A stress-cracking-resistant polyurethane oil cup material, a polyurethane oil cup article, and a preparation method and application thereof

Abstract

The application belongs to the technical field of polymer material processing, and relates to a polyurethane oil cup material, a polyurethane oil cup product, and a preparation method and application thereof. The polyurethane oil cup material comprises polyurethane resin, core-shell structure toughening agent and nano filler in specific proportions. The core-shell structure toughening agent and the nano filler are added to realize synergistic toughening. On the premise of not sacrificing the excellent oil resistance and heat resistance of the polyurethane resin, the impact toughness and stress cracking resistance of the material are significantly improved. In combination with a delayed pressure injection molding process, the molecular chain orientation stress and thermal stress of the polyurethane material in the injection molding process are actively inhibited and reduced, so that the finally obtained polyurethane oil cup product has excellent stress cracking resistance and long-term durability, and completely meets the most stringent use requirements.

Description

Technical Field

[0001] This invention belongs to the field of polymer material processing technology, and relates to a stress-cracking resistant polyurethane oil cup material, polyurethane oil cup products, their preparation methods and applications. Background Technology

[0002] As a core load-bearing and sealing component in key functional parts such as fuel systems, lubrication circuits, and hydraulic units, the long-term sealing reliability of the oil cup directly determines the operational safety and lifespan of the entire system. With the development of modern industrial equipment towards high performance, lightweight, and compactness, the structural design of oil cups is becoming increasingly complex, often integrating features such as thin walls, deep cavities, dense reinforcing ribs, irregularly shaped flow channels, and metal inserts.

[0003] Currently, oil cup components are typically manufactured using high-performance engineering plastics such as polyurethane (PU), polyamide (PA), polyphenylene sulfide (PPS), and polyoxymethylene (PCM) through injection molding. For example, CN110218439A discloses a high-hardness thermoplastic polyurethane elastomer and its preparation method. This invention uses an alicyclic diol or diamine combined with a low-molecular-weight small-molecule diol containing ether oxygen groups. This significantly improves the toughness of the high-hardness polyurethane elastomer while ensuring the product's hardness and heat resistance. Furthermore, the combined effect of internal and external lubricants results in low internal stress and low molding shrinkage in the product, leading to a polyurethane elastomer with a hardness of 81-85. D not only retains the wear resistance, weather resistance, and oil resistance of ordinary polyurethane elastomers, but also has high strength, high heat distortion temperature, and high glass transition temperature. Its light transmittance is greater than 85%, heat distortion temperature is higher than 125℃, glass transition temperature is higher than 120℃, notched impact strength is high, and molding shrinkage is less than 0.5%. It can be used to replace some engineering plastics and is applied in fields such as automotive oil cups. Although the material itself has excellent properties, when injection molded into complex oil cup products, due to its high hardness, high modulus, rapid crystallization, and the structural characteristics of oil cups, high internal stress will remain inside the product. When these internal stresses are superimposed with subsequent assembly stress, thermal stress from the hot oil environment, and swelling stress, they are very likely to cause visible or invisible microcracks at stress concentration points, and eventually expand into macroscopic cracking and leakage.

[0004] To address the aforementioned technical issues, there is an urgent need to develop a polyurethane oil cup material with excellent tensile properties, impact toughness, and stress cracking resistance. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a polyurethane oil cup material resistant to stress cracking, a polyurethane oil cup product, a preparation method thereof, and its application. The polyurethane oil cup material fundamentally improves the stress cracking resistance without sacrificing oil resistance and heat resistance, and is suitable for preparing oil cup products.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a polyurethane oil cup material resistant to stress cracking, wherein the polyurethane oil cup material comprises the following components in parts by weight: 100 parts by weight of polyurethane resin; 5-20 parts by weight of core-shell toughening agent; 0.5 to 5 parts by weight of nanofiller.

[0007] When polyurethane oil cup materials provided by existing technologies are used in injection molding complex structure oil cup products, the inherent properties of the material are not matched with the molding process, resulting in excessively high residual internal stress inside the product. Consequently, under the superposition of multiple stresses such as subsequent assembly, long-term immersion in high-temperature oil, and thermal shock, stress concentration points (such as around metal inserts and at the root of reinforcing ribs) are prone to be induced, which can lead to micro or macro stress cracking and ultimately cause the oil cup seal to fail.

[0008] Based on the above, this invention provides a polyurethane oil cup material resistant to stress cracking. The polyurethane oil cup material uses polyurethane resin as a matrix, and by adding specific weight parts of a core-shell toughening agent and nanofillers to achieve a synergistic effect, the resulting polyurethane oil cup material not only possesses excellent oil and heat resistance but also excellent impact toughness and inherent stress cracking resistance, making it suitable for manufacturing oil cup products. Specifically, the core-shell toughening agent can absorb and disperse impact energy through "voidification" and "shear banding" mechanisms, intervening in and blocking stress cracking from multiple levels. It can efficiently transfer externally applied stress from the polyurethane matrix to the soft internal core. The core-shell toughening agent can undergo large deformation under stress, dissipating energy, while the hard shell layer prevents crazes from developing into a fatal condition. The cracks, and the tips of the craters are blunted or deflected when they encounter another core-shell particle, thus dissipating energy by generating a large number of harmless micro-craters and preventing the rapid propagation of a single crack. The nanofiller provides a huge specific surface area, which can serve as a heterogeneous nucleation point, inducing the soft and hard segments of the polyurethane matrix to be arranged more orderly on its surface, thereby refining the size of the microphase separation. The smaller and more uniform "micro-regions" can more effectively disperse and transfer external stress, making the stress distribution more uniform and avoiding stress concentration around a few coarse hard segment phase regions. There is a strong interfacial interaction between the well-dispersed nanofiller and the polyurethane molecular chains, which can restrict the local movement of the molecular chains. When the material is under stress, these interfacial regions can dissipate energy through mechanisms such as friction and slip, thereby delaying the initiation and propagation of cracks.

[0009] The content of the core-shell toughening agent can be 5 parts by weight, 7 parts by weight, 9 parts by weight, 11 parts by weight, 13 parts by weight, 15 parts by weight, 17 parts by weight, 19 parts by weight, or 20 parts by weight, etc.

[0010] The content of the nanofiller can be 0.5 parts by weight, 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight, or 5 parts by weight, etc.

[0011] Preferably, the polyurethane resin is an oil-resistant polyurethane resin.

[0012] Preferably, the content of the core-shell toughening agent in the polyurethane oil cup material is 8-15 parts by weight.

[0013] Preferably, the core material of the core-shell toughening agent is cross-linked acrylate rubber.

[0014] Preferably, the shell material of the core-shell toughening agent is a polymer with a glass transition temperature ≥50℃ (e.g., 50℃, 52℃, 54℃, 56℃, 58℃, 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 75℃, 80℃, 85℃, 90℃, 95℃ or 100℃, etc.), and more preferably a polymer with a glass transition temperature ≥80℃.

[0015] As a preferred technical solution of the present invention, cross-linked acrylate rubber is selected as the core material, and a polymer with a glass transition temperature ≥50℃ is selected as the shell material. The cross-linked acrylate rubber, as the core, provides flexibility and energy dissipation. Its glass transition temperature (Tg) is much lower than room temperature (usually <-20℃), and it is very easy to undergo large deformation under stress. The combination with a harder polymer with a glass transition temperature ≥50℃ as the shell material achieves interfacial compatibility and stress transfer. The polarity and solubility parameters of the shell polymer (such as PMMA) are similar to those of the hard segments of polyurethane (usually formed by MDI / BDO, etc.), which can form good physical entanglement and interfacial bonding with the polyurethane matrix, avoiding becoming a weak interface. It can also act as a bridge. The hard shell acts as a "stress bridge", which can efficiently transfer the externally applied stress from the polyurethane matrix to the soft rubber core inside. The rubber core of a core-shell particle undergoes large deformation under stress, while the hard shell prevents crazes from developing into fatal cracks. The tip of a craze is blunted or deflected when it encounters another core-shell particle.

[0016] Preferably, the shell material of the core-shell toughening agent includes polymethyl methacrylate or methyl methacrylate-styrene copolymer.

[0017] Preferably, the amount of nanofiller in the polyurethane oil cup material is 0.5 to 2 parts by weight.

[0018] Preferably, the nanofiller is a nanofiller that has undergone surface treatment with a silane coupling agent.

[0019] As a preferred technical solution of the present invention, the nanofiller surface-treated with silane coupling agent can not only eliminate hydrogen bonds and greatly reduce the aggregation of particles due to hydrogen bonds formed by hydroxyl groups, but also improve compatibility, making the surface of the nanofiller particles change from hydrophilic to hydrophobic / oleophilic, which improves the compatibility with polyurethane resin, makes it easier to disperse, improves the compatibility with polyurethane matrix, and prevents the aggregation of nanoparticles.

[0020] Preferably, the average particle size of the nanofiller is 5~50 nm, such as 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm, and more preferably 10~20 nm.

[0021] Preferably, the nanofiller comprises nano-silica or organomontmorillonite.

[0022] Preferably, the nano-silica includes fumed silica.

[0023] Preferably, the silane coupling agent comprises 3-aminopropyltriethoxysilane.

[0024] Preferably, the polyurethane oil cup material also includes an antioxidant.

[0025] Preferably, the antioxidant content in the polyurethane oil cup material is 0.1 to 0.5 parts by weight, such as 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, or 0.5 parts by weight.

[0026] In a second aspect, the present invention provides a method for preparing a stress-cracking resistant polyurethane oil cup material as described in the first aspect. The preparation method includes: mixing the various components, melting and granulating them to obtain the stress-cracking resistant polyurethane oil cup material.

[0027] Preferably, the mixing is carried out in a mixer.

[0028] Preferably, the melting and granulation are carried out in a twin-screw extruder; Preferably, the melting temperature is 180~230℃, such as 180℃, 185℃, 190℃, 195℃, 200℃, 205℃, 210℃, 220℃ or 230℃.

[0029] Thirdly, the present invention provides a polyurethane oil cup product, wherein the raw material of the polyurethane oil cup product includes the stress-cracking resistant polyurethane oil cup material as described in the first aspect.

[0030] Fourthly, the present invention provides a method for preparing a polyurethane oil cup product as described in the third aspect, the method comprising: feeding a stress-cracking resistant polyurethane oil cup material as described in the first aspect into an injection molding machine, melting it and then injecting it into a mold cavity with a surface temperature of 80~100℃ (e.g., 80℃, 82℃, 84℃, 86℃, 88℃, 90℃, 92℃, 94℃, 96℃, 98℃ or 100℃, etc.), and then subjecting it to delayed pressure application and pressure holding molding to obtain the polyurethane oil cup product.

[0031] The method for preparing polyurethane oil cup products provided by this invention creatively employs a delayed pressurization process (the "delayed pressurization" refers to waiting for a period of time after the molten polyurethane oil cup material enters the mold cavity before pressure molding), which provides sufficient relaxation time for the polyurethane molecular chains and allows the melt in the gate area to rebound before pressurization. This reduces and suppresses the orientation stress and volume shrinkage stress of the material from the source, significantly improving the impact toughness and inherent stress crack resistance of the polyurethane oil cup products obtained by injection molding. Combined with limiting the surface temperature of the mold cavity to 80~100℃, the high mold temperature within the above surface temperature range, combined with the delayed pressurization process, provides even more sufficient relaxation time for the polyurethane molecular chains, further improving the impact toughness and stress crack resistance of the obtained polyurethane oil cup products.

[0032] Preferably, the step of drying the polyurethane oil cup material before feeding it into the injection molding machine as described in the first aspect is further included.

[0033] Preferably, the drying temperature is 100~120℃, such as 100℃, 102℃, 104℃, 106℃, 108℃, 110℃, 112℃, 114℃, 116℃, 118℃ or 120℃.

[0034] Preferably, the drying time is 4 to 6 hours, such as 4 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours, 5 hours, 5.2 hours, 5.4 hours, 5.6 hours, 5.8 hours, or 6 hours.

[0035] Preferably, the delay time for delayed pressurization is 0.5 to 2 s, such as 0.5 s, 0.7 s, 0.9 s, 1.1 s, 1.3 s, 1.5 s, 1.7 s, 1.9 s, or 2 s; during this delay time, the pressure in the mold cavity is or is infinitely close to 0.

[0036] Preferably, the pressure for the pressure holding molding is 50~60 MPa, such as 50 MPa, 51 MPa, 52 MPa, 53 MPa, 54 MPa, 55 MPa, 56 MPa, 57 MPa, 58 MPa, 59 MPa or 60 MPa, etc.

[0037] Preferably, the pressure holding and molding time is 3 to 5 seconds, such as 3 seconds, 3.2 seconds, 3.4 seconds, 3.6 seconds, 3.8 seconds, 4 seconds, 4.2 seconds, 4.4 seconds, 4.6 seconds, 4.8 seconds, or 5 seconds.

[0038] Preferably, the pressure-holding molding process further includes an annealing step to further eliminate internal stress.

[0039] Preferably, the annealing temperature is 80~100℃, such as 80℃, 82℃, 84℃, 86℃, 88℃, 90℃, 92℃, 94℃, 96℃, 98℃ or 100℃.

[0040] Preferably, the annealing time is 2 to 4 hours, such as 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, or 4 hours.

[0041] Fifthly, the present invention provides the application of the polyurethane oil cup article as described in the first aspect in an engine, transmission or hydraulic system.

[0042] Compared with the prior art, the present invention has the following beneficial effects: (1) The stress crack resistant polyurethane oil cup material provided by the present invention includes a specific number of parts of polyurethane resin, core-shell structure toughening agent and nano filler. By adding the core-shell structure toughening agent and nano filler for synergistic toughening, the impact toughness and stress crack resistance of the material are significantly improved without sacrificing the excellent oil resistance and heat resistance of polyurethane resin. Combined with the delayed pressure injection molding process, the molecular chain orientation stress and thermal stress of polyurethane material during the injection molding process are actively suppressed and reduced, so that the final polyurethane oil cup product has excellent stress crack resistance time and long-term durability, which fully meets the most demanding use requirements. (2) Specifically, the polyurethane oil cup material provided by the present invention, combined with a specific injection molding process, results in a polyurethane oil cup product that, in an acetic acid immersion test at 25°C, has a cracking time of 15-40 s, in a constant immersion test in high-temperature machine oil at 150°C, has a cracking time of 320-720 s, and in a rapid temperature cycling test in silicone oil medium, has a failure number of 48-68 times. It also has excellent chemical resistance, heat oil resistance and thermal shock resistance. Detailed Implementation

[0043] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0044] The following is detailed information about some of the raw materials involved in the specific implementation process: (1) Oil-resistant polyurethane resin: Specifically, the high-hardness thermoplastic polyurethane elastomer provided in Example 1 of CN110218439A, with a hardness of about Shore 85 D.

[0045] (2) Core-shell toughening agent: Mitsubishi Chemical Metalatn S-2001.

[0046] (3) KH550-treated fumed silica nanoparticles: with an average particle size of 7 nm, purchased from Evonik, brand name AEROSIL® R972, and surface treated with 3-aminopropyltriethoxysilane (KH550). The specific preparation method is as follows: first, KH550 and anhydrous ethanol are mixed at a mass ratio of 1:10 to form a KH550 ethanol solution, and then the fumed silica nanoparticles and KH550 ethanol solution are mixed by spraying in a coating modification equipment (Sichuan Tanggula Particle Machinery Co., Ltd., model T-MIX-10) at a temperature of 60℃ for 10 min. After standing in the equipment for 2 h, KH550-treated fumed silica nanoparticles are obtained.

[0047] (4) Polyester-type thermoplastic polyurethane elastomer: hardness approximately Shore 85A, purchased from Asahikawa Chemical, grade XCT-2285.

[0048] Example 1 A stress-cracking resistant polyurethane oil cup material, comprising the following components by weight: 100 parts by weight of oil-resistant polyurethane resin; 8 parts by weight of core-shell toughening agent; One part by weight of fumed nano-silica treated with KH550. Antioxidant 10100.5 parts by weight; The preparation method of the polyurethane oil cup material provided in this embodiment 1 includes: premixing oil-resistant polyurethane resin, core-shell toughening agent, fumed nano silica treated with KH550 and antioxidant 1010 in a high-speed mixer for 5 min, then feeding the obtained premix into an upper screw extruder at a screw speed of 300 rpm, melting and blending at a processing temperature of 200°C, and granulating to obtain the polyurethane oil cup material.

[0049] Example 2 A stress-cracking resistant polyurethane oil cup material, comprising the following components by weight: 100 parts by weight of oil-resistant polyurethane resin; 12 parts by weight of core-shell toughening agent; Two parts by weight of fumed nano-silica treated with KH550; Antioxidant 10100.5 parts by weight; The preparation method of the polyurethane oil cup material provided in this embodiment is the same as that in Embodiment 1.

[0050] Example 3 A stress-cracking resistant polyurethane oil cup material, comprising the following components by weight: 100 parts by weight of oil-resistant polyurethane resin; 15 parts by weight of core-shell toughening agent; Three parts by weight of fumed nano-silica treated with KH550. Antioxidant 10100.5 parts by weight; The preparation method of the polyurethane oil cup material provided in this embodiment is the same as that in Embodiment 1.

[0051] Comparative Example 1 A polyurethane oil cup material, which differs from Example 2 in that it does not contain a core-shell toughening agent or KH550-treated fumed silica, while the other substances, dosages and preparation methods are the same as in Example 2.

[0052] Comparative Example 2 A polyurethane oil cup material, comprising the following components by weight: 100 parts by weight of oil-resistant polyurethane resin; 14 parts by weight of polyester-type thermoplastic polyurethane elastomer; Antioxidant 10100.5 parts by weight; The preparation method of polyurethane oil cup material provided in this embodiment includes: premixing oil-resistant polyurethane resin, polyester thermoplastic polyurethane elastomer and antioxidant 1010 in a high-speed mixer for 5 min, then feeding the obtained premix into an upper screw extruder with a screw speed of 300 rpm, melting and blending at a processing temperature of 200°C, and granulating to obtain the polyurethane oil cup material.

[0053] Comparative Example 3 A polyurethane oil cup material differs from Example 2 only in that no core-shell toughening agent is added, and the amount of fumed silica added for surface treatment is 14 parts by weight. Other substances, amounts, and preparation methods are the same as in Example 1.

[0054] Comparative Example 4 A polyurethane oil cup material differs from Example 2 only in that it does not contain surface-treated fumed silica and the amount of core-shell toughening agent added is 14 parts by weight. All other substances, amounts, and preparation methods are the same as in Example 1.

[0055] Application Example 1 A polyurethane oil cup product is prepared by means of: first, drying the stress-cracking resistant polyurethane oil cup material provided in Example 1 at 100°C for 5 h, then feeding it into an injection molding machine, melting it and injecting it into a mold cavity with a surface temperature of 90°C, applying a pressure of 60 MPa after a 1 s delay, holding the pressure for 4 s, demolding, and then annealing it at 90°C for 3 h to obtain the polyurethane oil cup product.

[0056] Application Example 2 A polyurethane oil cup product is prepared by means of: first, drying the stress-cracking resistant polyurethane oil cup material provided in Example 2 at 100°C for 5 h, then feeding it into an injection molding machine, melting it and injecting it into a mold cavity with a surface temperature of 85°C, applying a pressure of 55 MPa after a delay of 1.5 s, holding the pressure for 5 s, demolding, and then annealing it at 85°C for 3.5 h to obtain the polyurethane oil cup product.

[0057] Application Example 3 A polyurethane oil cup product is prepared by means of: first, drying the stress-cracking resistant polyurethane oil cup material provided in Example 3 at 100°C for 5 h, then feeding it into an injection molding machine, melting it and injecting it into a mold cavity with a surface temperature of 95°C, applying a pressure of 55 MPa after a delay of 0.8 s, holding the pressure for 3.5 s, demolding, and then annealing it at 95°C for 2.5 h to obtain the polyurethane oil cup product.

[0058] Application Example 4 A polyurethane oil cup product differs from Application Example 1 only in that the delayed pressure holding time is shortened to 0.3 s, while the other steps and parameters are the same as in Application Example 1.

[0059] Compare and contrast examples 1-4 A polyurethane oil cup product differs from Application Example 2 only in that the polyurethane oil cup material provided in Comparative Examples 1-4 is used instead of the polyurethane oil cup material provided in Example 2; all other steps and parameters are the same as in Application Example 1. Comparative Application Example 5 A polyurethane oil cup product is prepared by means of: first, drying the stress-cracking resistant polyurethane oil cup material provided in Example 1 at 100°C for 5 hours, then feeding it into an injection molding machine, melting it, and injecting it into a mold cavity with a surface temperature of 90°C, immediately applying a pressure of 60 MPa, holding the pressure for 4 seconds, demolding, and then annealing it at 90°C for 3 hours to obtain the polyurethane oil cup product. Comparative Application Example 6 A polyurethane oil cup product differs from Application Example 1 only in that the surface temperature of the mold cavity is 70°C, while the other steps and parameters are the same as in Application Example 1.

[0060] Comparative Application Example 7 A polyurethane oil cup product differs from Application Example 1 only in that the surface temperature of the mold cavity is 110°C, while the other steps and parameters are the same as in Application Example 1.

[0061] (1) Performance testing of polyurethane oil cup material: ① Tensile properties: Tensile strength and elongation at break were tested in accordance with ISO 527 standard; ② Notched impact strength of simply supported beams: tested in accordance with ISO 179 standard;

[0062] The polyurethane oil cup materials provided in Examples 1-3 and Comparative Examples 1-4 were tested according to the above test methods. The test results are shown in Table 1. Table 1 According to the data in Table 1: The polyurethane oil cup materials provided in Examples 1-3 are significantly superior to those provided in Comparative Examples 1-4 in terms of mechanical properties, demonstrating the effectiveness of the synergistic modification of the core-shell toughening agent and nanofiller added in this invention. Among them, the polyurethane oil cup material provided in Example 2 has the highest tensile strength of 77 MPa, while maintaining excellent toughness and impact resistance. This indicates that the formulation achieves the best balance between reinforcement and toughening, and is the formulation with the best overall performance. The polyurethane oil cup material provided in Example 3 has the highest elongation at break (15.9%) and notched impact strength of simply supported beam (158 J / m), and the most outstanding toughness. This shows that further increasing the content of toughening agent can greatly improve the deformation capacity and impact resistance of the material, but the tensile strength will be sacrificed.

[0063] Compared with Example 2, the polyurethane oil cup material provided in Comparative Example 1 has the lowest performance data in all aspects, indicating that the unmodified polyurethane resin cannot meet the application requirements for high stress crack resistance.

[0064] Compared to Example 2, the polyurethane oil cup material provided in Comparative Example 2, which uses conventional TPU toughening, has a tensile strength of only 42.5 MPa, the lowest among all samples, demonstrating that the addition of conventional elastomer toughening leads to a significant decrease in strength.

[0065] Compared with Example 2, the performance of the polyurethane oil cup materials provided in Comparative Examples 3 and 4 is far inferior to that of Example 2. This shows that both nanofillers and core-shell toughening agents are indispensable, and their synergistic effect is the key to obtaining high performance.

[0066] (2) Performance testing of polyurethane oil cup products ①Cracking time in glacial acetic acid: Immerse an 80 mm × 10 mm × 4 mm standard specimen (obtained using the same injection molding method as the corresponding application example) in glacial acetic acid at 25°C and record the time (in seconds) when visible cracks appear on the specimen. ② Stress cracking time of engine oil at 150℃: The specimen with a single-sided notch (0.5 mm depth) (the standard specimen was obtained by injection molding using the same method as the corresponding application example) was completely immersed in 5W-30 synthetic engine oil at 150℃, and the time (in hours) when the specimen broke was recorded. ③ Thermal cycling performance: Oil cup products with metal inserts (interference of 0.1 mm) were placed in a thermal shock chamber and subjected to rapid temperature cycling in a silicone oil medium at -40℃ for 30 min and at 150℃ for 30 min. The samples were checked after every 5 cycles, and the number of cycles when leakage (or cracks extending to half the wall thickness) was recorded.

[0067] The polyurethane oil cup products provided in Test Cases 1-4 and Comparative Application Examples 1-7 were tested according to the above test methods. The results are shown in Table 2. Table 2 According to the data in Table 2: The polyurethane oil cup products provided in Application Examples 1-4 have a cracking time of 25-40 s against glacial acetic acid, a cracking time of 520-720 s against machine oil stress at 150℃, and a failure time of 48-68 thermal shock cycles, exhibiting excellent resistance to chemicals, hot oils, and thermal shock.

[0068] Compared with Application Example 2, the polyurethane oil cup products provided in Application Examples 1-4 have poorer chemical resistance, heat oil resistance, and thermal shock resistance, indicating that the raw material formulation is very important.

[0069] Compared to Application Example 1, the performance of Comparative Application Example 5 is significantly lower than that of Application Example 1, directly demonstrating that the delayed holding pressure process is crucial for reducing internal stress and improving durability.

[0070] Compared with Application Example 1, when the surface temperature of the mold cavity drops to 70°C (compared to Application Example 6) or rises to 110°C (compared to Application Example 7), all three properties decrease significantly, indicating that 80~100°C is a better process window.

[0071] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A polyurethane oil cup material resistant to stress cracking, characterized in that, The polyurethane oil cup material comprises the following components by weight: 100 parts by weight of polyurethane resin; 5-20 parts by weight of core-shell toughening agent; 0.5 to 5 parts by weight of nanofiller.

2. The polyurethane oil cup material according to claim 1, characterized in that, The polyurethane resin is an oil-resistant polyurethane resin; Preferably, the content of the core-shell toughening agent in the polyurethane oil cup material is 8-15 parts by weight; Preferably, the core material of the core-shell toughening agent is cross-linked acrylate rubber; Preferably, the shell material of the core-shell toughening agent is a polymer with a glass transition temperature ≥ 50°C, and more preferably a polymer with a glass transition temperature ≥ 80°C. Preferably, the shell material of the core-shell toughening agent includes polymethyl methacrylate or methyl methacrylate-styrene copolymer.

3. The polyurethane oil cup material according to claim 1 or 2, characterized in that, The amount of nanofiller in the polyurethane oil cup material is 0.5 to 2 parts by weight; Preferably, the nanofiller is a nanofiller that has undergone surface treatment with a silane coupling agent; Preferably, the average particle size of the nanofiller is 5-50 nm, more preferably 10-20 nm; Preferably, the nanofiller comprises nano-silica and / or organomontmorillonite; Preferably, the nano-silica comprises fumed silica; Preferably, the polyurethane oil cup material further includes an antioxidant; Preferably, the antioxidant content in the polyurethane oil cup material is 0.1 to 0.5 parts by weight.

4. A method for preparing a stress-cracking resistant polyurethane oil cup material as described in any one of claims 1 to 3, characterized in that, The preparation method includes: mixing the various components, melting and granulating them to obtain the stress crack resistant polyurethane oil cup material; Preferably, the melting and granulation are carried out in a twin-screw extruder; Preferably, the melting temperature is 180~230℃.

5. A polyurethane oil cup product, characterized in that, The raw materials for the polyurethane oil cup products include the stress-cracking resistant polyurethane oil cup material as described in any one of claims 1 to 3.

6. A method for preparing a polyurethane oil cup article as described in claim 5, characterized in that, The preparation method includes: feeding the stress-cracking resistant polyurethane oil cup material as described in any one of claims 1 to 3 into an injection molding machine, melting it and then injecting it into a mold cavity with a surface temperature of 80 to 100°C, and then molding it by delayed pressure application and pressure holding to obtain the polyurethane oil cup product.

7. The preparation method according to claim 6, characterized in that, The step of drying the polyurethane oil cup material before feeding it into the injection molding machine as described in any one of claims 1 to 3 is also included. Preferably, the drying temperature is 100~120℃ and the time is 4~6 h.

8. The preparation method according to claim 6 or 7, characterized in that, The delay time for delayed pressurization is 0.5~2s; Preferably, the pressure for the pressure holding molding is 50~60 MPa, and the time is 3~5 s.

9. The preparation method according to any one of claims 6 to 8, characterized in that, The pressure holding molding process also includes an annealing step. Preferably, the annealing treatment is performed at a temperature of 80~100℃ for 2~4 hours.

10. The use of a polyurethane oil cup article as described in claim 4 or 5 in an engine, transmission, or hydraulic system.

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