Preparation method and system of high-heat-resistance and high-toughness MPP power pipe

Abstract

This invention discloses a method and system for preparing high-heat-resistant and high-toughness MPP power pipes. The method includes: adding polypropylene base material, thermoplastic elastomer toughening agent, surface-modified nano-silica, and β-nucleating agent into a high-speed mixer at a mass ratio to generate a premix; conveying the premix to a twin-screw extruder for melt blending and extrusion, controlling the temperature of each heating zone to increase sequentially from the feed port to the die head, and generating modified polypropylene granules after pelletizing; drying the modified polypropylene granules and feeding them into a single-screw extruder, where they are plasticized by gradual heating in the melting section, and after passing through a spiral separator, they are extruded into a pipe die to generate an initial pipe blank; the initial pipe blank is sequentially passed through a spray cooling section and a sizing sleeve for gradient cooling and shaping, finally generating a high-heat-resistant and high-toughness MPP power pipe. Using this invention, the heat resistance and impact toughness of the MPP power pipe can be improved, achieving comprehensive enhancement of the pipe's mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of MPP power pipe technology, and in particular, it relates to a method and system for preparing a high heat-resistant and high-toughness MPP power pipe. Background Technology

[0002] MPP (modified polypropylene) power pipes are widely used in the field of power cable protection due to their excellent insulation and corrosion resistance. However, existing MPP pipe manufacturing methods suffer from the following technical defects: First, the polypropylene base material lacks sufficient impact toughness at room temperature and is prone to brittleness in low-temperature environments; second, its heat resistance is limited, and its strength decreases significantly under long-term use at high temperatures, leading to pipe deformation; third, in traditional blending modification processes, inorganic fillers (such as nano-silica) tend to agglomerate, exhibiting poor compatibility with the matrix and making it difficult to simultaneously achieve toughening and strengthening effects; fourth, conventional extrusion-molded pipes have residual stress inside, and the molecular chain orientation is singular, resulting in an imbalance between the circumferential and axial mechanical properties of the pipe. These problems limit the reliability of MPP power pipes in harsh conditions such as complex geological formations, high-temperature environments, and trenchless construction. Summary of the Invention

[0003] The purpose of this invention is to provide a method and system for preparing a high heat-resistant and high-toughness MPP power pipe, so as to overcome the shortcomings of the prior art, improve the heat resistance and impact toughness of the MPP power pipe, and achieve comprehensive enhancement of the mechanical properties of the pipe.

[0004] One embodiment of this application provides a method for preparing a high heat-resistant and high-toughness MPP power pipe, the method comprising: Polypropylene base material, thermoplastic elastomer toughening agent, surface modified nano silica and β nucleating agent are added into a high-speed mixer in a mass ratio and stirred at a set temperature until uniformly dispersed to generate a premix. The premixed material is fed into a twin-screw extruder for melt blending and extrusion. The temperature of each heating zone is controlled to increase sequentially from the feed port to the die head. At the same time, the screw speed is adjusted to apply a set shear rate. After pelleting, modified polypropylene granules are generated. The modified polypropylene granules are dried and fed into a single-screw extruder. In the melting section, they are plasticized by gradually increasing the temperature and then extruded into a pipe die after passing through a spiral separator to generate an initial pipe blank. The initial tube blank is sequentially cooled and shaped by a spray cooling section and a sizing sleeve. Then, it is stretched axially and circumferentially by a bidirectional stretching device under the drive of a traction machine. Finally, it is subjected to a hot air circulating annealing furnace to eliminate internal stress, thus producing a high heat-resistant and high-toughness MPP power pipe.

[0005] Another embodiment of this application provides a manufacturing system for a high heat-resistant and high-toughness MPP power pipe, the system comprising: The feeding module is used to feed polypropylene base material, thermoplastic elastomer toughening agent, surface modified nano silica and β nucleating agent into a high-speed mixer in a mass ratio, and stir at a set temperature until uniformly dispersed to generate a premix. The control module is used to feed the premix to a twin-screw extruder for melt blending and extrusion, control the temperature of each heating zone to increase sequentially from the feed port to the die head, and adjust the screw speed to apply a set shear rate, so that modified polypropylene granules are generated after pelleting. The plasticizing module is used to dry the modified polypropylene granules and feed them into a single screw extruder. In the melting section, the granules are plasticized by gradually increasing the temperature and then extruded into a pipe die after passing through a spiral separator to generate an initial pipe blank. The shaping module is used to sequentially pass the initial tube blank through a spray cooling section and a sizing sleeve for gradient cooling and shaping. Then, under the drive of a traction machine, it is stretched axially and circumferentially synchronously through a bidirectional stretching device. Finally, it is subjected to a hot air circulating annealing furnace to eliminate internal stress, ultimately producing a high heat-resistant and high-toughness MPP power pipe.

[0006] Another embodiment of this application provides a storage medium storing a computer program, wherein the computer program is configured to execute the method described in any of the preceding claims when running.

[0007] Another embodiment of this application provides an electronic device including a memory and a processor, wherein the memory stores a computer program and the processor is configured to run the computer program to perform the method described in any of the preceding claims.

[0008] Compared with the prior art, the present invention provides a method for preparing a high heat-resistant and high-toughness MPP power pipe, which can improve the heat resistance temperature and impact toughness of the MPP power pipe, and achieve comprehensive enhancement of the mechanical properties of the pipe. Attached Figure Description

[0009] Figure 1 A hardware structure block diagram of a computer terminal for a method of preparing a high heat-resistant and high-toughness MPP power pipe provided in an embodiment of the present invention; Figure 2 This is a schematic flowchart illustrating a method for preparing a high heat-resistant and high-toughness MPP power pipe according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the structure of a manufacturing system for a high heat-resistant and high-toughness MPP power pipe provided in an embodiment of the present invention. Detailed Implementation

[0010] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0011] This invention first provides a method for preparing a high heat-resistant and high-toughness MPP power pipe, which can be applied to electronic devices, such as computer terminals, specifically ordinary computers.

[0012] The following detailed explanation uses a computer terminal as an example. Figure 1 This is a hardware structure block diagram of a computer terminal for a method of preparing a high heat-resistant and high-toughness MPP power pipe according to an embodiment of the present invention. Figure 1 As shown, the computer device includes a processor, memory, and network interface connected via a system bus, wherein the memory may include non-volatile storage media and internal memory.

[0013] See Figure 2 The present invention provides a method for preparing a high heat-resistant and high-toughness MPP power pipe, which may include the following steps: S201, polypropylene base material, thermoplastic elastomer toughening agent, surface modified nano silica and β nucleating agent are added into a high-speed mixer in a mass ratio and stirred at a set temperature until uniformly dispersed to generate a premix; Specifically, 75-85 parts by mass of polypropylene base material, 10-20 parts by mass of thermoplastic elastomer toughening agent, 3-8 parts by mass of surface-modified nano silica and 0.1-0.5 parts by mass of β nucleating agent can be weighed separately, and after being calibrated by an electronic balance, they can be put into a premixing container to generate an accurately measured original powder mixture. The core of this step is to accurately measure and collect various modified raw materials based on standardized quality ratios. High-precision weighing calibration eliminates ratio errors, controlling the fundamental performance of MPP power pipe modification from the source of raw materials. This ensures that subsequent mixing, melting, and molding processes can stably produce pipes with satisfactory heat resistance and toughness. The specific implementation method is as follows: The mass fractions used in this step are the general proportioning and measurement standard for the production of polymer modified materials. These are relative measurement parameters with polypropylene as the core benchmark. All additive part numbers are relative to the proportion of the base material and can be flexibly converted to actual mass units according to industrial production scale. This adapts to the production needs of different capacity equipment and ensures consistent proportioning accuracy throughout the process. Polypropylene is the core matrix raw material of MPP power pipes, determining the structural rigidity, molding stability, and heat resistance of the pipe foundation. Its proportion range is set between 75 and 85 parts. This range ensures that the matrix material forms a stable supporting structure, preventing a decrease in pipe foundation strength due to excessive additive proportions, while also allowing sufficient space for the filling and integration of various modifying additives, fully utilizing their modifying effects. In this example, 80 parts of polypropylene base material are selected as the benchmark proportion to balance matrix structural stability and modification effect.

[0014] Thermoplastic elastomer toughening agents are core functional additives for improving the toughness, impact resistance, and bending resistance of pipes. They can effectively compensate for the inherent defects of pure polypropylene materials, such as high low-temperature brittleness and easy cracking under stress. The ratio range is 10 to 20 parts. This parameter range has been optimized through process adaptation. When the ratio is less than 10 parts, the proportion of toughening components is insufficient, which cannot effectively improve the brittleness of the matrix, and the improvement effect on the impact resistance of the pipe is weak. When the ratio is greater than 20 parts, the proportion of flexible additives is too large, which will significantly reduce the rigidity and heat resistance of the pipe and destroy the core performance. In the example, 15 parts of thermoplastic elastomer toughening agent are selected to achieve a two-way balance between the toughness and heat resistance of the pipe.

[0015] Surface-modified nano-silica is an inorganic reinforcing filler that improves the heat resistance, structural density, and wear resistance of pipes. After professional surface modification treatment, it can completely improve the problems of poor compatibility and easy agglomeration between ordinary nano-silica and polypropylene organic matrix. It can be uniformly filled in the intermolecular gaps of polypropylene. Its ratio range is 3 to 8 parts. This range can effectively improve the thermal stability and structural strength of the matrix. If the ratio is too low, it will not have the effect of filling, reinforcing, and heat-resistant modification. If the ratio is too high, powder will accumulate and agglomerate, which will reduce the toughness and molding smoothness of the pipe. In the example, 5 parts of surface-modified nano-silica are selected for the ratio filling.

[0016] β-nucleating agent is a trace functional additive that regulates the crystallization morphology of polypropylene. It can induce polypropylene to form a high-toughness β-type crystal structure after melting, replacing the conventional low-toughness α-type crystal structure, and simultaneously improving the impact resistance and heat distortion temperature of the pipe. Its proportion range is 0.1 parts to 0.5 parts. This additive has high activity characteristics. A trace amount can achieve directional regulation of the crystal structure. When the amount added is less than 0.1 parts, the nucleating activity is insufficient and a sufficient amount of β-type crystals cannot be generated, resulting in a weak modification effect. When the amount added exceeds 0.5 parts, the excessive nucleating agent will cause crystal structure defects, leading to a decrease in the mechanical properties of the pipe. In the example, 0.3 parts of β-nucleating agent are selected to achieve efficient crystallization modification.

[0017] After determining the proportions of each raw material, a high-precision electronic balance is used to weigh each of the four raw materials independently. The electronic balance can accurately identify minute mass deviations, avoiding the errors of manual estimation and ordinary weighing equipment. After each weighing, a second calibration is performed to verify the match between the actual weighing value of each raw material and the set proportion. The measurement error of all raw materials is strictly controlled within ±0.01 parts, eliminating problems such as uneven pipe performance and large batch differences caused by proportion deviations. After all raw materials have been accurately weighed and calibrated, they are sequentially put into clean, dry, and impurity-free sealed premixing containers. The sealed containers can effectively prevent the loss of light additives, the clumping of raw materials due to moisture, and the introduction of external impurities. After all raw materials are collected, a raw powder mixture with accurate component proportions, qualified raw material purity, and no impurities is formed, providing qualified base materials for subsequent preliminary mixing processes.

[0018] Pour the original powder mixture into the high-speed mixer in batches, start the agitator and mix for 300-500 rpm for 3-5 minutes to make the components macroscopically evenly distributed and generate coarse mixed material; The core of this step is to achieve a macroscopically uniform distribution of multi-component powders through gentle stirring at low speed and for short periods. This breaks down the initial accumulation, stratification, and local enrichment of raw materials, achieving preliminary fusion of various materials and avoiding the problem of uneven local modification that may occur during subsequent high-speed and high-temperature mixing. This lays a solid foundation for fine micro-dispersion. The specific implementation method is as follows: The raw powder mixture is fed into the high-speed mixer cavity in batches. Batch feeding is a core operating method adapted for powder mixing, avoiding problems such as material accumulation, dead zones, and surface material being fully agitated while bottom material remains stagnant, which can occur with large-scale feeding at once. The amount of material fed in each batch is strictly controlled to 50% to 60% of the maximum mixing volume of the high-speed mixer, ensuring that the mixing structure can contact and agitate all materials in all directions, ensuring no dead zones in the initial mixing. After all batches of materials have been fed, the three-dimensional multi-blade agitator of the high-speed mixer is activated. The agitator adopts a multi-angle bending structure, which can simultaneously drive the material to rotate in a circular motion and tumble longitudinally, achieving all-round material mixing inside the cavity.

[0019] The stirring speed setting range is 300 rpm to 500 rpm. This speed parameter represents the number of rotations of the stirring paddle per minute, which is in the low-speed and gentle stirring range. Under this condition, the mechanical shear force and frictional heat intensity generated by stirring are low, which will not cause problems such as premature softening and adhesion of thermoplastic elastomer toughening agents, thermal deactivation of β nucleating agents, and premature agglomeration of nano silica powder. It can complete macro-mixing while protecting the original properties of raw materials. In the example, the initial mixing speed is set to 400 rpm, which is in the middle of the range. The stirring force is stable, the mixing effect is uniform, and the equipment operating load is low.

[0020] The initial mixing time is between 3 and 5 minutes. This time parameter represents the continuous working time of low-speed stirring. The duration directly determines the macroscopic uniformity of the mixture. If the mixing time is less than 3 minutes, the material will only be turned over a limited number of times, failing to completely break up the stratified and piled-up state of the raw materials, and localized concentrations of single raw materials will still exist. If the mixing time exceeds 5 minutes, it will not improve the uniformity of the mixture, but will only needlessly increase production energy consumption and labor time. In the example, the initial mixing time is set to 4 minutes, which can fully complete the macroscopic homogenization of the material. During the continuous stirring at a speed of 400 rpm for 4 minutes, the polypropylene base material, toughening agent, nanoparticles and nucleating agent, which were originally stratified and locally agglomerated, continuously interweave, turn over and fuse with each other, gradually eliminating phenomena such as material color difference zoning and powder agglomeration.

[0021] After the set processing steps, the overall macroscopic state of the material is uniform and consistent, with no single raw material enrichment areas, no obvious stratification, and no large lumps. This achieves a macroscopically uniform distribution of multi-component materials, and the resulting material is a coarse mixture. This coarse mixture only achieves macroscopic material fusion; at the microscopic level, there are still issues such as slight agglomeration of nanoparticles, loose adhesion between additives and base materials, and uneven microscopic distribution of components. It can only be used as a pre-material for subsequent fine high-temperature dispersion and cannot be directly used for melt extrusion molding.

[0022] Increase the stirring speed of the high-speed mixer to 800-1200 rpm, and at the same time raise the material temperature to 110-130℃ through jacket heating. Use shear friction and heat conduction to promote the initial dispersion of nano-silica in the matrix. Keep the mixture warm for 8-12 minutes to generate a hot dispersion. The core of this step is to break down the microscopic agglomeration structure of nanoparticles through the synergistic effect of high-speed mechanical shearing and cavity jacket heating, combined with the dual effects of physical shear friction and heat conduction. This activates the properties of the additives, achieves deep fusion of the components at the microscopic level, and completes the initial uniform dispersion of the modified raw materials in the matrix. The specific implementation method is as follows: After the coarse mixture is prepared, the stirring speed of the high-speed mixer is gradually increased to stabilize in the high-speed range of 800 rpm to 1200 rpm. The high speed can significantly increase the shearing and tearing force and turbulence intensity of the stirring paddle on the material. The higher the speed, the stronger the squeezing, friction and shearing action between the material particles, and the easier it is to break up the micro-agglomerated particles of nano-silica. In the example, the high-speed stirring speed is set to 1000 rpm to balance the powder dispersion effect and the stability of equipment operation, and to avoid material splashing and equipment overload wear caused by excessive speed.

[0023] The high-speed mixer is equipped with a closed-loop jacketed heating system. The heat-conducting medium circulates inside the jacket, achieving uniform heating of the material inside the chamber through constant temperature circulation, eliminating localized hot spots. The material heating temperature control range is 110℃ to 130℃, which is the actual material temperature and is strictly below the melting point of the polypropylene base material. This ensures that the base material always maintains a solid powder form, preventing the powder from melting, sticking, and clumping. At the same time, this temperature can slightly soften thermoplastic elastomer particles, improving their compatibility with the polypropylene base material. It can also activate the molecular activity of β-nucleating agents, providing a basis for subsequent polypropylene crystallization modification. In the example, the insulation mixing temperature is set at 120℃ to suit the temperature resistance characteristics and modification requirements of all raw materials.

[0024] Under the condition of simultaneous high-speed stirring and constant-temperature heating, the material is continuously subjected to a dual effect to achieve micro-dispersion. The first is the shear friction effect, where high-speed stirring drives the material to move at high speed, and high-intensity shear friction is continuously generated between the material and the stirring paddle, between the material and the cavity wall, and between the materials themselves. This can effectively tear and disperse the nano-scale agglomerates of surface-modified nano-silica, solving the industry pain point of the difficulty in uniformly dispersing inorganic powders. The second is the heat conduction effect, where the heat energy generated by the jacket is uniformly transferred to each material particle, improving the kinematic activity of polypropylene molecules and additive molecules, reducing the interfacial binding resistance of the material, and assisting the nano-powder to penetrate and fill the micro-gap of the polypropylene matrix. The dual effects work together to promote the initial uniform dispersion of nano-silica in the polypropylene matrix.

[0025] The high-temperature, high-speed mixing time ranges from 8 to 12 minutes. This time determines the sufficiency of micro-dispersion. If the time is less than 8 minutes, the agglomerated powder will not be completely broken up, the micro-fusion of components will be insufficient, and the uniformity of the modified material will be insufficient. If the time exceeds 12 minutes, it will lead to the thermal aging failure of flexible additives and the attenuation of nucleating agent activity, while also wasting production energy. In the example, the mixing time is set to 10 minutes, which can achieve sufficient micro-dispersion while protecting the performance of raw materials. After continuous constant temperature and high-speed mixing for 10 minutes, the nano-silica inside the material is basically uniformly dispersed as single particles, the thermoplastic elastomer is uniformly attached to the surface of the base material particles, the β-nucleating agent is uniformly doped into the material system, and the micro-bonding of each component is tight, ultimately generating a hot dispersion with uniform temperature, excellent component dispersibility, and good modification activity.

[0026] After maintaining high-speed stirring and keeping it warm for the set time, stop stirring and discharge the mixture into a cooling container to cool naturally to below 40°C, finally producing a premix.

[0027] The core of this step is to ensure the uniform dispersion of the material after high-temperature, high-speed mixing. By smoothly stopping the machine, rapidly discharging the material, and gradually cooling it down, the problem of secondary agglomeration of the high-temperature material is prevented, and the microscopic distribution structure of each component is fixed. Ultimately, a stable premixed material that can be directly used in subsequent extrusion processes is obtained. The specific implementation method is as follows: Within the preset high-temperature, high-speed heat preservation and mixing cycle, the stirring speed is maintained at a stable 1000 rpm and the temperature at 120°C throughout the process. Equipment parameters are not arbitrarily adjusted, and the process is not prematurely terminated. This ensures that the materials remain in a constant dispersion environment throughout the process, guaranteeing uniform micro-dispersion and stable component structure, and completely avoiding localized uneven dispersion caused by fluctuations in operating conditions. Once the 10-minute heat preservation and mixing time has been fully achieved, the stirring system of the high-speed mixer is immediately shut down, terminating all mechanical stirring actions. This prevents over-stirring from damaging the already formed uniform component structure and avoids performance fluctuations caused by the breakage and refinement of material particles.

[0028] After the mixing process stops, immediately open the sealed discharge port at the bottom of the high-speed mixer to smoothly discharge all the high-temperature mixture inside the chamber into a dedicated open cooling container. The cooling container is made of a high-thermal-conductivity material and features an open ventilation structure, allowing for all-around heat dissipation. Simultaneously, the container's interior is flat and free of dead corners and impurities, preventing material accumulation, contamination, and localized heat buildup. This rapid discharge method minimizes the material's settling time in the high-temperature, sealed chamber, fundamentally preventing secondary agglomeration and stratification of nanoparticles and elastomer additives under high-temperature conditions, thus fully preserving the excellent dispersion state after high-temperature mixing.

[0029] After the high-temperature mixture enters the cooling container, it undergoes natural cooling at room temperature, abandoning rapid cooling methods such as forced air cooling and water cooling. Natural cooling allows for gradual and gradual heat dissipation from the material, ensuring a simultaneous and uniform decrease in temperature both inside and outside the material. This effectively avoids micro-stress within the material caused by excessive temperature differences, preventing damage to the component bonding structure and powder dispersion state from external temperature forces, and precisely locking in the uniform distribution structure of the modified material. The cooling termination temperature set for the process is below 40℃. This temperature is the critical temperature for stable storage of polymer premixed powder. When the material temperature is above 40℃, the molecular thermal activity is high, and there is still a risk of slight agglomeration and component displacement. After the temperature drops below 40℃, the molecular motion of the material tends to be smooth and stable, the micro-dispersion structure of each component is completely fixed, and the performance no longer fluctuates.

[0030] The overall temperature of the material is monitored in real time throughout the process. After all materials in the cooling container are free of local high-temperature points and the overall temperature is uniformly reduced to below 40°C, the distribution of polypropylene base material, thermoplastic elastomer toughening agent, surface-modified nano silica and β nucleating agent inside the material is completely fixed. There is no agglomeration, no layering, no clumping and no impurities. The uniformity of components and the stability of materials meet the process requirements of subsequent twin-screw melt blending extrusion. Thus, a qualified high heat-resistant and high-toughness MPP power pipe special premix is ​​finally produced.

[0031] S202, the premixed material is fed to a twin-screw extruder for melt blending and extrusion, the temperature of each heating zone is controlled to increase sequentially from the feed port to the die head, and the screw speed is adjusted to apply a set shear rate, and modified polypropylene granules are generated after pelleting; Specifically, the premixed material can be fed to the feed port of the twin-screw extruder at a constant rate of 20-50 kg / h using a loss-in-weight feeder, with the ratio of feed rate to screw speed set to 1:1.5-1:2 to generate a stable feed flow; The core of this step is to use a precise metering loss-in-weight feeding device to achieve continuous and uniform conveying of the premix. By matching the process ratio of feed rate to screw speed, problems such as feed fluctuations, material blockage, or material shortages and flow interruptions are eliminated, establishing a continuously stable feeding condition. This lays the foundation for the stability of subsequent melt blending. The specific implementation method is as follows: Loss-in-weight feeders are precision metering and conveying equipment specifically designed for polymer material extrusion processing. Operating on a closed-loop control principle based on real-time weighing feedback, the equipment monitors the rate of mass loss of the premixed material in the hopper in real time and automatically fine-tunes the conveying power to ensure a constant material conveying rate. Unlike the coarse conveying of ordinary screw feeders, this system effectively avoids problems such as powder material bridging and inconsistent conveying speeds. It is well-suited to the powder particle characteristics of the modified polypropylene premixed material used in this process, ensuring accurate feeding and metering. The 20-50 kg / h range set in the steps is the hourly conveying mass range of the premix. This parameter is determined by combining the bulk density and flowability of the polypropylene base material, nanofiller, and nucleating agent mixed in this formula. A conveying rate lower than 20 kg / h will result in low production line capacity and excessive material residence time in the barrel, leading to thermal aging and degradation. A conveying rate higher than 50 kg / h will cause the material feed to exceed the screw pushing load, resulting in overfilling and insufficient melting. In actual production, a constant conveying rate of 35 kg / h can be selected. This value is in the middle of the range and can balance production efficiency and material processing quality.

[0032] The feed rate to screw speed ratio of 1:1.5 to 1:2 refers to the material conveying rate of 1 kg per hour, corresponding to a screw rotation speed of 1.5 to 2 revolutions per minute in a twin-screw extruder. This ratio is a core matching parameter for the melting and plasticizing of materials in this system. Its core function is to ensure a high degree of matching between the screw's material pushing volume, shearing capacity, and feed rate, avoiding the accumulation caused by excessively low screw speed failing to push the feed material in time, or excessively high speed causing idling and shearing, wasting energy and damaging the material's molecular structure. In actual processes, an intermediate ratio of 1:1.75 can be selected. At this ratio, the material filling amount per screw revolution is uniform and stable, and the material pressure inside the barrel remains constant without significant fluctuations.

[0033] During equipment operation, the loss-in-weight feeder continuously delivers the premixed material to the twin-screw extruder feed port at a set constant rate. With a fixed feeding speed ratio, the material can enter the extruder continuously, uniformly, and quantitatively without any abnormalities such as material interruption, accumulation, or overflow. This results in a stable feed flow with stable flow rate, uniform material distribution, and minimal pressure fluctuations. This provides uniform material input conditions for subsequent gradient heating melting and uniform shear blending, ensuring the consistency of batch material processing from the source.

[0034] Start the heating system of the twin-screw extruder and control the temperature of Zone 1 to 170-180℃, Zone 2 to 180-190℃, Zone 3 to 190-200℃, Zone 4 to 200-210℃, and the die head temperature to 205-215℃, so that the material gradually melts during the conveying process and avoids local overheating, generating a temperature gradient field along the process. The core of this step is to use a twin-screw extruder with multi-zone independent heating and control, setting progressively increasing temperature zones to achieve a gradual processing of the premix from preheating and softening to complete melting. This eliminates material degradation and additive failure caused by localized high temperatures, and constructs a continuous and stable temperature gradient field along the process, ensuring a uniform and controllable melting state of the material. The specific implementation method is as follows: The twin-screw extruder heating system employs multi-segment independent temperature control modules, dividing the extruder barrel from the feeding end to the discharge end into four heating zones and a die head heating zone. Each zone is equipped with independent heating components and temperature sensors, enabling closed-loop temperature control with an accuracy of ±1℃. This allows for precise temperature matching based on the material conveying process, adapting to the melting characteristics of polypropylene base materials and the temperature resistance of functional additives. Zone 1 is the feed preheating zone, with a set temperature range of 170–180℃. This temperature is lower than the complete melting temperature of polypropylene. Its core function is to preheat, dry, soften, and loosen the room-temperature premix entering the barrel, eliminating trace amounts of moisture within the material and breaking up accumulated powder agglomerates. This prevents low-temperature powder from directly entering the high-temperature zone and causing temperature shock. In actual processes, the temperature of Zone 1 can be set to 175℃, which is sufficient for material preheating without causing premature melting and adhesion of the powder to the barrel.

[0035] Zone two is the initial melting zone, with a temperature range of 180–190℃, which can actually be set to 185℃. This temperature gradually breaks down the granular crystalline structure of the polypropylene matrix, causing the matrix to transform from a solid state to a viscoelastic state. Simultaneously, the surface-modified nano-silica and β-nucleating agent are initially infiltrated into the matrix system, achieving initial fusion of the components. At this stage, only partial melting is completed, retaining a certain solid state to prevent material slippage and maintain conveying efficiency. Zone three is the deep melting zone, with a temperature range of 190–200℃, which can actually be set to 195℃. This temperature reaches the main melting range of the polypropylene matrix, allowing most of the matrix to completely melt. The solid material is essentially transformed into a molten state, and the thermoplastic elastomer toughening agent is fully softened, making it ready to fuse with the matrix.

[0036] Zone 4 is the homogenization and plasticizing zone, with a temperature range of 200–210℃, which can be set to 205℃ in practice. This temperature can further refine the uniformity of the melt, eliminate residual small solid particles in the melt, and allow various functional additives to be fully dispersed in the melt system, completing the initial homogenization and mixing. The die head is the discharge and pressure stabilization zone, with a temperature range of 205–215℃, which can be set to 210℃ in practice. As the final port of material extrusion molding, the temperature of the die head is slightly higher than that of the heating zones in the barrel, which can effectively reduce the viscosity of the discharged melt, improve the melt flowability, and prevent the melt from condensing and clogging the die orifice due to excessively low die head temperature. At the same time, it can prevent the melt from undergoing thermal oxidative aging due to excessively high temperature.

[0037] Throughout the entire process, the temperature in each zone increases steadily from the feed inlet to the die head, forming a continuous temperature gradient field. The core advantage of this gradient field is that it allows the material to gradually absorb heat and melt step by step as it is conveyed, avoiding the problem of localized overheating caused by single high-temperature heating. Localized overheating can lead to defects such as high-temperature aging and failure of thermoplastic elastomer toughening agents, thermal decomposition of the nano-silica surface modification layer, and degradation of polypropylene molecular chains. The gradient heating mode can match the melting rate of the material, ensuring a high degree of uniformity in the material temperature and melting degree in each section of the barrel. This allows the material to complete the plasticization transition in a stable thermal environment, providing a uniform melt raw material for subsequent shearing and dispersion.

[0038] Adjust the screw speed to 200-350 rpm, so that the melt is subjected to a shear rate of 300-600 s⁻¹ between the threaded elements, which promotes the nano-dispersion of toughening agent and nano-silica in polypropylene matrix and generates a uniform melt blend. The core of this step is to precisely control the twin-screw speed to generate a suitable melt shear rate, thereby breaking down the agglomeration structure of functional additives through mechanical shearing. This achieves extreme dispersion of toughening agents and nanofillers in the polypropylene matrix, eliminates component segregation, and forms a melt blend system with uniform structure and consistent performance. The specific implementation method is as follows: The screw speed of 200-350 rpm refers to the number of revolutions per minute of the twin-screw extruder. It is a core mechanical parameter for controlling melt shear strength, material conveying speed, and mixing uniformity. The speed directly determines the intensity of the shearing, extrusion, and tumbling action of the screw element on the melt. When the screw speed is below 200 rpm, the mechanical shearing force is insufficient to break up the micron-sized agglomerates of nano-silica, nor can it achieve uniform spreading of thermoplastic elastomers, easily leading to localized enrichment of additives. When the screw speed is above 350 rpm, excessive shear friction generates a large amount of internal heat, exceeding the adjustment range of the temperature control system, causing localized overheating and degradation of the melt, and simultaneously damaging the polypropylene molecular chain structure, reducing the strength of the pipe matrix. In actual production, a screw speed of 280 rpm can be selected, which is within the optimal process range, balancing shear dispersion effect and material structure stability.

[0039] The shear rate of 300–600 s⁻¹ is a core process parameter characterizing the intensity of shear deformation in the melt. Physically, it represents the relative deformation ratio of the melt per unit time within the gap of the twin-screw screw thread element, expressed as a negative power per second. This parameter is directly related to the screw speed and the size of the thread gap; higher speeds and smaller gaps result in a higher shear rate. Shear rates below 300 s⁻¹ cannot overcome the agglomeration effect of nanofillers, leading to extremely poor dispersion. Shear rates above 600 s⁻¹ can cause structural damage to the additives and breakage of the matrix molecular chains. In practical processes, a shear rate of 450 s⁻¹ can be controlled to efficiently disperse the additives without damaging the original properties of the material.

[0040] The internal threaded elements of the twin-screw extruder have a unique intermeshing structure. During screw rotation, adjacent threaded elements form a closed shear cavity. Inside this cavity, the melt is continuously subjected to multiple combined actions of compression, shearing, stretching, and folding. The originally agglomerated surface-modified nano-silica particles are gradually broken down into nanoscale monomer particles under continuous mechanical shearing. Simultaneously, the thermoplastic elastomer toughening agent is stretched, spread, and evenly distributed within the molecular chain gaps of the polypropylene matrix. The polypropylene matrix is ​​the main skeletal structure of the entire modification system, bearing the core role of external force and shaping. The toughening agent and nano-silica, as functional modifying phases, are uniformly dispersed within the matrix, without agglomeration, voids, or delamination.

[0041] Under the synergistic effect of the set screw speed and shear rate, the various components break the initial macroscopic uniform state of mixing and achieve uniform distribution at the micro-nano scale. The β nucleating agent is also uniformly dispersed in the melt system, providing uniform nucleation sites for subsequent polypropylene crystallization modification. Finally, all components are completely fused and the structure is highly unified, generating a homogeneous melt blend with no component segregation, no structural defects, and uniform performance, providing a core guarantee for the performance uniformity of subsequent granule preparation and pipe forming.

[0042] The homogeneous molten blend is extruded into strips through a die with a diameter of 3-5 mm. After being cooled to below 60°C by an air-cooled conveyor belt, it is fed into a pelletizer. The rotating cutter cuts the strips at a frequency of 200-300 times per minute, with a pellet length of 2-3 mm, ultimately producing modified polypropylene pellets.

[0043] The core of this step is to extrude a regular melt strip through a sizing die, combined with gentle air cooling for shaping and precise frequency pelletizing, to prepare modified polypropylene granules with standard dimensions, regular morphology, and low internal stress. This ensures the uniformity of raw materials for subsequent pipe extrusion molding. The specific implementation method is as follows: The die orifice diameter of 3-5 mm is the through diameter of the melt extruded strip material. The die orifice is a regular circular through hole. The size of the orifice directly determines the uniformity of the thickness of the extruded strip. If the orifice diameter is less than 3 mm, it will cause excessive melt extrusion resistance, excessive die head pressure, and problems such as discharge jamming, strip breakage, and uneven thickness. If the orifice diameter is greater than 5 mm, it will cause the strip to be too thick, the internal cooling rate to be uneven, the core melt to be incompletely cooled, and the pellets to be prone to adhesion and deformation defects after cutting. In actual processes, a die orifice diameter of 4 mm can be selected, which produces melt strips with uniform thickness, smooth discharge, and stable pressure without fluctuation.

[0044] Under the pressure of the die head, the homogeneous molten blend is continuously extruded through a circular die at a uniform speed, forming a cylindrical melt strip with consistent thickness and dense texture. The high-temperature melt strip then enters an air-cooled conveyor belt for shaping and cooling. The air-cooled conveyor belt uses a normal-temperature clean air convection cooling mode, which, unlike the rapid cooling method of water cooling, allows for uniform and slow cooling of the melt strip from the outside to the inside. This effectively avoids internal stress and surface cracking problems caused by rapid temperature differences. The process requires cooling to below 60°C, which is the glass transition temperature of the modified polypropylene melt. When the melt strip temperature drops below 60°C, it completely transforms from a viscous flow state to a solid state, achieving structural stability and mechanical shear resistance. It can withstand subsequent pelletizing without deformation. In actual production, the final cooling temperature can be controlled at 55°C, fully meeting the shaping requirements and achieving optimal energy consumption.

[0045] After cooling and shaping, the solid strip material is continuously conveyed into the pelletizer, where a high-speed rotating cutter completes the fixed-length cutting. The working frequency of the cutter is 200 to 300 times per minute, which refers to the number of cutting actions of the cutter per unit time. This frequency needs to be precisely matched with the extrusion and conveying speed of the melt strip. A frequency lower than 200 times per minute will result in the strip material being conveyed too fast and the cutting length being too large. A frequency higher than 300 times per minute will result in the cutting being too dense, the pellet size being too small, and the generation of debris. In practice, the cutter frequency can be set to 250 times per minute, matching the discharge speed of the 4 mm die hole, and the cutting rhythm is stable.

[0046] The axial dimension of the final pellets is 2-3 mm in length. This size range is the optimal pellet specification for secondary extrusion molding of MPP power pipes. Particles with a length of less than 2 mm are too small, which can easily cause dust, bridging, and uneven feeding during secondary extrusion. Particles with a length of more than 3 mm are too large, and the plasticizing and melting rate of individual particles is inconsistent, which can easily cause uneven pipe wall thickness and performance fluctuations. The actual controllable pellet length is 2.5 mm, and the pellet size is regular and uniform, without debris, clumps, or irregular particles.

[0047] After a complete process of die extrusion, air cooling and shaping, and precise pelletizing, all pellets have a uniform morphology, size and structure, with uniform internal components, no internal stress and no impurities or defects. The resulting modified polypropylene pellets meet the requirements for high heat resistance and high toughness pipe processing and can be directly used in subsequent drying and pipe extrusion molding processes.

[0048] S203, the modified polypropylene granules are dried and fed into a single screw extruder, plasticized in the melting section by gradually increasing the temperature, and then extruded into a pipe die after passing through a spiral separator to generate an initial pipe blank; Specifically, modified polypropylene granules can be put into a circulating hot air dryer at 80-100℃ and dried for 2-4 hours to reduce the moisture content to below 0.05%. Then, they are fed into the hopper of a single screw extruder through a pneumatic conveying system at a pressure of 0.2-0.4 MPa to generate dried granules for storage. The core of this step is to perform constant-temperature hot air drying on the modified polypropylene granules to completely remove residual moisture from the granules, avoiding defects such as bubbles, voids, and decomposition caused by moisture during high-temperature plasticizing. Then, a constant-pressure pneumatic conveying method is used to achieve dust-free and damage-free transport of the dried granules, providing a stable reserve of raw materials with acceptable moisture content for subsequent extrusion and plasticizing processes. The specific implementation method is as follows: The circulating hot air dryer is a specialized device for dehumidifying and drying polymer granules. Its core working principle involves circulating hot air within a sealed chamber, allowing the high-temperature hot air to fully contact the modified polypropylene granules. This removes free and bound moisture adsorbed from the granule pores and surface. The entire device is a sealed structure, preventing secondary adsorption of moisture from the outside air onto the granule surface and ensuring stable drying results. The drying temperature range of 80–100℃ set in the steps is the optimal drying temperature for modified polypropylene. This temperature range is below the softening initiation temperature of polypropylene, maximizing moisture evaporation efficiency without damaging the original modified structure of the granules or causing granule adhesion and clumping. 80℃ is the minimum drying threshold to ensure normal moisture evaporation, while 100℃ is the maximum safe temperature to prevent localized softening and deformation of the granules. In actual production, a midpoint of 90℃ can be selected as the constant drying temperature, balancing drying efficiency and the integrity of the raw material structure.

[0049] A drying time of 2 to 4 hours is suitable for the process of removing moisture from granules. If the time is too short, the deep moisture inside the granules will not be completely removed. If the time is too long, it will waste energy and may cause slight thermal aging of the granules, affecting the heat resistance and toughness of the subsequent pipes. Among them, 2 hours is the shortest drying time, which is suitable for fresh granules with low initial moisture content. 4 hours is the longest drying time, which is suitable for granules that have been stacked for a long time and have absorbed a lot of moisture. In actual production, a drying time of 3 hours can be set to suit modified polypropylene granules under normal storage conditions. A moisture content of less than 0.05% is a core quality control indicator for modified polypropylene granules extrusion molding. This parameter represents the proportion of water mass in the granules to the total mass of the granules. When the moisture content is higher than 0.05%, the water will instantly vaporize and form bubbles during the high-temperature melting and plasticizing process of the granules. These bubbles will remain inside the pipe and form pore defects, which will significantly reduce the pipe's density, heat resistance, and mechanical strength. After this constant temperature drying process, the moisture content of the granules can be stably controlled at around 0.03%, which fully meets the raw material requirements for high-quality pipe extrusion.

[0050] Pneumatic conveying systems are commonly used closed conveying equipment for polymer granules. They rely on the airflow power of compressed air to transport the granules through pipelines, avoiding problems such as dust pollution, granule mixing, and material loss associated with manual conveying, thus ensuring the purity of the raw materials. The conveying air pressure range in this process is 0.2–0.4 MPa. The air pressure value represents the magnitude of the compressed air pressure. When the air pressure is below 0.2 MPa, the airflow power is insufficient, making it impossible to stably and uniformly convey the granules, easily leading to pipeline blockage and material interruption, resulting in unstable feed to the extruder. When the air pressure is above 0.4 MPa, the airflow velocity is too fast, causing the granules to collide and break violently, producing fine powder, affecting the uniformity of melt plasticization. In actual production, a constant conveying air pressure of 0.3 MPa can be selected to achieve continuous, stable, and complete pipeline conveying of the granules. After drying, dehumidification, and constant pressure conveying, the granules are uniformly stored inside the hopper of the single-screw extruder, forming a reserve of dry granules that are uniform in state, meet the moisture content standards, and are free of impurities and damage, thus providing a stable supply of raw materials for subsequent continuous plasticizing extrusion processes.

[0051] When the single-screw extruder is started, the dry granules in the hopper enter the screw channel by gravity. They are compacted and conveyed forward in the feeding section. After entering the melting section, the granules are completely plasticized by the heating coil that is gradually heated to 190-210°C, generating a viscous melt. The core of this step is to utilize the segmented function of a single-screw extruder to achieve continuous feeding, compaction, conveying, and gradient heating plasticization of the dried granules. This uniformly transforms the solid granular raw material into a viscous melt with good flowability and homogeneous composition, completely eliminating solid particle residue and providing qualified melt raw material for subsequent pipe forming. The specific implementation method is as follows: The single-screw extruder is a core plasticizing equipment for plastic pipe forming. It relies on the rotational motion of the screw within the barrel to achieve material conveying, compaction, shearing, and melting plasticization. The equipment is divided into three core functional sections: the feeding section, the melting section, and the homogenization section. These sections work together to complete the continuous processing of granules. The hopper is a raw material storage and feeding structure at the top of the equipment. The dry granules stored inside continuously and evenly fall into the screw groove of the lower barrel under their own gravity, without the need for external force to push them, achieving uninterrupted continuous feeding and ensuring continuous production.

[0052] The feeding section is the front section of the extruder barrel. This section does not have a high-temperature heating function. Its core function is to compress and compact loose, dry granules. After the loose granules enter the screw channel, the volume of the screw channel gradually changes as the screw rotates and advances. The gaps between the granules are continuously compressed, and the loose particles are compacted into a dense solid layer. This effectively removes residual air from the gaps between the granules, preventing air from mixing into the melt and forming bubble defects. At the same time, it achieves uniform forward conveying of materials, ensuring a stable and uniform feed rate in the subsequent melting section and eliminating uneven plasticization caused by sudden changes in feeding speed.

[0053] The melting section is the core plasticizing area in the middle and rear section of the extruder barrel. It is equipped with multiple independently controlled heating coils to achieve a segmented, gradual temperature control mode, avoiding the problems of localized scorching and incomplete plasticization caused by a single high-temperature heating. The plasticizing temperature range of the melting section is 190–210℃, which is suitable for the melting characteristics of the modified polypropylene base material. 190℃ is the initial melting temperature of the polypropylene granules, achieving preliminary softening. 210℃ is the optimal temperature for complete plasticization, preventing thermal decomposition of the thermoplastic elastomer and nano-silica modified components in the modified system, and fully preserving the high heat resistance and high toughness of the raw material. Gradual heating is the core plasticizing process in this step. It means that the temperature of the melting section increases gradually from the feed end to the discharge end, from the initial 190℃ to 210℃. This allows the granules to soften slowly first, then melt gradually, and finally be completely plasticized. This gradient heating method can ensure that each raw material is heated evenly, avoiding the delamination defects of the outer layer being scorched at high temperature and the inner layer not being plasticized.

[0054] In actual production, the initial temperature of the melting section can be set to 190℃ and the final temperature to 200℃. After gradient heating, the compacted solid granules are continuously heated in the barrel. Combined with the shear friction heat generated by the screw rotation, the solid granules are completely transformed into a homogeneous, fine, and fluid viscous melt. There are no solid particles, coke, or agglomerated impurities inside the melt. All modified components are uniformly dispersed in the polypropylene matrix, which fully meets the melt quality requirements for subsequent pipe extrusion molding.

[0055] The viscous melt is driven by the rotating screw and passes through the spiral distributor. This distributor transforms the rotating flow into an axial linear flow and controls the melt pressure fluctuation within ±0.5 MPa, generating a uniform and stable melt flow. The core of this step is to correct the flow state of the melt and stabilize the melt delivery pressure by using a spiral fluid divider. This eliminates the problems of melt swirling turbulence and fluctuating pressure caused by screw rotation, allowing the melt to form a linear flow state with uniform velocity and stable pressure. This ensures the dimensional accuracy and structural uniformity of the subsequent pipe extrusion molding. The specific implementation method is as follows: After being plasticized in the melting section, the viscous melt is propelled forward at a uniform speed along the barrel axis under the thrust of the continuously rotating single screw, and finally delivered to the spiral flow divider structure at the die head. The spiral flow divider is a key rectifying and pressure-stabilizing component in pipe extrusion molding. It has a built-in spiral guide structure, specifically adapted to the melt conveying conditions of the extruder, and can specifically solve problems such as melt swirling, turbulence, and uneven flow velocity caused by screw rotation. Conventional unrectified melt will generate circumferential swirling flow following the screw rotation, with chaotic melt flow direction and uneven local flow velocity. Direct extrusion will lead to defects such as uneven pipe wall thickness, disordered surface texture, and excessive dimensional deviation. The core function of the spiral flow divider is fluid rectification. Through the fixed spiral guide channel inside, it disrupts the rotational trajectory of the melt, and unifies and corrects the chaotic swirling and turbulent flow into a straight flow parallel to the die axis, so that the overall flow direction of the melt is highly uniform.

[0056] The melt pressure fluctuation of ±0.5 MPa is the core pressure stabilization and quality control parameter in this step. This parameter represents the deviation range between the real-time pressure and the standard working pressure during melt delivery. The smaller the pressure fluctuation value, the more stable the melt delivery state and the higher the pipe forming accuracy. Positive deviation means that the real-time pressure is higher than the standard pressure, and negative deviation means that the real-time pressure is lower than the standard pressure. When the pressure fluctuation exceeds ±0.5 MPa, the melt extrusion volume will fluctuate, directly causing quality defects such as pipe wall thickness deviation, unstable outer diameter, and unevenness on the pipe surface. The spiral fluid distributor, through its integrated structure of internal flow restriction, pressure stabilization, and flow guidance, can buffer the pressure peaks and troughs during melt delivery, offset the pressure fluctuations caused by screw rotation and material flow, and accurately control the melt pressure fluctuation within the qualified range. In actual production, the melt pressure fluctuation can be stably controlled within ±0.3 MPa, which is better than the process standard requirements, further improving melt stability.

[0057] After undergoing spiral flow rectification and pressure stabilization treatment, the originally viscous melt with turbulent flow and fluctuating pressure is transformed into a uniform and pressure-stabilized melt flow with uniform flow velocity, constant pressure, and uniform flow direction. The overall composition of the melt is uniformly distributed and the fluidity is consistent, with no local material accumulation, no dead zones in flow velocity, and no sudden pressure changes, providing a core guarantee for the subsequent uniform extrusion of the die and the regular forming of the pipe.

[0058] The uniformly pressurized melt flow enters the annular gap between the core mold and the die in the pipe mold. The annular gap is 2 to 6 mm wide. After being evenly distributed along the mold flow channel, it is extruded and formed. It is then preliminarily shaped under a vacuum sizing device under a negative pressure of -0.02 to -0.04 MPa, and finally the initial pipe blank is generated.

[0059] The core of this step is to utilize the annular gap of the mold to achieve uniform annular extrusion of the melt, matched with a precise negative pressure vacuum shaping process, so that the molten melt can be quickly formed into a tubular initial blank with a regular structure, preliminary dimensions, and stable shape, completing the core shaping process of pipe forming. The specific implementation method is as follows: The pipe die consists of two core structures: a core mold and a die. The core mold is a columnar core structure inside the die, while the die is an annular sleeve structure outside the die. Both are coaxially mounted and fixed, forming an annular space in the middle, which is the forming channel for melt extrusion, also known as the annular gap in the process. The annular gap width of 2–6 mm refers to the vertical distance between the outer surface of the core mold and the inner surface of the die. This width directly determines the initial wall thickness of the pipe blank and is a core reference parameter for pipe wall thickness forming. When the annular gap width is less than 2 mm, the melt extrusion channel is too narrow, resulting in excessive extrusion resistance and problems such as melt blockage, extrusion interruption, and melt overheating and scorching. When the annular gap width is greater than 6 mm, the melt extrusion volume is too large, leading to a large initial deviation in the pipe blank wall thickness, which is difficult to correct in subsequent shaping and stretching, thus failing to guarantee the dimensional accuracy of the pipe. In actual production, a 4 mm annular gap width can be selected to meet the basic forming requirements of conventional MPP power pipes, balancing extrusion smoothness and wall thickness reference accuracy.

[0060] After the uniformly pressurized melt flow enters the mold, it spreads evenly along the smooth annular flow channel. Under constant pressure and uniform flow, the melt fills the entire annular channel without any local material shortage, accumulation, or flow deviation, ensuring that the melt thickness, flow rate, and density are completely consistent at all positions of the annular cross-section. It is then continuously extruded from the annular port of the mold to form a hollow tubular molten billet. The vacuum sizing device is a specialized piece of equipment for the initial shaping of the pipe. It relies on negative pressure adsorption to rapidly shape and fix the high-temperature molten billet. In this process, -0.02 to -0.04 MPa is the shaping negative pressure parameter. The negative sign in the value indicates that the internal air pressure of the equipment is lower than the external standard atmospheric pressure. The larger the absolute value of the negative pressure, the stronger the adsorption and shaping force.

[0061] A negative pressure of -0.02 MPa is the minimum shaping negative pressure, which can achieve basic shaping of the tube blank and avoid tube blank collapse and deformation. A negative pressure of -0.04 MPa is the maximum safe negative pressure. Excessive negative pressure will cause the incompletely solidified molten tube blank to be over-adsorbed and stretched, resulting in problems such as thinning of the tube wall, local depressions, and dimensional distortion. In actual production, a negative pressure value of -0.03 MPa can be selected to achieve precise and appropriate shaping. After the high-temperature molten tubular blank is extruded, it immediately enters the vacuum sizing device. Under the constant negative pressure adsorption, the outer wall of the tube blank is tightly attached to the inner wall of the sizing structure, quickly fixing the annular tubular shape and constraining the outer diameter of the tube blank. At the same time, it allows the molten melt to quickly and initially solidify, completely solving the problems of easy deformation, collapse, and bulging of the high-temperature melt. Finally, an initial tube blank with a regular shape, symmetrical annular structure, uniform wall thickness, and initially sized is generated, providing qualified blank raw materials for subsequent gradient cooling, stretching, annealing and finishing processes.

[0062] S204, the initial tube blank is sequentially cooled and shaped by a spray cooling section and a sizing sleeve, and then stretched axially and circumferentially by a bidirectional stretching device under the drive of a traction machine. Finally, the internal stress is eliminated by a hot air circulating annealing furnace, and a high heat-resistant and high-toughness MPP power pipe is generated.

[0063] Specifically, the initial tube blank can be traction-into the first cooling section at a speed of 0.5 to 1.5 meters per minute, and high-pressure atomizing nozzles can be used to spray cooling water at 20 to 30 degrees Celsius, so that its surface can be rapidly cooled to 80 to 100 degrees Celsius within 3 to 5 seconds, forming a tube with a preliminary solidified shell. The core of this step is to rapidly gradient cool the surface of the freshly extruded, high-temperature molten initial tube blank. By precisely controlling the traction speed, cooling water temperature, cooling time, and final temperature, the outer surface of the tube is rapidly solidified while preserving the molten and plasticized state inside the tube. This avoids forming defects such as hollowness, collapse, and wrinkles that may occur due to rapid overall cooling of the tube blank, laying the foundation for subsequent precision sizing and stretching processes. The specific implementation method is as follows: The initial tube blank is a high-temperature molten tubular blank formed after extrusion through a single-screw extruder die. It is in a viscous, plasticized state, lacking fixed structural strength and highly susceptible to deformation. Therefore, a first cooling section is needed for surface shaping pretreatment. The traction speed parameter ranges from 0.5 to 1.5 meters per minute. This parameter represents the linear movement speed of the tube blank along the production line and directly determines the dwell time and cooling effect in the first cooling section. Too slow a speed will lead to over-cooling and premature solidification of the tube blank, making subsequent stretching impossible. Too fast a speed will result in insufficient surface cooling and insufficient shell thickness, leading to tube deformation. In actual production, a midpoint of 1.0 meter per minute can be selected to meet the cooling and forming requirements of standard-specification MPP power pipes, ensuring a stable and uniform cooling rhythm.

[0064] The first cooling section is a dedicated primary cooling area in the pipe forming production line, equipped with an array of high-pressure atomizing nozzles. Unlike traditional water jet spray structures, these nozzles cut liquid cooling water into micron-sized droplets, ensuring even coverage of the pipe blank's outer surface without any cooling dead zones. This solves the problems of uneven cooling and localized stress concentration in traditional spray systems. The cooling water temperature is controlled between 20 and 30°C. This temperature range represents both ambient and moderate cooling temperatures, preventing drastic temperature differences between the low-temperature cooling water and the high-temperature pipe blank, thus preventing surface cracking and embrittlement defects. 20°C is the lower limit for cooling efficiency, while 30°C is the upper limit for the most gentle cooling. In actual production, a constant temperature of 25°C can be selected to balance cooling efficiency and pipe forming quality.

[0065] The rapid cooling time for the tube blank surface is controlled within 3-5 seconds. This timeframe is a precise control range for surface curing. 3 seconds is the shortest cooling time, allowing for initial surface crust formation, while 5 seconds is the longest, ensuring a uniform and stable shell thickness. In actual production, 4 seconds is selected as the cooling time, which allows for rapid surface shaping without causing internal melt to cool and solidify. After a short period of rapid cooling, the tube blank surface temperature drops to 80-100℃. This temperature range is the critical temperature range for surface curing of modified polypropylene materials. 80℃ is the temperature for complete initial curing, and 100℃ is the initial curing temperature. The actual controlled final surface temperature is 90℃. At this point, a uniformly thick solidified shell layer forms on the outer wall of the tube blank, while the interior remains in a molten, viscous state, forming an externally solid and internally molten structure. This completes the initial curing of the shell layer in the tube, effectively ensuring the integrity of the overall tube structure in subsequent sizing processes.

[0066] The pipe with the shell layer initially cured is passed through a sizing sleeve with a length of 500 to 800 mm. Under the negative pressure adsorption of -0.02 to -0.06 MPa on the inner wall of the sizing sleeve, the outer diameter tolerance is precisely controlled to ±0.2 mm. The temperature is then further reduced to 50 to 70℃ to produce a dimensionally accurate shaped pipe. The core of this step is to utilize the physical limiting and negative pressure adsorption of the sizing sleeve to calibrate the outer diameter of the pre-cured pipe and perform secondary gradient cooling. This corrects dimensional deviations generated during extrusion and pre-cooling, locks in the basic outer diameter of the pipe, and continuously reduces the overall temperature of the pipe, improving its structural stability and producing a shaped pipe with dimensional accuracy and uniform structure. The specific implementation method is as follows: The sizing sleeve is the core precision tooling for shaping the outer diameter of the pipe. Its effective working length is set to 500-800 mm. The length parameter determines the contact time between the pipe and the sizing sleeve and the shaping accuracy. 500 mm is the shortest shaping length, which is suitable for small-diameter rapid forming pipes, while 800 mm is the longest shaping length, which is suitable for large-diameter, thick-walled, high-precision pipes. In actual production, a sizing sleeve with a length of 650 mm is selected to meet the shaping requirements of mainstream MPP power pipes, ensuring that the pipe is subjected to uniform force and fully shaped during its movement, and preventing the outer diameter from fluctuating.

[0067] The inner wall of the sizing sleeve continuously generates a negative pressure adsorption force of -0.02 to -0.06 MPa. This pressure value is a negative pressure value relative to standard atmospheric pressure. The core function of the negative pressure is to tightly adhere the partially solidified outer wall of the pipe to the smooth inner wall of the sizing sleeve. The tooling's precise inner diameter constrains the outer diameter of the pipe, counteracting the natural expansion and deformation of the pipe in its molten state. Among them, -0.02 MPa is the minimum negative pressure value, suitable for shaping thin-walled pipes, and -0.06 MPa is the maximum negative pressure value, suitable for shaping thick-walled, large-diameter pipes. In actual production, a negative pressure value of -0.04 MPa is selected, which has a moderate adsorption force, ensuring that the pipe fits tightly to the tooling without causing the pipe wall to sink and thin due to excessive negative pressure.

[0068] During the negative pressure adsorption shaping process, the outer diameter tolerance of the pipe is precisely controlled within ±0.2 mm. This tolerance parameter refers to the maximum allowable deviation range between the actual outer diameter of the pipe and the standard design outer diameter. A positive deviation indicates that the outer diameter is too large, and a negative deviation indicates that the outer diameter is too small. The deviation threshold of 0.2 mm can meet the industry precision requirements for power pipeline laying and docking installation, and eliminate problems such as loose pipe splicing and misalignment due to dimensional deviation.

[0069] As the pipe travels inside the sizing sleeve, it undergoes a continuous gradient cooling process. The overall temperature decreases from the initial 80-100℃ to 50-70℃. This cooling range is a progressive low-temperature curing range. 50℃ is the deep curing temperature, at which point the pipe structure is basically completely cured. 70℃ is the initial deep curing temperature, which significantly improves the stability of the pipe structure. In actual production, the final temperature is controlled at 60℃. The slow gradient cooling eliminates the temperature difference stress between the surface and the interior of the pipe, avoiding structural cracks caused by a one-time large-scale cooling. After dimensional calibration and secondary cooling, the overall dimensions of the pipe are uniform and the structure is stable, ultimately producing a precisely sized shaped pipe.

[0070] The shaped tube enters the bidirectional stretching device under the drive of the traction machine. An axial tension of 80 to 150 Newtons is applied by the axial differential roller, and a circumferential expansion force of 0.1 to 0.3 MPa is applied by the internal compressed air. The stretching ratio is 1.2 to 1.5 times in the axial direction and 1.1 to 1.3 times in the circumferential direction, so as to achieve synchronous stretching and orientation in the axial and circumferential directions and generate a reinforced tube with molecular orientation. The core of this step is to mechanically reinforce and modify the shaped pipe through a bidirectional synchronous stretching process. By utilizing the synergistic effect of axial tensile force and circumferential expansion force, the disordered molecular chain structure inside the polypropylene matrix is ​​disrupted, causing the molecular chains to align oriented along the stretching direction. This optimizes the pipe structure at the microscopic level, significantly improving the pipe's heat resistance and toughness, and producing a structurally reinforced pipe blank. The specific implementation method is as follows: The traction machine provides uniform propulsion for the pipe stretching process, ensuring the shaped pipe enters the biaxial stretching device at a constant speed. This eliminates problems such as uneven stretching and inconsistent wall thickness caused by pipe jamming and speed fluctuations, guaranteeing the continuity and stability of the stretching process. The biaxial stretching device is the core equipment for achieving two-dimensional molecular orientation enhancement of the pipe. It integrates axial stretching and circumferential expansion stretching structures, enabling simultaneous and precise axial and circumferential stretching operations.

[0071] The axial differential roller is the core component that provides axial tension. It generates a constant axial tensile force by relying on the speed difference between the front and rear roller sets. The tension value ranges from 80 to 150 Newtons. 80 Newtons is the minimum axial tension, which is suitable for stretching small-diameter thin-walled pipes to avoid insufficient tension from failing to achieve molecular orientation. 150 Newtons is the maximum axial tension, which is suitable for stretching large-diameter thick-walled pipes to avoid excessive tension from cracking the pipe wall. In actual production, an axial tension of 110 Newtons is selected to meet the stretching requirements of conventional pipe specifications and can smoothly pull the pipe to complete the axial extension stretching.

[0072] Compressed air is filled inside the pipe to create a circumferential expansion force. The pressure range is 0.1 to 0.3 MPa. This air pressure acts on the inner wall of the pipe, evenly expanding the pipe body outward to achieve circumferential stretching without dead angles. 0.1 MPa is the minimum expansion pressure, with a smaller circumferential stretching amplitude, while 0.3 MPa is the maximum expansion pressure, with the largest circumferential stretching amplitude. In actual production, a compressed air pressure of 0.2 MPa is selected to ensure uniform circumferential stretching of the pipe and consistent force on all parts of the pipe wall circumference, preventing local overstretching or understretching.

[0073] The stretch ratio is a core parameter for measuring the degree of tensile deformation of pipes, directly determining the molecular orientation effect and the mechanical properties of the pipes. The axial stretch ratio is controlled between 1.2 and 1.5, referring to the ratio of the axial length of the pipe after stretching to the original axial length before stretching. 1.2 times represents low stretching, and 1.5 times represents high stretching. A practical selection of 1.3 times the axial stretch ratio allows for full orientation of the axial molecular chains, improving the axial tensile strength and bending toughness of the pipe. The circumferential stretch ratio is controlled between 1.1 and 1.3, referring to the ratio of the circumferential circumference of the pipe after stretching to the original circumferential circumference before stretching. 1.1 times represents low circumferential stretching, and 1.3 times represents high circumferential stretching. A practical selection of 1.2 times the circumferential stretch ratio optimizes the circumferential structural strength of the pipe, improving its resistance to external pressure and impact.

[0074] During the synchronous stretching process in the axial and circumferential directions, the originally disordered polypropylene molecular chains, modified nano-silica fillers, and elastomer toughening agent molecules inside the pipe will simultaneously stretch and arrange themselves in the axial and circumferential directions, forming a regular micro-network structure. This oriented molecular structure can effectively improve the thermal stability and structural toughness of the pipe. After the synchronous stretching and orientation treatment, a reinforced pipe with molecular orientation and significantly enhanced mechanical properties is finally generated.

[0075] The reinforced tube is passed through a hot air circulating annealing furnace with a length of 2 to 4 meters. It is held at an annealing temperature of 120 to 140°C for 10 to 20 minutes to relax the molecular chains and eliminate internal stress. Then it is naturally cooled to room temperature, finally producing a high heat-resistant and high-toughness MPP power tube with an outer diameter of 110 to 250 mm and a wall thickness of 5 to 15 mm.

[0076] The core of this step is to eliminate residual internal stress generated inside the tube during the stretching process through hot air circulating annealing, regulate and orient the molecular chain structure, stabilize the microstructure and macroscopic dimensions of the tube, and finally obtain a finished MPP power tube with standardized dimensions, stable performance, and a combination of heat resistance and toughness through natural cooling and shaping. The specific implementation method is as follows: The hot air circulating annealing furnace is a specialized temperature control device for eliminating internal stress in pipes. Its effective heating and holding length is 2–4 meters. The furnace length determines the effective annealing time for the pipes. 2 meters is the shortest annealing length, suitable for rapid annealing of small-diameter pipes, while 4 meters is the longest, suitable for thorough annealing of large-diameter, thick-walled pipes. In actual production, a 3-meter annealing furnace is selected to ensure that the pipes pass through the furnace at a uniform speed, with uniform heating throughout the process and no localized temperature differences. The furnace uses a hot air circulating heating mode, which achieves uniform temperature distribution without dead zones, controlling temperature fluctuations within ±2℃, avoiding uneven annealing effects caused by excessively high or low local temperatures.

[0077] The annealing temperature is controlled between 120 and 140℃. This temperature range is the optimal temperature range for the relaxation of molecular chains in modified polypropylene materials, which is consistent with the structural stability temperature characteristics of β-crystalline polypropylene. 120℃ is the lower limit of annealing temperature, and the molecular chain relaxation rate is relatively slow, which is suitable for annealing thin-walled pipes. 140℃ is the upper limit of annealing temperature, and the molecular chain relaxation efficiency is the highest, which is suitable for annealing thick-walled pipes. In actual production, a constant temperature of 130℃ is selected for annealing, which can ensure that the molecular chains oriented after stretching are fully relaxed and reset in a regular manner, without causing the pipe to soften and deform or the molecular orientation structure to fail due to excessive temperature.

[0078] The holding time of the pipe in the annealing furnace is 10 to 20 minutes. The holding time determines the degree of internal stress elimination. 10 minutes is the shortest holding time, which can eliminate most of the surface internal stress. 20 minutes is the longest holding time, which can completely eliminate all residual internal stress from the surface layer to the core layer of the pipe wall. In practice, 15 minutes is selected as the holding time to ensure that the overall temperature of the pipe wall is uniform. The mechanical residual stress generated during the stretching process is completely released, and the molecular chain structure tends to be stable and regular, effectively solving the problems of deformation, cracking and warping in the later use of the pipe.

[0079] After annealing and heat preservation, the reinforced tube is removed from the constant temperature furnace and naturally cooled to room temperature under normal temperature and pressure. Natural cooling is a slow cooling process, which avoids the new temperature stress generated by rapid forced cooling and further stabilizes the microstructure and macroscopic dimensions of the tube. After cooling, the finished tube is obtained. The outer diameter of the finished tube ranges from 110 to 250 mm, covering the small, medium and large diameter pipe specifications commonly used in power engineering. 110 mm is the smallest diameter, suitable for small cable laying, and 250 mm is the largest diameter, suitable for large-scale centralized laying of power cables. The wall thickness ranges from 5 to 15 mm, with 5 mm being the thin-walled specification and 15 mm being the thick-walled specification. The wall thickness and diameter are matched to adapt to different buried pressure resistance and heat resistance application scenarios. The actual finished product can be selected with a conventional engineering specification of 160 mm outer diameter and 8 mm wall thickness. After a complete set of process treatments, the tube has excellent high temperature resistance, impact resistance, and bending toughness, and is finally formed into a high heat-resistant and high-toughness MPP power pipe.

[0080] Another embodiment of the present invention provides a manufacturing system for a high heat-resistant and high-toughness MPP power pipe, see [link to documentation]. Figure 3 The system may include: The input module 301 is used to input polypropylene base material, thermoplastic elastomer toughening agent, surface modified nano silica and β nucleating agent into a high-speed mixer in a mass ratio, and stir at a set temperature until uniformly dispersed to generate a premix. Control module 302 is used to convey the premix to a twin-screw extruder for melt blending and extrusion, control the temperature of each heating zone to increase sequentially from the feed port to the die head, and adjust the screw speed to apply a set shear rate, and generate modified polypropylene granules after pelletizing. Plasticizing module 303 is used to feed the dried modified polypropylene granules into a single screw extruder, where they are plasticized by gradually increasing the temperature in the melting section, and then extruded into a pipe die after passing through a spiral flow divider to generate an initial pipe blank. The shaping module 304 is used to sequentially pass the initial tube blank through the spray cooling section and the sizing sleeve for gradient cooling and shaping. Then, under the drive of the traction machine, it is stretched axially and circumferentially synchronously through the bidirectional stretching device. Finally, the internal stress is eliminated by the hot air circulating annealing furnace, and a high heat-resistant and high-toughness MPP power pipe is generated.

[0081] This invention also provides a storage medium storing a computer program, wherein the computer program is configured to execute the steps in any of the above method embodiments when running.

[0082] This invention also provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to perform the steps in any of the above method embodiments.

[0083] Specifically, the aforementioned electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the aforementioned processor, and the input / output device is connected to the aforementioned processor.

[0084] The above description, based on the embodiments shown in the figures, details the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.

Claims

1. A preparation method of a high-heat-resistant high-toughness MPP power tube, characterized in that, The method includes: Polypropylene base material, thermoplastic elastomer toughening agent, surface modified nano silica and β nucleating agent are added into a high-speed mixer in a mass ratio and stirred at a set temperature until uniformly dispersed to generate a premix. The premixed material is fed into a twin-screw extruder for melt blending and extrusion. The temperature of each heating zone is controlled to increase sequentially from the feed port to the die head. At the same time, the screw speed is adjusted to apply a set shear rate. After pelleting, modified polypropylene granules are generated. The modified polypropylene granules are dried and fed into a single screw extruder. In the melting section, they are plasticized by gradually increasing the temperature. After passing through a spiral separator, they are extruded into a pipe die to form an initial pipe blank. The initial tube blank is sequentially cooled and shaped by a spray cooling section and a sizing sleeve. Then, it is stretched axially and circumferentially by a bidirectional stretching device under the drive of a traction machine. Finally, it is subjected to a hot air circulating annealing furnace to eliminate internal stress, thus producing a high heat-resistant and high-toughness MPP power pipe.

2. The method of claim 1, wherein, The process involves adding polypropylene base material, thermoplastic elastomer toughening agent, surface-modified nano silica, and β-nucleating agent to a high-speed mixer in a specific mass ratio, and stirring at a set temperature until uniformly dispersed to generate a premix, comprising: Weigh 75-85 parts by mass of polypropylene base material, 10-20 parts by mass of thermoplastic elastomer toughening agent, 3-8 parts by mass of surface-modified nano silica and 0.1-0.5 parts by mass of β nucleating agent, and put them into a premixing container after calibration with an electronic balance to generate an accurately measured original powder mixture. Pour the original powder mixture into the high-speed mixer in batches, start the agitator and mix for 300-500 rpm for 3-5 minutes to make the components macroscopically evenly distributed and generate coarse mixed material; Increase the stirring speed of the high-speed mixer to 800-1200 rpm, and at the same time raise the material temperature to 110-130℃ through jacket heating. Use shear friction and heat conduction to promote the initial dispersion of nano-silica in the matrix. Keep the mixture warm for 8-12 minutes to generate a hot dispersion. After maintaining high-speed stirring and keeping the temperature for the set time, stop stirring and discharge the mixture into a cooling container to cool naturally to below 40°C, thus producing a premix.

3. The method of claim 2, wherein, The process of feeding the premixed material into a twin-screw extruder for melt blending and extrusion, controlling the temperature of each heating zone to increase sequentially from the feed port to the die head, and simultaneously adjusting the screw speed to apply a set shear rate, resulting in modified polypropylene granules after pelletizing, includes: The premixed material is fed to the feed port of the twin-screw extruder at a constant rate of 20-50 kg / h using a loss-in-weight feeder. The ratio of feed rate to screw speed is set to 1:1.5-1:2 to generate a stable feed flow. Start the heating system of the twin-screw extruder and control the temperature of Zone 1 to 170-180℃, Zone 2 to 180-190℃, Zone 3 to 190-200℃, Zone 4 to 200-210℃, and the die head temperature to 205-215℃, so that the material gradually melts during the conveying process and avoids local overheating, generating a temperature gradient field along the process. Adjust the screw speed to 200-350 rpm, so that the melt is subjected to a shear rate of 300-600 s⁻¹ between the threaded elements, which promotes the nano-dispersion of toughening agent and nano-silica in polypropylene matrix and generates a uniform melt blend. The homogeneous molten blend is extruded into strips through a die with a diameter of 3-5 mm. After being cooled to below 60°C by an air-cooled conveyor belt, it is fed into a pelletizer. The rotating cutter cuts the strips at a frequency of 200-300 times per minute, with a pellet length of 2-3 mm, ultimately producing modified polypropylene pellets.

4. The method of claim 3, wherein, The modified polypropylene granules are dried and fed into a single-screw extruder, where they are plasticized by gradual heating in the melting section, and then extruded through a spiral separator before being extruded into a pipe die to generate an initial pipe blank. This process includes: Modified polypropylene granules are put into a circulating hot air dryer at 80-100℃ and dried for 2-4 hours to reduce the moisture content to below 0.05%. Then, they are fed into the hopper of a single screw extruder through a pneumatic conveying system at a pressure of 0.2-0.4 MPa to generate dried granules for storage. When the single-screw extruder is started, the dry granules in the hopper enter the screw channel by gravity. They are compacted and conveyed forward in the feeding section. After entering the melting section, the granules are completely plasticized by the heating coil that is gradually heated to 190-210°C, generating a viscous melt. The viscous melt is driven by the rotating screw and passes through the spiral distributor. This distributor transforms the rotating flow into an axial linear flow and controls the melt pressure fluctuation within ±0.5 MPa, generating a uniform and stable melt flow. The uniformly pressurized melt flow enters the annular gap between the core mold and the die in the pipe mold. The annular gap is 2 to 6 mm wide. After being evenly distributed along the mold flow channel, it is extruded and formed. It is then preliminarily shaped under a vacuum sizing device under a negative pressure of -0.02 to -0.04 MPa, and finally the initial pipe blank is generated.

5. The method of claim 4, wherein, The initial tube blank is sequentially passed through a spray cooling section and a sizing sleeve for gradient cooling and shaping. Then, driven by a traction machine, it undergoes simultaneous axial and circumferential stretching via a bidirectional stretching device. Finally, internal stress is eliminated through a hot air circulating annealing furnace, ultimately producing a high-heat-resistant, high-toughness MPP power pipe, comprising: The initial tube blank is traction-into the first cooling section at a speed of 0.5 to 1.5 meters per minute. High-pressure atomizing nozzles are used to spray cooling water at 20 to 30 degrees Celsius, so that the surface temperature is rapidly reduced to 80 to 100 degrees Celsius within 3 to 5 seconds, forming a tube with a preliminary solidified shell. The pipe with the shell layer initially cured is passed through a sizing sleeve with a length of 500 to 800 mm. Under the negative pressure adsorption of -0.02 to -0.06 MPa on the inner wall of the sizing sleeve, the outer diameter tolerance is precisely controlled to ±0.2 mm. The temperature is then further reduced to 50 to 70℃ to produce a dimensionally accurate shaped pipe. The shaped tube enters the bidirectional stretching device under the drive of the traction machine. An axial tension of 80 to 150 Newtons is applied by the axial differential roller, and a circumferential expansion force of 0.1 to 0.3 MPa is applied by the internal compressed air. The stretching ratio is 1.2 to 1.5 times in the axial direction and 1.1 to 1.3 times in the circumferential direction, so as to achieve synchronous stretching and orientation in the axial and circumferential directions and generate a reinforced tube with molecular orientation. The reinforced tube is passed through a hot air circulating annealing furnace with a length of 2 to 4 meters. It is held at an annealing temperature of 120 to 140°C for 10 to 20 minutes to relax the molecular chains and eliminate internal stress. Then it is naturally cooled to room temperature, finally producing a high heat-resistant and high-toughness MPP power tube with an outer diameter of 110 to 250 mm and a wall thickness of 5 to 15 mm.

6. A preparation system of high-heat-resistance and high-toughness MPP power tube, characterized in that, The system includes: The feeding module is used to feed polypropylene base material, thermoplastic elastomer toughening agent, surface modified nano silica and β nucleating agent into a high-speed mixer in a mass ratio, and stir at a set temperature until uniformly dispersed to generate a premix. The control module is used to feed the premix to a twin-screw extruder for melt blending and extrusion, control the temperature of each heating zone to increase sequentially from the feed port to the die head, and adjust the screw speed to apply a set shear rate, so that modified polypropylene granules are generated after pelleting. The plasticizing module is used to dry the modified polypropylene granules and feed them into a single screw extruder. In the melting section, the granules are plasticized by gradually increasing the temperature and then extruded into a pipe die after passing through a spiral separator to generate an initial pipe blank. The shaping module is used to sequentially pass the initial tube blank through a spray cooling section and a sizing sleeve for gradient cooling and shaping. Then, under the drive of a traction machine, it is stretched axially and circumferentially synchronously through a bidirectional stretching device. Finally, it is subjected to a hot air circulating annealing furnace to eliminate internal stress, ultimately producing a high heat-resistant and high-toughness MPP power pipe.

7. The system of claim 6, wherein, The input module is specifically used for: Weigh 75-85 parts by mass of polypropylene base material, 10-20 parts by mass of thermoplastic elastomer toughening agent, 3-8 parts by mass of surface-modified nano silica and 0.1-0.5 parts by mass of β nucleating agent, and put them into a premixing container after calibration with an electronic balance to generate an accurately measured original powder mixture. Pour the original powder mixture into the high-speed mixer in batches, start the agitator and mix for 300-500 rpm for 3-5 minutes to make the components macroscopically evenly distributed and generate coarse mixed material; Increase the stirring speed of the high-speed mixer to 800-1200 rpm, and at the same time raise the material temperature to 110-130℃ through jacket heating. Use shear friction and heat conduction to promote the initial dispersion of nano-silica in the matrix. Keep the mixture warm for 8-12 minutes to generate a hot dispersion. After maintaining high-speed stirring and keeping the temperature for the set time, stop stirring and discharge the mixture into a cooling container to cool naturally to below 40°C, thus producing a premix.

8. The system of claim 7, wherein, The control module is specifically used for: The premixed material is fed to the feed port of the twin-screw extruder at a constant rate of 20-50 kg / h using a loss-in-weight feeder. The ratio of feed rate to screw speed is set to 1:1.5-1:2 to generate a stable feed flow. Start the heating system of the twin-screw extruder and control the temperature of Zone 1 to 170-180℃, Zone 2 to 180-190℃, Zone 3 to 190-200℃, Zone 4 to 200-210℃, and the die head temperature to 205-215℃, so that the material gradually melts during the conveying process and avoids local overheating, generating a temperature gradient field along the process. Adjust the screw speed to 200-350 rpm, so that the melt is subjected to a shear rate of 300-600 s⁻¹ between the threaded elements, which promotes the nano-dispersion of toughening agent and nano-silica in polypropylene matrix and generates a uniform melt blend. The homogeneous molten blend is extruded into strips through a die with a diameter of 3-5 mm. After being cooled to below 60°C by an air-cooled conveyor belt, it is fed into a pelletizer. The rotating cutter cuts the strips at a frequency of 200-300 times per minute, with a pellet length of 2-3 mm, ultimately producing modified polypropylene pellets.

9. A storage medium, characterized by The storage medium stores a computer program, wherein the computer program is configured to execute the method of any one of claims 1-5 when it is run.

10. An electronic device comprising a memory and a processor, characterized in that, The memory stores a computer program, and the processor is configured to run the computer program to perform the method of any one of claims 1-5.

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