A hydrogel microparticle-reinforced polyurethane composite material, its preparation method and application

Abstract

This invention discloses a hydrogel microparticle-reinforced polyurethane composite material, which is prepared by heating, extruding, granulating, and melt injection molding of multi-crosslinked hydrogel microparticles and polyurethane matrix granules. The mass percentage ratio of the multi-crosslinked hydrogel microparticles and polyurethane matrix granules is 5-15 wt% and 85-95 wt%, respectively. The preparation method of the multi-crosslinked hydrogel microparticles includes the following steps: dispersing carboxylated cellulose nanofibers in an aqueous solution to obtain a cellulose nanofiber suspension; adding polyvinyl alcohol powder and boric acid powder to the obtained suspension in sequence, heating and stirring until completely dissolved to obtain a homogeneous sol; pouring the obtained sol into a polytetrafluoroethylene mold, and achieving sol-gel conversion through multiple freeze-thaw cycles to obtain hydrogel A; immersing the obtained hydrogel A in an aqueous solution of FeCl3 to obtain ionically crosslinked hydrogel B; and washing, annealing, and naturally cooling and crushing the obtained hydrogel B to obtain multi-crosslinked hydrogel microparticles.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to polyurethane composite materials, their preparation methods, and applications. Background Technology

[0002] Currently, thermoplastic polyurethane is widely used in water-lubricated bearing-stern shaft systems of various ships and underwater vehicles due to its ease of processing, excellent mechanical strength and physicochemical stability, and inherent damping properties. However, the weak hydrophilicity of polyurethane combined with the low viscosity of water makes it difficult to maintain continuous and stable water lubrication at the friction interface. Under operating conditions such as low speed, start-stop, reversing, and navigation in harsh sea conditions, the lubrication state of the water-lubricated bearing friction interface can easily deteriorate into boundary lubrication or dry friction, leading to abnormal wear and surface damage, and even causing severe vibration and noise. These phenomena seriously affect the reliability, operational stability, and stealth of underwater equipment. Therefore, improving the tribological properties of water-lubricated bearings and reducing frictional vibration and noise is of great significance for improving the service performance of various ships and underwater vehicles.

[0003] Stick-slip behavior is one of the main sources of friction-induced vibration and noise, and it is closely related to frictional excitation force and material damping. Therefore, the most common methods to solve this problem are to reduce frictional excitation force and enhance the damping capacity of friction materials. Among the many methods to reduce frictional excitation force, adding two-dimensional layered nanoparticles with self-lubricating properties to improve the lubrication performance of polyurethane composites is the most common and effective; however, it may reduce the mechanical and damping properties of the material, thereby reducing its service life. In addition, traditional strategies to improve the damping performance of polymer materials include enhancing the internal friction of polymer chains or introducing additional damping mechanisms by adding damping additives; however, both of these methods often impair their tribological properties, limiting their widespread application.

[0004] In view of the current state of technology and the development needs of water-lubricated bearing materials, there is an urgent need to develop a polyurethane-based bearing composite material with low friction and high damping dissipation properties. Summary of the Invention

[0005] To address the problem of frictional vibration and noise induced by insufficient lubrication and damping performance of polyurethane-based water-lubricated bearing materials, this invention provides a hydrogel microparticle-reinforced polyurethane composite material for water-lubricated bearings. This material can reduce the frictional excitation force during friction, convert the induced vibration energy into heat energy, and ultimately dissipate the vibration and noise induced by the friction of polyurethane water-lubricated bearings through the water lubrication medium.

[0006] To achieve the above objectives, the following technical solution is adopted: A hydrogel microparticle-reinforced polyurethane composite material is prepared by heating, extruding, granulating, and melt injection molding of multi-crosslinked hydrogel microparticles and polyurethane matrix granules; the mass percentages of the multi-crosslinked hydrogel microparticles and polyurethane matrix granules are 5~15wt% and 85~95wt%, respectively.

[0007] According to the above scheme, the Shore hardness of the polyurethane matrix granules is 90~95A and the particle size is 1~2 mm.

[0008] According to the above scheme, the preparation method of the multi-crosslinked hydrogel microparticles includes the following steps: (1) A cellulose nanofiber suspension was obtained by dispersing carboxylated cellulose nanofibers in an aqueous solution; (2) Polyvinyl alcohol powder and boric acid powder were added to the obtained suspension in sequence, and the mixture was heated and stirred until completely dissolved to obtain a homogeneous sol solution. (3) The obtained sol solution is poured into a polytetrafluoroethylene mold, and the sol-gel conversion is achieved through multiple freeze-thaw cycles to obtain hydrogel A; (4) The obtained hydrogel A was immersed in an aqueous solution of FeCl3 to obtain ion-crosslinked hydrogel B; (5) The obtained hydrogel B was washed, annealed and naturally cooled and crushed to obtain multi-crosslinked hydrogel microparticles.

[0009] According to the above scheme, the raw materials used are as follows by weight: 0.1~0.9 parts of carboxylated cellulose nanofibers; 12~15 parts of polyvinyl alcohol powder; 0.5~1.5 parts of boric acid powder; and 100 parts of water.

[0010] According to the above scheme, the average diameter of the carboxylated cellulose nanofibers is 10~20 nm and the length is 1~2 mm; the viscosity of the polyvinyl alcohol is 54.0~66.0 mPa.s and the degree of alcoholysis is 98.0~99.0 mol.

[0011] According to the above scheme, the heating temperature in step 2 is 80~95℃, and the heating and stirring time is 4~6h.

[0012] According to the above scheme, in step 3, the freezing temperature of the freeze-thaw cycle is -40~-20℃, and the time is 6~8h; the thawing temperature is 20~25℃, and the time is 3~5h; the number of repetitions is 2~6 times, optimized to 5 times.

[0013] According to the above scheme, the concentration of FeCl3 aqueous solution in step 4 is 0.2~0.25 M, and the immersion time is 24~48 h.

[0014] According to the above scheme, the annealing temperature in step 5 is 100~120℃ and the time is 1~2h.

[0015] The preparation method of the above-mentioned hydrogel microparticle-reinforced polyurethane composite material includes the following steps: Multi-crosslinked hydrogel microparticles are premixed with polyurethane matrix granules and then fed into the screw cavity of a twin-screw extruder. After heating and melting, extrusion and granulation, the mixture is then melt-injected through an injection molding machine to obtain a multi-crosslinked hydrogel microparticle-reinforced polyurethane composite material.

[0016] According to the above scheme, the heating temperature of the twin-screw extruder is 180~200℃ and the rotation speed is 80~100 r / min; the pressure of the injection molding machine is 10~15MPa and the temperature is 190~200℃.

[0017] This invention also provides the application of the above-mentioned hydrogel microparticle-reinforced polyurethane composite material as a water-lubricated bearing material.

[0018] The multi-crosslinked hydrogel microparticles of this invention are prepared using polyvinyl alcohol as the hydrogel matrix and carboxylated cellulose nanofibers as the reinforcing phase, through multiple reversible interactions as crosslinking sites. By introducing the excellent lubrication and damping properties of the soft, wet hydrogel material into the polyurethane matrix, and further enhancing the mechanical load-bearing capacity of the hydrogel microparticles by doping with cellulose nanofibers, the invention also constructs a multi-reversible interaction network (including metal ion-carboxylate coordination crosslinking, dynamic borate ester bonds, and hydrogen bonds) to enrich the energy dissipation mechanism in the hydrogel, thereby improving its damping and vibration absorption performance. This reduces the frictional excitation force during friction while converting the induced vibration energy into heat energy, and ultimately dissipates the vibration and noise induced by the friction of the polyurethane water-lubricated bearing through the water lubrication medium.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: Multi-crosslinked hydrogels use polyvinyl alcohol (PVA) as the hydrogel matrix. The mechanical load-bearing capacity of the PVA hydrogel is improved by adding carboxylated cellulose nanofibers, while a multi-reversible interaction network is constructed to enrich the energy dissipation mechanism within the hydrogel. 3+ Ions and carboxyl groups (COO) in carboxylated cellulose - Reversible coordination crosslinking occurs; the same-sided hydroxyl groups (-OH) in polyvinyl alcohol can form reversible dynamic borate ester bonds with borate ions dissolved in water; furthermore, a rich hydrogen bond network can be formed between the polar hydrophilic functional groups of cellulose and polyvinyl alcohol. These reversible interactions (Fe... 3+ -COO - Coordination (dynamic borate ester bonds and hydrogen bonds) can break and dissipate energy under the action of external force, and can quickly recombine after the external force disappears to achieve reversible energy dissipation.

[0020] When these soft and wet multi-crosslinked hydrogel microparticles are introduced into the polyurethane matrix material, the adhesion-deformation-sliding process on the polyurethane friction interface is exactly the opposite of this fracture-dissipation-reorganization process, realizing the conversion of friction-induced vibration energy into internal energy, which is ultimately dissipated through the water lubrication medium.

[0021] The water absorption and hydration lubrication properties of hydrogel materials effectively reduce the excitation force at the friction interface. The synergistic effect of the reduced frictional excitation force and the enhanced damping dissipation performance suppresses the friction-induced vibration and noise behavior of polyurethane water-lubricated bearings. Attached Figure Description

[0022] Figure 1 Raman spectrum of multi-crosslinked hydrogel.

[0023] Figure 2 : UV spectrum of multi-crosslinked hydrogel.

[0024] Figure 3 SEM image of multi-crosslinked hydrogel microparticles.

[0025] Figure 4 (a) Cross-sectional SEM image of the hydrogel microparticle-reinforced polyurethane composite material of Example 1; (b) XRD patterns of multi-crosslinked hydrogel microparticles, comparative example 1 and the hydrogel microparticle-reinforced polyurethane composite material of Example 1.

[0026] Figure 5 Real-time friction coefficient graphs of polyurethane composite materials in Comparative Example 1, Example 1, and Example 2 under water lubrication conditions with a load of 10N and a sliding frequency of 0.5Hz.

[0027] Figure 6 Comparative Example 1 polyurethane and Example 1 hydrogel microparticle reinforced polyurethane composite material under different strain conditions of 5~30% at a compression rate of 10 mm / min, cyclic compression curves (a) and (b), and their corresponding energy dissipation (c).

[0028] Figure 7 Frictional vibration (a) and noise (b) of hydrogel microparticle-reinforced polyurethane composites of Comparative Example 1 and Example 1 under water lubrication conditions with a load of 20 N and a sliding frequency of 1 Hz. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] This invention provides a gel microparticle-reinforced polyurethane composite material for marine water-lubricated bearings. By designing and preparing hydrogel microparticles with excellent lubrication and damping dissipation properties, and combining them with the preparation process of water-lubricated bearing polymer materials, a novel gel microparticle-reinforced polyurethane composite material for marine water-lubricated bearings is prepared. This reduces the frictional excitation force at the contact interface during friction and wear, improves the damping dissipation performance and mechanical load-bearing performance of the water-lubricated bearing polymer material, thereby suppressing the formation of frictional excitation vibration noise at the friction contact interface, improving the reliability and concealment of the water-lubricated bearing material, and promoting the practical application of water-lubricated bearing polymer materials.

[0031] To better understand this invention, the hydrogel microparticle-reinforced polyurethane composite material was injection molded into a circle solely for performance testing purposes, to more clearly describe the vibration reduction and noise reduction performance of this invention, and not to limit the invention.

[0032] The present invention discloses a gel microparticle-reinforced polyurethane composite material for water-lubricated bearings of ships, comprising multi-crosslinked hydrogel microparticles and a thermoplastic polyurethane matrix, wherein the multi-crosslinked hydrogel microparticles are uniformly distributed in the polyurethane matrix.

[0033] The polyurethane matrix material used in the specific implementation of the water-lubricated bearing is a commercially available granular material with stable chemical properties. The polyurethane granules were purchased from Bayer AG, Germany, model 3690AU, with a Shore hardness of 90A and an average particle size of 1 mm. The multi-crosslinked hydrogel microparticles use polyvinyl alcohol as the hydrogel matrix, carboxylated cellulose nanofibers as the reinforcing phase, and various reversible interactions as crosslinking sites. The specific implementation method uses a polyvinyl alcohol hydrogel matrix with a viscosity of 54.0~66.0 mPa·s (4wt% aqueous solution, viscometer at 20℃) and a degree of alcoholysis of 98.0~99.0 mol%. The carboxylated cellulose nanofibers used have an average diameter of 10~20 nm and a length of 1~2 mm.

[0034] A specific embodiment provides a multi-crosslinked hydrogel microparticle, which is prepared by the following method: 0.7 parts of carboxylated cellulose nanofibers (cCNFs) were dispersed in 100 parts of distilled water and ultrasonically treated for 10-15 min to form a cellulose fiber dispersion network. Then, 15 parts of polyvinyl alcohol (PVA) and 1.5 parts of boric acid (BA) were added to the cCNFs dispersion and stirred thoroughly for 6 h until completely dissolved and the ortho-diol groups of BA and PVA formed reversible dynamic borate ester bonds.

[0035] The prepared homogeneous sol solution was placed in a polytetrafluoroethylene mold and subjected to five freeze-thaw cycles to form PVA microcrystalline domains, which constitute the structural framework of the hydrogel, thus obtaining PVA-BA-cCNFs hydrogel. The freezing temperature of each freeze-thaw cycle was -20℃ for 8 h, and the thawing temperature was 25℃ for 4 h.

[0036] The above hydrogel was immersed in a solution containing 0.2 M Fe³ + PVA-BA-cCNFs-Fe³ was obtained by soaking the sample in an aqueous solution for 24 h. + Hydrogel. During this process, iron ions permeate into the interior of the hydrogel and form reversible coordination bonds with the carboxyl groups of cCNFs.

[0037] PVA-BA-cCNFs-Fe 3+ Hydrogel is immersed in distilled water to remove excess Fe³ + The particles were then subjected to heat annealing at 110°C for 1 hour, and after natural cooling, they were pulverized to obtain multi-crosslinked hydrogel microparticles.

[0038] Characterization of the prepared hydrogel microparticles as follows Figure 1-3 As shown: Figure 1 The absorption peaks at 457 cm⁻¹ and 798 cm⁻¹ in the mid-Raman spectrum belong to OBO and BOC, respectively, indicating that dynamic borate ester bonds were successfully constructed in the multi-crosslinked hydrogel network. Figure 1 The shift of the characteristic peak belonging to the hydroxyl group indicates a rich hydrogen bond cross-linking network in the system. Figure 2 The absorption peak at 361 nm in the mid-ultraviolet absorption spectrum indicates that Fe was successfully constructed in the multi-crosslinked hydrogel network. 3+ -COO- coordination crosslinking. Figure 3 The image shows a SEM image of the uniform microparticles obtained after pulverizing the prepared multi-crosslinked hydrogel. The average particle size of the hydrogel microparticles is clearly visible to be 30-50 μm.

[0039] Example 1 Multi-crosslinked hydrogel microparticles and polyurethane granules (Shore hardness 90A) were mixed in a ratio of 10:90. The premix was melt-blended at 180°C using a dual-track extrusion mixer to obtain a hydrogel microparticle-reinforced polyurethane composite material. The hydrogel microparticle-reinforced polyurethane composite material granules were then injection molded at 190°C and 10MPa using an injection molding machine to obtain the hydrogel microparticle-reinforced polyurethane composite material.

[0040] The characterization of the hydrogel microparticle-reinforced polyurethane composite material prepared in Example 1 is as follows: Figure 4 As shown. Figure 4 Uniformly distributed hydrogel particles are clearly visible in the SEM of the cross-section of the composite material in section a. Figure 4The XRD diffraction pattern in b shows that the introduction of hydrogel microparticles has little effect on the crystallinity of the polyurethane matrix, and the above results indicate the successful preparation of hydrogel microparticle-reinforced polyurethane composites.

[0041] Example 2 Example 2 differs only in that the mass ratio of added hydrogel microparticles is 6:94; all other steps and conditions are the same as in Example 1. The specific steps are as follows: Multi-crosslinked hydrogel microparticles and polyurethane granules were mixed at a ratio of 6:94. The premix was melt-blended at 180°C using a dual-track extrusion mixer to obtain a hydrogel microparticle-reinforced polyurethane composite material. The hydrogel microparticle-reinforced polyurethane composite material granules were injection molded at 190°C and 10MPa using an injection molding machine to obtain the hydrogel microparticle-reinforced polyurethane composite material.

[0042] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that no hydrogel microparticles were added; all other steps and conditions were the same as in Example 1.

[0043] Lubrication performance test: The hydrogel microparticle-reinforced polyurethane composites prepared in Examples 1, 2, and Comparative Example 1 were used as test specimens, and copper balls were used as friction pair materials. Friction tests were conducted on a tribometer at room temperature. The test conditions were water lubrication, a 10 N load, and a 0.5 Hz reciprocating frequency for 30 min. The test results are as follows: Figure 5 As shown, compared to the polyurethane bearing material shown in Comparative Example 1, the hydrogel microparticle-reinforced polyurethane composite material of the present invention exhibits a lower and more stable coefficient of friction under water lubrication conditions. Furthermore, the coefficient of friction in Comparative Example 1 is lower and more stable than that in Comparative Example 2, thus improving the stability of the friction interface of the bearing material. At the friction interface, the hydrogel microparticles can absorb the lubricating medium and form a hydrated lubricating layer on their surface, thereby improving the lubrication performance of the bearing material, reducing the direct contact of the friction pair, and lowering the frictional excitation force at the friction interface. Experimental results demonstrate that the hydrogel microparticle-reinforced polyurethane composite material effectively improves the lubrication performance of polyurethane bearing materials in a water environment.

[0044] Energy dissipation performance test: The hydrogel microparticle-reinforced polyurethane composites prepared in Example 1 and Comparative Example 1 were used as test specimens. Cyclic compression performance tests were conducted on a comprehensive mechanical testing machine at room temperature to evaluate the energy dissipation performance of the composites. The test conditions were: compression at a compression rate of 10 mm / min within different compression strain ranges of 5–30%. The results are shown in the figure. Figure 6 As shown. Figure 6As shown in a and b, compared to the polyurethane bearing material shown in Comparative Example 1, the hydrogel microparticle-reinforced polyurethane composite material in Example 1 exhibits a larger hysteresis loop area under different strains, corresponding to higher energy dissipation. Figure 6 c), indicating its better energy dissipation performance. Experimental results demonstrate that hydrogel microparticle-reinforced polyurethane composites effectively improve the damping dissipation performance of polyurethane bearing materials.

[0045] Friction vibration noise performance test: The hydrogel microparticle-reinforced polyurethane composites prepared in Example 1 and Comparative Example 1 were used as test specimens, and copper balls were used as the friction pair material. Friction and vibration tests were conducted on a tribological testing machine at room temperature using a vibration and noise acquisition system. The test conditions were water lubrication, a 20 N load, and a 0.5 Hz reciprocating frequency for 30 min. Vibration and noise signals were acquired during the stable friction phase, with an acquisition period of 6 s. The test results are as follows: Figure 7 As shown. Compared with the polyurethane bearing material shown in Comparative Example 1, the hydrogel microparticle-reinforced polyurethane composite material of the present invention exhibits better performance in suppressing friction-excited vibration noise under water lubrication conditions (the root mean square value (RMS) and sound pressure level (SPL) of the vibration signal in Example 1 are smaller than those in Comparative Example 1).

[0046] The above results demonstrate that hydrogel microparticle-reinforced polyurethane composites significantly improve the lubrication performance of water-lubricated bearing materials, thereby reducing the frictional excitation force at the friction interface; in addition, they enhance the damping dissipation performance of the bearing materials, thus effectively reducing the formation of friction-induced vibration noise.

[0047] Unlike existing technologies, this invention discloses a hydrogel microparticle-reinforced polyurethane composite material for water-lubricated bearings and its preparation method. The hydrogel microparticle-reinforced polyurethane composite material for water-lubricated bearings is prepared by blending a polyurethane matrix material with multi-crosslinked hydrogel microparticles possessing excellent lubrication and energy dissipation properties. The multi-crosslinked hydrogel microparticles are prepared using polyvinyl alcohol as the hydrogel matrix, carboxylated cellulose nanofibers as the reinforcing phase, and various reversible interactions as crosslinking sites. The hydrogel microparticle-reinforced polyurethane composite material prepared by introducing hydrogel microparticles into the polyurethane matrix significantly reduces the frictional excitation force at the friction interface, improves the energy dissipation performance of the bearing material, thereby effectively reducing friction-induced vibration noise behavior and improving the stability and concealment of water-lubricated bearings.

[0048] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A hydrogel microparticle-reinforced polyurethane composite material, characterized in that... It is prepared by heating, extruding, granulating, and melt injection molding of multi-crosslinked hydrogel microparticles and polyurethane matrix granules; the mass percentage ratio of the multi-crosslinked hydrogel microparticles and polyurethane matrix granules is 5~15wt% and 85~95wt%, respectively. The preparation method of the multi-crosslinked hydrogel microparticles includes the following steps: (1) Disperse carboxylated cellulose nanofibers in an aqueous solution to obtain a cellulose nanofiber suspension; (2) Polyvinyl alcohol powder and boric acid powder were added to the obtained suspension in sequence, and the mixture was heated and stirred until completely dissolved to obtain a homogeneous sol solution. (3) The obtained sol solution is poured into a polytetrafluoroethylene mold, and the sol-gel conversion is achieved through multiple freeze-thaw cycles to obtain hydrogel A; (4) The obtained hydrogel A was immersed in an aqueous solution of FeCl3 to obtain ion-crosslinked hydrogel B; (5) The obtained hydrogel B was washed, annealed and naturally cooled and crushed to obtain multi-crosslinked hydrogel microparticles.

2. The hydrogel microparticle-reinforced polyurethane composite material as described in claim 1, characterized in that... The polyurethane matrix granules have a Shore hardness of 90~95A and a particle size of 1~2 mm.

3. The hydrogel microparticle-reinforced polyurethane composite material as described in claim 1, characterized in that... The raw materials used, by weight, are: 0.1-0.9 parts carboxylated cellulose nanofibers; 12-15 parts polyvinyl alcohol powder; and 0.5-1.5 parts boric acid powder. 100 portions of water.

4. The hydrogel microparticle-reinforced polyurethane composite material as described in claim 1, characterized in that... The carboxylated cellulose nanofibers have an average diameter of 10-20 nm and a length of 1-2 mm; the polyvinyl alcohol has a viscosity of 54.0-66.0 mPa·s and a degree of alcoholysis of 98.0-99.0 mol%.

5. The hydrogel microparticle-reinforced polyurethane composite material as described in claim 1, characterized in that... In step 2, the heating temperature is 80~95℃ and the heating and stirring time is 4~6h; in step 3, the freezing temperature of the freeze-thaw cycle is -40~-20℃ and the time is 6~8h; the thawing temperature is 20~25℃ and the time is 3~5h; the number of repetitions is 2~6 times.

6. The hydrogel microparticle-reinforced polyurethane composite material as described in claim 1, characterized in that... In step 4, the concentration of the FeCl3 aqueous solution is 0.2~0.25 M, and the immersion time is 24~48 h; in step 5, the annealing temperature is 100~120℃, and the time is 1~2 h.

7. The method for preparing the hydrogel microparticle-reinforced polyurethane composite material according to claim 1, characterized in that... Includes the following steps: Multi-crosslinked hydrogel microparticles are premixed with polyurethane matrix granules and then fed into the screw cavity of a twin-screw extruder. After heating and melting, extrusion and granulation, the mixture is then melt-injected through an injection molding machine to obtain a multi-crosslinked hydrogel microparticle-reinforced polyurethane composite material.

8. The method for preparing the hydrogel microparticle-reinforced polyurethane composite material as described in claim 7, characterized in that... The heating temperature of the twin-screw extruder is 180~200℃, and the rotation speed is 80~100 r / min; the pressure of the injection molding machine is 10~15MPa, and the temperature is 190~200℃.

9. The application of the hydrogel microparticle-reinforced polyurethane composite material of claim 1 as a water-lubricated bearing material.

Images