Porous oil-containing material based on injection molding process and preparation method thereof

Abstract

The invention relates to the technical field of lubricating materials, in particular to a porous oil-containing material based on an injection molding process and a preparation method thereof.The preparation method comprises the following steps that S1, a mixed solution of polypropylene powder and lubricating oil is placed in a planetary stirrer to be mixed; and S2, pouring the mixed solution obtained in the step S1 into an injection molding machine, and carrying out injection molding extrusion to obtain the porous oil-containing material. The porous oil-containing material has the beneficial effects that the porous oil-containing material prepared by an injection molding method has excellent mechanical properties, oil retention performance and friction performance. The optimal process parameters of the porous oil-containing material obtained by the orthogonal experiment method are as follows: the temperature is 180 DEG C; the injection molding pressure is controlled in a subsection mode, the first section is 20 MPa, the second section is 30 MPa, and the third section is 50 MPa; and the injection molding speed is controlled by sections: the first section is 30 mm / s, the second section is 20 mm / s, and the third section is 50 mm / s.

Description

Technical Field

[0001] This invention relates to the field of lubricating materials technology, specifically to a porous oil-containing material based on injection molding process and its preparation method. Background Technology

[0002] With the rapid development of industry, the application of mechanical equipment is becoming increasingly widespread, and the requirements for lubricating materials are also becoming higher. Friction pairs are widely used in mechanical equipment, and their lubrication effect directly affects the service life of the equipment and the quality of the products. Traditional lubrication solutions mainly include periodically adding lubricating grease and designing an oil supply system, but these methods are cumbersome, costly, and prone to contamination.

[0003] Porous oil-containing materials, due to their internal pores capable of storing and slowly releasing lubricating oil to form a stable oil film, have become an effective solution to the aforementioned problems. In existing technologies, cold pressing and sintering is the main preparation method for porous oil-containing materials, but it suffers from drawbacks such as long production cycles, low efficiency, and uneven pore distribution. Furthermore, the friction coefficient and oil retention rate of existing materials still have room for improvement, and their adaptability to extreme environments is insufficient.

[0004] Therefore, developing a novel method for preparing porous oil-containing materials can not only achieve uniform and controllable pore structure, but also significantly reduce the friction coefficient, improve oil retention rate and thermal stability, while solving the problems of low efficiency and high cost of traditional processes, which is of great practical significance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a porous oil-containing material based on injection molding process and its preparation method, which has high production efficiency, low friction coefficient and high oil retention rate.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: providing a porous oil-containing material based on injection molding process, comprising the following steps: S1. The mixture of polypropylene powder and lubricating oil is placed in a planetary mixer for mixing; the viscosity of the mixture is 10500-12000 mPa•s, and the oil content of the mixture is 60-80%; S2. Pour the mixture obtained in step S1 into an injection molding machine and extrude it to obtain a porous oil-containing material.

[0007] The injection molding process parameters are as follows: Injection temperature: 180℃; Set the injection pressure to be controlled in stages: Stage 1: 20 MPa, Stage 2: 30 MPa, Stage 3: 50 MPa; Set the injection speed to be controlled in segments: segment 30 mm / s, segment 20 mm / s, segment 50 mm / s; Furthermore, in the above-mentioned method for preparing porous oil-containing materials based on injection molding process, the oil content of the mixture in step S1 is 70%.

[0008] Furthermore, in the above-mentioned method for preparing porous oil-containing materials based on injection molding process, the viscosity of the mixture in step S1 is 11613 mPa•s.

[0009] Furthermore, in the above-mentioned method for preparing porous oil-containing materials based on injection molding process, the mixing conditions in step S1 are as follows: rotation speed of 1500 r / min and mixing time of 5 min.

[0010] Furthermore, in the above-mentioned method for preparing porous oil-containing materials based on injection molding process, step S1 is followed by step S11: adding a set colorant to the mixture obtained in step S1 and continuing to stir for 5 min.

[0011] Furthermore, in the above-mentioned method for preparing porous oil-containing materials based on injection molding process, step S11 is followed by step S12: the mixed solution obtained in step S11 is placed into a vacuum defoaming system for defoaming for 10 min.

[0012] Furthermore, in the above-mentioned method for preparing porous oil-containing materials based on injection molding process, 0.5% by mass of PTFE is added to the mixture in step S1.

[0013] Furthermore, in the above-mentioned method for preparing porous oil-containing materials based on injection molding process, 2.5% by mass of MoS2 is added to the mixture in step S1.

[0014] Another technical solution provided by the present invention is: to provide a porous oil-containing material prepared by the above-mentioned method for preparing porous oil-containing materials based on injection molding process.

[0015] The beneficial effects of this invention are as follows: porous oil-containing materials prepared by injection molding exhibit excellent mechanical properties, oil retention properties, and frictional properties. The optimal process parameters for the porous oil-containing materials obtained by orthogonal experimental design are as follows: temperature: 180℃; segmented control of injection pressure: stage 1: 20 MPa, stage 2: 30 MPa, stage 3: 50 MPa; segmented control of injection speed: stage 1: 30 mm / s, stage 2: 20 mm / s, stage 3: 50 mm / s. The coefficient of friction of the porous oil-containing material with 70% oil content is 0.022, while the lowest coefficient of friction for porous oil-containing materials prepared by cold pressing and sintering is 0.126. The porous oil-containing material prepared by injection molding exhibits superior performance. Attached Figure Description

[0016] Figure 1The figure shows the oil retention rate of porous oil-containing materials with different oil contents in Example 1 of the specific embodiments of the present invention; Figure 2 The figure shows the frictional properties of porous oil-containing materials with different oil contents in Example 1 of the specific embodiments of the present invention; Figure 3 The figure shows the long-term frictional properties of porous oil-containing materials with different oil contents in Example 1 of the present invention. Detailed Implementation

[0017] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0018] Example 1

[0019] The method for preparing porous oil-containing materials based on injection molding in this embodiment includes the following steps: First, polypropylene powder and lubricating oil were added to a beaker in a certain proportion and mixed in a planetary mixer. The mixing process was set as follows: rotation speed 1500 r / min, mixing time 5 min. Next, the selected colorant was added to the system, and stirring was continued for 5 min to obtain a mixed solution. The prepared mixed solution was then placed in a vacuum defoaming system for 10 min to remove physical bubbles generated during mechanical stirring.

[0020] Subsequently, the defoamed mixture is poured into an injection molding machine, and a porous oil-containing material is obtained through injection molding extrusion. The injection molding process parameters are as follows: Injection temperature: 180℃; Set the injection pressure to be controlled in stages: Stage 1: 20 MPa, Stage 2: 30 MPa, Stage 3: 50 MPa; Set the injection speed to be controlled in segments: segment 30 mm / s, segment 20 mm / s, segment 50 mm / s; The effects of the above-mentioned preparation method of porous oil-containing material based on injection molding process on the mechanical properties, frictional properties and oil retention rate of porous oil-containing material under different injection molding process parameters were tested.

[0021] Characterization methods: (1) Hardness test: The hardness test shall be conducted at room temperature in accordance with GB / T531.1-2008. The sample shall be placed in a horizontal position, and 10 relatively dispersed points shall be measured. The highest and lowest values ​​shall be removed, and the average value shall be taken as the test result.

[0022] (2) Viscosity test: The viscosity test shall be conducted in accordance with GB / T 10247-2008. The sample solution shall be placed in a beaker with a diameter of not less than 70 mm and a height of not less than 120 mm, and a digital viscometer shall be used to select an appropriate rotor and speed for the test.

[0023] (3) Microscopic morphology test: The prepared porous oil-containing material was cut using a cooling ultrathin slicer to obtain ultrathin porous oil-containing material sample slices, and then the pore structure of the sample was observed and photographed using an optical microscope. Using Image-Pro Plus 6.0 software, combined with optical imaging photographs, the number and size of micropores in the porous oil-containing material were measured and counted.

[0024] (4) Field emission scanning electron microscopy: The extracted porous oil-containing material was sputtered with gold and the test voltage was 15 Ω.

[0025] (5) Friction test: The friction test instrument used was a universal friction and wear tester. The upper sample was a 4 mm 304 stainless steel ball, and the lower sample was a porous oil-containing polypropylene material. The working parameters of the friction test were: load 5 N, stroke 20 mm, speed 20 mm / s, test temperature: room temperature and 70 ℃, relative humidity: 50%.

[0026] (6) Oil content test: The direct weighing method was used. The porous oil-containing material was placed in petroleum ether and left to stand for 4 h, then centrifuged in a centrifuge, and then placed in a ventilated place for 72 h. The mass of the material before and after centrifugation was weighed. The porosity calculation formula is: θ=(1-m / M)*100%; where: M—total mass of sample; m—mass of sample after extraction.

[0027] (7) Oil retention rate test: The material was placed on a high-speed turntable with the following operating parameters: rotation speed 1500 r / min, and the weight was measured every 20 minutes for a total of 60 minutes. ρ = ((m1-m2) / m1) * 100%; where: m1—total mass of the sample; m2—mass of the sample after centrifugation.

[0028] (8) Specific surface area test: The specific surface area test was conducted according to the conditions of GB / T 19587-2017. The sample was placed in the instrument, and the nitrogen isotherm adsorption curve was obtained. The specific surface area of ​​the material was calculated using the BET theory formula.

[0029] (9) Thermal stability test (TG): The test conditions are as follows: sample mass 5-8 mg, nitrogen flow rate 50 mL / min, the sample is heated from room temperature to 800 ℃ at a heating rate of 20 ℃ / min, and the heating curve is recorded.

[0030] 1. Orthogonal experimental design of injection molding process parameters As a core piece of equipment in modern plastics processing, injection molding machines offer advantages primarily in terms of efficiency, precision control, automation, and process flexibility. Firstly, injection molding machines enable high-speed, continuous molding processes. Molten plastic is injected into the mold cavity under high pressure, and then rapidly cooled and solidified to form the finished product. This highly efficient molding method is particularly suitable for mass production, significantly improving production efficiency. Secondly, injection molding machines can precisely control process parameters such as temperature, pressure, and injection speed during the molding process, ensuring high dimensional accuracy and excellent surface quality of the products, meeting the manufacturing requirements of high-precision parts. Furthermore, modern injection molding machines are generally equipped with high-level automated control systems, automating operations from raw material feeding, plasticizing, injection to demolding. This not only reduces manual intervention but also minimizes human error, further improving production stability and product consistency. Simultaneously, injection molding machines have strong process adaptability. By changing molds and adjusting process parameters, they can produce plastic products with complex shapes and diverse structures, meeting diverse production needs. Finally, the injection molding process minimizes material waste. Through precise metering and control, it achieves efficient utilization of raw materials, aligning with the concepts of green manufacturing and sustainable development. In conclusion, injection molding machines have significant advantages in improving production efficiency, ensuring product quality, reducing production costs, and adapting to diverse production needs, making them an indispensable key piece of equipment in the processing industry.

[0031] Before conducting orthogonal experimental design, the primary task is to clarify the various factors that constitute the orthogonal experiment, as well as the corresponding levels and ranges of each factor.

[0032] Polypropylene, as the matrix material, melts within a temperature range of 160℃ to 220℃. Studies have shown that when the temperature reaches above 180℃, the material exhibits significant softening characteristics and gradually achieves complete melting. Based on process optimization considerations, the experiment optimized the processing temperature range to 180℃ to 210℃. This adjustment effectively improved the material's melting efficiency while ensuring molding quality.

[0033] In the injection molding process of porous oil-containing materials, the appropriate setting of molding pressure is a key process parameter determining the quality of the finished product. Studies have shown that when the pressure is below a reasonable range, the melt fails to achieve good mold filling, which not only affects the uniform distribution of the material but also hinders effective subsequent performance testing. Conversely, if the pressure exceeds the reasonable range, the porosity of the porous structure will significantly decrease, thus affecting the oil-containing properties of the material and causing it to lose its core advantage of self-lubrication. Based on the above analysis, the optimized control of molding pressure is particularly important. To determine the optimal process parameter range, this study conducted systematic single-factor experiments before carrying out orthogonal experimental design, ultimately determining that the suitable range for molding pressure is 20 MPa to 50 MPa.

[0034] In the injection molding process, the control of the injection rate is crucial. If the rate is too high, it can easily lead to material jetting and internal porosity, among other quality problems. Conversely, if the rate is too low, it may produce flow marks, weld lines, and surface unevenness, all of which affect the functional stability of porous oil-containing materials. Therefore, selecting an appropriate injection rate is critical. This selection should comprehensively consider the mold's morphological characteristics, flow performance limitations, and other parameters that may affect stability. In the preliminary work of this study, through in-depth analysis of a series of single-factor experiments, the suitable range for the injection rate was determined to be 20 mm / s to 50 mm / s.

[0035] Taking all factors into consideration, the following table is designed to show the factors and levels of injection temperature, injection pressure, and injection speed: Table 1.

[0036] Table 1

[0037] Table 1 is a table of a 7-factor, 4-level orthogonal experiment, using L12000-level orthogonal arrays. 32 (47) The standard orthogonal experimental design table is used to plan and design experiments. The orthogonal experimental design scheme is shown in Table 2-3.

[0038] Table 2

[0039] Table 3

[0040] Based on the process parameters provided in the experimental design, porous material samples were prepared and their performance was tested, mainly including oil content, specific surface area, and Shore hardness, which were used as indicators to evaluate the performance of the porous material. This study successfully prepared porous oil-containing material samples according to the process parameters set in the experimental scheme, and systematically characterized their performance. The characterization mainly included three key performance indicators: oil content, specific surface area, and Shore hardness. Among them, oil content reflects the material's oil storage capacity, specific surface area characterizes the pore structure characteristics of the material, and Shore hardness is used to evaluate the mechanical properties of the material. The test results are shown in Table 4.

[0041] Table 4

[0042] Analysis of variance was performed on the oil content, specific surface area, and hardness of the oil-containing materials; the calculation process is omitted here, and the statistical results are shown below: As shown in Table 5, a factor significance test was performed, and the critical value table of the F-distribution was consulted: F0.10(3, 10) = 5.25; F0.05(3, 10)=8.84; F0.01(3, 10)= 27.49; Since FA > F0.10(3,10) = 5.25, the change in factor A (injection temperature) level has a significant impact on the oil content of the material.

[0043] Factors B (pressure stage 1), C (pressure stage 2), D (pressure stage 3), E (speed stage 1), F (speed stage 2), and G (speed stage 3) have no significant effect on the oil content of porous materials.

[0044] Table 5

[0045] As shown in Table 6, since FF > F0.10(3,10) = 5.25, the change in the level of factor F (velocity stage 2) has a significant impact on the specific surface area of ​​the material.

[0046] Factors A (pressure level 1), B (pressure level 1), C (pressure level 2), D (pressure level 3), E (speed level 1), and G (speed level 3) have no significant effect on the specific surface area of ​​the material.

[0047] Table 6

[0048] As shown in Table 7, since FB > F0.10(3,10) = 5.25, the change in the level of factor B (pressure stage) has a significant impact on the hardness of the material.

[0049] Factors A (pressure level 1), C (pressure level 2), D (pressure level 3), E (speed level 1), F (speed level 2), and G (speed level 3) have no significant effect on the hardness of the material.

[0050] Table 7

[0051] Based on the results of the three variance analyses above, the key variables that significantly affect the properties of porous oil-containing materials in the injection molding process parameters can be identified as: processing temperature, first-stage pressure, and second-stage injection speed.

[0052] The performance evaluation of porous oil-impregnated materials mainly revolves around three core indicators: oil content, mechanical properties, and specific surface area. Among these, oil content is a key parameter, and its value is positively correlated with the lubrication efficiency of porous materials. Higher oil content helps achieve continuous lubrication and effectively reduces friction loss. In terms of mechanical properties, the material needs to possess excellent hardness characteristics and structural stability, both of which directly determine the material's wear resistance and reliability during operation. Furthermore, specific surface area is an important indicator for measuring the pore connectivity of a material. A larger specific surface area means better pore connectivity, which not only promotes the full utilization of lubricating oil but also significantly improves the stability of the lubrication system and effectively prevents oil supply interruptions.

[0053] As temperature rises, the oil content of porous materials decreases, attributed to the substrate "expansion" effect caused by increased temperature. This effect leads to shrinkage of the pore structure, thus reducing the material's actual oil-containing capacity. In terms of mechanical properties, the performance of porous materials is positively correlated with injection pressure. Increased injection pressure leads to increased density and reduced porosity during plasticizing, thereby enhancing the material's hardness. Increased injection speed negatively impacts specific surface area, as it further compresses the pore structure, resulting in a smaller specific surface area. Oil content and specific surface area are key indicators for evaluating the performance of porous oil-containing materials; the former directly affects the material's continuous lubrication efficiency, while the latter relates to its oil supply capacity. Considering the material's mechanical properties, specific surface area, actual oil content, and the measured results of injection-molded samples, the final determined process parameters are: temperature set at T1; injection pressure divided into three segments: P11, P22, and P34; and injection speed also divided into three segments: V12, V21, and V34.

[0054] 2. Effects of different oil contents on the properties of porous oil-impregnated materials Orthogonal experimental design was employed to optimize injection molding process parameters, focusing on their impact on key performance indicators (including hardness, oil content, and specific surface area) of porous oil-containing materials. Based on the optimized process parameters, the mechanism by which different oil contents affect the tribological properties and oil storage capacity of the materials was systematically investigated by adjusting the component ratios in the material formulation. Three groups of porous oil-containing material samples were prepared from mixed solutions with oil contents of 60%, 70%, and 80% for subsequent performance comparison and analysis.

[0055] Please see Figure 1 To evaluate the oil retention performance of porous oil-containing materials, a continuous oil retention rate test was conducted on porous oil-containing materials with different oil contents. The experimental setup was a rotation speed of 1500 r / min, using a 20-minute interval weighing method, with a test duration of 60 minutes. The experimental results are as follows: Figure 1As shown, the oil retention performance of materials with different oil contents varies significantly. Porous oil-containing materials with oil contents of 60% and 70% exhibited excellent oil retention performance, maintaining an oil retention rate above 95% throughout the test. Notably, the 80% oil-containing sample, due to its higher initial oil content, showed more lubricating oil precipitation during the test, but its sustained oil retention rate remained above 89%, demonstrating good oil retention characteristics. This phenomenon may be related to the excessively high pore saturation of the high-oil-content material, making it more prone to lubricating oil loss under high-speed centrifugation conditions.

[0056] Frictional properties were tested on porous oil-impregnated materials with different oil contents. These materials filled the bearing clearances, where point contact was predominant and the contact load was relatively small during bearing operation. Therefore, the contact load force was relatively low during the frictional performance testing.

[0057] Please see Figure 2 and Figure 3 ,like Figure 2 As shown, porous oil-containing materials with a 70% oil content exhibit the best frictional properties and stable material performance. (a) 60% oil content; (b) 70% oil content; (c) 80% oil content; like Figure 3 As shown, the friction coefficient of porous materials fluctuates less with increasing contact load. This is because, during the gradual increase of contact load, the lubricating oil in porous materials is subjected to pressure, causing it to precipitate from the pores and improving the material's friction performance. Porous oil-containing materials extruded by injection molding have nearly six times better friction performance than those formed by cold pressing and sintering. Compared to other porous materials with different oil contents, the 60% oil-containing porous material has a higher base content, resulting in better mechanical and wear resistance. Furthermore, its friction performance is more stable and does not fluctuate significantly with increasing contact load. When the contact load increases to 15 N, indentations appear on the contact surface of the porous material, increasing the contact area and causing a large change in the friction coefficient. Porous oil-containing materials with 80% oil content have lower mechanical and wear resistance than other materials with different oil contents due to their higher oil content. As the contact load increases, the friction and wear of the porous material increase, leading to a corresponding increase in the friction coefficient.

[0058] 3. Conclusion (1) The relationship between process parameters and the properties of porous oil-containing materials was studied through orthogonal experiments. The optimal injection molding process parameters were found to be: temperature: T1 (180℃); injection pressure (first stage 20 MPa, second stage 30 MPa, third stage 50 MPa); P11, P22, P34; injection speed (first stage 30 mm / s, second stage 20 mm / s, third stage 50 mm / s): V12, V21, V34.

[0059] (2) When the oil content is 70%, the friction coefficient of the porous oil-containing material prepared by injection molding is 0.022, while the friction coefficient of the porous oil-containing material prepared by cold pressing and sintering is 0.126. Injection molding is beneficial to improving the friction performance of porous oil-containing materials.

[0060] (3) The study investigated the effect of different oil contents on the properties of porous oil-impregnated materials and found that oil content is an important parameter affecting the frictional properties of porous oil-impregnated materials. When the oil content is 70%, the frictional and mechanical properties of the porous oil-impregnated materials are optimal. The oil retention rate of porous oil-impregnated materials prepared with different oil contents is maintained at 90% or above.

[0061] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing porous oil-containing materials based on injection molding process, characterized in that, Includes the following steps: S1. The mixture of polypropylene powder and lubricating oil is placed in a planetary mixer and mixed; the viscosity of the mixture is 10500-12000 mPa•s, and the oil content of the mixture is 60-80%; S2. Pour the mixture obtained in step S1 into an injection molding machine and extrude it to obtain a porous oil-containing material. The injection molding process parameters are as follows: Injection temperature: 180℃; Set the injection pressure to be controlled in stages: Stage 1: 20 MPa, Stage 2: 30 MPa, Stage 3: 50 MPa; Set the injection speed to be controlled in segments: segment 1: 30 mm / s, segment 2: 20 mm / s, segment 3: 50 mm / s.

2. The method for preparing porous oil-containing materials based on injection molding process according to claim 1, characterized in that, The oil content of the mixture in step S1 is 70%.

3. The method for preparing porous oil-containing materials based on injection molding process according to claim 1, characterized in that, The viscosity of the mixture in step S1 is 11613 mPa•s.

4. The method for preparing porous oil-containing materials based on injection molding process according to claim 1, characterized in that, The mixing conditions in step S1 are as follows: rotation speed of 1500 r / min and mixing time of 5 min.

5. The method for preparing porous oil-containing materials based on injection molding process according to claim 1, characterized in that, The step S1 is followed by step S11: adding the set colorant to the mixture obtained in step S1 and continuing to stir for 5 minutes.

6. The method for preparing porous oil-containing materials based on injection molding process according to claim 5, characterized in that, The step S11 is followed by step S12: the mixed solution obtained in step S11 is placed in a vacuum defoaming system and defoamed for 10 minutes.

7. The method for preparing porous oil-containing materials based on injection molding process according to claim 1, characterized in that, In step S1, 0.5% by mass of PTFE is also added to the mixture.

8. The method for preparing porous oil-containing materials based on injection molding process according to claim 1, characterized in that, The mixture in step S1 also contains 2.5% by mass of MoS2.

9. A porous oil-containing material prepared by the method for preparing porous oil-containing materials based on injection molding process according to any one of claims 1-8.

Images