A polymer friction pair material for use in water-related applications and its preparation method

Abstract

This invention discloses a polymer friction pair material for use in water-related applications and its preparation method. The composite material consists of cobalt phosphate nanomaterials and an ultra-high molecular weight polyethylene (UHMWPE) matrix, wherein the mass fraction of the cobalt phosphate nanomaterials is 1–10 wt.%. First, the cobalt phosphate nanomaterials are synthesized and then mechanically blended uniformly with the UHMWPE matrix powder. The mixed powder is placed in a mold, and a hot-pressing method is used to heat and mold the powder until it melts and solidifies. After cooling and demolding, the polymer friction pair material is obtained. This invention utilizes the rough-surfaced granular cobalt phosphate to increase the interfacial bonding force with the matrix, making it less prone to peeling off during friction, thus enhancing the polymer matrix's ability to withstand frictional loads and shear forces. Furthermore, the two-dimensional lamellar cobalt phosphate enters the friction interface to form a lubricating film, significantly improving the composite material's friction-reducing and wear-resistant properties, reliability, and service life.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and relates to a material for manufacturing water-related engineering equipment, specifically a polymer friction pair material for water-related working conditions and its preparation method. Background Technology

[0002] Traditional metal friction pair materials are highly susceptible to electrochemical reactions with other media in aquatic environments, leading to severe corrosion and accelerating frictional damage to moving parts. Furthermore, they require lubrication with oil or grease during use, consuming significant amounts of mineral oil and precious metal resources. Considering resource conservation and environmental protection, the environmental pollution caused by leaks of oil / grease lubricants used in metal friction pairs is a significant concern. Therefore, self-lubricating polymers are widely used as friction pair materials to replace metals in water-lubricated bearings, guide rails, and gaskets in marine equipment, aerospace, and rail transportation. Ultra-high molecular weight polyethylene (UHMWPE) possesses excellent self-lubricating properties, chemical inertness, and good mechanical properties. Due to its non-toxicity, environmental friendliness, and extremely low water absorption, UHMWPE is considered a potential friction pair material for marine engineering equipment. However, the high wear rate of UHMWPE limits its application in water-related engineering equipment, necessitating further optimization. Recent research has revealed the significant advantages of nanomaterials in tribology; as lubricating fillers, they can significantly reduce the coefficient of friction and provide excellent anti-wear effects. Cobalt phosphate, as an inorganic nanomaterial, can simultaneously form two structures during its synthesis: rough-surfaced nanoparticles and two-dimensional nanosheets. This gives it great potential to improve the friction-reducing and wear-resistant properties of UHMWPE materials under water-related conditions. However, there are currently no research reports on its influence as a filler on the tribological properties of polymers. Summary of the Invention

[0003] The purpose of this invention is to provide a polymer friction pair material and its preparation method for use in water-related working conditions, thereby preparing a polymer friction pair material with excellent anti-wear properties, which greatly improves the tribological properties of friction pair materials for water-related engineering equipment under harsh working conditions and extends their service life.

[0004] The polymer friction pair material prepared by this invention is a UHMWPE-based system material, comprising 90-99 wt% UHMWPE matrix powder and 1-10 wt% cobalt phosphate nanomaterial reinforcing phase powder. First, a divalent soluble cobalt salt solution is added dropwise to a stirred buffer solution with a pH of 8-12. The mixture is stirred until the solution changes from purple to pink. After separating the precipitate and drying, cobalt phosphate nanomaterials are obtained. These nanomaterials are then mechanically mixed with ultra-high molecular weight polyethylene powder until homogeneous. The mixed powder is placed in a mold, and a hot-press molding method is used to heat and melt the mixed powder, followed by solidification. After cooling and demolding, the polymer friction pair material is obtained. This invention utilizes the functionality of different structures of cobalt phosphate nanomaterials. The rough-surfaced granular cobalt phosphate increases the interfacial bonding force with the matrix, making it less prone to peeling off during friction, thus enhancing the polymer matrix's ability to withstand frictional loads and shear forces. Meanwhile, the two-dimensional lamellar cobalt phosphate enters the friction interface to form a lubricating film, significantly improving the friction-reducing and wear-resistant properties of the composite material.

[0005] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0006] This invention provides a polymer friction pair material for use in water-related applications, which is composed of ultra-high molecular weight polyethylene and cobalt phosphate nanomaterials.

[0007] As a preferred technical solution, the cobalt phosphate is cobalt phosphate octahydrate nanoflower, which is a spherical structure composed of thick sheets with different growth directions, and each thick sheet is composed of multiple nanoscale thin sheets stacked together.

[0008] As a preferred technical solution, both the ultra-high molecular weight polyethylene and the cobalt phosphate nanomaterials of this invention are in powder form. As a preferred technical solution, the preparation principle of the cobalt phosphate is as follows:

[0009] A divalent soluble cobalt salt solution was added dropwise to a buffer solution with a pH of 8-12 that was being stirred. The solution was stirred until it changed from purple to pink. After separating the precipitate and drying it, cobalt phosphate nanomaterials, i.e. cobalt phosphate nanomaterial powder, were obtained.

[0010] As a preferred technical solution, the molding principle of polymer friction pair materials is as follows:

[0011] Ultra-high molecular weight polyethylene powder and fully dried cobalt phosphate nanomaterial powder are mechanically mixed and then cured and molded by hot press to form a friction-reducing and wear-resistant polymer material for water-related engineering equipment. The corresponding components are obtained by using molds of the required shape and structure.

[0012] This invention utilizes the functionality of different structures of cobalt phosphate nanomaterials. The two-dimensional layered cobalt phosphate, deposited as multilayer nanosheets, increases the interfacial bonding force with the matrix, making it less prone to peeling during friction. This enhances the polymer matrix's ability to withstand frictional loads and shear forces. Furthermore, the cobalt phosphate enters the friction interface to form a lubricating film, significantly improving the friction-reducing and wear-resistant properties of the composite material. The prepared polymer friction pair material is of great significance for improving the reliability of polymer friction pair components and extending their service life under water-related conditions.

[0013] This invention also provides a method for preparing a polymer friction pair material, comprising the following steps:

[0014] Step 1: Prepare cobalt phosphate nanomaterials;

[0015] Step 2: Select ultra-high molecular weight polyethylene powder; select cobalt phosphate nanomaterial powder;

[0016] Step 3: Mix the ultra-high molecular weight polyethylene powder and cobalt phosphate nanomaterial powder obtained in Step 2 evenly to form a mixed powder;

[0017] Step 4: Place the mixed powder in the mold, use a hot press to pre-press, then solidify and shape, and finally cool and demold.

[0018] Preferably, the preparation process of cobalt phosphate nanomaterials in step 1 is as follows:

[0019] First, a divalent soluble cobalt salt solution was added dropwise to a buffer solution with a pH of 8-12 that was being stirred. The solution was stirred until it changed from purple to pink. After separating the precipitate and drying it, cobalt phosphate nanomaterials were obtained.

[0020] Preferably, the alkaline buffer solution is a disodium hydrogen phosphate solution.

[0021] Preferably, the divalent soluble cobalt salt solution is cobalt acetate.

[0022] The cobalt phosphate nanomaterial is cobalt phosphate nanoflower octahydrate. The microstructure of the cobalt phosphate nanoflower octahydrate is a spherical structure composed of thick sheets with different growth directions. Each thick sheet is composed of multiple nanoscale thin sheets stacked together.

[0023] Preferably, the thickness of the sheet is 3-10 nanometers.

[0024] Preferably, the diameter of the spherical structure of the cobalt phosphate nanoflower octahydrate is 3-15 micrometers.

[0025] Preferably, the specific steps in step 2 are as follows: weigh a certain amount of raw materials according to the weight ratio and mix them, that is, weigh a certain amount of ultra-high molecular weight polyethylene powder and cobalt phosphate nanomaterial powder, and mechanically mix them using a planetary ball mill for 1 to 2 hours.

[0026] Preferably, the mixed powder is dried in a drying oven at 50-60°C before being hot-pressed in the mold.

[0027] Preferably, in step 3, the molding process is as follows: the dried blended powder raw material is loaded into the mold and pre-pressed using a pressure of 30-50 MPa, 2-5 times, each time for 3-5 minutes; after pre-pressing, curing is performed, the mold temperature is set to 160-180℃, the mold is heated, and when the temperature controller shows that the temperature has reached the set temperature, the temperature is maintained for 2-4 hours, and then the heating is stopped; the mold is placed in the air to cool naturally, and when the temperature controller shows 107-113℃, a pressure of 20-30 MPa is applied for holding; when the temperature has cooled to 97-103℃, a pressure of 40-50 MPa is applied for holding; when the temperature has cooled to 87-93℃, a pressure of 70-80 MPa is applied for holding; when the temperature has cooled to 77-83℃, a pressure of 120-150 MPa is applied for holding; when the mold has cooled naturally to room temperature, the pressure is released and the mold is demolded.

[0028] Preferably, both the ultra-high molecular weight polyethylene and the cobalt phosphate nanomaterial are in powder form. The two powder materials are physically blended and then melted and solidified in a hot press to prepare a polymer friction pair material for engineering equipment.

[0029] Preferably, the content of cobalt phosphate nanomaterials in the polymer friction pair material is 1-10 wt.%.

[0030] The beneficial effects of this invention are:

[0031] (1) This invention uses ultra-high molecular weight polyethylene (UHMWPE) powder as the base material, and adds cobalt phosphate nanomaterials to it for hot pressing to obtain a UHMWPE friction-reducing and wear-resistant polymer material sample for water-related engineering equipment. Based on the functionality of different structures of cobalt phosphate nanomaterials, the rough surface of the granular cobalt phosphate increases the interfacial bonding force with the UHMWPE matrix, making it less likely to be peeled off during friction, thus enhancing the ability of the UHMWPE matrix to withstand friction loads and shearing action. Meanwhile, the two-dimensional lamellar cobalt phosphate enters the friction interface to form a lubricating film, significantly improving the friction-reducing and wear-resistant performance of the composite material.

[0032] (2) Under seawater lubrication conditions, the UHMWPE composite material shows a significant change in friction reduction compared to pure UHMWPE material. Tribological tests were conducted on the UHMWPE composite material under seawater lubrication conditions. The coefficient of friction and wear rate of the composite material were lower than those of pure UHMWPE material, indicating that the prepared UHMWPE composite material has better self-lubricating and wear-resistant properties in water-related environments. Attached Figure Description

[0033] Figure 1a This is a 2000x magnified scanning electron microscope image of the cobalt phosphate nanomaterials prepared in Example 1 of this invention;

[0034] Figure 1b This is a 18,000x magnified scanning electron microscope image of the cobalt phosphate nanomaterials prepared in Example 1 of this invention;

[0035] Figure 1c This is a scanning electron microscope image of the cobalt phosphate nanomaterial prepared in Example 1 of the present invention, magnified 18,000 times from another perspective.

[0036] Figure 2 The graph shows the relationship between the friction coefficient and friction time of the UHMWPE friction pair material for water-related engineering equipment in this invention under seawater lubrication conditions. In the graph, curve Comparative Example 1 is the friction coefficient curve of the pure UHMWPE material for water-related engineering equipment, and curve Examples 1 to 3 are the friction coefficient curves of the UHMWPE friction-reducing polymer friction pair material for water-related engineering equipment.

[0037] Figure 3 This is a wear volume diagram of the UHMWPE friction-reducing polymer friction pair material for water-related engineering equipment prepared in Comparative Example 1 and Examples 1-3 of the present invention under seawater lubrication conditions. Detailed Implementation

[0038] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following detailed description, in conjunction with the accompanying drawings and application examples, provides a specific embodiment of a polymer friction pair material for water-related applications and its preparation method based on the present invention. The following comparative examples and embodiments are only used to more clearly illustrate the technical solution of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0039] Comparative Example 1: Hot-press curing of ultra-high molecular weight polyethylene powder and cobalt phosphate nanomaterial powder: 0 wt.% of cobalt phosphate nanomaterial raw material and 100 wt.% of UHMWPE raw material powder were weighed and mechanically ground and blended using a planetary ball mill for 1 hour. The powder was then dried at 50°C for 12 hours. The molding process is as follows: The dried raw material is loaded into the mold and pre-pressed at 30MPa pressure three times, each time for 3 minutes. After pre-pressing, curing is carried out. The mold temperature is set to 165℃, and heating of the mold begins. When the temperature controller shows that the set temperature has been reached, the temperature is maintained for 3 hours, and then heating is stopped. The mold is placed in the air to cool naturally. When the temperature controller shows 110℃, a pressure of 24MPa is applied and held. When the temperature cools to 100℃, a pressure of 46MPa is applied and held. When the temperature cools to 90℃, a pressure of 77MPa is applied and held. When the temperature cools to 80℃, a pressure of 126MPa is applied and held. When the mold cools to room temperature naturally, the pressure is released and the mold is demolded to obtain UHMWPE material.

[0040] Example 1:

[0041] S1. Preparation of cobalt phosphate nanomaterials: First, a disodium hydrogen phosphate buffer solution with a pH of 9 was prepared and continuously stirred at 180 rpm. Then, a cobalt acetate solution (cobalt acetate to buffer solution volume ratio of 0.5:1) was added to the stirred buffer solution in a specific ratio. Stirring continued until the solution changed from purple to pink. The precipitate was separated and repeatedly washed. After drying at 60℃ for 48 h, cobalt phosphate nanomaterials were obtained. Electron microscopy characterization was performed as follows: Figures 1a to 1c As shown.

[0042] S2. Hot pressing and curing of ultra-high molecular weight polyethylene powder and cobalt phosphate nanomaterial powder: Weigh 1 wt.% of cobalt phosphate nanomaterial raw material and 99 wt.% of UHMWPE raw material powder, and mechanically grind and blend them using a planetary ball mill for 1 hour. Then dry the powder at 50°C for 12 hours. The molding process is then carried out: the dried raw material is loaded into the mold and pre-pressed at 30MPa pressure three times, each time for 3 minutes; after pre-pressing, curing is performed, the mold temperature is set to 165℃, and heating of the mold begins. When the temperature controller shows that the set temperature has been reached, the temperature is maintained for 3 hours and then heating is stopped; the mold is placed in the air to cool naturally. When the temperature controller shows 110℃, a pressure of 24MPa is applied and held; when the temperature cools to 100℃, a pressure of 46MPa is applied and held; when the temperature cools to 90℃, a pressure of 77MPa is applied and held; when the temperature cools to 80℃, a pressure of 126MPa is applied and held; when the mold cools naturally to room temperature, the pressure is released and the mold is demolded to obtain the polymer friction pair material for water-related engineering equipment.

[0043] Example 2:

[0044] S1. For the preparation of cobalt phosphate nanomaterials, see Example 1.

[0045] S2. Hot pressing and curing of ultra-high molecular weight polyethylene powder and cobalt phosphate nanomaterial powder: Weigh 5 wt.% of cobalt phosphate nanomaterial raw material and 95 wt.% of UHMWPE raw material powder, and mechanically grind and blend them using a planetary ball mill for 1 hour. Then dry the powder at 50°C for 12 hours. The molding process is then carried out: the dried raw material is loaded into the mold and pre-pressed at 30MPa pressure three times, each time for 3 minutes; after pre-pressing, curing is performed, the mold temperature is set to 165℃, and heating of the mold begins. When the temperature controller shows that the set temperature has been reached, the temperature is maintained for 3 hours and then heating is stopped; the mold is placed in the air to cool naturally. When the temperature controller shows 110℃, a pressure of 24MPa is applied and held; when the temperature cools to 100℃, a pressure of 46MPa is applied and held; when the temperature cools to 90℃, a pressure of 77MPa is applied and held; when the temperature cools to 80℃, a pressure of 126MPa is applied and held; when the mold cools naturally to room temperature, the pressure is released and the mold is demolded to obtain the polymer friction pair material for water-related engineering equipment.

[0046] Example 3:

[0047] S1. For the preparation of cobalt phosphate nanomaterials, see Example 1.

[0048] S2. Hot pressing and curing of ultra-high molecular weight polyethylene powder and cobalt phosphate nanomaterial powder: Weigh 10 wt.% of cobalt phosphate nanomaterial raw material and 90 wt.% of UHMWPE raw material powder, and mechanically grind and blend them using a planetary ball mill for 1 hour. Then dry the powder at 50°C for 12 hours. The molding process is then carried out: the dried raw material is loaded into the mold and pre-pressed at 30MPa pressure three times, each time for 3 minutes; after pre-pressing, curing is performed, the mold temperature is set to 165℃, and heating of the mold begins. When the temperature controller shows that the set temperature has been reached, the temperature is maintained for 3 hours and then heating is stopped; the mold is placed in the air to cool naturally. When the temperature controller shows 110℃, a pressure of 24MPa is applied and held; when the temperature cools to 100℃, a pressure of 46MPa is applied and held; when the temperature cools to 90℃, a pressure of 77MPa is applied and held; when the temperature cools to 80℃, a pressure of 126MPa is applied and held; when the mold cools naturally to room temperature, the pressure is released and the mold is demolded to obtain the polymer friction pair material for water-related engineering equipment.

[0049] The tribological properties of the UHMWPE composite material samples prepared in Comparative Example 1 and Examples 1-3 were compared, and the results are shown in the figure. Figures 2-3 .

[0050] The tribological test under seawater lubrication conditions was conducted on a pin-disc friction and wear tester. The mating parts of the kinematic pair were φ8mm balls made of GCr15 bearing steel. The working load was 30N, the speed was 1.10m / s (rotational speed 500r / min), the rotation radius was 21mm, and the working time was 30min.

[0051] like Figures 2 to 3 As shown, comparing the pure UHMWPE sample of Comparative Example 1 with the UHMWPE composite material sample of Example 1, the friction coefficient of the polymer composite material is reduced, and the wear volume is also significantly reduced. The UHMWPE composite material prepared in this invention exhibits superior friction reduction and wear resistance under seawater lubrication conditions when the content of cobalt phosphate nanomaterial powder is within the range of 1-10 wt.% of the total weight percentage and 90-99 wt.% of UHMWPE raw material powder.

[0052] The above embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Although the invention has been described in detail with reference to the embodiments, those skilled in the art should understand that various combinations, modifications, or equivalent substitutions of the technical solutions of the invention do not depart from the spirit and scope of the invention and should be covered within the scope of the claims of the invention.

Claims

1. A polymeric tribological pair material for wading conditions, characterized by: Ultra-high molecular weight polyethylene, cobalt phosphate; The cobalt phosphate is a spherical structure of cobalt phosphate nanoflower with eight water molecules, which is composed of thick slices with different growth directions, and each thick slice is stacked by nanoscale multi-layer slices; The preparation method of the cobalt phosphate is: a divalent soluble cobalt salt solution is added dropwise into a buffer solution with pH of 8-12 under stirring, the solution is stirred until it changes from purple to pink, the precipitate is separated and dried to obtain the cobalt phosphate nanomaterial; The content of the cobalt phosphate nanoflower with eight water molecules in the polymer friction pair material is 1-10 wt.%; The buffer solution is a sodium phosphate solution; The divalent soluble cobalt salt solution is cobalt acetate.

2. A method of making a polymeric tribological pair material for wading conditions as claimed in claim 1, characterised in that, The method comprises the following steps: Step 1, preparation of cobalt phosphate nanomaterial; Step 2, selection of ultra-high molecular weight polyethylene powder and selection of cobalt phosphate nanomaterial powder; Step 3, mixing the ultra-high molecular weight polyethylene powder and the cobalt phosphate nanomaterial powder obtained in step 2 to form a mixed powder; Step 4, placing the mixed powder in a mold, pre-pressing with a hot press, then curing and forming, and finally cooling and demolding.

3. The method of making a polymeric tribological material for wading conditions of claim 2, wherein: Before hot pressing in the mold, the mixed powder is dried in a drying oven at 50-60℃.

4. The method of making a polymeric tribological material for wading conditions of claim 2, wherein: In step 4, the pre-pressing pressure is 30-50 MPa, and the pre-pressing is performed 2-5 times, each time for 3-5 min.

5. The method of making a polymeric tribological material for wading conditions of claim 4, wherein: In step 4, the curing and forming mold is set to a temperature of 160-180℃, and the curing time is 2-4 h.

6. The method of making a polymeric tribological pair material for a wading condition as claimed in claim 5, wherein: In step 4, after 2-4 h of heat preservation during curing and forming, the heating of the mold is stopped, and the mold is naturally cooled in air, and during the cooling process, the pressure of the hot press is gradually increased according to the decrease of the mold temperature until the hot pressing pressure is 120-150 MPa, and when the mold is naturally cooled to room temperature, the pressure is released and demolded to obtain the polymer friction pair material.

7. A method of making a polymeric tribological material for a wading condition as claimed in claim 6, characterised in that: During the cooling process in step 4, the hot press pressure parameters are: when the temperature of the temperature controller is 107-113℃, the pressure is 20-30 MPa, when the temperature is cooled to 97-103℃, the pressure is 40-50 MPa, when the temperature is cooled to 87-93℃, the pressure is 70-80 MPa, and when the temperature is cooled to 77-83℃, the pressure is 120-150 MPa until the temperature is cooled to room temperature.

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