A high-strength modified high-density polyethylene double-wall corrugated pipe and a preparation method thereof

Abstract

The application discloses a high-strength modified high-density polyethylene double-wall corrugated pipe and a preparation method thereof, relates to the technical field of high-density polyethylene double-wall corrugated pipes, and the high-strength modified high-density polyethylene double-wall corrugated pipe is prepared from the following components: high-density polyethylene, ultra-high molecular weight polyethylene, reinforcing filler, compatilizer, antioxidant and lubricant. The preparation method comprises the following steps: surface modification of the reinforcing filler; melt blending of the components to prepare a modified composite material; extrusion molding of the modified composite material into a double-wall corrugated pipe; cooling, shaping and cutting. According to the application, the UHMWPE and the reinforcing filler are introduced, and the compatilizer is combined to improve the interface bonding, so that the high molecular chain of the UHMWPE is entangled to form a strong and tough network, the reinforcing filler provides rigid support, and the high-temperature modulus and the creep resistance are improved in cooperation; in addition, the antioxidant effectively inhibits high-temperature oxidative degradation, increases the slow crack growth time, and increases the service life.

Description

Technical Field

[0001] This invention relates to the field of high-density polyethylene double-wall corrugated pipe technology, and more particularly to a high-strength modified high-density polyethylene double-wall corrugated pipe and its preparation method. Background Technology

[0002] High-density polyethylene (HDPE) double-wall corrugated pipes are widely used in municipal drainage, sewage transportation, industrial pipelines, and ground source heat pump systems due to their advantages such as light weight, easy installation, and low cost. Their structural features include a smooth inner wall to reduce fluid resistance and a corrugated outer wall to enhance ring stiffness, effectively withstanding external pressure and providing good flexibility. However, existing HDPE double-wall corrugated pipes have significant drawbacks in high-temperature environments: as temperature increases, the molecular chain movement of HDPE material intensifies, the crystal structure loosens, leading to decreased tensile strength, reduced creep modulus, accelerated oxidative degradation and slow crack growth, and a shortened service life. These problems severely limit the reliability and safety of the pipes, especially in scenarios such as high surface temperatures in summer, industrial heat medium transportation, or ground source heat pump pipelines. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a high-strength modified high-density polyethylene double-wall corrugated pipe and its preparation method. The specific technical solution is as follows:

[0004] A high-strength modified high-density polyethylene double-wall corrugated pipe, by weight, comprises the following components: 70-85 parts high-density polyethylene, 10-20 parts ultra-high molecular weight polyethylene, 5-10 parts reinforcing filler, 2-5 parts compatibilizer, 0.5-1 part antioxidant, and 0.5-1 part lubricant.

[0005] Preferably:

[0006] The reinforcing filler is potassium titanate whiskers with a length of 10~50μm, and the surface is modified with a silane coupling agent;

[0007] The compatibilizer is maleic anhydride-grafted polyethylene with a grafting rate of 1% to 1.5%.

[0008] The antioxidants include hindered phenolic antioxidants;

[0009] The lubricant is polyethylene wax.

[0010] Preferably, it further includes: 1-2 parts of nano-silica, 3-5 parts of ethylene-octene copolymer, and 0.3-0.5 parts of initiator.

[0011] Preferably:

[0012] The potassium titanate whiskers are modified by a composite of silane coupling agents KH-550 and KH-570.

[0013] The particle size of the nano-silica is 20~30 nm;

[0014] The melt index of the ethylene-octene copolymer is 0.5~1 g / 10min;

[0015] The initiator is dicumyl peroxide.

[0016] Preferably:

[0017] The surface of the potassium titanate whiskers is coated with low molecular weight polyethylene.

[0018] The nano-silica surface is grafted with 3,5-di-tert-butyl-4-hydroxybenzoate, with a grafting rate of 2%~2.5%.

[0019] The antioxidants also include phosphite antioxidants.

[0020] The present invention also provides a preparation method for preparing a high-strength modified high-density polyethylene double-wall corrugated pipe as described in any one of the above claims, the preparation method comprising the following steps:

[0021] a. Surface modification treatment of reinforcing fillers;

[0022] b. Prepare a modified composite material by melt blending high-density polyethylene, ultra-high molecular weight polyethylene, surface-modified reinforcing filler, compatibilizer, antioxidant and lubricant;

[0023] c. The modified composite material is extruded into a double-walled corrugated pipe using a rotary shear extrusion process;

[0024] d. The extruded double-wall corrugated pipe is obtained by cooling, shaping, and cutting.

[0025] Preferably:

[0026] In step a, the reinforcing filler is potassium titanate whiskers, and the modification treatment includes adding potassium titanate whiskers to an ethanol solution mixed with silane coupling agent and ultrasonically dispersing for 30-40 minutes, and drying at 75-85°C for 3-5 hours.

[0027] In step b, the melt blending is carried out in a twin-screw extruder at a temperature of 180~220℃, a screw speed of 150~260rpm, and a mixing time of 30~40 minutes.

[0028] In step c, the rotary shear extrusion uses a rotary mandrel extruder with a mandrel speed of 5~15 rpm and an extrusion temperature of 190~210℃;

[0029] In step d, the cooling and shaping process adopts vacuum shaping with a negative pressure of -0.05 to -0.08 MPa and a cooling water temperature of 25 to 40°C.

[0030] Preferably:

[0031] In step a, the silane coupling agent is a compound solution of KH-550 and KH-570 in a mass ratio of 1:1, with a mass concentration of 2% to 2.5%.

[0032] In step b, the melt blending is a two-stage process, specifically including:

[0033] First stage: High-density polyethylene, ethylene-octene copolymer and maleic anhydride grafted polyethylene are blended at 180~190℃ and screw speed of 240~260 rpm for 15~20 minutes;

[0034] In the second stage, ultra-high molecular weight polyethylene, surface-modified potassium titanate whiskers, nano-silica and dicumyl peroxide are added and mixed for 15-20 minutes at 200-210℃ and screw speed of 150-230 rpm.

[0035] In step c, the rotational speed of the rotary shear extrusion mandrel is 8~10 rpm, and the extrusion temperature is 195~205℃;

[0036] In step d, the cooling and shaping process adopts segmented cooling. The first stage cooling water temperature is 40℃, the second stage cooling water temperature is 25℃, and the vacuum degree is -0.05 MPa.

[0037] Preferably, in step a, the potassium titanate whiskers are further coated with low molecular weight polyethylene by in-situ polymerization, specifically by reacting the silane-modified potassium titanate whiskers with ethylene monomer and 0.1% concentration of dicumyl peroxide at 180°C and 2 MPa for 2 hours.

[0038] Preferably:

[0039] The nano-silica was grafted with 3,5-di-tert-butyl-4-hydroxybenzoate on its surface through the following steps: 1.5% concentration of silane coupling agent KH-560 was added to a toluene solution in which nano-silica was dispersed, and the mixture was stirred at 60°C for 2 hours. Then, 0.5% concentration of hindered phenolic groups was added, and the mixture was reacted at 80°C for 4 hours. The mixture was then filtered and dried.

[0040] The ultra-high molecular weight polyethylene is modified by grafting maleic anhydride. Specifically, 1.5% maleic anhydride and 0.2% dicumyl peroxide are added to a xylene solution containing ultra-high molecular weight polyethylene, the mixture is reacted at 130°C for 3 hours, and then precipitated, washed, and dried.

[0041] The high-strength modified high-density polyethylene double-wall corrugated pipe provided by this invention introduces UHMWPE and reinforcing fillers, and combines them with compatibilizers to improve interfacial bonding. This allows the polymer chains of UHMWPE to entangle and form a strong and tough network, while the reinforcing fillers provide rigid support, synergistically improving high-temperature modulus and creep resistance. Furthermore, the antioxidants effectively inhibit high-temperature oxidative degradation, increase the resistance to slow crack growth time, and extend service life. Detailed Implementation

[0042] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0043] This embodiment provides a high-strength modified high-density polyethylene double-wall corrugated pipe, which is made of the following components by weight: 70-85 parts of high-density polyethylene, 10-20 parts of ultra-high molecular weight polyethylene, 5-10 parts of reinforcing filler, 2-5 parts of compatibilizer, 0.5-1 part of antioxidant, and 0.5-1 part of lubricant.

[0044] In this embodiment, the tensile strength of the pipe at high temperatures is increased by introducing UHMWPE and reinforcing fillers. The polymer chains of UHMWPE entangle to form a strong and tough network, while the reinforcing fillers provide rigid support, synergistically improving the high-temperature modulus and creep resistance.

[0045] The filler in the formula improves the thermal conductivity of the pipe, effectively disperses local thermal stress, and reduces the risk of high-temperature deformation.

[0046] Antioxidants effectively inhibit high-temperature oxidative degradation, increase the resistance to slow crack growth time, and extend service life, making them suitable for high-temperature drainage and industrial conveying applications.

[0047] The lubricant reduces melt viscosity, improves the processing resistance caused by the high viscosity of UHMWPE, reduces extrusion pressure, and is compatible with existing HDPE production lines.

[0048] This embodiment is the first to apply potassium titanate whiskers to UHMWPE composites in HDPE double-wall corrugated pipes, and combines them with compatibilizers to improve interfacial bonding, breaking through the limitations of traditional materials.

[0049] The high-strength modified high-density polyethylene double-wall corrugated pipe provided in this embodiment introduces UHMWPE and reinforcing fillers, and combines them with compatibilizers to improve interfacial bonding. This allows the polymer chains of UHMWPE to entangle and form a strong and tough network, while the reinforcing fillers provide rigid support, synergistically improving high-temperature modulus and creep resistance. Furthermore, the antioxidants effectively inhibit high-temperature oxidative degradation, increase the resistance to slow crack growth time, and extend service life.

[0050] Furthermore:

[0051] The reinforcing filler is potassium titanate whiskers with a length of 10~50μm, and the surface is modified with a silane coupling agent.

[0052] The compatibilizer is maleic anhydride-grafted polyethylene with a grafting rate of 1% to 1.5%.

[0053] Antioxidants include hindered phenolic antioxidants.

[0054] The lubricant is polyethylene wax.

[0055] Among them, potassium titanate whiskers are modified with silane coupling agents, and their surface hydroxyl groups form hydrogen bonds and van der Waals forces with HDPE and UHMWPE, which improves the interfacial shear strength, significantly reduces the risk of microcrack propagation caused by interfacial separation at high temperatures, and increases the resistance to slow crack growth time.

[0056] Maleic anhydride-grafted polyethylene chemically bonds with whiskers through polar groups, while simultaneously forming molecular chain entanglements with HDPE / UHMWPE, improving the uniformity of the composite material, reducing the risk of phase separation, and decreasing the deviation in crystallinity distribution.

[0057] Hindered phenolic antioxidants effectively capture free radicals under high-temperature conditions, delaying the oxidative degradation of HDPE and UHMWPE, increasing the high-temperature oxidation induction time, and are expected to extend service life, making them suitable for high-temperature industrial conveying scenarios.

[0058] Polyethylene wax acts as a lubricant to reduce melt viscosity, thereby reducing the extrusion pressure caused by the high viscosity of UHMWPE, improving the surface smoothness of the pipe, and reducing the defect rate.

[0059] Furthermore, it also includes: 1-2 parts of nano-silica, 3-5 parts of ethylene-octene copolymer, and 0.3-0.5 parts of initiator.

[0060] Among them, the hydroxyl groups on the surface of nano-silica form physical bridges with whiskers and polymers, which improves the interfacial bonding energy, reduces the coefficient of thermal expansion, reduces the accumulation of internal stress under high temperature cycling, and improves the resistance to slow crack growth time.

[0061] Ethylene-octene copolymers absorb impact energy through flexible chain segments, improve low-temperature notched impact strength, compensate for the decrease in toughness caused by whiskers, and enhance the pipe's resistance to brittle fracture in cold environments.

[0062] Initiator-induced in-situ grafting of MAH-g-PE with HDPE / UHMWPE forms a chemical bond network, further enhancing interfacial shear strength and reducing slow crack growth rate.

[0063] nanometer In synergy with POE, it increases tensile strength at high temperatures while maintaining constant ring stiffness, thus meeting the requirements of high-temperature industrial pipeline networks.

[0064] Furthermore:

[0065] Potassium titanate whiskers were modified by a composite of silane coupling agents KH-550 and KH-570.

[0066] The particle size of nano-silica is 20~30 nm.

[0067] The melt index of the ethylene-octene copolymer is 0.5~1 g / 10min.

[0068] The initiator is dicumyl peroxide.

[0069] Among them, KH-550 and KH-570 are combined in a 1:1 ratio to modify potassium titanate whiskers. The amino group provides polar bonding, and the double bond participates in the grafting reaction. This improves the interfacial shear strength, increases the resistance to slow crack growth time, and significantly reduces the risk of microcrack propagation at high temperatures.

[0070] Nanoparticles with a particle size of 20~30 nm It has a high specific surface area, which enhances the interface bridging effect, further reduces the coefficient of thermal expansion, and reduces high-temperature cyclic stress.

[0071] POE with a melt index of 0.5~1 g / 10min ensures good compatibility with HDPE / UHMWPE, forming a uniform toughness network, stable low-temperature impact strength, and improved impact resistance, making it suitable for all-weather applications.

[0072] Using dicumyl peroxide as an initiator, in-situ grafting of MAH-g-PE to the matrix is ​​precisely induced, improving grafting efficiency and further optimizing interfacial bonding strength and high-temperature modulus.

[0073] Furthermore:

[0074] The surface of potassium titanate whiskers is coated with low molecular weight polyethylene.

[0075] 3,5-di-tert-butyl-4-hydroxybenzoate was grafted onto the surface of nano-silica, with a grafting rate of 2%~2.5%.

[0076] Antioxidants also include phosphite antioxidants.

[0077] Among them, potassium titanate whiskers are modified with silane and coated with low molecular weight polyethylene to form a physically anchored shell, which improves the interfacial shear strength, enhances whisker dispersion, and increases the resistance to slow crack propagation time.

[0078] nanometer Surface grafting with 3,5-di-tert-butyl-4-hydroxybenzoate provides long-term antioxidant protection, prolongs oxidation induction time at high temperatures, and increases service life; at the same time, it enhances interfacial bonding energy, reduces the coefficient of thermal expansion, and reduces high-temperature stress concentration.

[0079] The combination of hindered phenolic and phosphite antioxidants synergistically captures free radicals and decomposes peroxides, improving high-temperature anti-aging performance and ensuring the long-term stability of the pipes in extreme environments.

[0080] Increased high-temperature tensile strength, improved low-temperature impact strength, and increased thermal conductivity meet the requirements of high-temperature industrial pipeline networks.

[0081] This embodiment also provides a preparation method for preparing a high-strength modified high-density polyethylene double-wall corrugated pipe as described in any one of the above embodiments. The preparation method includes the following steps:

[0082] a. Surface modification treatment of reinforcing fillers.

[0083] b. Prepare a modified composite material by melt blending high-density polyethylene, ultra-high molecular weight polyethylene, surface-modified reinforcing filler, compatibilizer, antioxidant and lubricant.

[0084] c. The modified composite material is extruded into a double-walled corrugated pipe using a rotary shear extrusion process.

[0085] d. The extruded double-wall corrugated pipe is obtained by cooling, shaping, and cutting.

[0086] Among them, the rotary shear extrusion process applies a circumferential shear force field by rotating the mandrel, which induces the molecular chains of HDPE and UHMWPE to align in an oriented manner and form a tandem crystal structure, which significantly improves the circumferential tensile strength of the pipe, increases the creep modulus, and significantly improves its high-temperature resistance to deformation.

[0087] In step a, the surface modification of the reinforcing filler enhances the chemical bonding with the polymer matrix, strengthens the interfacial shear strength, reduces the risk of microcrack propagation at high temperatures, and increases the resistance to slow crack growth time.

[0088] The melt blending process in step b ensures uniform dispersion of components, and the lubricant reduces extrusion resistance. The cooling and shaping process in step d controls the cooling rate, reduces residual stress, and reduces the defect rate.

[0089] The preparation method is compatible with existing twin-screw extruders and corrugated pipe forming equipment, making it suitable for industrial production. The pipes produced by this process combine high-temperature strength and flexibility, making them suitable for high-temperature industrial pipe networks, ground source heat pumps, and municipal drainage, with performance superior to traditional HDPE pipes.

[0090] Furthermore:

[0091] In step a, the reinforcing filler is potassium titanate whiskers, and the modification treatment includes adding potassium titanate whiskers to an ethanol solution mixed with silane coupling agent and ultrasonically dispersing for 30-40 minutes, and drying at 75-85°C for 3-5 hours.

[0092] In step b, melt blending is carried out in a twin-screw extruder at a temperature of 180~220℃, a screw speed of 150~260rpm, and a mixing time of 30~40 minutes.

[0093] In step c, the rotary shear extrusion uses a rotary mandrel extruder with a mandrel speed of 5~15 rpm and an extrusion temperature of 190~210℃.

[0094] In step d, cooling and shaping are performed using vacuum shaping with a negative pressure of -0.05 to -0.08 MPa and a cooling water temperature of 25 to 40°C.

[0095] In step a, potassium titanate whiskers are modified with a silane coupling agent, which increases the surface active groups and enhances the interfacial bonding force with the polymer matrix, effectively suppressing high-temperature microcracks.

[0096] The twin-screw extrusion in step b ensures uniform dispersion of HDPE, UHMWPE and whiskers, reduces the deviation in crystallinity distribution, and improves the stability of the pipe's mechanical properties.

[0097] The rotating mandrel extrusion-induced crystal structure in step c improves circumferential tensile strength, increases creep modulus, and significantly enhances high-temperature deformation resistance.

[0098] Step d involves vacuum shaping to control the cooling rate, reducing residual stress, decreasing pipe wall thickness deviation, and lowering the defect rate.

[0099] The process parameters are compatible with existing twin-screw extruders and corrugated pipe forming equipment, making it suitable for industrial production.

[0100] Furthermore:

[0101] In step a, the silane coupling agent is a compound solution of KH-550 and KH-570 in a mass ratio of 1:1, with a mass concentration of 2% to 2.5%.

[0102] In step b, melt blending is a two-stage process, specifically including:

[0103] First stage: High-density polyethylene, ethylene-octene copolymer and maleic anhydride grafted polyethylene are blended at 180~190℃ and screw speed of 240~260 rpm for 15~20 minutes.

[0104] In the second stage, ultra-high molecular weight polyethylene, surface-modified potassium titanate whiskers, nano-silica and diisopropylbenzene peroxide are added and mixed for 15-20 minutes at 200-210℃ and screw speed of 150-230 rpm.

[0105] In step c, the rotational shear extrusion mandrel speed is 8~10 rpm, and the extrusion temperature is 195~205℃.

[0106] In step d, the cooling and shaping process adopts segmented cooling. The first stage cooling water temperature is 40℃, the second stage cooling water temperature is 25℃, and the vacuum degree is -0.05 MPa.

[0107] In step a, KH-550 and KH-570 are used in combination with silane. The active groups on the whisker surface are synergistically enhanced, the interfacial shear strength is improved, the slow crack propagation time is increased, and the risk of microcracks at high temperatures is reduced.

[0108] The two-stage process in step b first forms a tough matrix, and then high-viscosity UHMWPE and fillers are added, which improves the dispersion uniformity and enhances the impact strength.

[0109] Step c optimizes the mandrel rotation speed and temperature, enhances the efficiency of crystal chain formation, improves high-temperature tensile strength, and increases creep modulus.

[0110] Step d's segmented cooling precisely controls the cooling rate, reducing residual stress, wall thickness deviation, and defect rate.

[0111] The combination of two-stage blending and segmented cooling with composite coupling agents overcomes the dispersion limitations of traditional single-stage blending and is superior to existing technologies.

[0112] Furthermore, in step a, the potassium titanate whiskers are also coated with low molecular weight polyethylene through in-situ polymerization. Specifically, the silane-modified potassium titanate whiskers are reacted with ethylene monomer and 0.1% dicumyl peroxide at 180°C and 2 MPa for 2 hours.

[0113] Among them, the whiskers are modified with silane and then polymerized in situ to coat low molecular weight polyethylene to form a physically anchored shell, which improves the interfacial shear strength, enhances the whisker dispersion, and increases the resistance to slow crack propagation time.

[0114] The LMW-PE shell forms a transition layer with the HDPE / UHMWPE molecular chains, reducing interfacial stress concentration, improving high-temperature tensile strength, and lowering the coefficient of thermal expansion.

[0115] LMW-PE coating reduces the frictional resistance between whiskers and high-viscosity UHMWPE, resulting in lower extrusion pressure, fewer surface defects, and a lower defect rate.

[0116] Furthermore:

[0117] Nano-silica was grafted with 3,5-di-tert-butyl-4-hydroxybenzoate on its surface via the following steps: 1.5% concentration of silane coupling agent KH-560 was added to a toluene solution in which nano-silica was dispersed, and the mixture was stirred at 60°C for 2 hours. Then, 0.5% concentration of hindered phenolic groups was added, and the mixture was reacted at 80°C for 4 hours. The mixture was then filtered and dried.

[0118] Ultra-high molecular weight polyethylene is modified by grafting maleic anhydride. Specifically, 1.5% maleic anhydride and 0.2% dicumyl peroxide are added to a xylene solution containing ultra-high molecular weight polyethylene, and the mixture is reacted at 130°C for 3 hours, followed by precipitation, washing, and drying.

[0119] Among them, nano Grafting with 3,5-di-tert-butyl-4-hydroxybenzoate (KH-560 bridging) imparts antioxidant function, prolongs the high-temperature oxidation induction time, and increases service life; it also improves interfacial bonding energy, reduces the coefficient of thermal expansion, and reduces high-temperature stress concentration.

[0120] Grafting maleic anhydride onto UHMWPE increases polar groups, improves compatibility with HDPE and whiskers, reduces crystallinity distribution deviation, enhances high-temperature chain entanglement strength, and increases high-temperature creep modulus.

[0121] Functional In synergy with MAH-g-UHMWPE, it increases high-temperature tensile strength, low-temperature impact strength, and thermal conductivity, meeting the needs of high-temperature industries and ground source heat pumps.

[0122] Modified UHMWPE reduces melt viscosity, further reduces extrusion pressure, lowers the defect rate, and is compatible with existing production lines.

[0123] Functional The introduction of MAH-g-UHMWPE, combined with bilayer modified whiskers and two-stage blending, breaks through the performance bottleneck of traditional modification processes and outperforms existing technologies.

[0124] Specific embodiments are provided below. These embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way.

[0125] Example 1

[0126] Weigh 5 kg of potassium titanate whiskers and place them in a 20 L stainless steel reactor. Prepare a 9:1 ethanol / water solution (9 L ethanol + 1 L deionized water) and add 0.05 kg of KH-550. Add the whiskers to the solution and disperse using an ultrasonic disperser for 35 min at a stirring speed of 300 rpm. After filtration, dry in an oven (80℃) for 4 h to obtain modified whiskers for later use.

[0127] Weigh out 80 kg of HDPE, 15 kg of UHMWPE, 5 kg of modified whiskers, 3 kg of MAH-g-PE, 0.5 kg of antioxidant, and 0.5 kg of lubricant. Place the materials in a twin-screw extruder and set the temperature zones as follows: 180℃ (feed section), 200℃ (compression section), 210℃ (metering section), and 200℃ (die). Set the screw speed to 200 rpm, the mixing time to 30 min, extrude and granulate, and cool to room temperature to obtain modified composite material granules.

[0128] The composite material particles are added to a rotary shear extruder, and the temperature is set to 190℃ (feed section), 195℃ (forming section), and 195℃ (die head). The mandrel speed is 8 rpm, and a double-walled corrugated pipe with an inner diameter of 200 mm and a wall thickness of 5 mm is extruded. The traction speed is 1 m / min to ensure uniform corrugation.

[0129] A vacuum shaping device (negative pressure -0.05 MPa) was used, with cooling water temperature at 40℃ and a water flow rate of 10 L / min. After cooling, the sections were cut at 1 m / s using an automatic cutting machine, and the appearance and dimensions were inspected.

[0130] Samples were taken for performance testing.

[0131] High-temperature tensile strength was tested using a tensile testing machine.

[0132] Standard: ISO 527-2, Specimen type 1A, size 150 mm × 10 mm × 4 mm.

[0133] Test conditions: 80℃, preheating chamber for 30 min, tensile speed 50 mm / min.

[0134] Record the tensile strength (MPa) and take the average value of 5 specimens.

[0135] Testing cryogenic notched impact strength using an impact testing machine:

[0136] Standard: ISO 180, notch type A, specimen size 80 mm × 10 mm × 4 mm.

[0137] Test conditions: -20℃, pre-cooled in a freezer for 30 min, pendulum energy 5.5 J.

[0138] Record the impact strength (kJ / m2) and take the average value of 5 samples.

[0139] Ring stiffness was tested using a ring stiffness testing machine.

[0140] Standard: ISO 9969, specimen length 300 mm, inner diameter 200 mm.

[0141] Test conditions: compression speed 12.5 mm / min, record the force value at 3% deformation, and calculate the ring stiffness (kN / m2).

[0142] Take the average value of the three samples.

[0143] Resistance to slow crack growth was tested using a constant temperature water bath and tensile fixture:

[0144] Standard: ISO 13479, the specimen is a pipe slice with a notch depth of 1 mm.

[0145] Test conditions: 80℃, constant stress 4 MPa, record crack propagation time to failure (h).

[0146] Take the average value of the three samples.

[0147] Thermal conductivity was tested using a thermal conductivity meter.

[0148] Standard: ASTM C518, specimen size 50 mm × 50 mm × 5 mm.

[0149] Test conditions: 25℃, laser pulse method, thermal conductivity (W / m·K) recorded.

[0150] Take the average value of the three samples.

[0151] Inspection defect rate: Statistical analysis of the percentage (%) of appearance defects (rough surface, uneven wall thickness) in 100 m of pipe.

[0152] Detect wall thickness deviation: Measure the wall thickness (5 mm nominal) of 10 pipe sections with vernier calipers and record the deviation (± mm).

[0153] The test data is shown in the table below:

[0154]

[0155] Example 2

[0156] Weigh 6 kg of potassium titanate whiskers and place them in a 20 L stainless steel reactor. Prepare a 9:1 ethanol / water solution (9 L ethanol + 1 L deionized water), and add 0.12 kg of a 1:1 mixture of KH-550 and KH-570. Disperse the mixture using an ultrasonic disperser for 40 min at a stirring speed of 300 rpm. After filtration, dry the mixture in an oven (80℃) for 6 h to obtain modified whiskers for later use.

[0157] Weigh 1.5 kg of nano Mix with modified whiskers, place in ethanol / water solution, ultrasonically disperse for 10 min, dry at 80℃ for 2 h, and set aside for later use.

[0158] Weigh 73 kg of HDPE, 4 kg of POE, and 4 kg of MAH-g-PE, and add them to a twin-screw extruder. Temperature zones: 180℃ (feed section), 185℃ (compression section), 190℃ (metering section), and 190℃ (die). Screw speed: 250 rpm. Blend for 15 min. Add 15 kg of UHMWPE, 6 kg of modified whiskers, and nano-... 1.5 kg of DCP, 0.4 kg of antioxidant, 0.7 kg of lubricant, and 0.5 kg of compound were mixed at different temperatures: 200℃ (feed section), 205℃ (compression section), 210℃ (metering section), and 200℃ (die). The screw speed was 150 rpm, and the mixture was blended for 15 min. The mixture was then extruded and granulated, and cooled to room temperature to obtain modified composite material particles.

[0159] Modified composite material particles were fed into a rotary shear extruder, and the temperatures were set to 190℃ (feed section), 195℃ (forming section), and 195℃ (die). The mandrel speed was 8 rpm, and a double-walled corrugated pipe with an inner diameter of 200 mm and a wall thickness of 5 mm was extruded. The traction speed was 1 m / min to ensure uniform corrugation formation.

[0160] A vacuum shaping device (negative pressure -0.05 MPa) was used, with the first stage cooling water temperature at 40℃ (10 L / min) and the second stage at 25℃ (10 L / min). After cooling, the sections were cut at 1 m / s, and the appearance and dimensions were inspected.

[0161] Samples were taken for performance testing.

[0162] The test method is the same as in Example 1, including:

[0163] High-temperature tensile strength: ISO 527-2, 80℃, 50 mm / min, 5 specimens.

[0164] Low-temperature notched impact strength: ISO 180, -20℃, 5.5 J pendulum, 5 specimens.

[0165] Ring stiffness: ISO 9969, 12.5 mm / min, 3 specimens.

[0166] Resistance to slow crack growth: ISO 13479, 80℃, 4 MPa, 3 specimens.

[0167] Thermal conductivity: ASTM C518, 25°C, 3 specimens.

[0168] Processability: defect rate (proportion of appearance defects per 100 m of pipe), wall thickness deviation (10 samples).

[0169] The test data is shown in the table below:

[0170]

[0171] Example 3

[0172] Weigh 6 kg of whiskers and place them in a 20 L reactor. Add 10 L of a 9:1 ethanol / water solution and 0.12 kg of a 1:1 mixture of KH-550 and KH-570. Disperse the mixture ultrasonically for 40 min and dry at 80 °C for 6 h. Place the silane-modified whiskers in a high-pressure reactor, add 0.3 kg of ethylene monomer and 30 g of DCP, and react at 180 °C and 2 MPa for 2 h. Cool and dry to obtain bilayer modified whiskers.

[0173] Weigh 1.5 kg of nano The mixture was dispersed in 5 L of toluene, and 22.5 g of KH-560 was added. The mixture was stirred at 60 °C for 2 h (500 rpm). Then, 7.5 g of 3,5-di-tert-butyl-4-hydroxybenzoate was added, and the mixture was reacted at 80 °C for 4 h. After filtration and drying, the functionalized product was obtained. .

[0174] Weigh 15 kg of UHMWPE, dissolve it in 5 L of xylene (130℃), add 0.225 kg of maleic anhydride and 0.03 kg of DCP, react for 3 h, precipitate, wash and dry to obtain MAH-g-UHMWPE.

[0175] Weigh 73 kg of HDPE, 4 kg of POE, and 4 kg of MAH-g-PE, and add them to a twin-screw extruder. Temperature zones: 180℃ (feed section), 185℃ (compression section), 190℃ (metering section), and 190℃ (die). Screw speed: 250 rpm. Blend for 15 min. Add 15 kg of UHMWPE, 6 kg of bilayer modified whiskers, and functionalized nanoparticles. 1.5 kg of DCP, 0.4 kg of antioxidant, 0.7 kg of lubricant, and 0.5 kg of compound were mixed at different temperatures: 200℃ (feed section), 205℃ (compression section), 210℃ (metering section), and 200℃ (die). The screw speed was 150 rpm, and the mixture was blended for 15 min. The mixture was then extruded and granulated, and cooled to room temperature to obtain modified composite material particles.

[0176] Modified composite material particles were fed into a rotary shear extruder, and the temperatures were set to 190℃ (feed section), 195℃ (forming section), and 195℃ (die). The mandrel speed was 8 rpm, and a double-walled corrugated pipe with an inner diameter of 200 mm and a wall thickness of 5 mm was extruded. The traction speed was 1 m / min to ensure uniform corrugation formation.

[0177] A vacuum shaping device (negative pressure -0.05 MPa) was used, with the first stage cooling water temperature at 40℃ (10 L / min) and the second stage at 25℃ (10 L / min). After cooling, the sections were cut at 1 m / s, and the appearance and dimensions were inspected.

[0178] Samples were taken for performance testing.

[0179] The test method is the same as in Example 1, including:

[0180] High-temperature tensile strength: ISO 527-2, 80℃, 50 mm / min, 5 specimens.

[0181] Low-temperature notched impact strength: ISO 180, -20℃, 5.5 J pendulum, 5 specimens.

[0182] Ring stiffness: ISO 9969, 12.5 mm / min, 3 specimens.

[0183] Resistance to slow crack growth: ISO 13479, 80℃, 4 MPa, 3 specimens.

[0184] Thermal conductivity: ASTM C518, 25°C, 3 specimens.

[0185] Processability: defect rate (proportion of appearance defects per 100 m of pipe), wall thickness deviation (10 samples).

[0186] The test data is shown in the table below:

[0187]

[0188] Comparative Example 1

[0189] Weigh 100 kg of HDPE, 0.5 kg of antioxidant, and 0.5 kg of lubricant, and mix them in a high-speed mixer (500 rpm) for 5 min.

[0190] The mixed raw materials were added to a twin-screw extruder, and the temperature zones were set as follows: 180℃ (feed section), 190℃ (compression section), 200℃ (metering section), and 190℃ (die). The screw speed was 200 rpm, the mixing time was 30 min, and the mixture was extruded and granulated. After cooling to room temperature, HDPE granules were obtained.

[0191] HDPE granules are added to a fixed-mandrel corrugated pipe extruder. Temperatures are set at 190℃ (feed section), 190℃ (forming section), and 190℃ (die). A double-walled corrugated pipe with an inner diameter of 200 mm and a wall thickness of 5 mm is extruded at a traction speed of 1 m / min.

[0192] A vacuum shaping device (-0.05 MPa) was used, with a cooling water temperature of 40℃ and a water flow rate of 10 L / min.

[0193] After cooling, cut the material into 1 m sections using an automatic cutting machine and check the appearance and dimensions.

[0194] Samples were taken for performance testing.

[0195] The test method is the same as in Example 1, including:

[0196] High-temperature tensile strength: ISO 527-2, 80℃, 50 mm / min, 5 specimens.

[0197] Low-temperature notched impact strength: ISO 180, -20℃, 5.5 J pendulum, 5 specimens.

[0198] Ring stiffness: ISO 9969, 12.5 mm / min, 3 specimens.

[0199] Resistance to slow crack growth: ISO 13479, 80℃, 4 MPa, 3 specimens.

[0200] Thermal conductivity: ASTM C518, 25°C, 3 specimens.

[0201] Processability: defect rate (proportion of appearance defects per 100 m of pipe), wall thickness deviation (10 samples).

[0202] The test data is shown in the table below:

[0203]

[0204] Comparative Example 2

[0205] Weigh 80 kg of HDPE, 15 kg of UHMWPE, 3 kg of MAH-g-PE, 0.5 kg of antioxidant, and 0.5 kg of lubricant, and mix them in a high-speed mixer (500 rpm) for 5 min.

[0206] The mixed raw materials are added to a twin-screw extruder at the following temperatures: 180℃ (feed section), 200℃ (compression section), 210℃ (metering section), and 200℃ (die). The screw speed is 200 rpm, the mixing time is 30 min, and the material is extruded, granulated, and then cooled.

[0207] The granules are fed into a fixed-mandrel corrugated pipe extruder. The temperatures are: 190℃ (feed section), 195℃ (forming section), and 195℃ (die). A double-walled corrugated pipe with an inner diameter of 200 mm and a wall thickness of 5 mm is extruded at a traction speed of 1 m / min.

[0208] Vacuum shaping (-0.05 MPa), cooling water temperature 40℃, 10 L / min. Cut in 1 m / segment, and check appearance and dimensions.

[0209] Samples were taken for performance testing.

[0210] The test method is the same as in Example 1, including:

[0211] High-temperature tensile strength: ISO 527-2, 80℃, 50 mm / min, 5 specimens.

[0212] Low-temperature notched impact strength: ISO 180, -20℃, 5.5 J pendulum, 5 specimens.

[0213] Ring stiffness: ISO 9969, 12.5 mm / min, 3 specimens.

[0214] Resistance to slow crack growth: ISO 13479, 80℃, 4 MPa, 3 specimens.

[0215] Thermal conductivity: ASTM C518, 25°C, 3 specimens.

[0216] Processability: defect rate (proportion of appearance defects per 100 m of pipe), wall thickness deviation (10 samples).

[0217] The test data is shown in the table below:

[0218]

[0219] The data above show that, compared to Comparative Example 1 (pure HDPE), Examples 1-3 exhibit significant improvements in high-temperature performance, durability, and thermal conductivity, solving the high-temperature failure problem of pure HDPE. Compared to Comparative Example 2 (traditional UHMWPE composite), Examples 1-3, through whisker reinforcement, interface optimization, and process improvements, comprehensively surpass existing technologies, achieving toughness and processability close to or better than pure HDPE.

[0220] Example 1 establishes a foundation for high-temperature strength and durability, superior to Comparative Example 2. Example 2 utilizes nanotechnology... POE and optimized processes significantly improve toughness, durability, and processability. Example 3 achieves a breakthrough in comprehensive performance through functional modification and compound antioxidants, with optimal strength, toughness, and durability.

[0221] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. The above are merely preferred embodiments 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 within the scope of protection of the present invention.

Claims

1. A high-strength modified high-density polyethylene double-wall corrugated pipe, characterized by, The high-strength modified high-density polyethylene double-wall corrugated pipe is prepared by using the following components by weight: high-density polyethylene 70-85 parts, ultra-high molecular weight polyethylene 10-20 parts, reinforcing filler 5-10 parts, compatibilizer 2-5 parts, antioxidant 0.5-1 part, lubricant 0.5-1 part, nano-silica 1-2 parts, ethylene-octene copolymer 3-5 parts, and initiator 0.3-0.5 part. In the formula, The reinforcing filler is potassium titanate whisker with a length of 10-50 μm, and the surface is modified by using silane coupling agents KH-550 and KH-570 in combination and coated with low molecular weight polyethylene. The compatibilizer is maleic anhydride grafted polyethylene with a grafting rate of 1%-1.5%. The nano-silica has a particle size of 20-30 nm and is grafted with 3,5-di-tert-butyl-4-hydroxybenzoate on the surface with a grafting rate of 2%-2.5%. The initiator is dicumyl peroxide.

2. The high-strength modified high-density polyethylene double-wall corrugated pipe according to claim 1, wherein the antioxidant comprises hindered phenolic antioxidant; and the lubricant is polyethylene wax.

3. The high-strength modified high-density polyethylene double-wall corrugated pipe according to claim 1, wherein the ethylene-octene copolymer has a melt index of 0.5-1 g / 10 min.

4. The high-strength modified high-density polyethylene double-wall corrugated pipe according to claim 3, wherein the antioxidant further comprises phosphite antioxidant.

5. A method for preparing the high-strength modified high-density polyethylene double-wall corrugated pipe according to any one of claims 1-4, the method comprising the following steps: a) surface modification treatment of the reinforcing filler; b) melt blending of high-density polyethylene, ultra-high molecular weight polyethylene, surface-modified reinforcing filler, compatibilizer, antioxidant and lubricant to prepare a modified composite material; c) extrusion molding of the modified composite material into a double-wall corrugated pipe by using a rotary shear extrusion process; 5. A method of manufacture characterised by, d) cooling, setting and cutting of the extrusion-molded double-wall corrugated pipe to obtain the high-strength modified high-density polyethylene double-wall corrugated pipe; wherein in step b, the melt blending is a two-stage process, specifically comprising: first stage: blending of high-density polyethylene, ethylene-octene copolymer and maleic anhydride grafted polyethylene at 180-190℃ and screw rotation speed of 240-260 rpm for 15-20 minutes; second stage: addition of ultra-high molecular weight polyethylene, surface-modified potassium titanate whisker, nano-silica and dicumyl peroxide, and blending at 200-210℃ and screw rotation speed of 150-230 rpm for 15-20 minutes.

6. The method according to claim 5, wherein in step a, the reinforcing filler is potassium titanate whisker, and the modification treatment comprises ultrasonic dispersion of the potassium titanate whisker in an ethanol solution mixed with silane coupling agent for 30-40 minutes, and drying at 75-85℃ for 3-5 hours; and in step b, the melt blending is carried out in a twin-screw extruder at a temperature of 180-220℃, a screw rotation speed of 150-260 rpm and a mixing time of 30-40 minutes. ​ ​ ​ ​ ​ ​ In step c, the rotary shearing extrusion adopts a rotary mandrel extruder, the mandrel rotation speed is 5-15 rpm, and the extrusion temperature is 190-210 DEG C. In step d, the cooling and shaping adopts vacuum shaping, the negative pressure is-0.05 to-0.08 MPa, and the cooling water temperature is 25-40 DEG C.

7. The preparation method of claim 6, wherein: In step a, the silane coupling agent is a compounded solution of KH-550 and KH-570 with a mass ratio of 1:1, and the mass concentration is 2%-2.5%. In step c, the rotary shearing extrusion mandrel rotation speed is 8-10 rpm, and the extrusion temperature is 195-205 DEG C. In step d, the cooling and shaping adopts segmented cooling, the first segment cooling water temperature is 40 DEG C, the second segment cooling water temperature is 25 DEG C, and the vacuum degree is-0.05 MPa.

8. The production method according to claim 7, characterized by, In step a, the potassium titanate whisker is also coated with low molecular weight polyethylene by in-situ polymerization, specifically, the silane modified potassium titanate whisker is reacted with ethylene monomer and 0.1% concentration of dicumyl peroxide at 180 DEG C, 2 MPa for 2 hours.

9. The production method according to claim 8, characterized by, In step b: The nano-silicon dioxide is grafted with 3,5-di-tert-butyl-4-hydroxybenzoate on the surface by the following steps: adding 1.5% concentration of silane coupling agent KH-560 in the toluene solution containing nano-silicon dioxide, stirring at 60 DEG C for 2 hours, then adding 0.5% concentration of hindered phenol group, reacting at 80 DEG C for 4 hours, filtering and drying; The ultra-high molecular weight polyethylene is modified by maleic anhydride grafting, specifically, adding 1.5% concentration of maleic anhydride and 0.2% concentration of dicumyl peroxide in the xylene solution containing ultra-high molecular weight polyethylene, reacting at 130 DEG C for 3 hours, precipitating, washing and drying.

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