A polymer-based composite material filled with carbon nanotube nanocapsules containing a lubricant and a method for preparing the same

Abstract

This invention belongs to the field of polymer-based composite materials technology, and discloses a polymer-based composite material with higher mechanical strength and the ability to release liquid lubricant during friction. The polymer-based composite material is prepared by curing oil-containing carbon nanotube microcapsules and polymer materials. The preparation method is as follows: First, lubricant is filled into the cavities of carbon nanotubes to obtain nanocapsules internally loaded with lubricant, wherein the carbon nanotubes are 80-90 parts and the lubricant is 10-20 parts; second, the nanocapsules are added to the polymer material and mixed evenly, with 1-10 parts of nanocapsules and 99-10 parts of polymer material added; finally, the mixture is placed in a mold for cold pressing and then placed in an oven for curing to obtain the polymer-based composite material. Compared with ordinary polymer materials, the polymer-based composite material has higher mechanical strength and self-lubricating properties, and can be used in bearings and other parts.

Description

Technical Field

[0001] This invention belongs to the field of polymer-based composite materials technology, and relates to a polymer-based composite material with higher mechanical strength and the ability to release liquid lubricant during friction. Specifically, it relates to a polymer-based composite material that can be used in self-lubricating bearings, bushings, and other friction components. Background Technology

[0002] Polymer materials have low coefficients of friction and good thermal stability, making them commonly used in the machinery, materials, and aerospace industries to manufacture friction components such as bearings and bushings. However, common polymers have high coefficients of linear expansion and poor creep resistance. Therefore, they are often modified with graphite, MoS2, carbon fiber, and glass fiber to meet application requirements. Carbon nanotubes (CNTs) possess high strength, with tensile strength reaching 200 GPa, making them an ideal reinforcing phase for polymer composites. High-hardness, fibrous CNTs can more tightly entangle within the polymer crystal system during curing, enhancing the mechanical properties of the polymer. The friction performance of polymer / CNT composites is also superior to that of pure polymers because the CNTs that detach during friction can act as a third body distributed on the friction interface, isolating the rough contact of the friction pair interface and providing a certain degree of self-lubrication.

[0003] CNTs possess a unique cavity structure with an inner diameter ranging from 5 to 50 nm. Under suitable conditions, other substances can be introduced into the cavities of CNTs to improve their electrical conductivity, magnetic properties, and tribological properties. The inventors proposed filling the cavities of CNTs with various lubricants to prepare nanocapsules. This method introduces more lubricating components into the CNT molecules, further improving their lubrication characteristics. Using these nanocapsules as fillers in polymer materials, the CNTs can protect the lubricant during the polymer curing process, resulting in a liquid lubricant within the polymer. During friction, the nanocapsules release the lubricant, effectively improving the lubrication performance of the polymer. The nanocapsules also better integrate into the polymer, enhancing the bonding between CNTs and the polymer and further improving its mechanical properties. Summary of the Invention

[0004] To improve the mechanical and tribological properties of polytetrafluoroethylene (PTFE), this invention proposes using carbon nanotubes (CNTs@T321 nanocapsules) with an internal cavity loaded with the lubricant sulfurized isobutylene (T321) as a reinforcing phase for PTFE. During friction, the nanocapsules release T321, further enhancing the self-lubricating properties of PTFE. This invention first prepares CNTs@T321 nanocapsules using the lubricant sulfurized isobutylene (T321), and then fills PTFE with these nanocapsules to prepare a composite material. Compared with ordinary CNTS, the influence of nanocapsule filling on the mechanical and tribological properties of PTFE is studied. The mechanism by which the nanocapsules in PTFE release T321 and form a self-lubricating layer during friction is analyzed, achieving both improved mechanical strength and enhanced self-lubricating properties of PTFE. This research lays the foundation for formulation selection and preparation processes when this novel PTFE composite material is applied to self-lubricating bearings.

[0005] According to a first aspect of the present invention, the present invention provides CNTs@T321 nanocapsules, wherein the microcapsules are formed by filling the cavities of carbon nanotubes with lubricant to obtain nanocapsules internally loaded with lubricant.

[0006] In some embodiments of the present invention, the lubricant is sulfurized isobutylene (T321), and the carbon nanotube is a multi-walled carbon nanotube, more preferably a multi-walled carbon nanotube that has undergone acidification pretreatment.

[0007] According to a second aspect of the present invention, a method for preparing CNTs@T321 nanocapsules is provided, comprising the following steps:

[0008] T321 was dissolved in a solvent, and then 20g of pre-treated acidified CNTs were added. The mixture was thoroughly mixed and then vacuum-stirred under these conditions. After ultrasonication, the mixture was vacuum-filtered and washed with solvent to remove unfilled CNTs. The filter cake was then dried and pulverized by ultra-microball milling to obtain CNTs@T321 nanocapsules. Preferably, 10g of T321 was dissolved in 400mL of acetone, and then 20g of pre-treated CNTs were added. The mixture was thoroughly mixed and placed in a spherical flask under vacuum to -0.1MPa. Under these conditions, the mixture was ultrasonically stirred for 2 hours at 65℃. After ultrasonication, the mixture was vacuum-filtered and washed with acetone to remove unfilled T321. The filter cake was then dried in a 75℃ oven for 12 hours and pulverized by ultra-microball milling to obtain CNTs@T321 nanocapsules.

[0009] Preferably, the method for acid pretreatment of CNTs is as follows: 50g of CNTs are added to 1500ml of 40% concentrated nitric acid, the mixture is placed in a three-necked flask, heated under reflux at 80°C for 8 hours, and magnetic stirring is applied at a speed of 500r / min. Finally, the mixture is vacuum filtered, and the resulting filter cake is dried at 85°C and then ball-milled for 10 hours to obtain acid-treated CNTs.

[0010] According to a third aspect of the present invention, the present invention provides an application of the CNTs@T321 nanocapsules, wherein the CNTs@T321 nanocapsules are cured with polytetrafluoroethylene to form a polymer-based composite material with self-lubricating properties; the polymer-based composite material is used as a lubricant for bearings, bushings and other components during operation.

[0011] Preferably, the method for curing CNTs@T321 nanocapsules with polytetrafluoroethylene is as follows: CNTs@T321 nanocapsules are added to PTFE at a mass fraction of 1%-9%, mechanically stirred until uniform, and then processed in a ball mill. They are then placed into figure-eight cavity molds and annular cavity molds respectively, pressed into figure-eight block samples and annular samples, and then placed in an oven for curing.

[0012] More preferably, a cold pressing process is used during sample preparation, with a molding pressure of 30 MPa. After pressing, the sample is left to stand for 24 hours, and then placed in an oven for curing. The maximum curing temperature is 315℃, with a temperature rise rate of 10℃ / h. After reaching the curing temperature, the sample is held at that temperature for 2 hours and then allowed to cool naturally. The figure-eight block sample is used for mechanical property testing, and the ring sample is made into a pin sample for friction testing.

[0013] More preferably, during the curing process, the amount of CNTs@T321 nanocapsules added is 1%-6%.

[0014] This invention provides a polymer-based composite material filled with CNT nanocapsules that can meet the lubrication requirements of bearings, bushings, and other components during operation, enabling self-lubrication in oil-free or low-oil environments. The polymer-based composite material prepared using CNT nanocapsules has the following main advantages:

[0015] (1) The cavity size of CNTs is moderate, with an inner diameter between 10 and 50 nm. The size is relatively consistent with the lubricant molecules, making it suitable for various lubricants to enter and form nanocapsules that can carry lubricating oil inside.

[0016] (2) The thermal decomposition temperature of CNTs is above 500℃. CNT nanocapsules can provide sufficient protection for the lubricating oil inside, preventing the lubricating oil from being damaged during the curing process of polymer materials.

[0017] (3) CNT nanocapsules have high strength. When filled with polymer materials, they can be used as a reinforcing phase to improve the tensile strength of the materials.

[0018] (4) During the friction process, as the polymer material wears down, the CNTs nanocapsules can release the lubricating oil in them to the friction interface to form a lubricating film, thereby reducing the coefficient of friction and alleviating wear. Attached Figure Description

[0019] Figure 1 Thermogravimetric and differential thermal analysis results for T321, ordinary CNTs and nanocapsules. Figure 2 Infrared spectrum and TEM image of the nanocapsule sample.

[0020] Figure 3 Infrared spectra of PTFE, nanocapsules and composites, and SEM images of composites.

[0021] Figure 4 The graph shows the effect of the mass fraction of nanocapsules on the tensile strength and hardness of PTFE composites.

[0022] Figure 5 The graph shows the effect of the mass fraction of nanocapsules on the friction coefficient and wear rate of PTFE composite materials.

[0023] Figure 6 The figure shows the effect of sliding speed on the friction coefficient and wear rate of pure PTFE, PTFE / CNTs, and PTFE / microcapsule composites under a load of 50N.

[0024] Figure 7 The graph shows the variation of the friction coefficient and wear rate of the three materials with load when the sliding speed is 0.5 m / s.

[0025] Figure 8 The SEM morphology and EDS energy dispersive spectroscopy of selected regions of the polished surfaces are shown for ordinary PTFE, PTFE / CNTs composites and PTFE / microcapsule composites.

[0026] Figure 9 XPS spectra of C(a), O(b), S(c), and F(d) on the surfaces of GCr15 steel, PTFE, PTFE / CNTs composites, and PTFE / microcapsule composites.

[0027] Figure 10 This is a model diagram of the contact area between the PTFE / microcapsule composite material and the frictional contact area. Detailed Implementation

[0028] Multi-walled carbon nanotubes (CNTs) were purchased from Shanghai Aladdin Reagent Co., Ltd., with a purity of 99% and an inner diameter of 20–50 nm.

[0029] Pretreatment of CNTs: Since commercially available CNTs have a large aspect ratio, which is not conducive to filling, the CNTs are first shortened and pretreated. During the treatment, 50g of CNTs are added to 1500ml of 40% concentrated nitric acid. The mixture is then placed in a three-necked flask and heated under reflux at 80℃ for 8h while magnetic stirring is applied at a speed of 500r / min. Finally, the mixture is vacuum filtered, and the resulting filter cake is dried at 85℃ and then ball-milled for 10h to obtain pretreated CNTs.

[0030] Preparation of CNTs@T321 nanocapsules: 10g of T321 was dissolved in 400mL of acetone, and then 20g of pretreated CNTs were added. The mixture was thoroughly mixed and placed in a spherical flask under vacuum to -0.1MPa. Under these conditions, the mixture was ultrasonically stirred for 2 hours at 65℃. After ultrasonication, the mixture was vacuum filtered and washed with acetone to remove any unfilled T321. Finally, the filter cake was dried in a 75℃ oven for 12 hours and then pulverized by ultra-micro ball milling to obtain CNTs@T321 nanocapsules (hereinafter referred to as nanocapsules).

[0031] Performance and structural characterization:

[0032] The microstructure of the samples was observed using a FEI TECNAI G20 transmission electron microscope (TEM) with an accelerating voltage of 200 kV during testing. Thermogravimetric analysis of CNTs and nanocapsules was performed using a STA449 integrated thermal analyzer with a temperature rise range of 20℃-800℃ and a rate of 20℃ / min.

[0033] M111 type polytetrafluoroethylene (PTFE) powder was purchased from Daikin Industries, Ltd., Japan. Pretreated CNTs and nanocapsules were added to the PTFE at mass fractions of 1%-9%, respectively. After mechanical mixing, the mixture was processed in a ball mill for 8 hours. The resulting samples were then pressed into figure-eight block specimens (Ф40mm×10mm) and ring specimens (Ф30mm×12mm) using both figure-eight and ring molds. Cold pressing was used for sample preparation at a molding pressure of 30MPa. After pressing, the samples were allowed to stand for 24 hours, then cured in an oven at a maximum temperature of 315℃ with a temperature rise rate of 10℃ / h. After reaching the curing temperature, the samples were held at that temperature for 2 hours and then allowed to cool naturally. The figure-eight block specimens were used for mechanical property testing, while the ring specimens were further processed into pin specimens for friction testing.

[0034] The tensile strength of the figure-eight block was tested on an RG 4100 material testing machine at a tensile rate of 1 mm / min, and the deformation curve during tensile testing was recorded by computer. The hardness of the composite material was tested using an HR-150A hardness tester with an indenter diameter of Ф3.175 mm, a preload of 98 N, and a main load of 980 N. Hardness values ​​were measured at four locations (three points were measured at each location), and the average was taken. The tribological properties of the material were tested using a pin-disc friction pair on an MMW-1 tribological testing machine. The test disc was made of GCr15 steel with an outer diameter of Ф30 mm and an inner diameter of Ф30 mm. Hardness 59-61 HRC, R a =0.2μm. Experimental conditions: water lubrication, room temperature approximately 25℃, test time 10min; First, the effect of filler mass fraction on the tribological properties of the material was investigated under a load of 50N and a sliding speed of 0.5m / s; Second, the tribological properties of the material were tested under a load of 50N and a sliding speed varying from 0.1 to 0.9m / s, and under a sliding speed of 0.5m / s and a load varying from 20 to 80N, with a filler mass fraction of 5%. Three parallel tests were conducted for each group. The coefficient of friction was calculated using μ = T / (Pr) (where T is the frictional torque, P is the experimental load, and r is the radius of the contact point trajectory), and the average value within 10min was taken. The mass of the sample pin before and after wear was weighed, and the wear rate was calculated using W = ΔV / (Pd) (where ΔV is the wear volume and d is the sliding distance).

[0035] The infrared spectra of the PTFE and nanocapsule mixture before and after curing were measured using a Nicolet 6700 infrared spectrometer. The microstructure of the PTFE composite material was observed using a SIRION-100 field emission scanning electron microscope. A 5% filler sample was used as a grinding ring under experimental conditions of 50 N load and 0.5 m / s sliding speed, and was ultrasonically cleaned with acetone for 30 min. The binding energy of the main elements on the worn surface was analyzed using an AXISUltra DLD X-ray photoelectron spectroscopy (XPS) instrument with an electron pass energy of 80 eV, using a monochromatic AlKα ray source, and contaminated carbon C. 1s The binding energy is 284.8 eV as an internal standard.

[0036] Example 1 Characterization of nanocapsules and PTFE composite materials

[0037] Thermogravimetric and differential thermal analyses of T321, ordinary CNTs, and nanocapsules are as follows: Figure 1 As shown. By Figure 1As shown in Figure (a), the thermogravimetric curve of ordinary CNTs changes relatively smoothly, while the thermogravimetric curve of CNTs@T321 nanocapsules shows a significant weight loss process at around 300℃. This is the result of T321 escaping from the microcapsule due to heat, which also proves the presence of T321 inside the CNTs tube. The filling rate (η) of T321 in CNTs can be calculated according to Equation (1).

[0038] η = H f / H p ×100% (1-3)

[0039] In the formula, H f f The latent heat of phase transition of T321 filled in CNTs, J / g; H p The latent heat of phase transition for T321 is expressed in J / g. For example... Figure 1 (b) The DSC curve of the microcapsules shows that the latent heat of phase change of T321 is 31.3 J / g, while the latent heat of phase change of T321 under the same conditions is 121.6 J / g. It can be calculated that the filling rate of T321 in CNTs is 25.7%.

[0040] Figure 2 (a) shows the infrared spectra of ordinary CNTs, acid-treated CNTs, and T321 nanocapsules. Figure 2 As can be seen in (a), after acid treatment, CNTs are at 3432 cm⁻¹ -1 1822cm -1 The appearance of new absorption peaks near the wavelength should be attributed to hydroxyl and carboxyl groups, indicating that the acidified CNTs have bonded oxygen-containing groups, which has a good effect on improving the bonding strength between CNTs and PTFE during curing; in addition, at 1630 cm⁻¹... -1 The nearby peaks should be attributed to the planar absorption peaks of the carbon ring structure, proving that CNTs retain their tubular structure, which is a prerequisite for T321 to fill the tubes. No new characteristic peaks were detected in the infrared spectrum of the nanocapsules; the characteristic peaks were a partial superposition of the characteristic peaks of acidified CNTs and T321, proving that during the T321 filling of CNTs, the two mainly undergo physical bonding, without chemical reaction. Using TEM to observe the microstructure of carbon nanotubes, the state of T321 within the CNT tubes can be directly determined. The TEM images of the nanocapsules are shown below. Figure 2 As shown in (b), several sections inside the CNTs tube are clearly wetted by T321, which is a relatively intuitive proof of the presence of T321 inside the CNTs tube.

[0041] The curing process of PTFE is quite complex, and CNTs@T321 nanocapsules may be destroyed during curing. Therefore, it is essential to study the stability of the microcapsules during curing and their compatibility with PTFE. Figure 3 The thermogravimetric curves of CNTs and nanocapsules show that the nanocapsules only undergo significant weight loss above 300℃, a temperature that can resist the curing temperature of PTFE. Figure 3 (a) shows the infrared spectra of PTFE, microcapsules, mixtures thereof, and cured products, with the peak value of the microcapsule infrared spectrum at 1628 cm⁻¹. -1 2583cm -1 2924cm -1 3424cm -1 The absorption peaks represent the vibrations of the carbon nanotube framework, CH stretching vibration, CH deformation vibration, and OH bond stretching vibration, respectively. The first three peaks are clearly present in the infrared spectrum of the cured product, indicating that the framework structure of CNTs in the microcapsules was not destroyed during the curing process, which provides sufficient protection for the T321 inside. Figure 3 (b) shows the optical and SEM images of the PTFE composite tissue. It can be seen that the microcapsules are evenly distributed in the composite tissue in the form of clumps of particles. Each particle is an oil-containing microcapsule. During the friction process, the particles break and release T321 evenly to play a lubricating role.

[0042] Example 2 Mechanical Properties

[0043] Figure 4 The effect of different mass fractions of CNTs or microcapsules on the tensile strength and hardness of PTFE composites. Figure 4 As shown in (a), the tensile strength of the material initially increases and then decreases with increasing filler content. This is mainly due to the high surface activity of CNT particles. The numerous unsaturated residual bonds and active groups on their surface enable them to undergo physical or chemical cross-linking with the polymer chains on PTFE, enhancing the adhesion at the interface of the material bonding. Further addition of CNTs may lead to their aggregation, thereby reducing this cross-linking effect and decreasing the strength of the PTFE composite material. The optimal CNT content is approximately 3%, and when the filler content is around 6%, the strength of the PTFE composite material is still comparable to that of pure PTFE. The filling of nanocapsules has a more significant impact on the strength and hardness of PTFE composite materials because the microcapsules have a smaller aspect ratio and a tighter bonding with the PTFE material. Figure 4 As can be seen in (b), the hardness of the composite material decreases as the mass fraction of the filler increases. In practice, the appropriate filler amount can be selected according to the performance requirements of the bearing.

[0044] Example 3 Tribological Properties

[0045] 3.1 Effect of Filler Content on Friction Coefficient and Wear Rate of PTFE Composites

[0046] Figure 5The effect of the mass fraction of CNTs or microcapsules on the friction coefficient and wear rate of PTFE material under a load of 50 N and a sliding speed of 0.5 m / s. Figure 5 As shown in (a), at lower mass fractions, CNT filling has a certain effect on improving the friction coefficient of PTFE. This is because the molecular structure of CNTs is destroyed during friction, and the resulting products are adsorbed and deposited on the friction interface, producing a certain friction-reducing effect. However, when the filling amount exceeds 4% and continues to increase, the friction-reducing effect is not very obvious. This is because more CNTs are released to the friction surface, which instead acts as an obstacle. Filling with nanocapsules can more significantly reduce the friction coefficient of PTFE. This is because during friction, the nanocapsules in PTFE release T321, which is adsorbed on the friction interface, forming a more sufficient lubrication, thereby playing a friction-reducing role. Figure 5 As shown in (b), pure PTFE exhibits a high wear rate. PTFE can form a transfer film at the friction interface, but its bonding strength is low, resulting in a high wear rate. Filling with CNTs or microcapsules can reduce the wear rate of PTFE. When the filling amount is 15% and 10%, the minimum wear rate can be approximately 2.8 × 10⁻⁶, respectively. - 5 mm 3 / N·m and 1.9×10 -5 mm 3 The wear rate increases with increasing N·m content. While CNTs' friction products adsorb and deposit on the friction interface, producing a friction-reducing effect, they also weaken the formation of the PTFE transfer film, thus reducing the wear of the composite material. However, continuously increasing the filler content affects the hardness of the composite material, leading to an increased wear rate. At various contents, the wear rate of the microcapsule-filled composite material is lower than that of the CNT-filled composite material, proving that the microcapsules release T321 during friction. The lubricating layer formed by T321 has a better resistance to PTFE adhesion and transfer, thus exhibiting a more significant anti-wear effect.

[0047] 3.2 Effect of sliding speed on the friction coefficient and wear rate of PTFE composite materials

[0048] Figure 6This study investigates the effect of sliding speed on the friction coefficient and wear rate of pure PTFE, PTFE / CNTs, and PTFE / microcapsule composites under a load of 50 N, with CNTs or microcapsules accounting for 5% of the filling amount. It shows that the friction coefficient of all three materials tends to decrease with increasing speed, mainly due to changes in temperature, deformation, roughness, and vibration at the contact surfaces caused by increased speed. At various rotational speeds, the friction coefficient of PTFE / CNTs is lower than that of pure PTFE, with the PTFE / microcapsule composite exhibiting the lowest friction coefficient. The wear rate of all three increases with increasing speed, with the PTFE / microcapsule composite showing the lowest wear rate. For PTFE / microcapsule materials, higher speeds result in higher temperatures at the friction interface, which should be more conducive to the release and adsorption of T321, leading to a more complete lubricating layer and a more pronounced decreasing trend in the friction coefficient. The linear velocity of the rotating bearing can reach around 40 m / s; friction under these high-speed conditions should be more conducive to the lysis of microcapsules and promote the release of T321 and the formation of the lubricating layer.

[0049] 3.3 Effect of test load on the friction coefficient and wear rate of PTFE composite materials

[0050] Figure 7 The friction coefficients and wear rates of the three materials change with load at a sliding speed of 0.5 m / s. It can be seen that the friction coefficients of pure PTFE and PTFE / CNTs composites gradually increase. This is because as the load increases, the frictional contact area increases, resulting in greater heat generation and increased PTFE adhesion. The friction coefficient of PTFE / microcapsule composites, however, does not change significantly and may even decrease. This is because the increased load also accelerates wear, releasing more T321 and forming a more complete transfer film and lubricating layer. Under various loads, the friction coefficient of PTFE / CNTs is lower than that of ordinary PTFE, with PTFE / microcapsule material exhibiting the lowest friction coefficient and a more pronounced decreasing trend. With increasing load, the wear rates of all three materials show a continuous increasing trend, with PTFE / microcapsule material exhibiting the lowest wear rate. This indicates that within a certain range, higher loads are more conducive to the release of T321 and the formation of a lubricating layer.

[0051] Example 4: Analysis of the formation mechanism of the nano-microcapsule-released lubricant and self-lubricating layer

[0052] 4.1 SEM testing of the ground surface

[0053] Figure 8 SEM morphology and EDS energy dispersive spectroscopy of selected regions of the polished surfaces of ordinary PTFE, PTFE / CNTs composites, and PTFE / microcapsule composites are shown. Figure 8As shown in (a)-10(c), PTFE has deeper surface grooves on the grinding surface, CNT-filled PTFE material has better surface quality, and PTFE / microcapsule composite material has the smoothest surface. Additionally, there is a significant amount of adhering material on the PTFE grinding surface, which should be the transfer film formed by PTFE. PTFE / CNTs material shows less adhesion to the grinding surface, while PTFE / microcapsule material shows almost none. In PTFE / CNTs material, CNTs participate in the friction process, reducing PTFE adhesion and improving the surface quality of the grinding surface. The microcapsules release T321, further reducing PTFE adhesion, and the resulting lubricating layer also has a certain polishing effect, further improving surface quality. Figure 8 As shown in (a′)-10(c′), PTFE has a higher content of F and C elements on the grinding surface, mainly due to the transfer of PTFE material to the metal surface. When CNTs and microcapsule-filled PTFE are used, the C content increases significantly, while the F content decreases significantly. This proves that CNTs decompose and deposit on the metal surface during friction, forming a lubricating layer. When nanocapsules are used, T321 can be released to the friction surface, further increasing the C content and forming a more complete lubricating layer, reducing PTFE adhesion.

[0054] 4.2 XPS Surface Composition Analysis of the Polished Surface

[0055] To further determine the properties and composition of the self-lubricating layer, XPS energy dispersive spectroscopy analysis was performed on the main elements on the grinding surfaces of several materials. The results are as follows: Figure 9 As shown in the figure. XPSPEAK 41 software was used to separate the C and O peaks, and the fitted peaks and their possible corresponding functional groups are labeled in the figure. Table 1 shows the relative atomic concentrations of each element on the wear surface. It can be seen that the peak shapes of the C and O energy spectra on the GCr15 steel surface are single, mainly representing oxygen from contaminating carbon and iron oxides. Compared with the GCr15 steel surface, the C and O energy spectra on the PTFE wear surface both show two new peak shapes. These new peaks are mainly attributed to the adhered fragments of PTFE. In Table 1, compared with the GCr15 steel surface, the relative atomic concentration of C on the PTFE wear surface increases while that of O decreases. This proves the adhesion of PTFE fragments. This adhesion mainly relies on van der Waals forces, hydrogen bonds, and electrostatic forces, and some fragments also combine with Fe atoms through chemical bonds, resulting in a decrease in the relative concentration of O.

[0056] The peak shape of carbon (C) on the PTFE / CNTs composite surface is similar to that of pure PTFE. The fitted peak 2 should primarily be attributed to carbon species in CC, CO, and C=O / CF. Table 1 shows that the PTFE / CNTs composite exhibits the highest relative atomic concentration of C during friction, demonstrating the adsorption and deposition of CNT friction products, forming a lubricating layer different from that of ordinary PTFE. During friction, the molecular structure of CNTs is disrupted; some fragments are carbonized and deposited on the grinding surface to reduce friction, while others are adsorbed onto the grinding surface, also contributing to friction reduction. While the lubricating layer formed by CNTs on the grinding surface provides some friction reduction, the lack of effective lubrication groups in CNT molecules limits the friction-reducing effect of CNTs on PTFE. However, CNTs can reduce PTFE adhesion, contributing to anti-wear properties.

[0057] Table 1. Relative atomic concentrations of major elements on the grinding surface of different materials.

[0058]

[0059] Figure 9 In (c), obvious sulfur peaks appeared on the PTFE / microcapsule composite grinding surface, at 161.2 eV and 168.3 eV respectively. These should be attributed to the sulfur types in CS and Fe-S, which fully proves the release of T321 lubricant during the friction process. Figure 9 In (a), on the PTFE / microcapsule composite grinding surface, the peak shape of C is similar to that on the PTFE / CNTs composite grinding surface, while the fitted peak attributable to CO is stronger, and the peak shape of O is more complex. This indicates that CNTs in the nanocapsules participate in the friction process, and also proves that the release of T321 from the nanocapsules affects the formation process of the CNTs lubricating layer. As shown in Table 1, among the three grinding surfaces, the PTFE / microcapsule composite grinding surface has the lowest relative atomic concentration of C, the highest relative atomic concentration of O, and the Fe element concentration is in the middle. During the friction process, the composite material releases T321. The S element in the T321 molecule is highly reactive and easily combines with iron atoms through chemical adsorption, which leads to an increase in the relative concentration of O and Fe elements and a decrease in the relative element concentration of C.

[0060] Figure 10A model of the contact area during the action of PTFE / microcapsule composite material is presented. During the friction process, the nanocapsules release T321. The friction products of T321 and CNTs work together to form a more adequate lubricating layer on the grinding surface. T321 can also enhance the chemical adsorption effect. The formed lubricating layer has three functions: ① friction reduction, which reduces the friction coefficient of PTFE; ② anti-adhesion, which reduces the adhesion of PTFE structure on the grinding surface and reduces the wear rate of PTFE; ③ polishing effect, which improves the surface quality of the grinding surface.

[0061] in conclusion

[0062] (1) CNTs@T321 nanocapsules were successfully prepared with a filling rate of about 25%. Thermogravimetric analysis showed that the nanocapsules had high thermal stability.

[0063] (2) After filling PTFE with nanocapsules, its tensile strength and hardness are reduced, but when the filling amount is within a certain range, it can still meet the mechanical performance requirements of the bearing in actual use.

[0064] (3) CNTs@T321 nanocapsules can resist the curing temperature of PTFE, and their structure is not destroyed during the curing process; the nanocapsules exist in the PTFE structure in the form of clumps of particles, which provides good protection for the T321 in them.

[0065] (4) The filling of nanocapsules can significantly reduce the friction coefficient and wear rate of PTFE. Within a certain range, the higher the filling amount, the more obvious the improvement effect on the friction coefficient. With the increase of test speed and load, the friction coefficient of PTFE / microcapsule composite material also tends to decrease, but the wear rate increases.

[0066] (5) During the friction process, the PTFE / microcapsule composite material releases T321, which is adsorbed on the grinding surface and works together with CNTs to form a lubricating layer. The surface layer of the contact area formed by the combined action of the two components plays the role of reducing friction, resisting wear and improving surface quality.

[0067] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An application of CNTs@T321 nanocapsules, wherein the CNTs@T321 nanocapsules are cured with polytetrafluoroethylene to form a polymer-based composite material with self-lubricating properties; the polymer-based composite material is used as a lubricant for bearings and bushing components during operation; The CNTs@T321 nanocapsules are obtained by filling the cavities of carbon nanotubes with a lubricant to obtain nanocapsules with an internal lubricant load; the lubricant is isobutylene sulfide (T321), and the carbon nanotubes are multi-walled carbon nanotubes.

2. According to claim 1, the CNTs@T321 nanocapsules are prepared by the following method, comprising the following steps: T321 was dissolved in a solvent, and then 20g of acid-pretreated CNTs were added. The two were thoroughly mixed and vacuumed, and then ultrasonically stirred under these conditions. After ultrasonication, the mixture was vacuum filtered and washed with solvent to remove any unfilled T321. Finally, the filter cake was dried and then pulverized by ultra-micro ball milling to obtain CNTs@T321 nanocapsules.

3. According to claim 2, the CNTs@T321 nanocapsules are prepared by the following method, comprising the following steps: dissolving 10g of T321 in 400mL of acetone, adding 20g of pretreated CNTs, mixing the two thoroughly, placing them in a spherical flask, and evacuating to -0.1MPa. Under these conditions, the mixture is ultrasonically stirred for 2h at 65℃. After ultrasonication, the mixture is vacuum filtered and washed with acetone to remove any unfilled T321. Finally, the filter cake is dried in a 75℃ oven for 12h and then pulverized by ultra-micro ball milling to obtain CNTs@T321 nanocapsules.

4. According to claim 3, the method for pretreating CNTs is as follows: 50g of CNTs are added to 1500ml of 40% concentrated nitric acid, the mixture is placed in a three-necked flask, heated under reflux at 80°C for 8 hours, and magnetic stirring is applied at a speed of 500r / min; finally, the mixture is vacuum filtered, and the resulting filter cake is dried at 85°C and then ball-milled for 10 hours to obtain acid-treated CNTs.

5. According to the use described in claim 1, the method for curing the CNTs@T321 nanocapsules with polytetrafluoroethylene is as follows: CNTs@T321 nanocapsules are added to PTFE at a mass fraction of 1%-9%, mechanically stirred until uniform, and then processed in a ball mill. The samples are then placed into a figure-eight cavity mold and a ring cavity mold respectively, pressed into figure-eight block samples and ring samples, and then placed in an oven for curing.

6. According to the application described in claim 5, the sample is prepared by cold pressing with a molding pressure of 30 MPa. After pressing, the sample is left to stand for 24 hours and then placed in an oven for curing. The maximum curing temperature is 315°C, the temperature rise rate is 10°C / h, and the sample is kept at the curing temperature for 2 hours and then allowed to cool naturally.

7. In the application according to claim 5, the amount of CNTs@T321 nanocapsules added during the curing process is 1%-6%.

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