Hierarchical pore oil-containing composite material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of modified preparation of porous oil-containing materials, and provides a hierarchical porous oil-containing composite material as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing a polymer and a corresponding polymer covalent organic framework material, and sequentially carrying out cold pressing and hot sintering to obtain the hierarchical porous polymer composite material. And placing the hierarchical porous composite material in lubricating oil, and carrying out vacuum impregnation to obtain the hierarchical porous oil-containing composite material. The hierarchical porous oil-containing composite material prepared by the preparation method provided by the invention realizes self-adaptive oil supply within a wide rotating speed range and under different centrifugal forces, can meet the characteristics of maintenance-free property, high precision, high reliability, maintenance-free property and environmental friendliness of the material, and meets the upgrading of high-end equipment towards long service life and intelligence; and meanwhile, the balance of enhanced adsorption and high oil content (20%)-high oil retention rate (gt; 90%) of the lubricating oil is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of modified preparation of porous oil-containing materials, in particular to a multi-level porous oil-containing composite material and a preparation method and application thereof. BACKGROUND

[0002] Porous oil-containing polymer lubricating material is a kind of precision driving functional material based on porous structure-polymer-lubricating medium, which has the advantages of light weight, high strength, easy synthesis, easy processing and modification, fast response speed, adjustable function, high precision, good chemical stability, and friction reduction and wear resistance. It has been widely used in mechanical parts, food processing, medical devices and aerospace high-end equipment fields. The specific working mechanism is as follows: the three-dimensional porous structure is used to store lubricating medium, and under external stimulation, the lubricating medium is continuously released to the two-phase contact surface to form a thin liquid lubricating film, realizing friction reduction and wear resistance; when the work is stopped, the surface oil is sucked back to the pores of the polymer matrix under the action of capillary force, avoiding waste and realizing long-term recycling of lubricating oil. Compared with polymer dry friction and external oil lubrication system, it has the advantages of maintenance-free, high reliability, high precision, long service life and environmental friendliness. One of the main applications of porous oil-containing polymer lubricating material is bearing retainer material, but the current commonly used single-pore-size polymer material faces the problem of compatible balance between high oil content and high oil retention. Because the porosity usually increases with the increase of pore size: (1) the polymer parts with large pore structure can achieve high oil content, but due to weak capillary force, they cannot achieve high oil retention; (2) small pore size can achieve high oil retention, but due to low porosity, it is difficult to achieve high oil content; in addition, during the operation of the rolling bearing, the oil supply is driven by centrifugal force, and the oil supply performance is highly dependent on the rotation speed, so single-pore-size can only be used for bearing lubrication under fixed rotation speed conditions (such as large pore size for lubricating oil supply at low rotation speed, and small pore size for lubricating oil supply at high rotation speed due to its ability to overcome higher capillary force threshold), which cannot realize "self-adaptive" controllable oil supply under continuous different rotation speeds. This is not conducive to the smooth and precise operation of high-end equipment and the upgrading to intelligent direction. SUMMARY

[0003] Therefore, the present application aims to provide a multi-level pore oil-containing composite material and a preparation method and application thereof. The preparation method provided by the present application not only introduces micro-nano multi-level pores due to the chemical structural similarity of the polymer matrix and the polymer covalent organic framework material, but also has excellent thermal performance and load-bearing capacity. The multi-level pore oil-containing composite material prepared has a sustained and stable release under different centrifugal forces in a wide speed range compared with a single pore size polymer, meets the characteristics of maintenance-free, high precision, high reliability, maintenance-free and environmental friendliness, improves the application potential of the material in the bearing cage field, conforms to the upgrading of high-end equipment to long service life and intelligence, and realizes enhanced adsorption of lubricating oil and balance between high oil content (20%) and high oil content retention rate (>90%).

[0004] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions: The present application provides a preparation method of a multi-level pore oil-containing composite material, comprising the following steps: Mixing a polymer and a polymer covalent organic framework material, and sequentially performing cold pressing and heat sintering to obtain a multi-level pore polymer composite material; Placing the multi-level pore composite material in lubricating oil and performing vacuum impregnation to obtain the multi-level pore oil-containing composite material; The polymer and the polymer covalent organic framework material have similar polymerization units.

[0005] Preferably, the polymer comprises polyimide, and the polymer covalent organic framework material comprises polyimide covalent organic framework material.

[0006] Preferably, the polyimide covalent organic framework material comprises one or more of pyromellitic dianhydride-tris(4-aminophenyl)amine polymer (PMDA-TAPA, PI-COF-1), pyromellitic dianhydride-1,3,5-tris(4-aminophenyl)benzene polymer (PMDA-TAPB, PI-COF-2) and pyromellitic dianhydride-5-(4-amino[1,1-biphenyl]-4-yl)[1,1:4,1:3,1:4,1-pentakisphenyl]-4,4-diamine polymer (PMDA-TABPB, PI-COF-3).

[0007] Preferably, the mass of the polymer covalent organic framework material is 0.001-10% of the mass of the polymer.

[0008] Preferably, the pressure of the cold pressing is 5-25 MPa, and the pressure holding time is 10-120 min.

[0009] Preferably, the temperature of the heat sintering is 300-380 DEG C, and the holding time is 30-120 min.

[0010] Preferably, the lubricating oil is a mechanical lubricating oil, and the mechanical lubricating oil is one or more of a PAO10 base lubricating oil, a PAO4 base lubricating oil, a dimethyl silicone oil, and an aerospace special oil. The temperature of the vacuum impregnation is 50-150 DEG C, the vacuum degree is -0.08 MPa, and the time is 0.5-72 h.

[0011] The application further provides a multi-level pore oil-containing composite material prepared by the preparation method.

[0012] Preferably, the multi-level pore polymer composite material comprises micron pores and intrinsic nanopores of a polymer covalent organic framework material obtained by cold pressing and hot sintering, the micron pores have a pore size of 0.5-10 mu m, the nanopores have a pore size of less than or equal to 500 nm, and the porosity is less than or equal to 50%, and the porosity is not 0.

[0013] The application further provides application of the multi-level pore oil-containing composite material in the field of lubrication.

[0014] The application provides a preparation method of a multi-level pore oil-containing composite material.

[0015] The preparation method of the application takes a polymer as a main precursor material for preparing a multi-level pore polymer composite material, the polymer is fused and accumulated to form micron pores in a hot sintering process, and then intrinsic nanopores of a corresponding polymer covalent organic framework material are added to endow the multi-level pore polymer composite material with micron pores and nanopores; the coexistence of the micron pores and the nanopores provides a structural basis for storage and transportation of lubricating oil; after the lubricating oil is stored, enhanced adsorption of the lubricating oil is realized, a balance between high oil content (20%) and high oil content retention rate (>90%) is achieved, and self-adaptive oil supply under different centrifugal forces in a wide rotation speed range is realized; the multi-level pore oil-containing composite material can meet the characteristics of maintenance-free, high precision, high reliability, maintenance-free and environmental friendliness, and conforms to the upgrading of high-end equipment to long service life and intelligence. Meanwhile, the polymer and the polymer covalent organic framework material have similar polymerization units and good compatibility, the influence of incompatibility on mechanical properties is avoided, and the mechanical strength of the multi-level pore polymer composite material is improved, which is essential for the use of high-end equipment mechanical parts and the realization of low wear performance. The application first introduces a porous material polymer covalent organic framework material, successfully prepares a multi-level pore oil-containing composite material, improves the current limitations of a single pore size polymer, and due to the similarity in chemical structure, not only improves the oil content but also has excellent thermal performance and load capacity, which is essential for the use of mechanical parts and the realization of low wear performance. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 are optical photos of PI-COF-1 powder (left) and YS20 powder (right); Figure 2 are pore size distribution graph (a) and nitrogen adsorption-desorption curve (b) of PI-COF-1 powder; Figure 3 are advancing and receding mercury curves (a and c) and pore size distribution graphs (b and d) of PPI and HPPI; Figure 4 are cross-section SEM photos of PPI (a), 2wt% HPPI (b), 3wt% HPPI (c) and 5wt% HPPI (d); (e) is a local magnified SEM photo of (d); Figure 5 are oil content comparisons of the materials; Figure 6 are oil retention rate comparisons of the materials in PAO4 medium under different centrifugal forces and at 3000rpm for different times; Figure 7 are oil retention rate comparisons of the materials in PAO10 medium under different centrifugal forces and at 3000rpm for different times; Figure 8 are DSC curves of the materials; Figure 9 are TGA curves of the materials; Figure 10 are hardness histogram (a), compressive strength histogram (b), compressive modulus histogram (c) and stress-strain curve (d) of the materials. DETAILED DESCRIPTION

[0017] The present application provides a preparation method of a multi-level pore oil-containing composite material, comprising the following steps: mixing a polymer and a polymer covalent organic framework material, and sequentially performing cold pressing and thermal sintering to obtain a multi-level pore polymer composite material; immersing the multi-level pore composite material in lubricating oil to obtain the multi-level pore oil-containing composite material through vacuum immersion; The polymer and the polymer covalent organic framework material have similar polymerization units.

[0018] Unless otherwise specified, the raw materials used in the present application are preferably commercially available products.

[0019] The present application mixes a polymer and a polymer covalent organic framework material, and sequentially performs cold pressing and thermal sintering to obtain a multi-level pore polymer composite material.

[0020] In the present application, the polymer preferably comprises polyimide (PI). In a specific embodiment of the present application, the polyimide is YS20. In the present application, the polymer is preferably used in the form of a polymer powder. In the present application, the polymer is preferably pretreated before use, and the pretreatment preferably comprises the following step: sieving the polymer to remove large particles to obtain a uniform powder.

[0021] In the present application, the polymer covalent organic framework material preferably comprises polyimide covalent organic framework material (PI-COF). In the present application, the PI-COF is a kind of crystalline organic polymer network with regular channels and abundant functional groups, high modulus and excellent thermal stability. This provides a structural basis for subsequent hierarchical porous oil-containing composites with excellent mechanical properties and oil-containing properties. In the present application, the polyimide covalent organic framework material (PI-COF) preferably comprises one or more of pyromellitic dianhydride-tris(4-aminophenyl)amine polymer (PMDA-TAPA, PI-COF-1), pyromellitic dianhydride-1,3,5-tris(4-aminophenyl)benzene polymer (PMDA-TAPB, PI-COF-2) and pyromellitic dianhydride-5-(4-amino[1,1-biphenyl]-4-yl)[1,1:4,1:3,1:4,1-pentakisphenyl]-4,4-diamine polymer (PMDA-TABPB, PI-COF-3), and further preferably PI-COF-1. In a specific embodiment of the present application, the synthesis steps of the PI-COF-1 preferably refer to Designed synthesis of large-pore crystalline polyimide covalent organic frameworks. Nature Communication, 2014, 5, 4503. In the present application, the polymer covalent organic framework material is preferably used in the form of a polymer covalent organic framework material powder.

[0022] In the present application, the mass of the polymer covalent organic framework material is preferably 0.001-10% of the mass of the polymer, further preferably 1-5%, and specifically preferably 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10%.

[0023] In the present application, the mixing is preferably physical blending, and the present application does not specifically limit the operation of the physical blending as long as the polymer and the polymer covalent organic framework material can be fully mixed.

[0024] In the present application, the polymer covalent organic framework material (COF) is a crystalline microporous organic polymer network formed by connecting organic monomers through reversible covalent bonds, which exhibits strong controllability of structure, high specific surface area, long-range order, uniform pore size and narrow distribution range, and the pore size and specific surface area can be precisely controlled by adjusting the spatial structure and size of the monomer. Due to the regular pores and easy-to-process design of COF, and the similar chemical structure to the polymer bulk, it is very advantageous for designing and preparing new multi-level porous composite materials.

[0025] In the present application, the pressure of the cold pressing is preferably 5-25 MPa, further preferably 8-15 MPa, and specifically preferably 5 MPa, 10 MPa, 15 MPa, 20 MPa or 25 MPa; the holding time is preferably 10-120 min, further preferably 30-90 min, and specifically preferably 10 min, 20 min, 30 min, 60 min, 90 min or 120 min.

[0026] In the present application, the temperature of the hot sintering is preferably 300-380℃, further preferably 320-370℃, and specifically preferably 300℃, 320℃, 340℃, 350℃, 360℃ or 380℃; the holding time is preferably 30-120 min, and more preferably 50-90 min, and specifically preferably 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min or 120 min. In the present application, the atmosphere of the hot sintering is preferably air.

[0027] After the hot sintering, the present application preferably further comprises sequentially cutting, washing and drying the obtained hot sintering product. The present application does not specifically limit the cutting method, and in a specific embodiment of the present application, the hot sintering product is cut into samples with a size of 10 mm x 10 mm x 2 mm. In the present application, the reagent used for washing is preferably water, and the washing is preferably carried out under ultrasonic conditions, and the present application does not have special requirements for the specific implementation process of the ultrasonic. In the present application, the drying is preferably vacuum drying; the present application does not specifically limit the parameters of the vacuum drying, as long as the reagent used for washing can be completely removed.

[0028] After obtaining the multi-level porous polymer composite material, the present application places the multi-level porous composite material in lubricating oil, and performs vacuum impregnation to obtain the multi-level porous oil-containing composite material.

[0029] In the present application, the lubricating oil is preferably a mechanical lubricating oil, which is preferably one or more of a PAO10 base lubricating oil, a PAO4 base lubricating oil, a dimethyl silicone oil and an aerospace special oil; in a specific embodiment of the present application, the mechanical lubricating oil is particularly preferably a PAO10 base lubricating oil or a PAO4 base lubricating oil.

[0030] In the present application, the temperature of the vacuum impregnation is preferably 50-150℃, further preferably 80-120℃, and particularly preferably 60℃, 70℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃; the vacuum degree is -0.08MPa, and the time is preferably 0.5-72h, further preferably 12-36h, and particularly preferably 0.5h, 1h, 6h, 12h, 15h, 18h, 21h, 24h, 30h, 36h, 42h, 48h, 54h, 60h, 66h or 72h.

[0031] The present application also provides a multi-level porous oil-containing composite material prepared by the preparation method described in the above technical solution, which comprises a multi-level porous polymer composite material and a lubricating oil loaded in the pores of the multi-level porous polymer composite material.

[0032] In the present application, the multi-level porous polymer composite material comprises micropores and nanopores; the pore size of the micropores is preferably 0.5-10μm, and further preferably 1-4μm; the pore size of the nanopores is less than or equal to 500nm, and further preferably 1-50nm; and the porosity is less than or equal to 50%, and the porosity is not 0, and further preferably 18-30%.

[0033] The multi-level porous oil-containing composite material prepared by the preparation method provided by the present application comprises a multi-level porous polymer composite material, which is a through micro-nano multi-level porous polymer composite material, and provides a structural basis for the storage and transport of lubricating oil. Moreover, taking polyimide as the polymer and PI-COF as the polymer covalent organic framework material, the two materials have similar imide rings and excellent intrinsic thermal and mechanical properties, so that the multi-level porous polymer composite material has excellent thermal and mechanical properties, effectively avoids the problem of reduced mechanical strength of the material, and ensures the use of the material in harsh working conditions; and after storing the lubricating medium, the multi-level porous oil-containing composite material realizes enhanced adsorption of the lubricating oil, a balance between high oil content (20%) and high oil content retention rate (>90%), and "self-adaptive oil supply" under different centrifugal forces in a wide speed range, and can meet the characteristics of maintenance-free, high precision, high reliability, maintenance-free and environmental friendliness, and meet the upgrading of high-end equipment to long service life and intelligence.

[0034] The present application also provides the application of the multi-level porous oil-containing composite material described in the above technical solution in the field of lubrication.

[0035] The application mode of the multi-level porous oil-containing composite material is not specifically limited in the present application, and a person skilled in the art can set it according to actual needs.

[0036] The multi-level porous oil-containing composite material, the preparation method and the application thereof provided by the present application will be described in detail below in combination with examples, but they should not be understood as limiting the protection scope of the present application.

[0037] Example 1 The polyimide powder (model YS20) was sieved to remove large particles to obtain uniform powder, and the sieved polyimide powder was weighed.

[0038] PI-COF-1 was prepared according to the reference Designed synthesis of large-pore crystalline polyimide covalent organic frameworks. Nature Communication, 2014, 5, 4503, and PI-COF-1 was ground to obtain PI-COF-1 powder.

[0039] The YS20 powder and the PI-COF-1 powder were as shown in Figure 1 .

[0040] The pore structure and specific surface area of the PI-COF-1 powder were characterized by BET method, and the results were as shown in Figure 2 . From Figure 2 , it can be seen that the specific surface area of the PI-COF-1 powder was 978.55 m 2 / g, and the nanopore size was concentrated in 2-4 nm.

[0041] The polyimide powder and the PI-COF-1 powder were physically blended in different proportions to obtain a mixed powder; for the mixed powder, the sample obtained by different content of PI-COF-1 powder was named Xwt%HPPI, wherein X represented the mass percentage of PI-COF-1 powder relative to the YS20 powder; for example, when the mass of PI-COF-1 was 2% of the mass of YS20 powder, the mixed powder was recorded as 2wt%HPPI. The mass of PI-COF-1 powder was 2wt%, 3wt% and 5wt% of the mass of YS20 powder, respectively.

[0042] The mixed powder is sequentially subjected to cold pressing and hot sintering, the pressure of cold pressing is 12 MPa, the pressure maintaining time is 60 min; the temperature of hot sintering is 350 DEG C, the heat preservation time is 80 min; the atmosphere of hot sintering is air; the hot sintering product is obtained after demoulding after cooling to room temperature, the hot sintering product is cut, the size of the cut sample is 10 mm x 10 mm x 2 mm, and the cut sample is sequentially subjected to water washing and drying to obtain the hierarchical porous polyimide composite for standby, which are named as 2wt%HPPI, 3wt%HPPI and 5wt%HPPI respectively.

[0043] As shown in a and b of FIG. 1, the mercury injection test results show that the micropore diameters of 2wt%HPPI and 5wt%HPPI are about 2.5 μm. Figure 3 As shown in the cross-sectional morphology of b~e of FIG. 1, the through micropores formed by powder particle accumulation are observed, and such pores provide good storage areas and transport channels for lubricating oil. Figure 4 As shown in the cross-sectional morphology of b~e of FIG. 1, the through micropores formed by powder particle accumulation are observed, and such pores provide good storage areas and transport channels for lubricating oil.

[0044] The hierarchical porous polyimide composite is immersed in PAO4 lubricating oil, the immersion temperature is 100 DEG C, the vacuum degree is -0.08 MPa, and the immersion time is 24 h, to obtain the hierarchical porous oil-containing composite.

[0045] The oil-containing performance of the hierarchical porous oil-containing composite is tested, as shown in a of FIG. 2, the oil-containing 2wt%HPPI, 3wt%HPPI and 5wt%HPPI provided by the application have almost the same oil content under the same preparation conditions, and the oil content is 20%, which has excellent oil storage performance. Figure 5 The oil-containing 2wt%HPPI, 3wt%HPPI and 5wt%HPPI provided by the application have almost the same oil content under the same preparation conditions, and the oil content is 20%, which has excellent oil storage performance. Figure 6The results show that the oil retention rate of 2wt% HPPI, 3wt% HPPI and 5wt% HPPI containing oil gradually increases with the gradual increase of the addition amount of PI-COF-1 within a certain time range (0-60 min) under different centrifugal force conditions (1000 rpm, 2000 rpm, 3000 rpm), showing a synergistic effect of "micropore dominance at low speed and nanometer pore reinforcement at high speed". The oil retention rate of HPPI remains at a high level at 1000-3000 rpm, because the capillary force adsorption of micropore diameter is sufficient to resist external centrifugal force. With the increase of speed, the advantage of HPPI gradually emerges due to the existence of more abundant pores and nanometer pores. The oil retention rate of 5wt% HPPI containing oil is still 94.17% after centrifugation at 3000 rpm for 60 min. The existing porous polyimide retainer prepared by YS20 can spin out the lubricating oil at a speed of 3000 rpm, and when the speed of the bearing is further increased, the oil ejection rate is too fast, which leads to the lubricating oil being spun out from the retainer in a short time, reducing the oil supply life of the bearing retainer, and being not suitable for high-speed bearings.

[0046] Example 2 The polyimide powder (model YS20) was sieved to remove large particles to obtain uniform powder, and the sieved polyimide powder was weighed.

[0047] PI-COF-1 (same as in Example 1) was ground to obtain PI-COF-1 powder.

[0048] The polyimide powder and 5wt% PI-COF-1 powder based on the mass of the polyimide powder were physically blended to obtain a mixed powder; the mixed powder was sequentially cold-pressed and hot-sintered, and the cold-pressing pressure was reduced to 10 MPa, and the pressure holding time was 60 min; thereby the micropore diameter was regulated, the hot-sintering temperature was 350℃, the holding time was 80 min, and the atmosphere was air; after hot-sintering, the temperature was lowered to room temperature, and the hot-sintered product was demolded; the hot-sintered product was cut, and the size of the cut product was 10 mm x 10 mm x 2 mm; the cut sample was sequentially washed with water and dried to obtain a hierarchical porous polyimide composite material, which was named as 5wt% HPPI-2.

[0049] As shown in Figure 3 The results of mercury injection testing show that the micropore diameter of 5wt% HPPI-2 is 1.63 μm, and the porosity is 18.78%.

[0050] The hierarchical porous polyimide composite material was immersed in PAO4 lubricating oil, the immersion temperature was 100℃, the vacuum degree was -0.08 MPa, and the immersion time was 24 h to obtain a hierarchical porous oil-containing composite material.

[0051] The oil content of the oil-containing 5wt% HPPI-2 provided by the embodiment is 16%, as indicated by b in Figure 5 Further oil supply tests of the oil-containing 5wt% HPPI-2 under different centrifugal forces are performed, as indicated by c and d in Figure 6 The oil retention performance of the oil-containing 5wt% HPPI-2 under different centrifugal force conditions (1000 rpm, 2000 rpm, 3000 rpm) and within a certain time range (0-60 min) is more excellent. The synergistic effect of “low-speed micropore dominance and high-speed nanopore reinforcement” is derived. At 1000-3000 rpm, the oil retention of the HPPI remains at a high level, because the capillary force adsorption of the micropore diameter is sufficient to resist the external centrifugal force. With the increase of the rotation speed, the advantage of the HPPI gradually highlights due to the existence of more abundant pores and nanopores. After centrifugation at 3000 rpm for 60 min, the oil retention of the oil-containing 5wt% HPPI-2 is still as high as 97.68%. With the same PI-COF-1 doping amount, because the micropore size of the 5wt% HPPI-2 is smaller than that of the 5wt% HPPI (1.63 μm vs 2.5 μm), the oil retention of the 5wt% HPPI-2 is higher after centrifugation under the same conditions.

[0052] Example 3 The multi-level porous polyimide composite 2wt% HPPI, 3wt% HPPI and 5wt% HPPI obtained in Example 1 are immersed in PAO10 lubricating oil, the immersion temperature is 100°C, the vacuum degree is-0.08MPa, and the immersion time is 24h, to obtain the multi-level porous oil-containing composite.

[0053] The oil content is tested, Figure 5 As indicated by a in the table, the oil content of the oil-containing HPPI provided by the application is almost the same as that of PAO4 under the same preparation conditions, both being 20%, and the oil storage performance is excellent. Further oil supply tests of the oil-containing 2wt% HPPI, 3wt% HPPI and 5wt% HPPI under different centrifugal forces are performed, as indicated by a and b in Figure 7 The results show that the oil retention of the oil-containing 2wt% HPPI, 3wt% HPPI and 5wt% HPPI gradually increases with the gradual increase of the PI-COF-1 addition amount under different centrifugal force conditions (1000 rpm, 2000 rpm, 3000 rpm) and within a certain time range (0-60 min). At 1000-3000 rpm, the oil retention of the oil-containing 2wt% HPPI, 3wt% HPPI and 5wt% HPPI remains at a high level. After centrifugation at 3000 rpm for 60 min, the oil retention of the oil-containing 5wt% HPPI is still 94.13%.

[0054] Example 4 The 5wt% HPPI-2 polyimide composite obtained in Example 2 was impregnated in PAO10 lubricating oil, the impregnation temperature was 100℃, the vacuum degree was -0.08 MPa, and the impregnation time was 24 h, to obtain the oil-containing composite material with hierarchical pores.

[0055] The oil-containing performance was tested, as shown in a and b of Figure 5 The oil content of the oil-containing 5wt% HPPI-2 provided by the embodiment was 16%, as shown in b of Figure 7 The oil retention performance of the oil-containing 5wt% HPPI-2 under different centrifugal forces (1000 rpm, 2000 rpm, 3000 rpm) within a certain time range (0-60 min) was more excellent, as shown in c and d of The synergistic effect of "low-speed micron pore dominance and high-speed nanopore reinforcement" was derived. At 1000-3000 rpm, the oil retention rate of the oil-containing 5wt% HPPI-2 remained at a high level, because the capillary force adsorption of the micron pore size was sufficient to resist the external centrifugal force. With the increase of the rotation speed, the advantages of HPPI gradually emerged due to the existence of more abundant pores and nanopores. The oil retention rate of the oil-containing 5wt% HPPI-2 was still as high as 97.28% after centrifugation at 3000 rpm for 60 min. With the same PI-COF-1 doping amount, because the micropore size of 5wt% HPPI-2 was smaller than that of 5wt% HPPI (2.5 vs 1.63 μm), the oil retention rate of 5wt% HPPI-2 was higher after centrifugation under the same conditions.

[0056] Comparative Example 1 Only polyimide (YS20) powder was weighed, and cold pressing and hot sintering were performed under the same preparation conditions as in Example 1 to obtain a porous polyimide (PPI) material.

[0057] As shown in a and b of Figure 3 and a of Figure 4 The pore structure and cross-sectional SEM image of PPI confirmed the through single pores, the micron pore size was about 3.2 μm, and the porosity was 25.45%, which provided a good storage area and transport channel for the lubricating oil.

[0058] The porous polyimide (PPI) material was impregnated in PAO4 lubricating oil, the impregnation temperature was 100℃, the vacuum degree was -0.08 MPa, and the impregnation time was 24 h, to obtain the oil-containing composite material.

[0059] The oil-containing performance was tested, as shown in a and b of Figure 5As shown in Figure a, the oil-containing PPI in this comparative example has an oil content almost identical to that of the HPPI composite material under the same preparation conditions, both being 20%, exhibiting excellent oil retention properties. Further oil supply tests were conducted on the oil-containing PPI under different centrifugal forces, such as... Figure 6 As shown in figures a and b, the oil retention rate of oil-containing PPI remains high at 2000 rpm and below, because the capillary adsorption of the micron-sized pores is sufficient to resist external centrifugal force. With increasing rotational speed, the oil retention rate of oil-containing PPI decreases significantly within a certain time range (0–60 min) at 3000 rpm. After centrifugation at 3000 rpm for 60 min, the oil retention rate of oil-containing PPI drops to 75.8%, indicating that lubricating oil is ejected from the sample in a short time, reducing the material's oil supply life.

[0060] Comparative Example 2 Only the polyimide (YS20) powder was weighed and cold-pressed and hot-sintered under the same preparation conditions as in Example 2 to obtain porous polyimide (PPI-2) material.

[0061] like Figure 3 As shown in c and d, the micron pore size of PPI-2 is approximately 2.5 μm, and the porosity is 20.61%.

[0062] PPI-2 was impregnated in PAO4 lubricating oil at a temperature of 100℃, a vacuum of -0.08MPa, and an impregnation time of 24h to obtain oil-containing PPI-2.

[0063] The oil-bearing properties were tested. Figure 5 As shown in b, the oil-containing PPI-2 provided in this comparative example has an oil content almost identical to that of the 5wt% oil-containing HPPI-2 under the same preparation conditions, both being 16%. Further oil supply tests were conducted on the oil-containing PPI-2 under different centrifugal forces, such as... Figure 6 As shown in figures c and d, the oil retention rate of oil-containing PPI-2 remains high at 2000 rpm and below, because the capillary adsorption of the micron-sized pores is sufficient to resist external centrifugal force. With increasing rotational speed, the oil retention rate of oil-containing PPI decreases significantly within a certain time range (0–60 min) at 3000 rpm. After centrifugation at 3000 rpm for 60 min, the oil retention rate of oil-containing PPI-2 drops to 82.48%, indicating that the lubricating oil is ejected from the sample in a short time, reducing the material's oil supply life. It is noteworthy that the HPPI composite oil-containing material, with the same micron-sized pores (2.5 μm) as PPI-2, not only exhibits excellent high oil content (20% vs 16%), but also shows significantly higher oil retention rate after different centrifugation speeds and prolonged centrifugation, achieving a balance between high oil content and high oil retention rate.

[0064] Comparative Example 3 The PPI of Comparative Example 1 was impregnated in PAO10 lubricating oil, the impregnation temperature was 100℃, the vacuum degree was -0.08 MPa, and the impregnation time was 24 h to obtain the oil-containing PPI.

[0065] The oil-containing property was tested, as shown in a of Figure 5 The oil-containing PPI provided by the present comparative example has almost the same oil content as the 5wt% HPPI-2 composite material under the same preparation conditions, both of which are 16%. Further oil supply test of the oil-containing PPI-2 under different centrifugal forces was carried out, as shown in c and d of Figure 7 The oil-containing PPI provided by the present comparative example has almost the same oil content as the 5wt% HPPI-2 composite material under the same preparation conditions, both of which are 16%. Further oil supply test of the oil-containing PPI-2 under different centrifugal forces was carried out, as shown in c and d of

[0066] Comparative Example 4 The PPI-2 of Comparative Example 2 was impregnated in PAO10 lubricating oil, the impregnation temperature was 100℃, the vacuum degree was -0.08 MPa, and the impregnation time was 24 h to obtain the oil-containing PPI-2.

[0067] The oil-containing property was tested, as shown in b of Figure 5 The oil-containing PPI provided by the present comparative example has almost the same oil content as the 5wt% HPPI-2 composite material under the same preparation conditions, both of which are 16%. Further oil supply test of the oil-containing PPI-2 under different centrifugal forces was carried out, as shown in c and d of Figure 7 The oil-containing PPI provided by the present comparative example has almost the same oil content as the 5wt% HPPI-2 composite material under the same preparation conditions, both of which are 16%. Further oil supply test of the oil-containing PPI-2 under different centrifugal forces was carried out, as shown in c and d of

[0068] Test Example 1 The HPPI composite material in Example 1 and the PPI material in Comparative Example 1 were subjected to thermal performance test. The DSC results are shown in Figure 8 , and the TGA results are shown in Figure 9As shown, the results show that with the increase of the doping amount of PI-COF-1, the glass transition temperature of HPPI shifts to 270℃ in the high temperature direction. Further combined with the TGA curve, the temperature of 5wt% thermal weight loss of PPI and HPPI with different doping amounts of PI-COF-1 is higher than 566℃, indicating that even if the doping amount of PI-COF-1 in HPPI reaches 5wt%, it still has excellent heat resistance, which lays a foundation for the application of the composite material in high temperature environment.

[0069] Test Example 2 The mechanical properties of the HPPI composite material in Example 1 and the PPI material in Comparative Example 1 were tested, and the results are shown in Table 2. Figure 10 , Figure 10 As shown, with the PI-COF-1 addition amount increasing from 0 to 5wt%, the Shore D hardness value increases from 78.8 to 80.96, the compressive strength increases from 96.68MPa to 104.31MPa, and the compressive modulus also increases from 364.40MPa to 408.77MPa. Excellent load-carrying capacity is essential for the use of mechanical parts and the realization of low wear performance.

[0070] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a multi-level porous oil-containing composite material, characterized in that, Includes the following steps: A multi-level porous polymer composite material is obtained by mixing a polymer and a polymer covalent organic framework material, followed by cold pressing and hot sintering. The multi-level porous composite material is placed in lubricating oil and then vacuum impregnated to obtain the multi-level porous oil-containing composite material. The polymers and polymer covalent organic framework materials have similar polymeric units.

2. The preparation method according to claim 1, characterized in that, The polymer includes polyimide, and the polymer covalent organic framework material includes polyimide covalent organic framework material.

3. The preparation method according to claim 2, characterized in that, The polyimide covalent organic framework material includes one or more of the following: pyromellitic dianhydride-tris(4-aminophenyl)amine polymer, pyromellitic dianhydride-1,3,5-tris(4-aminophenyl)benzene polymer, and pyromellitic dianhydride-5-(4-amino[1,1-biphenyl]-4-yl)[1,1:4,1:3,1:4,1-pentaphenyl]-4,4-diamine polymer.

4. The preparation method according to claim 1, 2, or 3, characterized in that, The mass of the polymer covalent organic framework material is 0.001 to 10% of the mass of the polymer.

5. The preparation method according to claim 1, characterized in that, The pressure of the cold press is 5~25MPa, and the holding time is 10~120min.

6. The preparation method according to claim 1, characterized in that, The hot sintering temperature is 300~380℃, and the holding time is 30~120min.

7. The preparation method according to claim 1, characterized in that, The lubricating oil is a mechanical lubricating oil, which is one or more of PAO10 base lubricating oil, PAO4 base lubricating oil, dimethyl silicone oil, and aerospace-grade oil. The vacuum impregnation temperature is 50~150℃, the vacuum degree is -0.08MPa, and the time is 0.5~72h.

8. The multi-level porous oil-containing composite material prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The multi-level porous oil-containing composite material includes a multi-level porous polymer composite material and lubricating oil loaded in the pores of the multi-level porous polymer composite material.

9. The multi-level porous oil-containing composite material according to claim 8, characterized in that, The multi-level porous polymer composite material includes micropores obtained by cold pressing and hot sintering and intrinsic nanopores of polymer covalent organic framework material; the pore size of the micropores is 0.5~10μm, the pore size of the nanopores is less than or equal to 500nm, the porosity is less than or equal to 50%, and the porosity is not 0.

10. The application of the multi-level porous oil-containing composite material according to any one of claims 8 to 9 in the field of lubrication.

Images