing technology of the capillary tube with excellent lubricating oil droplet desorption performance of the present embodiment includes the following steps:

S1: Select a 304 stainless steel metal capillary with a geometric size of Φ1.2×0.1, and use the precision milling method to machine an inner tapered surface at the outlet end of the capillary. The angle between the inner tapered surface and the end face of the outlet end is α=45°.

S2: Weigh each component raw material according to the following mass percentage ratio:

According to the above-mentioned proportions, polydimethylsiloxane and polyhexamethylene diisocyanate are first weighed into a measuring cup, and the measuring cup is put into a planetary mixer and stirred for 2 minutes to obtain a silicone rubber coating. Then, weigh the fluorocarbon resin and benzoyl peroxide into a measuring cup, and stir with a planetary mixer for 2 minutes to obtain a fluorocarbon resin coating. Finally, put the silicone rubber coating, fluorocarbon resin coating, nano-silica and xylene into a measuring cup, and use a planetary mixer to stir for 2 minutes to prepare an oleophobic polymer coating.

S3: Under the condition of room temperature, apply the oleophobic polymer coating in step S2 to the inner and outer walls of the capillary by dip coating, and then leave it in a ventilated place to wait for the surface solvent to evaporate, and then place the capillary at 100 After curing in a constant temperature oven for 2 h, an oleophobic polymer coating was finally prepared on the surface of the capillary, and the dry film thickness of the oleophobic polymer coating was measured to be 33 μm.

Comparative Example 1

This comparative example is a 304 stainless steel metal capillary with a geometric size of Φ1.2×0.1, the outlet end is not provided with an included angle, and is not coated with an oleophobic polymer coating.

Test Example 1

Surface characterization of the capillary: The surface characterization and analysis of the oleophobic polymer coating on the surface of the capillary in Example 1 were performed under a scanning electron microscope, and the results are shown in FIG. 5 .

Test Example 2

Contact angle measurement: The surface contact angle measuring instrument was used to measure the contact angle of the capillary material surface of PAO-10 aerospace-grade lubricating oil before and after modification. The results are shown in Figure 6.

It can be seen from Figure 6 that the capillary of Comparative Example 1 is not coated with an oleophobic polymer coating, and the static contact angle of the PAO-10 aerospace-grade lubricating oil on its surface is 23°. After the capillary of Example 1 is oleophobic modified, the static contact angle of the PAO-10 aerospace-grade lubricating oil on its surface is increased to 94°. After the capillary of Example 2 is oleophobic modified, the static contact angle of the PAO-10 aerospace-grade lubricating oil on its surface is increased to 116°. The oleophobic treatment significantly improved the oleophobic properties of the capillary surface.

Test Example 3

Comparison and verification of desorption performance: Using a micro-feed pump, the PAO-10 aerospace-grade lubricating oil was continuously micro-pumped along the capillary at a flow rate of 4 mm/s, and a high-speed camera was used to photograph the growth and desorption behavior of lubricating oil droplets at the outlet end of the capillary .

As shown in Figure 2, in the capillary of Comparative Example 1, the inner cone surface is not processed at the outlet end, and the surface oleophobic treatment is not carried out. . In addition, the droplets had an obvious upward climbing process during the growth process, and the lubricating oil remained on the outer wall of the capillary after the droplet necked and desorbed.

As shown in Figure 4, the capillary of Example 1 has an α=15° inner cone surface at the outlet end, and is treated with oleophobic surface. The contact angle is 94°, and the growth period of the lubricating oil droplet is about 15.2s. It shortened by 36.7%; the particle size decreased to 2.21mm when the droplet was desorbed, and the desorption particle size decreased by 13.7%; and the droplet did not climb up along the outer wall of the capillary during the growth process. This shows that the capillary in the present invention has good lubricating oil droplet desorption performance.

Test Example 4

Comparison and verification of desorption performance: Using a micro-feed pump, the PAO-8 aerospace-grade lubricating oil was continuously micro-pumped along the capillary at a flow rate of 3 mm/s, and a high-speed camera was used to photograph the growth and desorption behavior of lubricating oil droplets at the outlet end of the capillary. .

In the capillary of Comparative Example 1, the inner cone surface was not processed at the outlet end, and the surface oleophobic treatment was not carried out. During the process, there is an obvious upward creeping process, and the lubricating oil remains on the outer wall of the capillary after the droplet necks and desorbs.

In the capillary of Example 2, the growth period of lubricating oil droplets is about 12.7s, and the growth period is shortened by 53.5%; the particle size of the droplets during desorption is reduced to 1.53mm, and the desorption particle size is reduced by 22.7%. The droplets did not climb up along the outer wall of the capillary during the growth process, and the droplets gradually grew and expanded along the inner cone surface and desorbed smoothly at a smaller particle size. It shows that the capillary in the present invention has excellent lubricating oil droplet desorption performance.

Although the present invention has been described in detail above with general description and specific embodiments, some modifications or improvements can be made on the basis of the present invention, which will be obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention fall within the scope of the claimed protection of the present invention.

Claims (9)

1. a capillary with excellent lubricating oil droplet desorption performance, characterized in that the outlet end of the capillary is provided with an inner cone surface, and the angle between the inner cone surface and the end face is 15°～60°; the inner wall, outer wall and The inner cone surfaces are all coated with an oleophobic polymer coating. 2 . The capillary with excellent lubricating oil droplet desorption performance according to claim 1 , wherein the dry film thickness of the oleophobic polymer coating is 15-50 μm. 3 . 3. The capillary with excellent lubricating oil droplet desorption performance according to claim 1, wherein the oleophobic polymer coating comprises polydimethylsiloxane, polyhexamethylene diisocyanate, fluorine Carbon resin, benzoyl peroxide, nano silica. 4. The capillary with excellent lubricating oil droplet desorption performance according to claim 3, wherein the oleophobic polymer coating comprises the following components in parts by mass:

5. the processing technology of the capillary tube with excellent lubricating oil droplet desorption performance as claimed in claim 1, is characterized in that, comprises the following steps: S1: Process the inner cone surface at the outlet end of the capillary, and the angle between the inner cone surface and the outlet plane of the outlet end is 15°～60°; S2: Formulating oleophobic polymer coatings; S3: Coat the oleophobic polymer coating in step S2 on the inner and outer walls of the capillary, and after the solvent contained in the oleophobic polymer coating is volatilized, the capillary is cured at 100° C. for 2 hours, so that the oleophobic polymer coating is cured For oleophobic polymer coating. 6. the processing technique of the capillary tube with excellent lubricating oil droplet desorption performance according to claim 5, is characterized in that, in step S2, oleophobic polymer coating is made up of each material of following mass percentage:

7. the processing technique of the capillary with excellent lubricating oil droplet desorption performance according to claim 6, is characterized in that, in step S2, the preparation method of oleophobic polymer coating is: get the polydimethylsiloxane of formula quantity Alkane and polyhexamethylene diisocyanate, stir evenly to obtain a silicone rubber coating; then take the formula amount of fluorocarbon resin and benzoyl peroxide, stir evenly to obtain a fluorocarbon resin coating; finally take the silicone rubber coating, fluorocarbon resin Resin coating and formula amount of nano-silica and xylene, stir evenly, and get it. 8 . The process for processing a capillary tube with excellent lubricating oil droplet desorption performance according to claim 7 , wherein the stirring is performed by a planetary mixer, and the stirring time is 2 min. 9 . 9 . The processing technique of the capillary tube with excellent lubricating oil droplet desorption performance according to claim 5 , wherein the oleophobic polymer coating is coated on the inner wall surface and the outer wall surface of the capillary tube by means of dip coating. 10 .

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