Wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe and preparation method thereof

Abstract

The application belongs to the technical field of polymer composite pipes, and discloses a wear-resistant and pressure-resistant ultrahigh molecular weight polyethylene composite pipe and a preparation method thereof. The composite pipe comprises, from inside to outside, an inner wear-resistant layer, a reactive transition layer, a middle pressure-bearing layer and an outer protective layer. The inner wear-resistant layer is made of ultrahigh molecular weight polyethylene powder with a grafted surface of acrylic acid, the reactive transition layer is made of polyethylene material containing a glycidyl methacrylate unit, and the side of the transition layer facing the inner wear-resistant layer is provided with a mechanical locking structure. The inner wear-resistant layer material penetrates into the mechanical locking structure in a molten state and forms a reaction-interlocking composite interface with the transition layer. The composite pipe has excellent wear resistance, high interlayer bonding strength, ring pressure-bearing capacity and long-term service stability.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite pipe technology, specifically relating to a wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe and its preparation method. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) has been widely used in high-abrasion media transportation fields such as slurry transportation, tailings transportation, fly ash transportation, and dredging transportation due to its excellent wear resistance, corrosion resistance, self-lubrication, and low coefficient of friction. Especially in the transportation of slurries containing solid particles, UHMWPE materials typically exhibit better wear resistance than ordinary polyethylene, rubber, or metal lining materials, thus being considered an important candidate material for wear-resistant pipes. However, single-layer UHMWPE pipes still have significant shortcomings. On the one hand, UHMWPE itself has limited rigidity, insufficient compressive strength and circumferential load-bearing capacity, and is prone to creep deformation under high internal pressure or long-term load conditions, making it difficult to meet the requirements of high-pressure transportation conditions. On the other hand, UHMWPE has low surface energy and strong chemical inertness, resulting in poor interfacial adhesion with other pressure-bearing layer materials, leading to deficiencies in interlayer bonding strength and long-term interfacial stability in existing composite pipes. In existing technologies, interfacial bonding is typically improved by incorporating adhesive layers, compatibility layers, or mechanically roughened structures. However, relying solely on adhesive layers can easily lead to interfacial failure under long-term thermal cycling and alternating loads, while relying solely on mechanical bonding makes it difficult to simultaneously ensure interfacial density and long-term stability. Furthermore, ordinary ultra-high molecular weight polyethylene wear-resistant layers are mostly directly molded from conventional resin powders, lacking surface functional groups that can participate in interfacial interactions, making it difficult to form a stable chemical bond between the wear-resistant layer and the pressure-bearing layer. Summary of the Invention

[0003] To address the shortcomings mentioned in the background art, the present invention aims to provide a wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe and its preparation method. The inner wear-resistant layer is formed using ultra-high molecular weight polyethylene powder with surface grafted acrylic acid, and a reactive transition layer is formed using polyethylene material containing glycidyl methacrylate units. A mechanical interlocking structure is also incorporated to construct a reactive-interlocking composite interface that combines chemical bonding and mechanical interlocking. This approach maintains excellent wear resistance while improving interlayer bonding strength, pressure bearing capacity, and long-term service stability.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe, wherein the composite pipe comprises, from the inside out, an inner wear-resistant layer, a reactive transition layer, an intermediate pressure-bearing layer and an outer protective layer;

[0006] The inner wear-resistant layer comprises, by mass parts, 96-99.5 parts of ultra-high molecular weight polyethylene powder grafted with acrylic acid, 0.05-0.30 parts of antioxidant 1010, 0.03-0.20 parts of antioxidant 168, and 0.05-0.30 parts of calcium stearate;

[0007] The particle core of the surface-grafted acrylic acid ultra-high molecular weight polyethylene powder is ultra-high molecular weight polyethylene, and the particle surface has carboxyl groups formed by acrylic acid grafting and / or carboxyl groups formed by neutralization of the carboxyl group portion.

[0008] The reactive transition layer is made of polyethylene material containing glycidyl methacrylate units; a mechanical interlocking structure is provided on the side of the reactive transition layer facing the inner wear-resistant layer, the inner wear-resistant layer material is incorporated into the mechanical interlocking structure in a molten state, and the epoxy groups provided by the glycidyl methacrylate units react with the carboxyl groups and / or carboxyl groups on the surface of the inner wear-resistant layer to form a reaction-interlocking composite interface between the inner wear-resistant layer and the reactive transition layer, where chemical bonding and mechanical interlocking coexist.

[0009] More preferably, the ultra-high molecular weight polyethylene powder with surface-grafted acrylic acid satisfies one or more of the following conditions: weight-average molecular weight of 2.0 × 10⁻⁶. 6 ~6.0×10 6 The median particle size D50 is 50–250 μm, the grafting rate is 0.4–3.0 wt%, the content of surface carboxyl and / or carboxylate groups is 0.05–0.40 mmol / g, and the degree of carboxyl neutralization is 0–50%.

[0010] More preferably, the polyethylene material containing glycidyl methacrylate units in the reactive transition layer is glycidyl methacrylate-grafted polyethylene or ethylene-glycidyl methacrylate copolymer, the epoxy group content of the reactive transition layer is 0.10-1.50 mmol / g, and the thickness is 0.05-0.80 mm.

[0011] More preferably, the interfacial reaction is a ring-opening reaction between the epoxy groups in the reactive transition layer and the carboxyl groups and / or carboxyl groups on the surface of the inner wear-resistant layer.

[0012] More preferably, the mechanical locking structure is selected from one or more of the following: microporous structure, blind hole structure, groove structure, and mesh texture structure.

[0013] More preferably, when the mechanical locking structure is a microporous structure or a blind hole structure, the average pore size is 20–150 μm and the porosity is 5–30%; when the mechanical locking structure is a groove structure or a mesh texture structure, the groove depth or texture depth is 30–300 μm and the groove width or texture width is 50–500 μm; the thickness of the interface locking zone is 0.05–0.50 mm, the melting penetration depth of the inner wear-resistant layer material is 20–200 μm, and the proportion of continuous interface locking length is not less than 60%.

[0014] More preferably, the intermediate pressure-bearing layer comprises the following components by weight: 55-80 parts of high-density polyethylene, 10-30 parts of medium-density polyethylene, 5-20 parts of silane-treated chopped glass fiber, 2-10 parts of polyolefin elastomer, 0.05-0.30 parts of antioxidant 1010, and 0.05-0.20 parts of antioxidant 168.

[0015] More preferably, the outer protective layer comprises the following components by weight: 60-90 parts of high-density polyethylene, 10-35 parts of linear low-density polyethylene, 2-5 parts of carbon black masterbatch, 0.05-0.30 parts of antioxidant 1010, and 0.05-0.20 parts of antioxidant 168.

[0016] A method for preparing a wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe includes the following steps:

[0017] S1. After pre-irradiation, ultra-high molecular weight polyethylene powder is contacted with acrylic acid to carry out a grafting reaction. Then, after washing and drying, ultra-high molecular weight polyethylene powder with acrylic acid grafted on the surface is obtained.

[0018] S2. Polyethylene is mixed with glycidyl methacrylate and melt-treated to obtain a polyethylene transition layer material containing glycidyl methacrylate units;

[0019] S3. Mix high-density polyethylene, medium-density polyethylene and silane-treated chopped glass fibers, and form them by extrusion or molding to obtain the intermediate pressure-bearing layer.

[0020] S4. The transition layer material is shaped and a mechanical locking structure is formed on one side by pressing, etching or drilling, and then it is placed inside the intermediate pressure-bearing layer.

[0021] S5. Heat the ultra-high molecular weight polyethylene powder with surface-grafted acrylic acid to a molten state, and form it into an inner wear-resistant layer by extrusion or pressing, while simultaneously forming it into a composite layer with the transition layer and the intermediate pressure-bearing layer.

[0022] S6. High-density polyethylene and linear low-density polyethylene are mixed and an outer protective layer is formed outside the intermediate pressure-bearing layer. After cooling and shaping, the wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe is obtained.

[0023] More preferably, in step S1, when the ultra-high molecular weight polyethylene powder is contacted and treated with acrylic acid, the pre-irradiation dose is 20-80 kGy, the mass fraction of acrylic acid in the grafting solution is 5-30%, the treatment temperature is 40-80℃, and the treatment time is 0.5-6 h; in step S5, when the ultra-high molecular weight polyethylene powder with surface grafted acrylic acid is molded, the molding temperature is 190-235℃, the molding pressure is 5-30 MPa, and the holding time is 5-60 min.

[0024] The beneficial effects of this invention are:

[0025] This invention utilizes ultra-high molecular weight polyethylene (UHMWPE) powder grafted with acrylic acid as the inner wear-resistant layer. This allows the core particles to retain the excellent wear resistance of UHMWPE itself, while introducing carboxyl and / or carboxyl groups onto the particle surface, thus endowing the inner layer material with a certain degree of interfacial reactivity. Combined with a polyethylene reactive transition layer containing glycidyl methacrylate units, the epoxy groups in the transition layer and the polar groups on the surface of the inner wear-resistant layer form a stable interfacial bond during the composite molding process, significantly improving the problems of poor interfacial affinity and easy interlayer peeling between traditional UHMWPE and pressure-bearing layer materials. Simultaneously, this invention incorporates a mechanical interlocking structure on the side of the reactive transition layer facing the inner wear-resistant layer, allowing the molten inner wear-resistant layer material to penetrate into the interlocking structure and form a stable mechanical interlock. This establishes both chemical bonding and mechanical anchoring mechanisms at the interface, forming a reactive-interlocking composite interface. This interface structure not only improves interlayer peel strength but also facilitates effective load transfer between layers, reducing interfacial stress concentration, thereby improving the circumferential pressure-bearing capacity, creep resistance, and long-term service stability of the composite pipe. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1: Under conditions of lower grafting degree, thinner transition layer and shallower locking structure, the composite pipe of the present invention can still form a stable composite interface and have both wear resistance and pressure bearing properties.

[0028] A wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe, wherein the composite pipe comprises, from the inside out, an inner wear-resistant layer, a reactive transition layer, an intermediate pressure-bearing layer and an outer protective layer;

[0029] The preparation steps of the wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe are as follows:

[0030] S1. First, take 1000g of ultra-high molecular weight polyethylene powder, the weight-average molecular weight of which is 2.0×10⁻⁶. 6 The median particle size D50 was 50 μm. The powder was placed in a sealed bag and pre-irradiated with gamma rays under nitrogen protection, with an irradiation dose controlled at 20 kGy. 50 g of acrylic acid was added to 950 g of deionized water and stirred until homogeneous, yielding a 5% (w / w) acrylic acid solution. The pre-irradiated ultra-high molecular weight polyethylene (UHMWPE) powder was poured into the acrylic acid solution, heated to 40°C, and continuously stirred for 0.5 h. After treatment, the powder was filtered out and repeatedly rinsed with deionized water until the washing solution was nearly neutral. The washed powder was then placed in an oven and dried at 60°C for 12 h to obtain UHMWPE powder with surface grafted acrylic acid.

[0031] S2. Take 500g of high-density polyethylene and 25g of glycidyl methacrylate, mix them thoroughly in a mixer, and then add them to a twin-screw extruder. Control the temperature of each section of the extruder at approximately 170℃ and the screw speed at 60rpm. Extrude, cool, and pelletize to obtain a polyethylene transition layer material containing glycidyl methacrylate units. Then add this pellet to a single-screw extruder and extrude it into a transition layer film with a thickness of approximately 0.05mm.

[0032] S3. Take 550g of high-density polyethylene, 100g of medium-density polyethylene, 50g of silane-treated chopped glass fiber, 20g of polyolefin elastomer, 0.5g of antioxidant 1010, and 0.5g of antioxidant 168. First, put them into a high-speed mixer and mix for 10 minutes. After mixing evenly, add them to an extruder and melt-extrude at about 180℃ to make a pipe blank with an intermediate pressure-bearing layer.

[0033] S4. Place the transition layer film on the embossing mold and press a mechanical interlocking structure onto the side of the film facing the inner wear-resistant layer. The interlocking structure is controlled as follows: average pore diameter 20μm, porosity 5%, groove depth 30μm, and groove width 50μm. After embossing, attach the transition layer film to the inner side of the intermediate pressure-bearing layer and fix it by heating and pressing.

[0034] S5. Take 960g of ultra-high molecular weight polyethylene powder grafted with acrylic acid, 0.5g of antioxidant 1010, 0.3g of antioxidant 168, and 0.5g of calcium stearate, and dry mix them evenly. Add the mixed material to the inner layer molding mold, heat it at 190℃, and after the material melts, apply a pressure of 5MPa and hold the pressure for 5 minutes to form the inner layer material and press it into the aforementioned mechanical interlocking structure, while simultaneously bonding it with the transition layer and the intermediate pressure-bearing layer.

[0035] S6. Take 600g of high-density polyethylene, 100g of linear low-density polyethylene, 20g of carbon black masterbatch, 0.5g of antioxidant 1010, and 0.5g of antioxidant 168. Mix them thoroughly, then use an extruder to coat the outer protective layer around the middle pressure-bearing layer. After coating, allow it to cool and set naturally to obtain a wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe.

[0036] Example 2: The improved interfacial bonding strength, pressure bearing capacity, and overall performance of the composite pipe of the present invention under conditions of high surface activity, thicker transition layer, and stronger mechanical interlocking.

[0037] A wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe, wherein the composite pipe comprises, from the inside out, an inner wear-resistant layer, a reactive transition layer, an intermediate pressure-bearing layer and an outer protective layer;

[0038] The preparation steps of the wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe are as follows:

[0039] S1. First, take 1000g of ultra-high molecular weight polyethylene powder, the weight-average molecular weight of which is 6.0×10⁻⁶. 6 The median particle size D50 was 250 μm. Pre-irradiation with gamma rays was performed under nitrogen protection, with an irradiation dose controlled at 80 kGy. 300 g of acrylic acid was added to 700 g of deionized water and stirred until homogeneous, yielding a 30% (w / w) acrylic acid solution. The pre-irradiated ultra-high molecular weight polyethylene (UHMWPE) powder was poured into the acrylic acid solution, stirred in a reactor, heated to 80 °C, and treated for 6 h. After treatment, the powder was filtered out and repeatedly washed with deionized water until the washing solution was nearly neutral. The powder was then dried at 60 °C for 12 h. The grafted powder was then treated in an alkaline solution (0.5 mol / L sodium hydroxide aqueous solution) with a liquid-to-solid ratio controlled at 3:1. After stirring at room temperature for 30 min, the powder was filtered, washed with deionized water until neutral, and then dried at 60 °C for 8 h to obtain UHMWPE powder with surface grafted acrylic acid.

[0040] S2. Take 500g of polyethylene and 50g of glycidyl methacrylate, mix them thoroughly in a mixer, and then add them to a twin-screw extruder for melt treatment. The temperature of each section of the extruder is controlled at 165–210℃, with the final section temperature controlled at 210℃. The screw speed is controlled at 80 rpm. After extrusion, the material is cooled in a cooling water bath and then pelletized to obtain a polyethylene transition layer material containing glycidyl methacrylate units. This pellet is then added to a single-screw extruder and extruded into a transition layer film with a thickness of approximately 0.80 mm. The epoxy group content of this transition layer material is measured to be 1.50 mmol / g.

[0041] S3. Take 800g of high-density polyethylene, 300g of medium-density polyethylene, 200g of silane-treated chopped glass fiber, 100g of polyolefin elastomer, 3.0g of antioxidant 1010, and 2.0g of antioxidant 168. First, add them to a high-speed mixer and dry mix for 15 minutes to ensure that all components are as homogeneous as possible. After mixing, add the mixture to an extruder and melt-extrude it at 190-210℃ to produce a tube blank with an intermediate pressure layer.

[0042] S4. Lay the transition layer film flat on the embossing mold. Process the mechanical locking structure on the side facing the inner wear-resistant layer, using a micropore and groove composite structure. The control parameters are: average pore diameter 150μm, porosity 30%, groove depth 300μm, groove width 500μm, and the thickness of the interface locking zone is controlled at 0.50mm. After processing, place the side with the locking structure facing inward and attach it to the inner surface of the intermediate pressure-bearing layer. Press and fix it by heated rollers to obtain a pressure-bearing layer composite tube blank with a transition layer.

[0043] S5. Take 995g of ultra-high molecular weight polyethylene powder grafted with acrylic acid, 3.0g of antioxidant 1010, 2.0g of antioxidant 168, and 3.0g of calcium stearate, and dry mix them in a mixer for 10 minutes. Add the uniformly mixed material to the inner layer molding device, heat it at 235℃, and after the material is fully melted, apply a pressure of 30MPa and hold the pressure for 60 minutes to form the inner wear-resistant layer material, which then penetrates into the aforementioned mechanical interlocking structure in a molten state. Control the melt penetration depth of the inner wear-resistant layer material to 200μm, and control the continuous interlocking length ratio to be no less than 60%. After completion, the inner wear-resistant layer, transition layer, and intermediate pressure-bearing layer are composited into one unit.

[0044] S6. Take 900g of high-density polyethylene, 350g of linear low-density polyethylene, 50g of carbon black masterbatch, 3.0g of antioxidant 1010, and 2.0g of antioxidant 168. Mix them thoroughly in a mixer, then send them to an extruder for melt extrusion. Coat the extruded material onto the outside of the intermediate pressure-bearing layer to form an outer protective layer. After coating, cool and set the material to obtain a wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe.

[0045] Example 3: Under the condition of coordinated matching of various components and structural parameters, the composite pipe of the present invention demonstrates comprehensive performance in terms of wear resistance, interfacial bonding performance, and overall service stability.

[0046] A wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe, wherein the composite pipe comprises, from the inside out, an inner wear-resistant layer, a reactive transition layer, an intermediate pressure-bearing layer and an outer protective layer;

[0047] The preparation steps of the wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe are as follows:

[0048] S1. Take 1000g of ultra-high molecular weight polyethylene powder, wherein the weight-average molecular weight of the powder is 4.0×10⁻⁶. 6 The median particle size D50 was 150 μm. The powder was placed in a sealed bag and pre-irradiated with gamma rays under nitrogen protection, with the irradiation dose controlled at 50 kGy. 175 g of acrylic acid was added to 825 g of deionized water to prepare an acrylic acid solution with a mass fraction of 17.5%. The pre-irradiated ultra-high molecular weight polyethylene powder was added to the above solution, stirred in a reactor, heated to 60 °C, and maintained for 3.25 h. After treatment, the powder was filtered, repeatedly washed with deionized water until neutral, and then dried at 60 °C for 12 h. Subsequently, partial neutralization treatment was performed: the obtained grafted powder was added to a 0.3 mol / L sodium hydroxide solution, with a liquid-to-solid ratio controlled at 3:1, stirred at room temperature for 20 min, filtered, washed with deionized water until neutral, and then dried at 60 °C for 8 h to obtain the final surface-grafted acrylic acid ultra-high molecular weight polyethylene powder for use. The powder has a grafting rate of 1.7 wt%, a surface carboxyl and / or carboxylate group content of 0.225 mmol / g, and a carboxyl neutralization degree of 25%.

[0049] S2. Take 500g of high-density polyethylene and 37.5g of glycidyl methacrylate, mix them thoroughly in a mixer, and then add them to a twin-screw extruder for melt treatment. The extruder temperature is controlled at approximately 190℃, and the screw speed is controlled at 70rpm. After extrusion, cool and pelletize to obtain a polyethylene transition layer material containing glycidyl methacrylate units. Then, use a single-screw extruder to form a transition layer film with a thickness of approximately 0.425mm, and its epoxy content is measured to be 0.80mmol / g.

[0050] S3. Take 675g of high-density polyethylene, 200g of medium-density polyethylene, 125g of silane-treated chopped glass fiber, 60g of polyolefin elastomer, 1.75g ​​of antioxidant 1010, and 1.25g of antioxidant 168, and mix them in a high-speed mixer for 12 minutes. After mixing, add the mixture to an extruder and melt-extrude it at 190℃ to obtain the intermediate pressure-bearing layer tube blank.

[0051] S4. Place the transition layer film on an embossing mold and process a mechanical locking structure on the side facing the inner wear-resistant layer. In this embodiment, a micropore and groove composite structure is used, with the following control parameters: average pore diameter 85μm, porosity 17.5%, groove depth 165μm, groove width 275μm, and interface locking zone thickness approximately 0.275mm. After processing, the locking structure surface of the transition layer film is placed inward and bonded to the inner surface of the intermediate pressure-bearing layer, and then fixed by heating and pressing to obtain a pressure-bearing layer composite structure with a transition layer.

[0052] S5. Take 977.5g of ultra-high molecular weight polyethylene powder grafted with acrylic acid, 1.75g ​​of antioxidant 1010, 1.15g of antioxidant 168, and 1.75g ​​of calcium stearate, and dry mix them in a mixer for 10 minutes. Add the mixed material to the inner layer forming device, heat it to a molten state at 212.5℃, then apply a pressure of 17.5MPa and hold it for 32.5 minutes to form the inner wear-resistant layer material, which then penetrates into the mechanical interlocking structure in a molten state. Control the molten penetration depth of the inner wear-resistant layer material to approximately 110μm, and the continuous interlocking length ratio to approximately 80%, so that the inner wear-resistant layer, transition layer, and intermediate pressure-bearing layer are integrated into one unit.

[0053] S6. Take 750g of high-density polyethylene, 225g of linear low-density polyethylene, 35g of carbon black masterbatch, 1.75g ​​of antioxidant 1010, and 1.25g of antioxidant 168, and mix them evenly in a mixer. Then, extrude the mixture to coat the outer layer of the intermediate pressure-bearing layer, forming an outer protective layer. After coating, cool and set the material to obtain a wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe.

[0054] Comparative Example 1: No surface grafting modification

[0055] A wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe, wherein the composite pipe comprises, from the inside out, an inner wear-resistant layer, a reactive transition layer, an intermediate pressure-bearing layer and an outer protective layer;

[0056] In step S1 of this comparative example, the acrylic acid grafting treatment and partial neutralization treatment of the ultra-high molecular weight polyethylene powder are not performed. Unmodified ultra-high molecular weight polyethylene powder is directly used as the raw material for the inner wear-resistant layer. In step S5, the raw material for the inner wear-resistant layer is replaced with unmodified ultra-high molecular weight polyethylene powder. The raw materials used are 977.5g of unmodified ultra-high molecular weight polyethylene powder, 1.75g ​​of antioxidant 1010, 1.15g of antioxidant 168, and 1.75g ​​of calcium stearate. The remaining steps, raw material composition, and process parameters are the same as in Example 3.

[0057] Comparative Example 2: Structure without mechanical locking

[0058] A wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe, wherein the composite pipe comprises, from the inside out, an inner wear-resistant layer, a reactive transition layer, an intermediate pressure-bearing layer and an outer protective layer;

[0059] In step S4 of this comparative example, the mechanical locking structure is not processed on the side of the transition layer film facing the inner wear-resistant layer. The transition layer film maintains a smooth surface and is directly attached to the inner side of the intermediate pressure-bearing layer. The remaining steps, raw material composition and process parameters are the same as in Example 3.

[0060] Performance testing

[0061] 1. Wear rate test

[0062] Standard test pieces were prepared by cutting the inner wear-resistant layer and weighing their initial mass m1. Wear tests were conducted in a circulating abrasive system using a mixture of quartz sand and water as the abrasive. The quartz sand particle size was 0.1–0.3 mm, the solid content of the slurry was 30 wt%, the test load was 20 N, the rotation speed was 200 r / min, and the test time was 2 h. After the test, the pieces were cleaned and dried, and their final mass m2 was weighed to calculate the wear rate.

[0063] 2. Interlayer peel strength test

[0064] Cut 15mm wide strip samples along the pipe axis, peel the inner wear-resistant layer and transition layer apart by a certain length, and perform a 180° peel test at a tensile speed of 50mm / min. Record the stable load during the peeling process, and calculate the interlayer peel strength according to the sample width. Each group of samples should be tested at least 5 times, and the average value should be taken.

[0065] 3. Ring stiffness test

[0066] Cut a ring-shaped specimen of a specified length from the composite pipe and place it between two parallel pressure plates of a ring stiffness testing machine. Compress it radially at a rate of (5±1) mm / min at room temperature. Measure the load under 2.5% radial deformation and calculate the ring stiffness according to the pipe ring stiffness calculation formula. Test no fewer than 3 samples in each group and take the average value.

[0067] 4. Hydrostatic pressure test

[0068] Composite pipe samples of the same length were cut, sealed at both ends, and connected to a hydrostatic testing device. Water was injected into the pipe as the pressurizing medium, and the pressure was gradually increased at a rate of 0.1 MPa / s at room temperature, with each increment held for 1 minute. The pressure at which leakage, bulging, delamination, or rupture occurred was recorded as the ultimate hydrostatic pressure. Each group of samples was tested three times, and the average value was taken.

[0069] The results are shown in Table 1 below.

[0070] Table 1 Performance results of composite tubes for each sample

[0071] Example 1 18.3 4.8 17.3 5.7 Example 2 11.2 8.9 21.5 8.8 Example 3 13.6 7.6 20.4 7.5 Comparative Example 1 20.4 2.1 16.8 5.2 Comparative Example 2 15.7 3.2 17.1 5.4

[0072] As shown in Table 1, the wear rates of Examples 1-3 were all lower than those of Comparative Examples 1 and 2, with Example 2 having the lowest rate, followed by Example 3. Example 1 was slightly higher but still better than the Comparative Examples. Comparative Example 1, which used ungrafted ultra-high molecular weight polyethylene powder, had the highest wear rate, indicating that surface grafting treatment helps improve the stability of the material in the composite structure and reduces additional wear caused by interfacial micro-detachment. Although Comparative Example 2 retained the grafting modification, it lacked a mechanical interlocking structure and had insufficient interfacial support, making it prone to local peeling during the wear process, thus leading to an increased wear rate.

[0073] The interlayer peel strength results for Examples 2 and 3 are significantly higher than those for the two comparative examples, indicating that the inner wear-resistant layer grafted with acrylic acid can form a more effective interfacial bond with the transition layer containing glycidyl methacrylate units, and the mechanical interlocking structure further improves the interfacial anti-separation ability. Comparative Example 1, after removing the surface grafting modification, has insufficient interfacial reaction sites and the lowest peel strength; Comparative Example 2, after removing the mechanical interlocking structure, still has some interfacial reaction, but lacks structural interlocking effect, and the peel strength still decreases significantly.

[0074] The ring stiffness results show that Examples 1-3 are generally superior to the comparative examples, especially Examples 2 and 3, which show more significant improvements. In this invention, a stable composite interface is formed between the inner wear-resistant layer, the transition layer, and the pressure-bearing layer. Under pressure, they can jointly bear the external load, reducing interface slippage and local instability, thus exhibiting higher overall stiffness. Comparative Examples 1 and 2, due to insufficient interface coordination, are more prone to inconsistent interlayer deformation during radial compression, resulting in lower ring stiffness.

[0075] The hydrostatic pressure test results show that the ultimate pressure values ​​of Examples 2 and 3 are significantly higher than those of the comparative example. This indicates that under internal pressure, the reactive-interlocking composite interface constructed in this invention can more effectively limit interlayer separation, bulging, and early failure, resulting in a more uniform pressure distribution among the layers. Comparative Example 1, lacking surface grafting modification, has insufficient interfacial reactivity and is more prone to failure at the interface during pressure increase. Although Comparative Example 2 retains the reactive transition layer, it lacks a mechanical interlocking structure, resulting in insufficient impact and peel resistance at the interface, thus limiting its pressure resistance.

[0076] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0077] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe, characterized in that, The composite pipe comprises, from the inside out, an inner wear-resistant layer, a reactive transition layer, an intermediate pressure-bearing layer, and an outer protective layer. The inner wear-resistant layer comprises, by mass parts, 96-99.5 parts of ultra-high molecular weight polyethylene powder grafted with acrylic acid, 0.05-0.30 parts of antioxidant 1010, 0.03-0.20 parts of antioxidant 168, and 0.05-0.30 parts of calcium stearate; The particle core of the surface-grafted acrylic acid ultra-high molecular weight polyethylene powder is ultra-high molecular weight polyethylene, and the particle surface has carboxyl groups formed by acrylic acid grafting and / or carboxyl groups formed by neutralization of the carboxyl group portion. The reactive transition layer is made of polyethylene material containing glycidyl methacrylate units; a mechanical interlocking structure is provided on the side of the reactive transition layer facing the inner wear-resistant layer, the inner wear-resistant layer material is incorporated into the mechanical interlocking structure in a molten state, and the epoxy groups provided by the glycidyl methacrylate units react with the carboxyl groups and / or carboxyl groups on the surface of the inner wear-resistant layer to form a reaction-interlocking composite interface between the inner wear-resistant layer and the reactive transition layer, where chemical bonding and mechanical interlocking coexist.

2. The wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe according to claim 1, characterized in that, The ultra-high molecular weight polyethylene powder with surface-grafted acrylic acid meets one or more of the following conditions: weight-average molecular weight of 2.0×10⁶ to 6.0×10⁶, median particle size D50 of 50 to 250 μm, grafting rate of 0.4 to 3.0 wt%, surface carboxyl and / or carboxylate group content of 0.05 to 0.40 mmol / g, and carboxyl neutralization degree of 0 to 50%.

3. The wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe according to claim 1, characterized in that, The polyethylene material containing glycidyl methacrylate units in the reactive transition layer is glycidyl methacrylate-grafted polyethylene or ethylene-glycidyl methacrylate copolymer. The epoxy content of the reactive transition layer is 0.10–1.50 mmol / g, and the thickness is 0.05–0.80 mm.

4. The wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe according to claim 1 or 3, characterized in that, The interface reaction is a ring-opening reaction between the epoxy groups in the reactive transition layer and the carboxyl groups and / or carboxyl groups on the surface of the inner wear-resistant layer.

5. The wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe according to claim 1, characterized in that, The mechanical locking structure is selected from one or more of the following: microporous structure, blind hole structure, groove structure, and mesh texture structure.

6. The wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe according to claim 5, characterized in that, When the mechanical locking structure is a microporous structure or a blind hole structure, the average pore size is 20–150 μm and the porosity is 5–30%; when the mechanical locking structure is a groove structure or a mesh texture structure, the groove depth or texture depth is 30–300 μm and the groove width or texture width is 50–500 μm; the thickness of the interface locking zone is 0.05–0.50 mm, the melting penetration depth of the inner wear-resistant layer material is 20–200 μm, and the proportion of continuous interface locking length is not less than 60%.

7. The wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe according to claim 1, characterized in that, The intermediate pressure-bearing layer comprises the following components by weight: 55-80 parts high-density polyethylene, 10-30 parts medium-density polyethylene, 5-20 parts silane-treated chopped glass fiber, 2-10 parts polyolefin elastomer, 0.05-0.30 parts antioxidant 1010, and 0.05-0.20 parts antioxidant 168.

8. The wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe according to claim 1, characterized in that, The outer protective layer comprises the following components by weight: 60-90 parts of high-density polyethylene, 10-35 parts of linear low-density polyethylene, 2-5 parts of carbon black masterbatch, 0.05-0.30 parts of antioxidant 1010, and 0.05-0.20 parts of antioxidant 168.

9. A method for preparing a wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. After pre-irradiation, ultra-high molecular weight polyethylene powder is contacted with acrylic acid to carry out a grafting reaction. Then, after washing and drying, ultra-high molecular weight polyethylene powder with acrylic acid grafted on the surface is obtained. S2. Polyethylene is mixed with glycidyl methacrylate and melt-treated to obtain a polyethylene transition layer material containing glycidyl methacrylate units; S3. Mix high-density polyethylene, medium-density polyethylene and silane-treated chopped glass fibers, and form them by extrusion or molding to obtain the intermediate pressure-bearing layer. S4. The transition layer material is shaped and a mechanical locking structure is formed on one side by pressing, etching or drilling, and then it is placed inside the intermediate pressure-bearing layer. S5. Heat the ultra-high molecular weight polyethylene powder with surface-grafted acrylic acid to a molten state, and form it into an inner wear-resistant layer by extrusion or pressing, while simultaneously forming it into a composite layer with the transition layer and the intermediate pressure-bearing layer. S6. High-density polyethylene and linear low-density polyethylene are mixed and an outer protective layer is formed outside the intermediate pressure-bearing layer. After cooling and shaping, the wear-resistant and pressure-resistant ultra-high molecular weight polyethylene composite pipe is obtained.

10. The preparation method according to claim 9, characterized in that: In step S1, when the ultra-high molecular weight polyethylene powder is contacted and treated with acrylic acid, the pre-irradiation dose is 20-80 kGy, the mass fraction of acrylic acid in the grafting solution is 5-30%, the treatment temperature is 40-80℃, and the treatment time is 0.5-6 h. In step S5, when the ultra-high molecular weight polyethylene powder with surface grafted acrylic acid is molded, the molding temperature is 190-235℃, the molding pressure is 5-30 MPa, and the holding time is 5-60 min.