Uhmwpe composite material with low friction and wear resistance based on cadmium phosphate modification and preparation method thereof

Abstract

The application discloses a kind of based on cadmium phosphate modified UHMWPE friction-reducing wear-resistant composite and preparation method.The composite is composed of cadmium phosphate microparticle and ultra-high molecular weight polyethylene matrix, first by chemical synthesis reaction to obtain cadmium phosphate material, then it is mechanically blended with ultra-high molecular weight polyethylene matrix powder uniformly.Heat pressing forming method is used to heat and die pressure melt after mixed powder solidification forming, after cooling demoulding, UHMWPE friction-reducing wear-resistant composite can be obtained.Cadmium phosphate particle significantly reduces the friction and wear of UHMWPE composite, since cadmium phosphate particle is an irregular sheet layer stacking structure, in the process of mould pressing, polymer matrix molecular chain enters the indentation of cadmium phosphate surface and forms interlocking structure, which is not easy to peel off in the process of friction, after entering the friction interface, it is broken into cadmium phosphate nanosheet under the action of shear force and forms lubricating protective film, which effectively weakens the damage of composite friction surface.The UHMWPE friction-reducing wear-resistant composite prepared by the application has high application value in self-lubricating bearing, guide rail, gasket material and the like.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and relates to a material for manufacturing engineering equipment, specifically to a friction-reducing and wear-resistant composite material based on cadmium phosphate modification and its preparation method. Background Technology

[0002] Polymers and polymer-based composites possess characteristics such as low density, high toughness, corrosion resistance, excellent self-lubrication, and machinability, making them particularly promising for use as friction pair materials in engineering equipment. However, compared to metallic materials, polymers exhibit inherent defects such as low strength, creep, and aging. Furthermore, under low-speed, heavy-load conditions, they suffer from severe wear and vibration due to frictional heat and shear, significantly limiting their application as friction pair components in engineering equipment and placing higher demands on material properties. Ultra-high molecular weight polyethylene (UHMWPE) possesses good self-lubricating properties, chemical inertness, and good mechanical properties; however, its high wear rate limits its application in engineering equipment, necessitating further optimization.

[0003] Patent CN114539655A discloses a method for preparing a zirconium phosphate-modified UHMWPE friction-reducing and wear-resistant composite material. First, the surface of zirconium phosphate flakes is organically coupled and modified using a silane coupling agent KH-792. Then, it is mechanically mixed uniformly with ultra-high molecular weight polyethylene powder. The mixed powder is placed in a mold, and finally, a hot-press molding method is used to heat and press the mixed powder to melt and solidify it. After cooling and demolding, the UHMWPE friction-reducing and wear-resistant composite material is obtained. This invention utilizes the excellent lubrication properties, stable two-dimensional molecular structure, high surface reactivity, and controllable aspect ratio of zirconium phosphate to graft KH-792 onto the surface of the exfoliated zirconium phosphate flakes, improving the interfacial bonding ability between the filler and the matrix, thereby improving the friction-reducing and wear-resistant properties of ultra-high molecular weight polyethylene. The prepared UHMWPE friction-reducing and wear-resistant composite material shows a significant reduction in the coefficient of friction and wear volume under dry friction conditions. While zirconium phosphate modification of UHMWPE has certain positive effects, these effects are not yet sufficient for large-scale commercial use; therefore, it is necessary to find new modifying materials.

[0004] Unlike the stable two-dimensional molecular structure of zirconium phosphate, cadmium phosphate particles have an irregular layered stacked structure. Whether this special phosphate structure has good dispersibility in UHMWPE and whether it has friction-reducing and wear-resistant effects is still unknown. There are no relevant literature reports or patented technologies in the existing technology. Therefore, exploring the effects of cadmium phosphate particles on UHMWPE is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a friction-reducing and wear-resistant composite material based on cadmium phosphate modified UHMWPE and its preparation method, so as to prepare a polymer friction pair material with excellent wear resistance, which greatly improves the tribological properties of friction pair materials for engineering equipment under harsh working conditions and extends their service life.

[0006] The UHMWPE friction-reducing and wear-resistant composite material system prepared by this invention contains 92-99 wt% UHMWPE matrix powder and 1-8 wt% cadmium phosphate reinforcing phase powder. First, a divalent soluble cadmium salt solution is added dropwise to a buffer solution. After thorough reaction and separation of the precipitate, the cadmium phosphate material is obtained and dried. This cadmium phosphate is then mechanically blended 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 UHMWPE friction-reducing and wear-resistant composite material is obtained. Because cadmium phosphate particles have an irregular, layered, stacked structure, during molding, the polymer matrix molecular chains enter the depressions on the cadmium phosphate surface to form an interlocking structure, making them less prone to peeling off during friction. Upon entering the friction interface, they are broken into cadmium phosphate nanosheets under shear force, forming a lubricating protective film. This effectively reduces damage to the friction surface of the composite material and significantly improves its friction-reducing and wear-resistant properties.

[0007] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0008] This invention provides a friction-reducing and wear-resistant UHMWPE composite material modified with cadmium phosphate, which is composed of ultra-high molecular weight polyethylene and cadmium phosphate.

[0009] The microstructure of the cadmium phosphate is irregularly stacked, sheet-like particles.

[0010] The ultra-high molecular weight polyethylene and cadmium phosphate described in this invention are both in powder form. First, a divalent soluble cadmium salt solution is added dropwise to a buffer solution. After stirring and reacting fully, the precipitate is separated and dried to obtain cadmium phosphate material. Then, the ultra-high molecular weight polyethylene powder and the fully dried cadmium phosphate powder are mechanically mixed and solidified by a hot press to form a friction-reducing and wear-resistant polymer material for engineering equipment. The corresponding components are obtained by using a mold with the required shape and structure.

[0011] This invention also provides a method for preparing a UHMWPE friction-reducing and wear-resistant composite material, comprising the following steps:

[0012] Step 1: Select ultra-high molecular weight polyethylene powder; select cadmium phosphate powder;

[0013] Step 2: Mix the ultra-high molecular weight polyethylene powder and cadmium phosphate powder obtained in Step 1 evenly to form a mixed powder;

[0014] Step 3: Place the mixed powder in the mold, use a hot press to pre-press, then solidify and shape, and finally cool and demold.

[0015] Preferably, the cadmium phosphate powder is cadmium phosphate nanomaterial powder.

[0016] This invention prepares a friction-reducing and wear-resistant composite material for engineering equipment by blending ultra-high molecular weight polyethylene powder and cadmium phosphate powder and then melting and solidifying them in a hot press. During the hot pressing process, the molecular chains of ultra-high molecular weight polyethylene enter the depressions on the surface of cadmium phosphate nanoflowers to form an interlocking structure, which effectively enhances the interfacial bonding between the filler and the polymer matrix. During the friction process, the cadmium phosphate nanoflowers located on the material surface peel off and enter the friction interface, and break into cadmium phosphate nanosheets under shear force to form a lubricating protective film.

[0017] Preferably, the specific steps in step 1 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 cadmium phosphate nanomaterial powder, and mechanically mix them using a planetary ball mill for 1 to 2 hours.

[0018] Preferably, the mixed powder is dried in a drying oven at 50-80°C before being hot-pressed in the mold.

[0019] In step 3, the pre-compression pressure is 20~30MPa; pre-compression is performed 2~5 times, each time for 3~5 minutes.

[0020] Preferably, in step 3, the temperature of the mold for curing is set to 165~185℃, and the curing time is 2~4h.

[0021] Preferably, in step 3, during curing and molding, after holding the mold at a temperature of 2-4 hours, the heating of the mold is stopped, and the mold is placed in the air to cool naturally. During the cooling process, the pressure of the hot press is gradually increased according to the decrease in the mold temperature until the applied hot pressing pressure reaches 120-150 MPa and then the pressure is held. When the mold cools naturally to room temperature, the pressure is released and the mold is demolded to obtain the UHMWPE friction-reducing and wear-resistant composite material.

[0022] Preferably, the pressure parameters applied by the hot press during the cooling process in step 3 are as follows: when the temperature drops to 108~112℃, apply a pressure of 20~30MPa and hold; when the temperature cools to 98~102℃, apply a pressure of 50~60MPa and hold; when the temperature cools to 88~92℃, apply a pressure of 80~90MPa and hold; when the temperature cools to 78~82℃, apply a pressure of 120~150MPa and hold until it cools to room temperature.

[0023] Preferably, in step 3, the cavity of the mold is designed to the shape of the required component, and the component used for engineering equipment is obtained directly after molding.

[0024] Preferably, the content of cadmium phosphate nanomaterials in the UHMWPE friction-reducing and wear-resistant composite material is 1~8 wt.%.

[0025] This invention also provides a method for preparing cadmium phosphate nanoflowers, comprising the following steps:

[0026] A divalent soluble cadmium salt solution was added dropwise to a buffer solution, and after stirring to allow the reaction to proceed fully, the precipitate was separated and dried to obtain cadmium phosphate material.

[0027] Preferably, the alkaline buffer solution is a disodium hydrogen phosphate solution with a pH greater than 7.2.

[0028] Furthermore, the molar ratio of the divalent soluble cadmium salt solution to the phosphate buffer solution is 1:0.5-2.

[0029] Furthermore, the pH of the phosphate buffer solution is 8-12.

[0030] Preferably, the divalent soluble cadmium salt solution is cadmium sulfate or cadmium chloride.

[0031] Furthermore, the stirring reaction time is 1-2 hours, and the morphology of cadmium phosphate nanoflowers is controlled by selecting the reaction time to make the nanosheets randomly stacked into spheres.

[0032] The beneficial effects of this invention are:

[0033] (1) This invention uses ultra-high molecular weight polyethylene (UHMWPE) powder as the base material, and adds cadmium phosphate to it for hot pressing to obtain a UHMWPE friction-reducing and wear-resistant polymer material sample for engineering equipment. Since cadmium phosphate particles are an irregular layered stacked structure, during the molding process, the polymer matrix molecular chains enter the depressions on the surface of cadmium phosphate to form an interlocking structure, which is not easy to peel off during friction. After entering the friction interface, it is broken into cadmium phosphate nanosheets under shear force to form a lubricating protective film, which can effectively reduce the damage to the friction surface of the composite material and significantly improve the friction-reducing and wear-resistant performance of the composite material.

[0034] (2) Under dry friction conditions, the UHMWPE composite material shows a significant change in friction reduction compared to the pure UHMWPE material. Tribological tests were conducted on the UHMWPE composite material under dry friction conditions. The coefficient of friction and wear volume of the composite material were lower than those of the pure UHMWPE material, indicating that the prepared UHMWPE composite material has better self-lubricating properties and wear resistance. Attached Figure Description

[0035] Figure 1 The image shows a scanning electron microscope image of the cadmium phosphate material prepared in Example 1 of this invention.

[0036] Figure 2This is a graph showing the relationship between the friction coefficient and friction time of the UHMWPE friction pair material for engineering equipment in this invention under dry friction conditions. The curve 0% in the graph is the friction coefficient curve of the prepared pure UHMWPE material for engineering equipment, and the curves 1%, 5%, 8%, and 10% are the friction coefficient curves of the prepared UHMWPE friction-reducing and wear-resistant composite material for engineering equipment.

[0037] Figure 3 The images show the wear volume diagrams of the UHMWPE friction-reducing and wear-resistant composite materials for engineering equipment prepared in Comparative Example 1 and Examples 1-4 of this invention under dry friction 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 dry friction conditions 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 cadmium phosphate powder: 100 wt.% of UHMWPE raw material powder was weighed and mechanically ground using a planetary ball mill for 1.5 h. The powder was then dried at 60 °C for 12 h.

[0040] Hot pressing: The dried ultra-high molecular weight polyethylene powder is loaded into the mold and pre-pressed at 20 MPa for 3 times, each time for 4 minutes. After pre-pressing, curing is performed. The mold temperature is set to 170℃, 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 25 MPa is applied and held. When the temperature has cooled to 100℃, a pressure of 55 MPa is applied and held. When the temperature has cooled to 90℃, a pressure of 85 MPa is applied and held. When the temperature has cooled to 80℃, a pressure of 130 MPa is applied and held. When the mold has cooled to room temperature, the pressure is released and the mold is demolded to obtain UHMWPE material.

[0041] Example 1:

[0042] S1. Synthesis and preparation of cadmium phosphate nanoflowers: A buffer solution of disodium hydrogen phosphate with a pH greater than 7.2 was prepared and continuously stirred at a speed of 120-200 rpm. Then, cadmium sulfate solution was added dropwise to the stirred buffer solution (the molar ratio of cadmium sulfate solution to buffer solution was 1:2). After reacting for 1.5 hours, the precipitate was separated and repeatedly washed. After drying at 80℃ for 24 hours, cadmium phosphate granular powder was obtained, which is the cadmium phosphate nanoflower. Scanning electron micrographs of the cadmium phosphate nanoflowers are shown below. Figure 1 As shown, its microstructure consists of nanosheets randomly stacked into small particles, each of which is spherical with a diameter of about 10 micrometers, and there are deep gaps between the nanosheets.

[0043] S2, ultra-high molecular weight polyethylene powder and cadmium phosphate powder, hot-pressed and cured:

[0044] Powder mixing: Weigh 1 wt.% cadmium phosphate granular powder and 99 wt.% ultra-high molecular weight polyethylene powder, and mechanically grind and mix them using a planetary ball mill for 1.5 h. Then, dry the powder at 60℃ for 12 h to obtain the mixed powder.

[0045] Hot pressing: The dried mixed powder is loaded into the mold and pre-pressed at 20MPa pressure three times, each time for 4 minutes. After pre-pressing, curing is performed. The mold temperature is set to 170℃, 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 25MPa is applied and held. When the temperature cools to 100℃, a pressure of 55MPa is applied and held. When the temperature cools to 90℃, a pressure of 85MPa is applied and held. When the temperature cools to 80℃, a pressure of 130MPa is applied and held. When the mold cools to room temperature naturally, the pressure is released and the mold is demolded to obtain UHMWPE friction-reducing and wear-resistant composite material for engineering equipment.

[0046] Example 2:

[0047] S1. Synthesis and preparation of cadmium phosphate: Same as in Example 1.

[0048] S2, ultra-high molecular weight polyethylene powder and cadmium phosphate powder, hot-pressed and cured:

[0049] Powder mixing: Weigh 5 wt.% cadmium phosphate raw material and 95 wt.% UHMWPE raw material powder, and mechanically grind and mix them using a planetary ball mill for 1.5 h. Then dry the powder at 60℃ for 12 h to obtain a mixed powder.

[0050] Hot pressing: The dried mixed powder is loaded into the mold and pre-pressed at 20MPa pressure three times, each time for 4 minutes. After pre-pressing, curing is performed. The mold temperature is set to 170℃, 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 25MPa is applied and held. When the temperature cools to 100℃, a pressure of 55MPa is applied and held. When the temperature cools to 90℃, a pressure of 85MPa is applied and held. When the temperature cools to 80℃, a pressure of 130MPa is applied and held. When the mold cools to room temperature naturally, the pressure is released and the mold is demolded to obtain UHMWPE friction-reducing and wear-resistant composite material for engineering equipment.

[0051] Example 3:

[0052] S1. Synthesis and preparation of cadmium phosphate: Same as in Example 1.

[0053] S2, ultra-high molecular weight polyethylene powder and cadmium phosphate powder, hot-pressed and cured:

[0054] Powder mixing: Weigh 8 wt.% of cadmium phosphate raw material and 92 wt.% of UHMWPE raw material powder, and mechanically grind and mix them using a planetary ball mill for 1.5 h. Then dry the powder at 60 °C for 12 h to obtain a mixed powder.

[0055] Hot pressing: The dried mixed powder is loaded into the mold and pre-pressed at 20MPa pressure three times, each time for 4 minutes. After pre-pressing, curing is performed. The mold temperature is set to 170℃, 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 25MPa is applied and held. When the temperature cools to 100℃, a pressure of 55MPa is applied and held. When the temperature cools to 90℃, a pressure of 85MPa is applied and held. When the temperature cools to 80℃, a pressure of 130MPa is applied and held. When the mold cools to room temperature naturally, the pressure is released and the mold is demolded to obtain UHMWPE friction-reducing and wear-resistant composite material for engineering equipment.

[0056] Example 4:

[0057] S1. Synthesis and preparation of cadmium phosphate: Same as in Example 1.

[0058] S2, ultra-high molecular weight polyethylene powder and cadmium phosphate powder, hot-pressed and cured:

[0059] Powder mixing: Weigh 10 wt.% of cadmium phosphate raw material and 90 wt.% of UHMWPE raw material powder, and mechanically grind and mix them using a planetary ball mill for 1.5 h. Then dry the powder at 60℃ for 12 h to obtain a mixed powder.

[0060] Hot pressing: The dried mixed powder is loaded into the mold and pre-pressed at 20MPa pressure three times, each time for 4 minutes. After pre-pressing, curing is performed. The mold temperature is set to 170℃, 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 25MPa is applied and held. When the temperature cools to 100℃, a pressure of 55MPa is applied and held. When the temperature cools to 90℃, a pressure of 85MPa is applied and held. When the temperature cools to 80℃, a pressure of 130MPa is applied and held. When the mold cools to room temperature naturally, the pressure is released and the mold is demolded to obtain UHMWPE friction-reducing and wear-resistant composite material for engineering equipment.

[0061] The tribological properties of the UHMWPE composite material samples prepared in Comparative Example 1 and Examples 1-4 were compared, and the results are shown in the figure. Figures 2-3 .

[0062] Tribological tests under dry friction conditions were conducted on a ball-disc friction and wear testing machine, with the mating parts of the kinematic pair being made of GCr15 bearing steel. φ The ball is 8 mm in diameter, with a working load of 30 N, a speed of 0.66 m / s (300 r / min), a rotation radius of 21 mm, and a working time of 30 min.

[0063] from Figure 2 It can be seen that, compared with the pure UHMWPE sample of Comparative Example 1 and the UHMWPE composite material samples of Examples 1-4, the friction coefficient of the polymer composite material is significantly reduced, with a maximum reduction of over 90%; from Figure 3 It can be seen that the wear volume of the UHMWPE composite materials in Examples 1-3 is significantly reduced compared to the pure UHMWPE sample in Comparative Example 1, with a maximum reduction of over 90%. However, the wear volume in Example 4 is actually increased, indicating that the addition of excessive cadmium phosphate powder has an adverse effect on wear resistance. The UHMWPE composite material prepared in this invention exhibits superior friction reduction and wear resistance under dry friction conditions when the content of cadmium phosphate powder is within the range of 1-8 wt.% of the total weight percentage and UHMWPE raw material powder is 92-99 wt.%.

[0064] 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 UHMWPE based tribologically improved composite material modified with cadmium phosphate, characterized in that: Consists of ultra-high molecular weight polyethylene, cadmium phosphate; The micro-morphology of the cadmium phosphate is irregular lamellar stack-shaped particles; The ultra-high molecular weight polyethylene and the cadmium phosphate are both in powder form, a divalent soluble cadmium salt solution is added dropwise into a buffer solution, after sufficient stirring and reaction, the precipitate is separated and dried to obtain a cadmium phosphate material, then the ultra-high molecular weight polyethylene powder and the fully dried cadmium phosphate powder are mechanically mixed and cured by a hot press to form a friction-reducing and wear-resistant polymer material for engineering equipment, and the buffer solution is a sodium phosphate dibasic solution with a pH greater than 7.2; The divalent soluble cadmium salt solution is cadmium sulfate or cadmium chloride; The content of the cadmium phosphate nano-material in the UHMWPE friction-reducing and wear-resistant composite material is 1-8 wt.%.

2. A method for preparing a UHMWPE based anti-friction and anti-wear composite material modified by cadmium phosphate according to claim 1, characterized in that, Comprises the following steps: Step 1, selecting an ultra-high molecular weight polyethylene powder; selecting a cadmium phosphate powder; Step 2, mixing the ultra-high molecular weight polyethylene powder and the cadmium phosphate powder selected in step 1 uniformly to form a mixed powder; Step 3, placing the mixed powder in a mold, and using a hot press to pre-press, then cure and form, and finally cool and demold.

3. The preparation method of the UHMWPE friction-reducing and wear-resistant composite material based on cadmium phosphate modification as described in claim 2, characterized in that: Before the mixed powder is hot-pressed in the mold, it is first dried in a drying oven at 50-80 DEG C.

4. The preparation method of the UHMWPE friction-reducing and wear-resistant composite material based on cadmium phosphate modification as described in claim 2, characterized in that: In step 3, the pre-pressing pressure is 20-30 MPa; the pre-pressing is performed 2-5 times, and each time for 3-5 min.

5. The preparation method of the UHMWPE friction-reducing and wear-resistant composite material based on cadmium phosphate modification as described in claim 4, characterized in that: In step 3, the mold setting temperature for curing and forming is 165-185 DEG C, and the curing time is 2-4 h.

6. The preparation method of the UHMWPE friction-reducing and wear-resistant composite material based on cadmium phosphate modification as described in claim 5, characterized in that: In step 3, after curing and forming, the mold is cooled naturally in air after 2-4 h of heat preservation, and the hot press pressure is gradually increased according to the decrease of the mold temperature during the cooling process until the hot press pressure reaches 120-150 MPa for pressure retention; when the mold is naturally cooled to room temperature, the pressure is released and demolded, and the UHMWPE friction-reducing and wear-resistant composite material is obtained.

7. The preparation method of the UHMWPE friction-reducing and wear-resistant composite material based on cadmium phosphate modification as described in claim 6, characterized in that: In the cooling process of step 3, the hot press pressure parameters are as follows: when the temperature decreases to 108-112 DEG C, the pressure is applied at 20-30 MPa for pressure retention; when the temperature cools to 98-102 DEG C, the pressure is applied at 50-60 MPa for pressure retention; when the temperature cools to 88-92 DEG C, the pressure is applied at 80-90 MPa for pressure retention; and when the temperature cools to 78-82 DEG C, the pressure is applied at 120-150 MPa for pressure retention until it cools to room temperature.

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