A lip sheet formula for enhancing lip wear resistance and its production process

Abstract

The present invention discloses a lip sheet formula for enhancing the wear resistance of the lip and its production process, which belongs to the field of composite material technology. The lip sheet formula includes the following raw materials in parts by weight: 70-80 parts of PTFE, 10-15 parts of glass fiber, 3-5 parts of molybdenum disulfide, 1-3 parts of talc, and 1-5 parts of modified carbon nanotubes. The preparation steps are as follows: Step 1, refrigerate the PTFE, glass fiber, molybdenum disulfide, talc, and modified carbon nanotubes respectively, and then add them into a high-speed blender according to parts by weight and stir them uniformly, and then dry, crush, and sieve the crushed materials in sequence to obtain a crushed material; Step 2, press and sinter the crushed materials in sequence to obtain a lip sheet formula for enhancing the wear resistance of the lip and its production process. The raw materials are appropriately proportioned, and the prepared lip sheet material has excellent wear resistance and high overall strength. The production process is simple to operate, easy to implement, and suitable for large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials, and particularly relates to a lip sheet formula for enhancing the wear resistance of a lip and a production process thereof. Background Art

[0002] In various machines, seals prevent fluids or solid particles from leaking between adjacent mating surfaces, while also preventing external impurities such as dust, air, and moisture from entering the device. Therefore, the material selection for seals is crucial. Polytetrafluoroethylene (PTFE) possesses exceptional resistance to high and low temperatures and chemical corrosion, and is unaffected by nearly all strong acids, bases, oxidants, and salts. Due to these excellent properties, PTFE is widely used as a seal material in existing technologies.

[0003] PTFE lip material is mechanically drawn from a polytetrafluoroethylene (PTFE) disc, forming a trumpet-shaped lip during processing. The PTFE material's dimensional memory effect causes the frictional heat generated during operation to continuously contract. This allows the lip to grip the rotating shaft without the need for springs, preventing gaps between the lip and the shaft surface and compensating for wear, thereby improving seal life and reliability. The PTFE oil seal lip material is a key factor in determining the sealing performance of PTFE oil seals, determining their operating temperature range, friction, wear resistance, media resistance, and sealing performance. However, existing PTFE lip materials suffer from poor resilience, poor self-lubrication, and poor wear resistance, which severely impact their service life and sealing reliability. This poor wear resistance results in poor sliding lubrication when the lip contacts the rotating shaft, causing severe wear and shortening the product's service life. Furthermore, the poor resilience of PTFE oil seal lip lip results in poor followability of the rotating shaft, leading to rapid lubricant leakage and increased maintenance costs, limiting its practical application.

[0004] Therefore, how to improve the elasticity, flexibility and wear resistance of PTFE lip materials is a technical problem that needs to be solved urgently. Summary of the Invention

[0005] In order to improve the wear resistance of PTFE lip material, the present invention provides a lip formula for enhancing the wear resistance of the lip and a production process thereof.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a lip sheet formulation for enhancing the wear resistance of a lip, comprising the following raw materials in parts by weight:

[0008] PTFE 70-80 parts;

[0009] 10-15 parts of glass fiber;

[0010] 3-5 parts of molybdenum disulfide;

[0011] 1-3 parts talcum powder;

[0012] 1-5 parts of modified carbon nanotubes;

[0013] The modified carbon nanotubes are prepared by the following steps:

[0014] Carboxylated carbon nanotubes are added to thionyl chloride and N,N-dimethylformamide, refluxed and stirred at 70-75°C for 22-24 hours, evaporated at normal pressure, cooled to room temperature, heated to 100°C, vacuumed and then introduced with argon until normal pressure is restored, dodecylamine is added, refluxed and stirred at 90-92°C for 5-6 hours, cooled, filtered, washed, and vacuum dried to obtain modified carbon nanotubes.

[0015] As a further embodiment of the present invention, the usage ratio of carboxylated carbon nanotubes, thionyl chloride, N,N-dimethylformamide and dodecylamine is 0.5-0.6 g:95 mL:0.5 mL:10-10.5 g.

[0016] As a further embodiment of the present invention, the carboxylated carbon nanotubes are prepared by the following steps:

[0017] The carbon nanotubes were added to concentrated nitric acid, heated and refluxed with stirring, cooled to room temperature, washed to neutrality, and dried to obtain carboxylated carbon nanotubes; wherein the amount ratio of the carbon nanotubes to the concentrated nitric acid was 3 g:12 mL.

[0018] As a further solution of the present invention, the particle size of the carbon nanotubes is 30-50 nm.

[0019] As a further solution of the present invention, the glass fiber has a diameter of 14-16 μm and a length of 120-150 μm.

[0020] As a further embodiment of the present invention, the particle size of the molybdenum disulfide is 120-180 μm.

[0021] A second aspect of the present invention provides a production process for a lip sheet formulation for enhancing lip wear resistance, comprising the following steps:

[0022] Step 1: refrigerate PTFE, glass fiber, molybdenum disulfide, talc and modified carbon nanotubes respectively, add them into a high-speed blender according to weight parts, stir them evenly, and then dry, crush and sieve them in sequence to obtain a crushed material;

[0023] Step 2: Press and sinter the crushed materials in sequence to obtain the product.

[0024] As a further solution of the present invention, the refrigeration temperature is ≤-20°C and the refrigeration time is 24-36 hours.

[0025] As a further solution of the present invention, the process steps of the segmented sintering are as follows:

[0026] Heating from room temperature to 180°C at a rate of 20-25°C / 10min;

[0027] From 180℃ to 290℃, the heating rate is 10-15℃ / 10min;

[0028] Heat from 290°C to 330°C at a rate of 3-5°C / 10min, and keep at 330°C for 90-100min;

[0029] Heat from 330°C to 375°C at a rate of 3-5°C / 10min, and keep at 375°C for 180-200min.

[0030] Beneficial effects of the present invention:

[0031] The present invention provides a lip sheet formulation and production process for enhancing the wear resistance of lip openings. The lip sheet formulation comprises the following raw materials: PTFE, glass fiber, molybdenum disulfide, talc, and modified carbon nanotubes. Molybdenum disulfide has excellent lubricity, while glass fiber improves mechanical properties and synergistically improves the wear resistance and mechanical properties of polytetrafluoroethylene with the modified carbon nanotubes and molybdenum disulfide. Furthermore, during the production process, low-temperature refrigeration ensures uniform powder mixing, and sieving further controls the powder particle size, thereby improving the product's wear resistance.

[0032] In the present invention, the modified carbon nanotubes are first carboxylated with concentrated nitric acid, and then the carboxyl groups are chlorinated and reacted with dodecylamine to form aliphatic alkylamide-modified carbon nanotubes. This improves the dispersibility and compatibility of the carbon nanotubes in the polymer, making the composite material more evenly mixed. The good compatibility and mechanical strength can make the stress transfer effect more efficient, avoid stress concentration, and further improve the wear resistance of the composite material. In addition, the surface of the modified carbon nanotubes is grafted with long-chain molecules, which can form a certain network structure in the polytetrafluoroethylene material. The entangled molecular chains of the polytetrafluoroethylene reduce the peeling and shedding of the wafer during the friction process, thereby improving the wear resistance of the composite material. At the same time, the stress transfer effect with the polytetrafluoroethylene is good, the pulling effect is significant, and the tensile strength of the composite material is improved. On the other hand, the addition of the modified carbon nanotubes can act as a skeleton in the polytetrafluoroethylene material. The modified carbon nanotubes are enriched on the surface during the initial wear stage, and the exposed modified carbon nanotubes bear part of the load, thereby further reducing the wear rate of the polytetrafluoroethylene material and improving the wear resistance of the polytetrafluoroethylene.

[0033] The present invention provides a lip sheet formula for enhancing the wear resistance of the lip and its production process. The raw materials of each component are appropriately proportioned. The prepared lip sheet material has excellent wear resistance and high overall strength. The production process is simple to operate, easy to implement, and suitable for large-scale production. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0035] The carboxylated carbon nanotubes used in the examples and comparative examples of the present invention were prepared by the following steps:

[0036] 3 g of carbon nanotubes (particle size 50 nm) were added to 12 mL of concentrated nitric acid, refluxed and stirred at 120° C. for 12-14 h, cooled to room temperature, washed with deionized water until neutral, and dried in a vacuum drying oven at 70° C. for 24 h to obtain carboxylated carbon nanotubes.

[0037] The polytetrafluoroethylene used in the present invention is Japanese Daikin PTFE M-111.

[0038] Example 1

[0039] This embodiment provides a modified carbon nanotube, which is prepared by the following steps:

[0040] 0.5 g of carboxylated carbon nanotubes were added to 95 mL of thionyl chloride and 0.5 mL of N,N-dimethylformamide, refluxed and stirred at 70 ° C for 24 h, evaporated at normal pressure, cooled to room temperature, heated to 100 ° C, vacuumed, and then argon was introduced to restore normal pressure, 10 g of dodecylamine was added, refluxed and stirred at 90 ° C for 5 h, cooled to room temperature, diluted with anhydrous ethanol, filtered and washed three times, and placed in a vacuum drying oven at 60 ° C for 24 h to obtain modified carbon nanotubes.

[0041] Example 2

[0042] This embodiment provides a modified carbon nanotube, which is prepared by the following steps:

[0043] 0.55 g of carboxylated carbon nanotubes were added to 95 mL of thionyl chloride and 0.5 mL of N,N-dimethylformamide, refluxed and stirred at 70 ° C for 24 h, evaporated at normal pressure, cooled to room temperature, heated to 100 ° C, vacuumed, and then argon was introduced to restore normal pressure, 10.25 g of dodecylamine was added, refluxed and stirred at 90 ° C for 5 h, cooled to room temperature, diluted with anhydrous ethanol, filtered and washed three times, and placed in a vacuum drying oven at 60 ° C for 24 h to obtain modified carbon nanotubes.

[0044] Example 3

[0045] This embodiment provides a modified carbon nanotube, which is prepared by the following steps:

[0046] 0.6 g of carboxylated carbon nanotubes were added to 95 mL of thionyl chloride and 0.5 mL of N,N-dimethylformamide, refluxed and stirred at 70 ° C for 24 h, evaporated at normal pressure, cooled to room temperature, heated to 100 ° C, vacuumed, and then argon was introduced to restore normal pressure, 10.5 g of dodecylamine was added, refluxed and stirred at 90 ° C for 5 h, cooled to room temperature, diluted with anhydrous ethanol, filtered and washed three times, and placed in a vacuum drying oven at 60 ° C for 24 h to obtain modified carbon nanotubes.

[0047] Comparative Example 1

[0048] In this comparative example, commercially available carbon nanotubes (50 nm) were directly used as modified carbon nanotubes.

[0049] Example 4

[0050] This embodiment provides a lip sheet formula and production process for enhancing the wear resistance of the lip:

[0051] A lip sheet formula for enhancing the wear resistance of the lip, comprising the following raw materials in parts by weight:

[0052] 70 parts of PTFE, 10 parts of glass fiber (diameter 14 μm, length 120 μm), 4 parts of molybdenum disulfide (particle size 120 μm), 2 parts of talc, and 1 part of the modified carbon nanotubes in Example 1;

[0053] The preparation steps are as follows:

[0054] Step 1: refrigerate PTFE, glass fiber, molybdenum disulfide, talc and modified carbon nanotubes respectively at a temperature of ≤-20°C for 26 hours, add them into a high-speed blender according to weight, stir them uniformly, and then dry, crush and sieve them in sequence to obtain a crushed material;

[0055] Step 2: Press and sinter the crushed materials in sequence, wherein the process steps of the segmented sintering are: heating from room temperature to 180°C at a heating rate of 20°C / 10min; heating from 180°C to 290°C at a heating rate of 10°C / 10min; heating from 290°C to 330°C at a heating rate of 3°C / 10min, and keeping at 330°C for 90min; heating from 330°C to 375°C at a heating rate of 3°C / 10min, and keeping at 375°C for 180min.

[0056] Example 5

[0057] The only difference from Example 4 is that:

[0058] One part of the modified carbon nanotubes in Example 1 was replaced with three parts of the modified carbon nanotubes in Example 2.

[0059] Example 6

[0060] The only difference from Example 4 is that:

[0061] One part of the modified carbon nanotubes in Example 1 was replaced with five parts of the modified carbon nanotubes in Example 3.

[0062] Example 7

[0063] The only difference from Example 4 is that:

[0064] A lip sheet formula for enhancing the wear resistance of the lip, comprising the following raw materials in parts by weight:

[0065] 75 parts of PTFE, 10 parts of glass fiber (diameter of 14 μm, length of 140 μm), 4 parts of molybdenum disulfide (particle size of 160 μm), 2 parts of talc powder, and 2 parts of the modified carbon nanotubes in Example 1.

[0066] Example 8

[0067] The only difference from Example 4 is that:

[0068] A lip sheet formula for enhancing the wear resistance of the lip, comprising the following raw materials in parts by weight:

[0069] 80 parts of PTFE, 12 parts of glass fiber (diameter of 16 μm, length of 150 μm), 4 parts of molybdenum disulfide (particle size of 140 μm), 3 parts of talc powder, and 3 parts of the modified carbon nanotubes in Example 1.

[0070] Example 9

[0071] The only difference from Example 4 is that:

[0072] Step 2: Press and sinter the crushed materials in sequence, wherein the process steps of the segmented sintering are: heating from room temperature to 180°C at a heating rate of 25°C / 10min; heating from 180°C to 290°C at a heating rate of 15°C / 10min; heating from 290°C to 330°C at a heating rate of 5°C / 10min, and keeping at 330°C for 100min; heating from 330°C to 375°C at a heating rate of 5°C / 10min, and keeping at 375°C for 180min.

[0073] Comparative Example 2

[0074] The only difference from Example 4 is that:

[0075] The modified carbon nanotubes in Example 1 were replaced by the modified carbon nanotubes in Comparative Example 1 while keeping the amounts unchanged.

[0076] Comparative Example 3

[0077] The only difference from Example 4 is that:

[0078] One part of the modified carbon nanotubes in Example 1 was replaced with 0.5 parts of the modified carbon nanotubes in Example 1.

[0079] Comparative Example 4

[0080] The only difference from Example 4 is that:

[0081] One part of the modified carbon nanotubes in Example 1 was replaced with six parts of the modified carbon nanotubes in Example 1.

[0082] Comparative Example 5

[0083] The only difference from Example 4 is that:

[0084] A lip sheet formula for enhancing the wear resistance of the lip, comprising the following raw materials in parts by weight:

[0085] 60 parts of PTFE, 8 parts of glass fiber (diameter of 14 μm, length of 140 μm), 4 parts of molybdenum disulfide (particle size of 160 μm), 2 parts of talc powder, and 2 parts of the modified carbon nanotubes in Example 1.

[0086] Comparative Example 6

[0087] The only difference from Example 4 is that:

[0088] A lip sheet formula for enhancing the wear resistance of the lip, comprising the following raw materials in parts by weight:

[0089] 95 parts of PTFE, 18 parts of glass fiber (diameter: 14 μm, length: 140 μm), 3 parts of molybdenum disulfide (particle size: 160 μm), 0.5 parts of talc powder, and 2 parts of the modified carbon nanotubes in Example 1.

[0090] Comparative Example 7

[0091] The only difference from Example 4 is that:

[0092] Step 2: Press and sinter the crushed materials in sequence, wherein the process steps of the segmented sintering are: heating from room temperature to 180°C at a heating rate of 30°C / 10min; heating from 180°C to 290°C at a heating rate of 10°C / 10min; heating from 290°C to 330°C at a heating rate of 10°C / 10min, and keeping at 330°C for 100min; heating from 330°C to 375°C at a heating rate of 8°C / 10min, and keeping at 375°C for 180min.

[0093] The following performance tests were conducted on Examples 4-9 and Comparative Examples 2-7: (1) The tensile strength and elongation at break of the resulting formulated materials were tested in accordance with the provisions of GB / T 1040.2. (2) The lip sheet formulations in the Examples and Comparative Examples were prepared into lip sheet materials, which were processed into specimens with dimensions of 20 mm × 12 mm × 4 mm. The wear resistance of the surface layer was tested by a friction and wear test. The mating member was a GCr15 steel ball with a diameter of 6 mm and a hardness of 63 HRC. The load was 10 N, the sliding speed was 0.08 m / s, and the sliding distance was 600 m. The wear rate test results were measured and calculated as shown in Table 1:

[0094] Table 1

[0095]

[0096]

[0097] As can be seen from Table 1, compared with Comparative Examples 2-7, the lip materials obtained in Examples 4-9 have excellent mechanical properties and low wear loss, and have good wear resistance. The carbon nanotubes added in Comparative Example 2 have not been modified, and their tensile strength and elongation at break are both lower than those in Example 4. This shows that the unmodified carbon nanotubes have poor dispersion performance and poor compatibility with polytetrafluoroethylene, which makes the composite material mixed unevenly, thereby affecting the mechanical properties and wear resistance of the composite material. It can be seen from the data in Comparative Examples 3-7 that the amount of each raw material in the formula exceeds the range in the formula and the process is different, which will affect the mechanical properties and wear resistance of the lip material. In summary, the lip formula for enhancing the wear resistance of the lip provided by the present invention has an appropriate ratio of raw materials of each component, and the prepared lip material has excellent wear resistance and mechanical properties, and the production process is simple to operate, easy to implement, and suitable for large-scale production.

[0098] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0099] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A lip sheet formula for enhancing lip wear resistance, characterized in that: It includes the following raw materials in parts by weight: PTFE 70-80 parts; 10-15 parts of glass fiber; 3-5 parts of molybdenum disulfide; 1-3 parts talcum powder; 1-5 parts of modified carbon nanotubes; The modified carbon nanotubes are prepared by the following steps: Carboxylated carbon nanotubes are added to thionyl chloride and N,N-dimethylformamide, refluxed and stirred at 70-75°C for 22-24 hours, evaporated under normal pressure, cooled to room temperature, heated to 100°C, vacuumed, and then introduced with argon until the pressure returns to normal, dodecylamine is added, refluxed and stirred at 90-92°C for 5-6 hours, cooled, filtered, washed, and vacuum dried to obtain modified carbon nanotubes; The carboxylated carbon nanotubes are prepared by the following steps: Add carbon nanotubes to concentrated nitric acid, heat and reflux with stirring, cool to room temperature, wash until neutral, and dry to obtain carboxylated carbon nanotubes; wherein the amount ratio of carbon nanotubes to concentrated nitric acid is 3g:12mL; The production process of the lip sheet formula for enhancing the wear resistance of the lip includes the following steps: Step 1: refrigerate PTFE, glass fiber, molybdenum disulfide, talc and modified carbon nanotubes respectively, add them into a high-speed blender according to weight parts, stir them evenly, and then dry, crush and sieve them in sequence to obtain a crushed material; Step 2: Pressing and sintering the crushed materials in sequence to obtain; The process steps of the segmented sintering are as follows: Heating from room temperature to 180°C at a rate of 20-25°C / 10min; From 180℃ to 290℃, the heating rate is 10-15℃ / 10min; Heat from 290°C to 330°C at a rate of 3-5°C / 10min, and keep at 330°C for 90-100min; Heat from 330°C to 375°C at a rate of 3-5°C / 10min, and keep at 375°C for 180-200min.

2. The lip sheet formula for enhancing lip wear resistance according to claim 1, characterized in that: The usage ratio of carboxylated carbon nanotubes, thionyl chloride, N,N-dimethylformamide and dodecylamine is 0.5-0.6 g:95 mL:0.5 mL:10-10.5 g.

3. The lip sheet formula for enhancing lip wear resistance according to claim 1, characterized in that: The particle size of the carbon nanotubes is 30-50 nm.

4. The lip sheet formula for enhancing lip wear resistance according to claim 1, characterized in that: The glass fiber has a diameter of 14-16 μm and a length of 120-150 μm.

5. The lip sheet formula for enhancing lip wear resistance according to claim 1, characterized in that: The particle size of the molybdenum disulfide is 120-180 μm.

6. The production process of a lip sheet formula for enhancing lip wear resistance according to claim 1, characterized in that: The following steps are involved: Step 1: refrigerate PTFE, glass fiber, molybdenum disulfide, talc and modified carbon nanotubes respectively, add them into a high-speed blender according to weight parts, stir them evenly, and then dry, crush and sieve them in sequence to obtain a crushed material; Step 2: Press and sinter the crushed materials in sequence to obtain the product.

7. The production process of a lip sheet formula for enhancing lip wear resistance according to claim 6, characterized in that: The refrigeration temperature is ≤-20°C, and the refrigeration time is 24-36 hours.

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