Highly abrasion resistant supercritical foamed tpu material and method of making

Abstract

The application discloses a kind of high wear-resistant supercritical foaming TPU materials and preparation method thereof, it is related to high polymer material technical field, the material is made of the following weight parts of component: TPU granule 100 parts, wear-resistant filler 5~20 parts, compatible agent 3~10 parts, supercritical fluid foaming agent 3~5 parts, foaming aid 1~5 parts, antioxidant 0.5~2 parts and lubricant 0.5~2 parts;The wear-resistant filler is the compound of surface aminated modified nanometer silicon dioxide and surface carboxylated modified polytetrafluoroethylene micro powder, melt blending granulation is obtained to composite master batch by wear-resistant filler, TPU and other aid, after the master batch is shaped into sample, by supercritical fluid impregnation and fast pressure relief foaming, obtain final product.The application is still able to keep excellent wear resistance after supercritical foaming by unique wear-resistant system and interface design, solve the industry problem of poor wear resistance of foaming material, and process environment protection, easy to industrial production.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a high wear-resistant supercritical foamed TPU material and its preparation method. Background Technology

[0002] Thermoplastic polyurethane elastomer (TPU) is widely used in footwear, sporting goods, and automotive parts due to its excellent elasticity, abrasion resistance, oil resistance, and mechanical strength. Supercritical fluid foaming technology (usually using supercritical CO2 or N2) is an environmentally friendly and efficient microporous foaming technology that can produce microporous polymer materials with excellent properties such as lightweight, high cushioning, and heat insulation.

[0003] Supercritical foaming of TPU can significantly reduce the material density and improve its cushioning and energy return performance, making it very suitable for high-end sports shoe midsoles, protective pads, and other products. However, after foaming, the physical structure of TPU changes from a dense body to a porous structure, which usually significantly reduces its surface abrasion resistance. The abrasion resistance of traditionally foamed TPU often fails to meet the stringent requirements of high-end application scenarios (such as soles for long-term outdoor use), limiting its wider application.

[0004] In the prior art, the methods commonly used to improve the wear resistance of foamed materials are: (1) blending modification, such as adding wear-resistant fillers. However, conventional fillers (such as carbon black and ordinary silica) are prone to become heterogeneous nucleation points of cells during the foaming process, resulting in uneven cell size or affecting the foaming ratio, making it difficult to achieve both high wear resistance and high buffering. (2) Most wear-resistant fillers (especially PTFE) have poor compatibility with TPU and weak interfacial bonding. Under the dynamic stress of foaming and use, the fillers are prone to fall off from the matrix, which not only fails to play a reinforcing role, but the fallen particles will also accelerate the wear of the material like abrasives. (3) Uneven dispersion of fillers or poor interfacial bonding will lead to uneven distribution of heterogeneous nucleation points during supercritical foaming, which will easily form large and uneven cells, and even cell merging and collapse. This inferior cell structure will significantly reduce the mechanical properties and durability of the material.

[0005] Therefore, developing a supercritical foamed TPU material that can achieve a good foamed structure while also possessing excellent wear resistance, based on the material itself, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a high wear-resistant supercritical foamed TPU material and its preparation method.

[0007] Another objective of this invention is to provide a method for preparing the above-mentioned material, which is simple, environmentally friendly, and easy to industrialize.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention provides a high-wear-resistant supercritical foamed TPU material, which is made of the following components in parts by weight:

[0010] Thermoplastic TPU granules: 100 parts;

[0011] Wear-resistant filler: 5~20 parts;

[0012] Compatibilizer: 3-10 parts;

[0013] 3-5 parts of supercritical fluid foaming agent;

[0014] Foaming agent: 1-5 parts;

[0015] Antioxidant: 0.5-2 parts;

[0016] Lubricant: 0.5~2 parts.

[0017] The wear-resistant filler is prepared by the following method:

[0018] First, the silane coupling agent was mixed with a mixed solution of ethanol and water. The pH was adjusted with acetic acid to promote hydrolysis, and the mixture was stirred for a certain time. Then, nano-SiO2 was dispersed in anhydrous ethanol and sonicated to form a suspension. The hydrolyzed silane coupling agent was slowly added dropwise to the SiO2 suspension, and the mixture was stirred and refluxed at a certain temperature. After the reaction was complete, the modified SiO2 was separated by filtration and washed multiple times with ethanol to remove the physically adsorbed coupling agent. Finally, it was dried in a vacuum oven at 60℃ for one day to obtain aminated modified SiO2 (SiO2-NH2). The chemical reaction equation is as follows:

[0019]

[0020] PTFE micropowder was irradiated with Co-60 source gamma rays under an inert nitrogen atmosphere. The irradiation dose was controlled. The irradiated PTFE was then rapidly transferred to a reactor containing acrylic acid monomers and reacted at a specific temperature. After the reaction, the product was poured into a large amount of acetone to precipitate. Then, using a Soxhlet extractor with acetone as the solvent, continuous reflux extraction was performed for 24–48 hours to completely remove unreacted acrylic acid monomers and their homopolymers. The extracted product was dried in a vacuum oven at 60°C for one day to obtain pure grafted modified PTFE (PTFE-g-AA). The chemical reaction equation is as follows: .

[0021] Preferably, the thermoplastic TPU particles are polyester-type TPU with a Shore hardness between 85A and 95A.

[0022] Preferably, the wear-resistant filler is a compound of surface-aminated nano-sized SiO2 and surface-carboxylated polytetrafluoroethylene (PTFE) micro powder.

[0023] Preferably, the compatibilizer is maleic anhydride-grafted TPU (TPU-g-MAH).

[0024] Preferably, the supercritical fluid foaming agent is at least one of supercritical CO2 and N2.

[0025] Preferably, the foaming agent is zinc oxide or zinc stearate.

[0026] Preferably, the antioxidant is at least one of antioxidant 1010 (pentaerythritol ester), antioxidant 1076 (octadecyl propionate), antioxidant 168 (tris(2,4-di-tert-butylphenyl)phosphite), antioxidant 702 (4,4'-methylenebis(2,6-di-tert-butylphenol)), and antioxidant 300 (2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)trimethylbenzene).

[0027] Preferably, the lubricant is at least one of polyethylene wax and vinyl bis-stearamide.

[0028] Preferably, the silane coupling agent is one or a combination of two of KH-550, A-1100 and KH-602, and the amount of silane coupling agent used is 5 to 10% of the weight of nano-SiO2.

[0029] Preferably, the volume ratio of ethanol to water is 95:5, the pH is adjusted to 4-5 with acetic acid, and the hydrolysis is carried out for 30-60 minutes.

[0030] Preferably, the ultrasonic treatment lasts for 30 minutes, followed by heating to 70-80°C and reflux reaction for 6-8 hours.

[0031] Preferably, the irradiation dose is controlled at 10~20 kGy.

[0032] Preferably, the amount of acrylic monomer used is 10-30% of the weight of PTFE. The temperature is raised to 60-70°C, and the reaction is carried out for 4-6 hours.

[0033] This invention provides a method for preparing the above-mentioned high wear-resistant supercritical foamed TPU material, comprising the following steps:

[0034] S1. Preparation of wear-resistant filler:

[0035] S2. Preparation of wear-resistant filler and TPU composite masterbatch:

[0036] Modified SiO2-NH2 and PTFE-g-AA were placed in a high-speed mixer in a certain proportion and mixed at a certain speed at room temperature to initially and uniformly mix the two fillers with different properties. Thermoplastic TPU granules were dried in a vacuum oven to remove moisture. The dried thermoplastic TPU granules, premixed wear-resistant fillers, compatibilizers, and other additives (foaming aid ZnO, antioxidants, lubricants, etc.) were all added to the high-speed mixer according to the formula proportions. Mixing was carried out at room temperature for a certain time to ensure uniform dispersion of all components. Granulation was performed using a co-rotating twin-screw extruder. The mixed material was added from the hopper, and after melting, shearing, mixing, and reaction, it was extruded into strips from the die head. After cooling in a water tank, it was cut into uniform granules by a pelletizer to obtain high wear-resistant TPU composite masterbatch. The chemical reaction equation is as follows:

[0037] .

[0038] S3. Foaming molding and final product preparation:

[0039] The high wear-resistant TPU composite masterbatch prepared above is molded into strips of the required shape and size using a flat vulcanizing machine. The strips are then placed in a supercritical foaming reactor, sealed, and heated to the preset foaming temperature. Supercritical CO2 or N2 is injected into the reactor to bring the pressure to a certain value and stabilize it, allowing it to foam for a period of time. This allows the supercritical fluid to fully penetrate and dissolve into the high wear-resistant TPU composite masterbatch. The pressure inside the reactor is then quickly reduced to atmospheric pressure, and the foamed product is rapidly transferred to a cooling fixture for shaping to prevent cell collapse or overgrowth. Finally, a high wear-resistant supercritical foamed TPU material is obtained.

[0040] Furthermore, in step S2, the SiO2-NH2 and PTFE-g-AA are in a weight ratio of 2~4:1.

[0041] Furthermore, in step S2, the high-speed mixer rotates at 500-800 rpm for 5-15 minutes.

[0042] Furthermore, in step S2, the temperature of the vacuum oven is 80~100℃, and the drying time is 4~6 hours.

[0043] Furthermore, the temperature settings of the co-rotating twin-screw extruder in step S2 are as follows: from the feed port to the die head, the temperature ranges are set sequentially to 160℃, 170℃, 180℃, 185℃ and 180℃, and the screw speed is set to 200~400rpm.

[0044] Furthermore, in step S3, the temperature of the flat vulcanizing machine is 160~200℃. First, it is pre-pressed at 1 MPa for 2 minutes, then the pressure is increased to 15 MPa and held for 10 minutes. After the cooling system is turned on to cool down to below 40℃, the pressure is released and the mold is demolded.

[0045] Furthermore, the spline size in step S3 is 150mm × 100mm × 5mm.

[0046] Furthermore, in step S3, the foaming temperature is 150~170℃, the foaming pressure is 15~25 MPa, the foaming time is 1~3h, and the depressurization time is 1~5s.

[0047] Compared with the prior art, the beneficial effects of the present invention are:

[0048] 1. This invention innovatively uses a compound of surface-aminated nano-sized SiO2 and surface-carboxylated PTFE micro powder as a wear-resistant filler. SiO2 provides support as rigid particles, and PTFE reduces the coefficient of friction as a solid lubricant. Through synergistic effect, the two achieve a perfect combination of "reinforcement" and "lubrication". Experiments show that the wear resistance of the foamed material prepared by this invention is significantly improved compared with conventional foamed TPU of the same density, overcoming the technical bottleneck of decreased wear resistance caused by foaming.

[0049] 2. By performing surface functionalization modification on SiO2 and PTFE (introducing -NH2 and -COOH), and using maleic anhydride-grafted TPU as a compatibilizer, strong chemical bonds (such as amide bonds and ester bonds) can be formed between the filler and TPU during melt blending, rather than simple physical adsorption. This strong interfacial bonding can effectively transfer stress and prevent interfacial debonding, thus maintaining good mechanical strength of the material while ensuring wear resistance.

[0050] 3. Thanks to the good dispersibility of the modified filler and the bridging effect of the compatibilizer, coupled with the heterogeneous nucleation effect of the foaming agent, the present invention can form a microporous structure with small cell size and uniform distribution during the supercritical foaming process. This ideal cell morphology ensures that the material has high resilience, low compression set and excellent buffering performance.

[0051] 4. This invention adopts physical modification and supercritical fluid physical foaming technology throughout the process, without the need for harmful chemical foaming agents. The product is green and environmentally friendly. The preparation method has a clear process flow, good compatibility with existing plastic processing equipment (such as twin-screw extruders, flat vulcanizing machines, and supercritical foaming kettles), and strong controllability of process parameters, making it very suitable for large-scale industrial production.

[0052] 5. The material prepared by this invention has the unique advantages of being lightweight, highly elastic, and highly wear-resistant, which greatly expands the application range of foamed TPU. It is especially suitable for fields with stringent requirements for wear resistance, such as high-end sports shoe midsoles, industrial wear-resistant pads, conveyor belt rollers, and high-performance sealing and cushioning components, with huge market potential. Attached Figure Description

[0053] Figure 1 This is a flowchart illustrating the preparation process of the high wear-resistant supercritical foamed TPU in this invention. Detailed Implementation

[0054] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Example

[0055] The high abrasion-resistant supercritical foamed TPU material comprises the following components in parts by weight:

[0056] 100 parts of polyester-type TPU (Shore hardness 90A), 8 parts of wear-resistant filler, 6 parts of aminated modified SiO2 (SiO2-NH2), 2 parts of carboxylated modified PTFE (PTFE-g-AA), 3 parts of compatibilizer (TPU-g-MAH), 2 parts of foaming agent (ZnO), 0.5 parts of antioxidant 1010, 0.5 parts of antioxidant 168, 1 part of lubricant (polyethylene wax), and 4 parts of supercritical CO2 foaming agent.

[0057] The method for preparing the high wear-resistant supercritical foamed TPU material of the present invention, such as... Figure 1 As shown, it includes the following steps:

[0058] The wear-resistant filler is prepared by the following method:

[0059] Preparation of SiO2-NH2: γ-aminopropyltriethoxysilane (6% by weight of SiO2) was added to a 95:5 volume ratio ethanol / water mixed solution, the pH was adjusted to 4.5 with acetic acid, and hydrolysis was carried out for 45 min. Nano-SiO2 was dispersed in anhydrous ethanol and sonicated for 30 min. The hydrolyzed coupling agent solution was added dropwise to the solution, and the mixture was refluxed at 75 °C for 7 h. After the reaction, the mixture was filtered, washed with ethanol, and vacuum dried at 60 °C for 24 h.

[0060] Preparation of PTFE-g-AA: PTFE micro powder was irradiated with 15 kGy of γ-rays under a nitrogen atmosphere and then rapidly transferred to a reactor containing 20% ​​PTFE by weight of acrylic acid monomer. The reaction was carried out at 65°C for 5 h. After the reaction, the product was precipitated with acetone and Soxhlet extracted for 36 h, and then vacuum dried at 60°C for 24 h.

[0061] The method for preparing the high wear-resistant supercritical foamed TPU material of the present invention, such as... Figure 1 As shown, it includes the following steps:

[0062] S1. Preparation of wear-resistant filler:

[0063] S2. Preparation of wear-resistant filler and TPU composite masterbatch:

[0064] SiO2-NH2:PTFE-g-AA = 3:1 was placed in a high-speed mixer and mixed at 600 rpm for 8 minutes at room temperature to ensure that the two fillers with different properties were initially mixed evenly. The thermoplastic TPU granules were dried in a vacuum oven at 80℃ for 5 hours to remove moisture. The dried thermoplastic TPU granules, premixed wear-resistant fillers, compatibilizers and other additives (foaming aid ZnO, antioxidants, lubricants, etc.) were all added to the high-speed mixer according to the formula ratio and mixed at 600 rpm for 12 minutes at room temperature to ensure that all components were evenly dispersed. A co-rotating twin-screw extruder was used, with the temperature set sequentially to 160℃, 170℃, 180℃, 185℃ and 180℃, and the screw speed at 300 rpm. After melting, shearing, mixing and reaction, strips were extruded from the die head. After cooling in a water tank, they were cut into uniform granules by a pelletizer to obtain high wear-resistant TPU composite masterbatch.

[0065] S3. Foaming molding and final product preparation:

[0066] The high abrasion-resistant TPU composite masterbatch was placed on a flat vulcanizing machine. The temperature was first raised to 180℃, and the pressure was pre-pressed at 1MPa for 2 minutes. Then the pressure was increased to 15MPa and held for 10 minutes. After the cooling system was turned on and the temperature was lowered to below 40℃, the pressure was released and the mold was demolded. The molded sample was pressed into a 150mm×100mm×5mm sample. The sample was placed in a supercritical foaming kettle, and supercritical CO2 was injected into the kettle. The sample was foamed at 165℃ and 20MPa for 2 hours. Then the pressure was quickly released within 2 seconds, and the product was taken out and cooled and shaped rapidly. Example

[0067] The high abrasion-resistant supercritical foamed TPU material comprises the following components in parts by weight:

[0068] 100 parts of polyester-type TPU (Shore hardness 88A), 15 parts of wear-resistant filler, 10 parts of aminated modified SiO2 (SiO2-NH2), 5 parts of carboxylated modified PTFE (PTFE-g-AA), 5 parts of compatibilizer (TPU-g-MAH), 3 parts of foaming agent (ZnO), 10761 parts of antioxidant, 1.5 parts of lubricant (vinyl bis-stearamide), and 3.5 parts of supercritical CO2 foaming agent.

[0069] Preparation method:

[0070] The wear-resistant filler is prepared by the following method:

[0071] Preparation of SiO2-NH2: γ-aminopropyltriethoxysilane (8% of the weight of SiO2) was added to a 95:5 volume ratio ethanol / water mixed solution, the pH was adjusted to 4.5 with acetic acid, and hydrolysis was carried out for 45 min. Nano-SiO2 was dispersed in anhydrous ethanol and sonicated for 30 min. The hydrolyzed coupling agent solution was added dropwise to the solution, and the mixture was refluxed at 75 °C for 7 h. After the reaction, the mixture was filtered, washed with ethanol, and vacuum dried at 60 °C for 24 h.

[0072] Preparation of PTFE-g-AA: PTFE micro powder was irradiated with 12 kGy of γ-rays under a nitrogen atmosphere and then rapidly transferred to a reactor containing 25% PTFE by weight of acrylic acid monomer. The reaction was carried out at 65°C for 5 h. The product was then precipitated with acetone and Soxhlet extracted for 36 h, and then vacuum dried at 60°C for 24 h.

[0073] The method for preparing the high wear-resistant supercritical foamed TPU material of the present invention, such as... Figure 1 As shown, it includes the following steps:

[0074] S1. Preparation of wear-resistant filler:

[0075] S2. Preparation of wear-resistant filler and TPU composite masterbatch:

[0076] SiO2-NH2:PTFE-g-AA = 2:1 was placed in a high-speed mixer and mixed at 600 rpm for 8 minutes at room temperature to ensure that the two fillers with different properties were initially mixed evenly. The thermoplastic TPU granules were dried in a vacuum oven at 80℃ for 5 hours to remove moisture. The dried thermoplastic TPU granules, premixed wear-resistant fillers, compatibilizers and other additives (foaming aid ZnO, antioxidants, lubricants, etc.) were all added to the high-speed mixer according to the formula ratio and mixed at 600 rpm for 12 minutes at room temperature to ensure that all components were evenly dispersed. A co-rotating twin-screw extruder was used with the temperature set at 160℃, 170℃, 180℃, 185℃ and 180℃ and the screw speed at 250 rpm. After melting, shearing, mixing and reaction, strips were extruded from the die head. After cooling in a water tank, they were cut into uniform granules by a pelletizer to obtain high wear-resistant TPU composite masterbatch.

[0077] S3. Foaming molding and final product preparation:

[0078] The high abrasion-resistant TPU composite masterbatch was placed on a flat vulcanizing machine. The temperature was first raised to 180℃, and the pressure was pre-pressed at 1MPa for 2 minutes. Then the pressure was increased to 15MPa and held for 10 minutes. After the cooling system was turned on and the temperature was lowered to below 40℃, the pressure was released and the mold was demolded. The molded sample was pressed into a 150mm×100mm×5mm sample. The sample was placed in a supercritical foaming kettle, and supercritical CO2 was injected into the kettle. The sample was foamed at 155℃ and 18MPa for 2.5 hours. Then the pressure was quickly released within 3 seconds, and the product was taken out and cooled and shaped rapidly. Example

[0079] formula:

[0080] The high abrasion-resistant supercritical foamed TPU material comprises the following components in parts by weight:

[0081] 100 parts of polyether-type TPU (Shore hardness 92A), 10 parts of wear-resistant filler, 8 parts of aminated modified SiO2 (SiO2-NH2), 2 parts of carboxylated modified PTFE (PTFE-g-AA), 3 parts of compatibilizer (TPU-g-MAH), 1 part of foaming agent (ZnO), 0.8 parts of antioxidant 702, 0.5 parts of lubricant (polyethylene wax), and 4.5 parts of supercritical CO2 foaming agent.

[0082] Preparation method:

[0083] The wear-resistant filler is prepared by the following method:

[0084] Preparation of SiO2-NH2: γ-aminopropyltriethoxysilane (6% by weight of SiO2) was added to a 95:5 volume ratio ethanol / water mixed solution, the pH was adjusted to 4.5 with acetic acid, and hydrolysis was carried out for 45 min. Nano-SiO2 was dispersed in anhydrous ethanol and sonicated for 30 min. The hydrolyzed coupling agent solution was added dropwise to the solution, and the mixture was refluxed at 80 °C for 6 h. After the reaction, the mixture was filtered, washed with ethanol, and vacuum dried at 60 °C for 24 h.

[0085] Preparation of PTFE-g-AA: PTFE micro powder was irradiated with 15 kGy of γ-rays under a nitrogen atmosphere and then rapidly transferred to a reactor containing 20% ​​PTFE by weight of acrylic acid monomer. The reaction was carried out at 70°C for 4 h. The product was then precipitated with acetone and Soxhlet extracted for 36 h, and then vacuum dried at 60°C for 24 h.

[0086] The method for preparing the high wear-resistant supercritical foamed TPU material of the present invention, such as... Figure 1 As shown, it includes the following steps:

[0087] S1. Preparation of wear-resistant filler:

[0088] S2. Preparation of wear-resistant filler and TPU composite masterbatch:

[0089] SiO2-NH2:PTFE-g-AA = 4:1 was placed in a high-speed mixer and mixed at 600 rpm for 8 minutes at room temperature to ensure that the two fillers with different properties were initially mixed evenly. The thermoplastic TPU granules were dried in a vacuum oven at 80℃ for 5 hours to remove moisture. The dried thermoplastic TPU granules, premixed wear-resistant fillers, compatibilizers and other additives (foaming aid ZnO, antioxidants, lubricants, etc.) were all added to the high-speed mixer according to the formula ratio and mixed at 200 rpm for 15 minutes at room temperature to ensure that all components were evenly dispersed. A co-rotating twin-screw extruder was used, with the temperature set sequentially to 160℃, 170℃, 180℃, 185℃ and 180℃, and the screw speed at 300 rpm. After melting, shearing, mixing and reaction, strips were extruded from the die head. After cooling in a water tank, they were cut into uniform granules by a pelletizer to obtain high wear-resistant TPU composite masterbatch.

[0090] S3. Foaming molding and final product preparation:

[0091] The high abrasion-resistant TPU composite masterbatch was placed on a flat vulcanizing machine. The temperature was first raised to 180℃, and the pressure was pre-pressed at 1 MPa for 2 minutes. Then the pressure was increased to 15 MPa and held for 10 minutes. After the cooling system was turned on and the temperature was lowered to below 40℃, the pressure was released and the mold was demolded. The molded sample was pressed into a 150mm×100mm×5mm sample. The sample was placed in a supercritical foaming kettle, and supercritical CO2 was injected into the kettle. The sample was foamed at 170℃ and 22MPa for 1 hour. Then the pressure was released rapidly within 1 second, and the product was taken out and quickly cooled and shaped. Example

[0092] formula:

[0093] The high abrasion-resistant supercritical foamed TPU material comprises the following components in parts by weight:

[0094] 100 parts of polyester-type TPU (Shore hardness 95A), 14 parts of wear-resistant filler, 10 parts of aminated modified SiO2 (SiO2-NH2), 4 parts of carboxylated modified PTFE (PTFE-g-AA), 5 parts of compatibilizer (TPU-g-MAH), 5 parts of foaming aid (ZnO), 1.5 parts of antioxidant 300, 2 parts of lubricant (vinyl bis-stearamide), and 5 parts of supercritical CO2 foaming agent.

[0095] Preparation method:

[0096] The wear-resistant filler is prepared by the following method:

[0097] Preparation of SiO2-NH2: γ-aminopropyltriethoxysilane (10% of the weight of SiO2) was added to a 95:5 volume ratio of ethanol / water mixed solution, the pH was adjusted to 4.5 with acetic acid, and hydrolysis was carried out for 60 min. Nano-SiO2 was dispersed in anhydrous ethanol and sonicated for 30 min. The hydrolyzed coupling agent solution was added dropwise to the solution, and the mixture was refluxed at 75 °C for 7 h. After the reaction, the mixture was filtered, washed with ethanol, and vacuum dried at 60 °C for 24 h.

[0098] Preparation of PTFE-g-AA: PTFE micro powder was irradiated with 20 kGy of γ-rays under a nitrogen atmosphere and then rapidly transferred to a reactor containing 30% PTFE by weight of acrylic acid monomer. The reaction was carried out at 65°C for 5 h. After the reaction, the product was precipitated with acetone and Soxhlet extracted for 36 h, and then vacuum dried at 60°C for 24 h.

[0099] The method for preparing the high wear-resistant supercritical foamed TPU material of the present invention, such as... Figure 1 As shown, it includes the following steps:

[0100] S1. Preparation of wear-resistant filler:

[0101] S2. Preparation of wear-resistant filler and TPU composite masterbatch:

[0102] SiO2-NH2:PTFE-g-AA = 2.5:1 was placed in a high-speed mixer and mixed at 600 rpm for 8 minutes at room temperature to ensure that the two fillers with different properties were initially mixed evenly. The thermoplastic TPU granules were dried in a vacuum oven at 80℃ for 5 hours to remove moisture. The dried thermoplastic TPU granules, premixed wear-resistant fillers, compatibilizers and other additives (foaming aid ZnO, antioxidants, lubricants, etc.) were all added to the high-speed mixer according to the formula ratio and mixed at 600 rpm for 12 minutes at room temperature to ensure that all components were evenly dispersed. A co-rotating twin-screw extruder was used, with the temperature set sequentially to 160℃, 170℃, 180℃, 185℃ and 180℃, and the screw speed at 400 rpm. After melting, shearing, mixing and reaction, strips were extruded from the die head. After cooling in a water tank, the strips were cut into uniform granules by a pelletizer to obtain high wear-resistant TPU composite masterbatch.

[0103] S3. Foaming molding and final product preparation:

[0104] The high abrasion-resistant TPU composite masterbatch was placed on a flat vulcanizing machine. The temperature was first raised to 180℃, and the pressure was pre-pressed at 1 MPa for 2 minutes. Then the pressure was increased to 15 MPa and held for 10 minutes. After the cooling system was turned on and the temperature was lowered to below 40℃, the pressure was released and the mold was demolded. The molded sample was pressed into a 150mm×100mm×5mm sample. The sample was placed in a supercritical foaming kettle, and supercritical CO2 was injected into the kettle. The sample was foamed at 150℃ and 25MPa for 3 hours. Then the pressure was quickly released within 5 seconds, and the product was taken out and cooled and shaped rapidly.

[0105] Comparative Example 1:

[0106] Compared with Example 1, this comparative example does not use wear-resistant fillers (i.e., does not add SiO2-NH2 and PTFE-g-AA), but the remaining components and preparation process are exactly the same.

[0107] Comparative Example 2:

[0108] Compared with Example 1, this comparative example uses unmodified ordinary nano-SiO2 and unmodified ordinary PTFE micro powder as wear-resistant fillers, with the same compounding ratio, and the remaining components and preparation process are exactly the same.

[0109] Comparative Example 3:

[0110] Compared with Example 1, this comparative example does not use a compatibilizer (TPU-g-MAH), but the remaining components and preparation process are exactly the same.

[0111] Comparative Example 4:

[0112] Compared with Example 1, this comparative example uses only a single wear-resistant filler, that is, only 6 parts of SiO2-NH2 are added, and PTFE-g-AA is not added, so that the total number of wear-resistant fillers is 6 parts. The remaining components and preparation process are exactly the same.

[0113] Comparative Example 5:

[0114] Compared with Example 1, this comparative example uses only a single wear-resistant filler, that is, only 2 parts of PTFE-g-AA are added, and SiO2-NH2 is not added, so that the total number of wear-resistant fillers is 2 parts. The remaining components and preparation process are exactly the same.

[0115] Comparative Example 6:

[0116] Compared with Example 1, this comparative example does not use supercritical fluid foaming, but instead uses a traditional chemical foaming agent (AC foaming agent, added in 3 parts) to directly foam and mold during the twin-screw extrusion process.

[0117] Performance testing:

[0118] The TPU materials of Examples 1-4 and Comparative Examples 1-6 were subjected to the following performance tests:

[0119] 1. Density test:

[0120] Referring to GB / T 1033.1-2008 "Determination of density of non-foamed plastics", an electronic densitometer (based on Archimedes' water displacement method) was used to test the foamed samples. Each sample was tested 5 times and the average value was taken.

[0121] 2. Abrasion resistance test:

[0122] Referring to GB / T 9867-2008 "Determination of Abrasion Resistance of Vulcanized Rubber or Thermoplastic Rubber (Rotating Roller Abrasion Tester Method)", a DIN abrasion tester was used. Under specified pressure, the sample was rubbed against rotating sandpaper, and the volumetric abrasion amount or mass loss after a certain friction stroke was measured. The results are expressed as abrasion amount (mm³) or relative abrasion percentage. The lower the abrasion amount, the better the abrasion resistance.

[0123] 3. Mechanical property testing:

[0124] Compression set: Referring to GB / T 6669-2008 "Determination of compression set of flexible foam polymer materials", a compression set tester was used to compress the sample to 50% of its original thickness. After maintaining it at 70℃ for 22 hours, it was taken out and allowed to recover for 30 minutes. The residual deformation was measured and the compression set rate (%) was calculated. The lower the value, the better the resilience and creep resistance.

[0125] Rebound rate: Referring to GB / T 6670-2008 "Determination of rebound performance of flexible foam polymer materials by falling ball method", a falling ball rebound tester is used to drop a standard steel ball from a fixed height to impact the surface of the foam sample, and the percentage of its rebound height to the drop height is measured.

[0126] 4. Friction coefficient test:

[0127] Referring to GB / T 10006-2021 "Determination of the coefficient of friction of plastic films and sheets", a coefficient of friction meter was used. The foamed sample was dragged at a constant speed on the surface of a standard steel plate to measure the coefficient of dynamic friction.

[0128] The test results are shown in Table 1 below:

[0129] Table 1. Effects of different formulations and process parameters on the properties of TPU materials

[0130]

[0131] Data Analysis:

[0132] 1. Influence of formulation factors:

[0133] Comparative Examples 4-5 show that neither rigid particles (SiO2) nor lubricating particles (PTFE) alone can achieve the best results. The combination of surface-aminated SiO2 and surface-carboxylated PTFE creates a perfect synergy between "rigid support" and "friction lubrication". SiO2 bears the main wear stress and prevents the material from excessive deformation; while PTFE significantly reduces the surface friction coefficient and transforms sliding friction into rolling friction with less wear.

[0134] Surface modification is the foundation for achieving synergistic effects. The performance of Comparative Example 2 using unmodified filler is far inferior to that of Example 1 using modified filler. The surface functionalization of -NH2 and -COOH greatly enhances the interfacial compatibility between the filler and thermoplastic TPU particles. Through the "bridging" effect of the compatibilizer, a strong chemical bond is formed, preventing the filler from falling off during friction and ensuring the durability and effectiveness of the wear resistance effect.

[0135] Maleic anhydride-grafted TPU (TPU-g-MAH) serves as a compatibilizer. Its anhydride groups react with the functional groups on the surface of the modified filler, while its TPU segments are completely compatible with the thermoplastic TPU particles. In contrast, Comparative Example 3, lacking a compatibilizer, resulted in deteriorated cell structure, filler agglomeration, reduced heterogeneous nucleation points, coarse and uneven cells, and weakened interfacial bonding. Compared to Example 1, its mechanical properties (such as compression set) and abrasion resistance significantly decreased. Therefore, a compatibilizer is essential to ensure uniform filler dispersion, the formation of a stable and fine cell structure, and the achievement of strong interfacial bonding.

[0136] II. Influence of process factors:

[0137] Compared with the traditional chemical foaming process of Comparative Example 6, the supercritical CO2 foaming agent of Example 1 has significant advantages: superior cell quality; supercritical fluid has a density similar to liquid and diffusivity similar to gas, allowing it to penetrate more uniformly into the polymer matrix; excellent environmental performance, with no chemical residue in the physical foaming process, resulting in a cleaner and more environmentally friendly product; and superior performance, with the fine cell structure directly leading to higher resilience, lower compression set, and better cushioning performance.

[0138] Foaming temperature and pressure together determine the solubility and saturation state of supercritical fluids in polymers. Examples 1-4 show that a foaming temperature of 150-170°C and a foaming pressure of 15-25 MPa are suitable windows. Too low a temperature or insufficient pressure will lead to insufficient foaming; too high a temperature will reduce the strength of the polymer melt, causing cell merging or collapse. Rapid pressure relief is the key to forming a high cell density. The instantaneous pressure drop creates extremely high thermodynamic instability, inducing a large number of uniform cell nucleations, thereby inhibiting the excessive growth of individual cells.

[0139] A comparison of Examples 1 to 4 shows that the mixing and processing parameters, the temperature setting of the twin-screw extruder, and the screw speed directly affect the dispersion effect of the filler and the melt state of TPU. Among them, the optimized process parameters such as the temperature gradient and the 300 rpm speed in Example 1 are the prerequisites for preparing high-quality composite masterbatch.

[0140] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A highly abrasion resistant supercritical foamed TPU material characterized in that, The following components are prepared in parts by weight: Thermoplastic TPU particles: 100 parts; Wear-resistant filler: 5-20 parts; Compatibilizer: 3-10 parts; Supercritical fluid foaming agent: 3-5 parts; Foaming aid: 1-5 parts; Antioxidant: 0.5-2 parts; Lubricant: 0.5-2 parts; The compatibilizer is maleic anhydride grafted TPU; The wear-resistant filler is a compound of nano-sized silicon dioxide modified by surface amination and polytetrafluoroethylene micro-powder modified by surface carboxylation; the wear-resistant filler is prepared by the following method: First, mix the silane coupling agent with a mixed solution of ethanol and water, adjust the pH with acetic acid to promote hydrolysis, stir for a certain period of time, then disperse the nano-sized silicon dioxide in anhydrous ethanol, ultrasonic treatment to form a suspension, slowly add the hydrolyzed silane coupling agent to the silicon dioxide suspension, stir and reflux at a certain temperature, after the reaction is completed, separate the modified silicon dioxide by filtration, wash with ethanol several times to remove the physically adsorbed coupling agent, and finally dry in a vacuum oven at 60°C for one day to obtain the amination-modified silicon dioxide; irradiate the polytetrafluoroethylene micro-powder under an inert nitrogen atmosphere with a Co-60 source gamma ray, control the irradiation dose, quickly transfer the irradiated polytetrafluoroethylene micro-powder to a reactor containing acrylic monomer, heat to 60-70°C, and react for 4-6 hours; after the reaction, pour the product into a large amount of acetone to precipitate, then use a Soxhlet extractor, take acetone as the solvent, and continuously reflux extract for 24-48 hours to completely remove the unreacted acrylic monomer and its homopolymer, dry the extracted product in a vacuum oven at 60°C for one day to obtain pure carboxyl-modified polytetrafluoroethylene.

2. The high abrasion resistant supercritical foamed TPU material according to claim 1, characterized in that, The thermoplastic TPU particles are polyester TPU with a Shore hardness of 85A-95A.

3. The high abrasion resistant supercritical foamed TPU material of claim 1, wherein, The supercritical fluid foaming agent is at least one of supercritical CO2 and N2; the foaming aid is zinc oxide or zinc stearate.

4. The high abrasion resistant supercritical foamed TPU material of claim 1, wherein, The antioxidant is at least one of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 702, and antioxidant 300; the lubricant is at least one of polyethylene wax and vinyl bis-stearamide.

5. The high abrasion resistant supercritical foamed TPU material of claim 1, wherein, The silane coupling agent is one of KH-550, A-1100, and KH-602 or a combination of two; the amount of silane coupling agent is 5-10% of the weight of nano-sized silicon dioxide; the volume ratio of ethanol to water is 95:5, the pH is adjusted to 4-5 with acetic acid, hydrolysis is performed for 30-60 minutes, ultrasonic treatment is performed for 30 minutes, the temperature is raised to 70-80°C, and reflux reaction is performed for 6-8 hours.

6. The highly abrasion resistant supercritical foamed TPU material of claim 1, wherein, The irradiation dose is controlled at 10-20 kGy, and the amount of acrylic monomer is 10-30% of the weight of polytetrafluoroethylene.

7. A method for preparing a high-wear-resistant supercritical foamed TPU material according to any one of claims 1 to 6, characterized in that, The following steps are included: S1, preparation of the wear-resistant filler; S2, preparation of the wear-resistant filler and TPU compound master batch: The modified amino-modified nano-sized silica and carboxyl-modified polytetrafluoroethylene micro-powder are placed in a high-speed mixer and mixed at room temperature, and the thermoplastic TPU particles are dried in a vacuum oven to remove moisture; the dried thermoplastic TPU particles, pre-mixed wear-resistant fillers, compatibilizers and other additives are all put into a high-speed mixer according to the formula proportion, mixed at room temperature, and granulated using a co-rotating twin-screw extruder, the mixed material is added from a hopper, and after melting, shearing, mixing, and reaction, a strip-shaped product is extruded from the head, cooled in a water tank, and then cut into uniform particles by a pelletizer, thereby obtaining a high-wear-resistant TPU composite master batch; S3, foaming and forming and final product preparation: The high-wear-resistant TPU composite master batch prepared above is formed into a sample strip of a desired shape and size by a flat vulcanizing machine, the sample strip is placed in a supercritical foaming kettle, sealed, heated to a preset foaming temperature, supercritical CO2 or N2 is injected into the kettle, the pressure is stabilized to a certain value, and the high-wear-resistant TPU composite master batch is foamed for a period of time, the supercritical fluid is fully penetrated and dissolved into the high-wear-resistant TPU composite master batch, and then the pressure in the kettle is quickly reduced to normal pressure, the foamed product is quickly moved to a cooling tooling for shaping to prevent cell collapse or excessive growth, and finally a high-wear-resistant supercritical foaming TPU material is obtained.

8. The method for preparing a high wear-resistant supercritical foamed TPU material according to claim 7, characterized in that, In S2, the amino-modified nano-sized silica and carboxyl-modified polytetrafluoroethylene micro-powder are mixed at a weight ratio of 2-4:1, the high-speed mixer rotates at a speed of 500-800 rpm, the reaction time is 5-15 min, the vacuum oven temperature is 80-100℃, and the drying time is 4-6 h; the temperature of the co-rotating twin-screw extruder is set as follows: from the feeding port to the head, the temperature intervals are set as 160℃, 170℃, 180℃, 185℃ and 180℃, and the screw rotation speed is set at 200-400 rpm.

9. The method for preparing a high-wear-resistant supercritical foamed TPU material according to claim 7, characterized in that, In S3, the temperature of the flat vulcanizing machine is 160-200℃, the sample strip is pre-pressed at a pressure of 1 MPa for 2 min, then the pressure is increased to 15 MPa, and the pressure is maintained for 10 min, then the cooling system is opened to cool the sample strip to below 40℃, and then the sample strip is demolded; the size of the sample strip is 150 mm x 100 mm x 5 mm; the foaming temperature is 150-170℃, the foaming pressure is 15-25 MPa, the foaming time is 1-3 h, and the pressure relief time is 1-5 s.

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