TPU particle foaming equipment and foaming method

Abstract

The invention discloses TPU particle foaming equipment and a foaming method. The foaming method comprises the following steps: mixing TPU particles with a nucleating agent, and feeding the mixture into a double-screw extruder to form a preformed body containing a microporous blank body; the preformed body is guided into a multi-zone gradient foaming device, supercritical fluid injection, dynamic pressure field regulation and control and quenching shaping treatment are conducted in sequence, and a foaming body with a directional foam hole structure is formed; then, placing in multi-axial stretching equipment, synchronously applying axial stretching and radial expansion, acquiring thermodynamic parameters and cell form data in real time, and optimizing foaming pressure field parameters and quenching triggering opportunity through a digital twinborn model; and performing plasma activation treatment on the surface of the shaped body, and coating a functional coating to complete the preparation of the functional foaming product. Through the synergistic effect of gradient foaming and a dynamic pressure field, the cell diameter uniformity and rebound rate are improved, multi-axial stretching shaping is combined with digital twinning optimization, cell length-diameter ratio control and density deviation reduction are achieved, and the peel strength of a product is improved through surface functionalization treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of plastic foaming, and in particular to a TPU particle foaming device and a foaming method. Background Art

[0002] As electronic 3C products develop towards lightweight and high integration, the performance requirements for cushioning and protective materials are becoming increasingly stringent. TPU foam materials are widely used in mobile phone / tablet protective cases, smart wearable device buffer layers, precision component anti-vibration packaging and other fields due to their excellent resilience, weather resistance and processability. However, the drop impact protection requirements of electronic products (such as multiple drop tests from a height of 1.5 meters) require materials with ultra-thin thickness and low density (0.25-0.35 g / cm 3 ) and high energy absorption rate, and at the same time need to adapt to the precision molding of complex curved surface structures (such as the buffer layer of the folding screen shaft), which poses an extreme challenge to the directional control of the pore structure and fatigue resistance of TPU foam products.

[0003] In existing technology, TPU foaming often uses a chemical foaming agent (such as sodium bicarbonate) combined with a compression molding process, where the foaming agent decomposes at high temperatures to generate gas to form cells. However, this method suffers from the following drawbacks: uncontrolled cell structure, poor compatibility between the decomposition rate of the chemical foaming agent and melt viscosity, resulting in a discrete cell diameter distribution (CV value > 30%) and uneven cell wall thickness. Repeated impacts on electronic products can cause stress concentration fractures in the weak cell walls (cushioning performance degrades by >40% after 2,000 drop tests), failing to meet the long-term impact stability requirements of high-end electronic products.

[0004] In view of this, it is necessary to propose corresponding solutions to the problems of insufficient resilience, uneven density and poor fatigue resistance caused by the disordered pore structure in the TPU foaming process in the prior art. Summary of the Invention

[0005] The purpose of the present invention is to provide a TPU particle foaming device and a foaming method to solve the above technical problems.

[0006] To achieve this object, the present invention adopts the following technical solutions: A method for foaming TPU particles comprises the following steps: S1, the TPU pellets are mixed with a nucleating agent and fed into a twin-screw extruder, where they are plasticized and extruded at a preset temperature to form a preform containing a microporous embryo. The extrusion parameters are controlled in real time by a closed-loop control system; S2, introducing the preform into a multi-zone gradient foaming device, and sequentially performing supercritical fluid injection, dynamic pressure field regulation, and rapid cooling and shaping treatment to form a foam with a directional cell structure; S3, placing the foam body in a multi-axial stretching device to simultaneously apply axial stretching and radial expansion, maintaining the stretched state at a set temperature to complete the shaping of the foam structure, and obtaining an anisotropically arranged shaped body; S4, based on the thermodynamic parameters and cell morphology data collected in real time during the foaming process, dynamically optimizes the foaming pressure field parameters and the quenching triggering timing through the digital twin model; S5, performing plasma activation treatment on the surface of the shaped body and coating a functional coating, and then constructing a surface defect distribution map through non-destructive testing technology to complete the preparation of the functional foamed product.

[0007] Optionally, step S1 includes the following steps: S11, placing the TPU pellets in a vacuum drying oven and dehydrating them at 80-90° C. for 2-3 hours, while simultaneously performing surface hydroxylation modification on the nucleating agent under inert gas protection; S12, adding the dried TPU particles and the modified nucleating agent in a mass ratio of 10:1 into a high-speed mixer, and mixing them for 8-10 minutes under the synergistic effect of ultrasonic vibration and mechanical stirring to form uniformly dispersed composite particles; S13, the composite particles are fed into the segmented temperature control zone of the twin-screw extruder and sequentially undergo: The temperature of the feeding section is 150-155℃ for initial melting. The plasticizing temperature is 160-165℃ and the applied shear rate is 120-150 s -1 The strong shear flow field forms a molten mixture containing bubble nuclei; S14, injecting supercritical CO2 fluid at the end of the plasticizing section, allowing CO2 to evenly penetrate into the melt through the honeycomb microchannel array of the micropore distribution control module, and generating a microporous embryo with a first diameter in the preform.

[0008] Optionally, after step S14, the following steps may be further performed: S15 uses a laser diameter gauge to monitor the extrudate diameter in real time. When the diameter fluctuation exceeds the allowable threshold range, the PID controller synchronously adjusts the screw speed and the temperature at the end of the plasticizing section to maintain the stability of the preform diameter. S16, introducing the extruded preform into a water-cooled setting sleeve, and solidifying the microporous structure at a cooling rate of 30-50°C / s to obtain a preform with a smooth surface and a target microporous distribution density.

[0009] Optionally, step S2 specifically includes the following steps: S21, introducing the preform into the preheating zone of the gradient foaming device, and heating it to 175-180°C at a rate of 10°C / min under a nitrogen atmosphere to form an activation layer on the surface of the microporous embryo; S22, injecting a CO2 / N2 mixed supercritical fluid into the foaming initiation zone through a rotating supercritical fluid nozzle, and utilizing the centrifugal force field of the fluid nozzle to cause the mixed supercritical fluid to spirally penetrate along the axial direction of the preform to a penetration depth of 80-90% of the cross-sectional thickness of the preform; S23, after the preform enters the cell growth zone, a dual-frequency dynamic pressure field is applied, specifically: axial oscillating pressure and radial pulse pressure, to guide the cells to grow in a directional manner along an inclination angle of 45-60 degrees through the pressure wave interference effect; S24, rapid cooling using liquid nitrogen spray and copper cooling mold in the structural stability area; S25, collecting cell aspect ratio distribution data in real time through an embedded optical fiber array, and triggering a dynamic pressure field frequency compensation module when detecting that the aspect ratio deviation in a local area exceeds a preset value; S26, introducing the rapidly cooled foamed body into a vacuum degassing chamber to remove residual foaming gas, thereby obtaining a foamed body with an oriented cell structure having consistent cell inclination angles and pore size distribution CV values.

[0010] Optionally, step S24 specifically includes: S241, setting the operating parameters of the liquid nitrogen injection: liquid nitrogen flow rate 0.5-1.2 L / min, injection angle 30-45°; S242, a copper cooling groove array is pre-set on the inner wall of the mold; S243, forming a lattice reinforcement structure on the cell wall at the moment of cooling when contacting the inner wall of the mold.

[0011] Optionally, step S3 includes the following steps: S31, introducing the foam into a preheating chamber of a multi-axial stretching device, and heating the foam to 130-135° C. at a rate of 20-25° C. / min under argon protection to soften the cell walls to a preset storage modulus; S32, the servo motor group drives the axial stretching fixture and the hydraulic ring die radial expansion mechanism to apply force synchronously to implement the asymmetric stretching strategy; S33, transferring the stretched foam to a shaping mold, maintaining a biaxial prestressed state at 120-125°C for 90-120 seconds, and then curing the anisotropic arrangement structure by gradient cooling to obtain a shaped body with a preset rebound rate and density.

[0012] Optionally, the asymmetric stretching strategy is specifically: In the main stretching direction, the axial stretching ratio is 2.5:1; In the auxiliary stretching direction, the radial expansion ratio is 1.8:1; A transitional structure with a cell aspect ratio of 3.8-4.2 is formed.

[0013] Optionally, step S4 includes the following steps: S41, deploying multimodal sensor arrays at key locations of the foaming equipment to simultaneously collect thermodynamic parameters and cell morphology data, and constructing a foaming process dataset containing four-dimensional spatiotemporal features; S42, inputting the foaming process data set into the core computing module of the digital twin model. The physical field simulation layer of the digital twin model reconstructs the thermal-mechanical coupling field inside and outside the foam body based on the finite element method; the deep learning prediction layer uses an adaptive convolutional neural network to predict the cell merging trend and the critical point of rapid cooling; S43, based on the pressure field optimization instructions output by the digital twin model, dynamically controls the actuators of the foaming equipment, specifically including: Axial pressure oscillation frequency, PID adjustment based on cell extension rate feedback; The radial pulse pressure peak value is matched with the pressure value according to the hole wall stress concentration factor; Generate dynamic pressure field parameters that match the cellular growth dynamics; S44: When the confidence level of the rapid cooling trigger predicted by the digital twin model reaches the warning value, the multi-level rapid cooling decision system is activated, including: Rapid cooling: The liquid nitrogen injection flow rate is adaptively adjusted according to the current cell density; Secondary rapid cooling: cooling mold contact pressure is dynamically compensated according to the shrinkage rate of the foam; S45, compare the digital twin prediction value with the actual production data through the virtual reality verification interface. If the deviation exceeds the standard, the model parameter self-correction is triggered. The self-correction is specifically as follows: Update of thermodynamic field reconstruction weight coefficients; The cell growth kinetics equation is modified based on the real-time collected cell wall deformation rate data; Complete closed-loop optimization of process parameters and store the optimized process parameters.

[0014] Optionally, step S5 includes the following steps: S51, placing the shaped body in a plasma treatment device, introducing a mixed gas of an inert gas and an active gas, and exciting the plasma by dual-frequency radio frequency to form an activated surface on the surface; S52, using a spraying system to deposit a functional coating along the three-dimensional contour of the shaped body, forming a hydrophobic base layer and an antibacterial surface layer in sequence, and achieving chemical bonding between the coating and the shaped body through photothermal synergistic curing; S53 uses multi-band nondestructive testing technology to scan the coating surface and interface area, fuse the reflection signal with the optical imaging data, collect surface microcracks and coating thickness deviation data, and generate a surface defect distribution map; S54, based on the surface defect distribution map, drives the laser repair system to selectively clad or etch the defective area. After the functional parameters are verified to meet the standards by the machine learning model, the output is a functional foamed product.

[0015] The present invention also provides a TPU particle foaming device for implementing the TPU particle foaming method described above, wherein the foaming device specifically comprises: A raw material pretreatment module, including an ultrasonic mixing unit and a twin-screw extruder, is used to produce a preform containing a uniform microporous embryo; The multi-zone gradient foaming module includes a supercritical fluid rotating nozzle in the first zone, a dual-frequency dynamic pressure generator in the second zone, and a nano-groove quenching mold in the third zone, enabling dynamic control of the directional cell structure. Multi-axial stretching and shaping module, integrating a servo motor-driven axial stretching mechanism, a hydraulic annular expansion die and a multi-modal sensor array for synchronous asymmetric stretching; The digital twin optimization module includes an embedded fiber optic sensor network, edge computing nodes, and an actuator dynamic control interface to form a closed-loop optimization chain for process parameters; The surface functionalization module is equipped with a plasma treatment chamber, a multi-axis linkage spraying robot and a multi-spectral fusion detector to complete gradient coating deposition and defect repair.

[0016] Compared with the prior art, the present invention has the following beneficial effects: first, TPU particles are mixed with a nucleating agent and then plasticized by a twin-screw extruder to form a preform containing a microporous embryo, and the extrusion parameters are ensured to be stable through closed-loop control; then the preform is introduced into a multi-zone gradient foaming device, and supercritical fluid injection, dynamic pressure field regulation and rapid cooling and shaping are carried out in sequence to generate a foam with a directional cell structure; then, the foam is subjected to multi-axial synchronous stretching and radial expansion, and the anisotropic arrangement of the cells is completed at a set temperature; based on the real-time collected thermodynamics and cell morphology data, the preform is subjected to digital twin The model dynamically optimizes the foaming pressure field parameters and the timing of the rapid cooling trigger; finally, the shaped body is subjected to surface plasma activation, functional coating and non-destructive testing to obtain a foamed product with specific functionality; this method improves the uniformity of bubble diameter and rebound rate through the synergistic effect of gradient foaming and dynamic pressure field, and combines multi-axial stretching shaping with digital twin optimization to achieve bubble aspect ratio control and reduce density deviation, while improving production cycle; surface functionalization treatment improves the peel strength of the product, and constructs a defect distribution map to ensure quality consistency, comprehensively providing a high-rebound, lightweight and fatigue-resistant product. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] The structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not intended to limit the conditions under which the present invention can be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportional relationships, or adjustments in size should still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and objectives that can be achieved by the present invention.

[0019] Figure 1 This is a schematic diagram of a process of the foaming method of TPU particles of the first embodiment; Figure 2 This is a second flow chart of the foaming method of TPU particles of the first embodiment; Figure 3 This is the third flow chart of the foaming method of TPU particles in the first embodiment; Figure 4 This is a schematic diagram of the system layout of the TPU particle foaming equipment of the second embodiment. DETAILED DESCRIPTION

[0020] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] In the description of the present invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. It should be noted that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally located component.

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0023] Example 1: Combine Figures 1 to 3 As shown, an embodiment of the present invention provides a method for foaming TPU particles, comprising the following steps: S1, the TPU pellets are mixed with a nucleating agent and fed into a twin-screw extruder, where they are plasticized and extruded at a preset temperature to form a preform containing a microporous embryo. The extrusion parameters are controlled in real time by a closed-loop control system; A preform containing microporous bodies is formed by mixing TPU pellets with a nucleating agent and then plasticizing and extruding them through a twin-screw extruder. The addition of the nucleating agent provides evenly distributed nucleation sites for the subsequent foaming process. The shear plasticization effect of the twin-screw extruder at a preset temperature promotes the initial formation of the microporous bodies. A closed-loop control system monitors extrusion parameters (such as temperature, pressure, and diameter) in real time and dynamically adjusts screw speed and heating temperature to ensure dimensional stability and uniform micropore distribution in the preform.

[0024] S2, introducing the preform into a multi-zone gradient foaming device, and sequentially performing supercritical fluid injection, dynamic pressure field regulation, and rapid cooling and shaping treatment to form a foam with a directional cell structure; In a multi-zone gradient foaming device, supercritical fluid injection, dynamic pressure field control, and rapid cooling and shaping are sequentially implemented. A supercritical fluid (such as CO2) permeates the preform under high temperature and pressure, providing a gas source for cell growth. The dynamic pressure field, through the synergistic effect of axial oscillation and radial pulses, guides the cells to extend and grow in a specific direction, forming a directional structure. Rapid cooling and shaping locks in the cell morphology through rapid cooling, preventing excessive expansion or collapse. The coupling of gradient temperature control and the dynamic pressure field achieves directional control of the cell structure and enhances the anisotropy of the material's mechanical properties.

[0025] S3, placing the foam body in a multi-axial stretching device to simultaneously apply axial stretching and radial expansion, maintaining the stretched state at a set temperature to complete the shaping of the foam structure, and obtaining an anisotropically arranged shaped body; Multi-axial stretching equipment simultaneously applies axial stretching and radial expansion to the foam, finalizing the cell structure at a set temperature. Axial stretching further extends the cells along the primary force direction, while radial expansion adjusts the lateral cell density. The two synergistically form an anisotropic cell network. Heat preservation at a set temperature promotes molecular chain rearrangement, stabilizing the stretched cell structure. By optimizing the cell aspect ratio and spatial distribution through asymmetric stretching, the material's resilience and fatigue resistance are significantly enhanced.

[0026] S4, based on the thermodynamic parameters and cell morphology data collected in real time during the foaming process, dynamically optimizes the foaming pressure field parameters and the quenching triggering timing through the digital twin model; Based on real-time thermodynamic parameters (temperature, pressure) and cell morphology data (pore diameter, wall thickness), a digital twin model dynamically optimizes the foaming process. By simulating the thermal-mechanical coupling of the foaming process, the model predicts cell growth trends and the timing of quenching, and provides feedback to adjust dynamic pressure field parameters (such as oscillation frequency and pressure amplitude). This adaptive optimization of process parameters addresses the uneven cell structure caused by environmental fluctuations in traditional foaming, while also improving production efficiency and product consistency.

[0027] S5, plasma activation treatment is performed on the surface of the shaped body and a functional coating is applied, and then a surface defect distribution map is constructed through non-destructive testing technology to complete the preparation of the functional foamed product.

[0028] The surface of the shaped body is plasma activated to enhance surface energy, after which a functional coating (such as a hydrophobic or antibacterial coating) is applied. Nondestructive testing techniques are then used to construct a surface defect distribution map. Plasma treatment creates a nanoscale rough surface structure, enhancing coating adhesion. The functional coating imparts specific surface properties to the material. Terahertz wave and multispectral fusion detection technology accurately identifies defects such as microcracks and uneven coatings.

[0029] The working principle of the present invention is as follows: first, TPU particles are mixed with a nucleating agent and then plasticized by a twin-screw extruder to form a preform containing a microporous embryo, and the extrusion parameters are ensured to be stable through closed-loop control; then the preform is introduced into a multi-zone gradient foaming device, and supercritical fluid injection, dynamic pressure field regulation and rapid cooling and shaping are carried out in sequence to generate a foam with a directional cell structure; then the foam is subjected to multi-axial synchronous stretching and radial expansion, and the anisotropic arrangement of the cells is completed at a set temperature; based on the real-time collected thermodynamics and cell morphology data, the digital twin model is used for dynamic optimization. The foaming pressure field parameters and the timing of rapid cooling triggering are optimized; finally, the shaped body is subjected to surface plasma activation, functional coating and non-destructive testing to obtain a foamed product with specific functionality; this method improves the uniformity of bubble diameter and rebound rate through the synergistic effect of gradient foaming and dynamic pressure field, and combines multi-axial stretching shaping with digital twin optimization to achieve bubble aspect ratio control and reduce density deviation, while improving production rhythm; surface functionalization treatment improves the peeling strength of the product, and constructs a defect distribution map to ensure quality consistency, comprehensively providing a product with high rebound, lightweight and fatigue resistance.

[0030] In this embodiment, it is specifically explained that step S1 includes the following steps: S11, placing the TPU pellets in a vacuum drying oven and dehydrating them at 80-90° C. for 2-3 hours, while simultaneously performing surface hydroxylation modification on the nucleating agent under inert gas protection; Vacuum drying at 80-90°C effectively removes moisture adsorbed on the surface of TPU particles, preventing abnormal cell expansion or rupture due to evaporation of moisture during subsequent high-temperature processing. Hydroxylation of the nucleating agent under an inert gas (such as nitrogen) enhances the density of its surface active groups and improves its interfacial bonding with the TPU matrix, facilitating subsequent uniform dispersion and bubble nucleation. This temperature range prevents TPU particles from softening and sticking due to overheating while ensuring drying efficiency. The inert gas environment prevents oxidation and inactivation of the nucleating agent.

[0031] S12, adding the dried TPU particles and the modified nucleating agent in a mass ratio of 10:1 into a high-speed mixer, and mixing them for 8-10 minutes under the synergistic effect of ultrasonic vibration and mechanical stirring to form uniformly dispersed composite particles; A 10:1 TPU to nucleating agent mass ratio, combined with a synergistic mixing method using ultrasonic vibration (high-frequency cavitation) and mechanical agitation (shear dispersion), achieves uniform distribution of the nucleating agent within the TPU matrix within 8-10 minutes. Ultrasonic vibration disrupts nucleating agent agglomerates, while mechanical agitation enhances particle convection and diffusion. This dual effect significantly reduces local concentration gradients. This ratio ensures sufficient bubble nucleation density while preventing excessive nucleating agent from causing an abnormal increase in melt viscosity, which could affect subsequent plasticization and extrusion stability.

[0032] S13, the composite particles are fed into the segmented temperature control zone of the twin-screw extruder and sequentially undergo: The temperature of the feeding section is 150-155℃ for initial melting. The temperature of the plasticizing section is 160-165℃ and the shear rate is 120-150s. -1 The strong shear flow field forms a molten mixture containing bubble nuclei; The segmented temperature control design (150-155°C in the feeding section, 160-165°C in the plasticizing section) is tailored to the melting characteristics of TPU. The low temperature in the feeding section initially softens the pellets for stable feeding. The elevated temperature in the plasticizing section, combined with a high shear rate of 120-150s⁻¹, fully melts the TPU and, through the strong shear flow field, induces molecular chain orientation, promoting orderly arrangement of bubble nuclei. Controlling the shear rate within the 120-150s⁻¹ range avoids both low shear rates that lead to uneven dispersion and high shear rates that cause melt fracture or thermal degradation, achieving a balance between plasticizing quality and energy efficiency.

[0033] S14, supercritical CO2 fluid (pressure 8-10 MPa, temperature 155°C) is injected at the end of the plasticizing section, and the CO2 is uniformly infiltrated into the melt through the honeycomb microchannel array (pore size 0.1-0.3 mm) of the micropore distribution control module, generating a first microporous embryo with a diameter of 10-50 μm in the preform.

[0034] Supercritical CO2 is injected into the end of the plasticizing section at a pressure of 8-10 MPa and 155°C. At this point, the melt viscosity is moderate, and the CO2 diffusion rate matches the melt relaxation time, promoting uniform dissolution. A honeycomb microchannel array (pore size 0.1-0.3 mm) increases the fluid contact area and regulates the flow path, allowing the CO2 to penetrate the melt in a laminar manner, avoiding turbulent flow that can lead to cell merging. The microporous embryonic body is sized to 10-50 μm, providing a controllable initial cell structure for subsequent gradient foaming, preventing the direct generation of overly large cells that would hinder subsequent stretching and shaping.

[0035] S15 uses a laser diameter gauge to monitor the extrudate diameter in real time. When the diameter fluctuation exceeds the allowable threshold, the PID controller synchronously adjusts the screw speed (adjustment range ±5 rpm) and the temperature at the end of the plasticizing section (adjustment range ±2°C) to maintain the stability of the preform diameter. A closed-loop system combining a laser diameter gauge and a PID controller monitors extrudate diameter fluctuations in real time (e.g., a ±0.1mm threshold) and dynamically adjusts screw speed (±5rpm) and plasticizing zone temperature (±2°C). This allows for rapid compensation for dimensional deviations caused by changes in material viscosity or external interference. Small, incremental adjustments (e.g., a temperature change of just 2°C) prevent system oscillations caused by sudden parameter changes while maintaining preform geometric accuracy, providing consistent semi-finished products for subsequent gradient foaming.

[0036] S16, introducing the extruded preform into a water-cooled setting sleeve (water temperature 15-20°C), solidifying the microporous structure at a cooling rate of 30-50°C / s, and obtaining a preform with a smooth surface and a target micropore distribution density.

[0037] The water-cooled calibrating sleeve utilizes 15-20°C cooling water and a quench rate of 30-50°C / s. This rapidly solidifies the melt, locking in the microcellular structure and preventing secondary expansion or collapse of the cells due to slow cooling. The low-temperature water bath rapidly reduces the melt temperature to below the glass transition temperature, while the 30-50°C / s cooling rate ensures uniform internal cell wall thickness while preventing surface hardening, shrinkage, and cracking caused by excessive cooling. Achieving both surface smoothness and target microcellular density is directly linked to the controllable cell orientation during the subsequent foaming stage.

[0038] In this embodiment, it is specifically explained that step S2 specifically includes the following steps: S21, introducing the preform into the preheating zone of the gradient foaming device, and heating it to 175-180°C at a rate of 10°C / min under a nitrogen atmosphere to form an activation layer on the surface of the microporous embryo; The preform is heated to 175-180°C at a rate of 10°C / min under a nitrogen atmosphere. The inert atmosphere (nitrogen) inhibits oxidative degradation of the TPU material at high temperatures. This controlled heating rate of 10°C / min prevents both rapid heating, which can lead to an uneven activation layer on the microporous preform surface, and slow heating, which can waste energy.

[0039] S22, injecting a CO2 / N2 mixed supercritical fluid (CO2 content 60-70%, pressure 12-15 MPa, temperature 185°C) into the foaming initiation zone through a rotating supercritical fluid nozzle (rotation speed 200-300 rpm), and utilizing the centrifugal force field of the fluid nozzle to cause the mixed supercritical fluid to spirally penetrate along the axial direction of the preform to a penetration depth of 80-90% of the cross-sectional thickness of the preform; A rotating supercritical fluid nozzle with a rotational speed of 200-300 rpm, combined with a CO2 / N2 mixture (60-70% CO2), utilizes a centrifugal force field to infiltrate the fluid in a spiral path along the axial direction of the preform. This 60-70% CO2 ratio balances foaming efficiency (CO2's high solubility) with controllable cell growth (N2's low diffusion rate). A pressure of 12-15 MPa and a temperature of 185°C ensure high supercritical fluid diffusion while preventing premature cell fusion due to low melt viscosity. The penetration depth reaches 80-90% of the cross-section thickness, ensuring space for cell growth while leaving an unpenetrated core area for mechanical support, preventing structural collapse during foaming.

[0040] S23: After the preform enters the cell growth zone, a dual-frequency dynamic pressure field is applied, specifically: axial oscillating pressure (frequency 1-3 Hz, amplitude ±0.5 MPa) and radial pulse pressure (frequency 50-100 Hz, peak pressure 2-4 MPa), guiding the cells to grow in a directional manner at an inclination angle of 45-60° through the pressure wave interference effect; The dual-frequency dynamic pressure field design regulates the direction of bubble growth through the pressure wave interference effect: the axial oscillation pressure breaks the randomness of bubble growth with low-frequency disturbance, inducing the bubbles to align along the stretching direction; the radial pulse pressure suppresses the lateral expansion of the bubbles through high-frequency compression, forcing the bubbles to grow in a directional manner along an inclination angle of 45-60°.

[0041] The combined design of frequency and amplitude matches the melt relaxation time and the cell growth dynamics, avoiding the single frequency pressure field leading to the single cell orientation or local stress concentration.

[0042] S24, using liquid nitrogen spray and copper cooling mold to quickly cool the structural stability area; specifically: S241, set the liquid nitrogen injection operating parameters to: liquid nitrogen flow rate 0.5-1.2 L / min, injection angle 30-45°. This setting of a liquid nitrogen flow rate of 0.5-1.2 L / min and a 30-45° injection angle locks the cell inclination structure through a gradient cooling rate (rapid surface cooling, slow internal cooling). The lower flow rate limit (0.5 L / min) prevents cell shrinkage caused by insufficient cooling, while the upper limit (1.2 L / min) avoids surface embrittlement caused by excessive liquid nitrogen. The 30-45° injection angle increases the contact area between the liquid nitrogen and the foam, while reducing surface defects caused by jet impact.

[0043] S242, a copper cooling groove array is pre-set on the inner wall of the mold; the array structure has a groove depth of 20-50μm and a spacing of 100-200μm, which accelerates heat conduction by increasing the contact area between the inner wall of the mold and the foam.

[0044] S243 forms a lattice-strengthened structure in the cell walls upon contact with the mold's inner wall. Rapid cooling (coordinated by liquid nitrogen injection and a high-thermal-conductivity copper mold) aligns the molecular chains in the cell walls upon contact with the mold, forming an ordered, lattice-like structure. This structure enhances the cell wall's crystallinity and interfacial bonding strength, enhancing its resistance to compression set and fatigue.

[0045] S25, collecting cell aspect ratio distribution data in real time through an embedded optical fiber array, and triggering a dynamic pressure field frequency compensation module when detecting that the aspect ratio deviation in a local area exceeds a preset value; An embedded fiber array collects real-time data on cell aspect ratio distribution, triggering dynamic pressure field frequency compensation through an online feedback mechanism. For example, when the aspect ratio deviation exceeds a set threshold, the axial oscillation frequency or radial pulse peak pressure is adjusted to correct the cell growth path. This closed-loop control strategy incorporates the dynamic correlation between process parameters and structural evolution into the optimization system, significantly reducing batch-to-batch performance fluctuations.

[0046] S26, introducing the rapidly cooled foamed body into a vacuum degassing chamber to remove residual foaming gas, thereby obtaining a foamed body with an oriented cell structure having consistent cell inclination angles and pore size distribution CV values.

[0047] The vacuum degassing chamber extracts the CO2 / N2 gas remaining in the foam body through a negative pressure environment (such as -0.08MPa to -0.1MPa), eliminating the problems of cell collapse or uneven wall thickness caused by gas escape.

[0048] In this embodiment, it is specifically explained that step S3 includes the following steps: S31, introducing the foam into a preheating chamber of a multi-axial stretching device, and heating the foam to 130-135° C. at a rate of 20-25° C. / min under argon protection to soften the cell walls to a preset storage modulus; Under an argon atmosphere, the foam is heated to 130-135°C at a heating rate of 20-25°C / min. The inert gas (argon) isolates oxygen to prevent oxidative crosslinking or thermal degradation of the cell wall material at high temperatures. This heating rate ensures rapid reaching of the target temperature, improving production cycle time, while preventing excessive temperature differences between the inside and outside of the cell wall, which can lead to uneven softening. The target temperature (130-135°C) lies within the TPU's high elastic range, softening the cell walls to a preset storage modulus (e.g., 1-10 MPa). This allows the cell walls to deform sufficiently to accommodate subsequent stretching and orientation, while preventing excessive softening that could cause cell collapse or merging.

[0049] S32, the servo motor group drives the axial stretching fixture and the hydraulic ring die radial expansion mechanism to apply force synchronously to implement the asymmetric stretching strategy; The servo motor group drives the axial stretching fixture and the hydraulic ring mold radial expansion mechanism to apply force synchronously, and anisotropic control of the foam structure is achieved through an asymmetric stretching strategy (2.5:1 in the main stretching direction and 1.8:1 in the auxiliary direction).

[0050] S33, transferring the stretched foam to a shaping mold, maintaining a biaxial prestressed state at 120-125°C for 90-120 seconds, and then curing the anisotropic arrangement structure by gradient cooling (20°C / s→5°C / s) to obtain a shaped body with a preset rebound rate and density.

[0051] The stretched foam is transferred to a sizing mold and maintained in a biaxially prestressed state at 120-125°C for 90-120 seconds. This thermal relaxation process releases residual stress and stabilizes the molecular chain orientation of the cell walls. A gradient cooling strategy (20°C / s → 5°C / s) solidifies the structure in stages: an initial rapid cooling of 20°C / s locks the cell aspect ratio, followed by a slow cooling of 5°C / s to reduce internal thermal stresses caused by the sudden cooling, thereby preventing structural springback or warping.

[0052] In this embodiment, it is further explained that the asymmetric stretching strategy is specifically: In the main stretching direction, the axial stretching ratio is 2.5:1; through high-ratio stretching, the bubbles are induced to extend along the main force direction, thereby improving the longitudinal rebound rate and compressive strength.

[0053] In the auxiliary stretching direction, a moderate lateral expansion force is applied with a radial expansion ratio of 1.8:1 to compensate for the thinning of the cell wall thickness caused by pure axial stretching and avoid local stress concentration.

[0054] A transitional structure with a cell aspect ratio of 3.8-4.2 is formed. The biaxial synchronous force design ensures uniform force on the cell walls during stretching, reducing cell tearing or orientation disorder caused by differences in uniaxial stretching rates. Ultimately, a transitional structure with an aspect ratio of 3.8-4.2 is formed, providing an intermediate with both high orientation and mechanical balance for subsequent shaping.

[0055] In this embodiment, it is specifically explained that step S4 includes the following steps: S41, deploys multimodal sensor arrays at key locations of the foaming equipment to simultaneously collect thermodynamic parameters and bubble morphology data, and constructs a foaming process dataset containing four-dimensional spatiotemporal characteristics; among which thermodynamic parameters include temperature gradient and pressure fluctuation spectrum; bubble morphology data includes pore size distribution and pore wall thickness.

[0056] Deploy a multimodal sensing array (such as fiber optic temperature sensors, high-frequency pressure sensors, and high-speed microscopic imaging units) to synchronously collect temperature gradients, pressure fluctuation spectra, pore size distribution, and pore wall thickness data, and construct a foaming process dataset through multidimensional features.

[0057] S42, inputting the foaming process data set into the core computing module of the digital twin model. The physical field simulation layer of the digital twin model reconstructs the thermal-mechanical coupling field inside and outside the foam body based on the finite element method; the deep learning prediction layer uses an adaptive convolutional neural network to predict the cell merging trend and the critical point of rapid cooling; The digital twin model adopts a dual-modal architecture consisting of a physical field simulation layer and a deep learning prediction layer: Finite element method thermal-mechanical coupling field reconstruction: Based on the material constitutive equation and boundary conditions (such as the melt viscosity-temperature relationship and the supercritical fluid diffusion coefficient), it accurately reproduces the heat conduction and stress distribution inside and outside the foam, solving the bottleneck of difficult modeling of foam microstructure in traditional simulations; Adaptive Convolutional Neural Network (ACNN): Uses a spatiotemporal attention mechanism to focus on key areas (such as high-risk areas for cell merging) and predict the critical point of rapid cooling (such as the 0.5-1 second window before the cell wall thickness drops to the safety threshold).

[0058] The collaboration between physical models and data-driven models not only retains the interpretability of first principles but also enhances the prediction accuracy of nonlinear processes.

[0059] S43, based on the pressure field optimization instructions output by the digital twin model, dynamically controls the actuators of the foaming equipment, specifically including: The axial pressure oscillation frequency is PID-adjusted based on the feedback of the cell extension rate. According to the feedback of the cell extension rate (e.g., the frequency is reduced to 1Hz when the rate is greater than 5μm / ms), the cell necking and fracture caused by excessive stretching are suppressed. The radial pulse pressure peak is matched to the pressure value according to the hole wall stress concentration factor; based on the hole wall stress concentration factor (for example, when the local stress is greater than 15MPa, the peak pressure is increased to 4MPa), and the lateral expansion trend is offset by the compression force; Generate dynamic pressure field parameters that match the cellular growth dynamics. By embedding the cellular growth dynamics equations (such as the diffusion-deformation coupling equation) into the control algorithm, the pressure field parameters (frequency, amplitude, phase) adapt in real time to the current cellular evolution stage (nucleation, growth, stabilization).

[0060] S44: When the confidence level of the rapid cooling trigger predicted by the digital twin model reaches the warning value, the multi-level rapid cooling decision system is activated, including: Rapid cooling: The liquid nitrogen injection flow rate is adaptively adjusted according to the current bubble density; the first-stage rapid cooling (liquid nitrogen flow rate adaptive) suppresses the merging of bubbles in high-density areas by increasing the cooling intensity according to the real-time bubble density.

[0061] Secondary rapid cooling: The contact pressure of the cooling mold is dynamically compensated according to the shrinkage rate of the foam. Secondary rapid cooling (mold contact pressure compensation): Based on the shrinkage rate of the foam (for example, when the shrinkage rate is greater than 8%, the mold clamping force is increased to 50kN), to offset the deviation of the cell inclination angle caused by shrinkage stress.

[0062] S45, compare the digital twin prediction value with the actual production data through the virtual reality verification interface. If the deviation exceeds the standard, the model parameter self-correction is triggered. The self-correction is specifically as follows: Update the thermodynamic field reconstruction weight coefficient; when the temperature gradient prediction error is greater than 10%, adjust the finite element mesh density or heat conduction coefficient weight to improve the boundary condition fit; The cell growth kinetics equation is modified based on real-time cell wall deformation rate data. Based on the cell wall deformation rate data (e.g., if the difference between the measured rate and the predicted value is greater than 15%), a strain rate sensitivity factor (e.g., an m-value correction term) is introduced to update the kinetics equation. Complete closed-loop optimization of process parameters and store them. Optimized process parameters (such as pressure field frequency bandwidth and quench trigger timing) are stored in a knowledge base and associated with product batch numbers, providing data support for subsequent process iterations.

[0063] In this embodiment, it is specifically explained that step S5 includes the following steps: S51, placing the shaped body in a plasma treatment device, introducing a mixed gas of an inert gas and an active gas, and exciting the plasma by dual-frequency radio frequency to form an activated surface on the surface; A mixture of inert gas (such as argon) and reactive gas (such as oxygen) is introduced, and the plasma is excited using dual-frequency radio frequency (e.g., high frequency 13.56 MHz and low frequency 2 MHz). This dual-frequency coupling effect expands the plasma's uniform coverage. The inert gas maintains discharge stability, while the ionized reactive gas generates reactive groups (such as ·O and ·OH) that undergo a grafting reaction with the TPU surface, forming an active layer rich in polar functional groups. This active layer enhances coating adhesion by increasing the surface energy (e.g., from 30 mN / m to 45 mN / m). Dual-frequency excitation also avoids localized overetching or uneven activation caused by a single frequency, providing a uniform chemically active substrate for subsequent gradient coating deposition.

[0064] S52, using a spraying system to deposit a functional coating along the three-dimensional contour of the shaped body, forming a hydrophobic base layer and an antibacterial surface layer in sequence, and achieving chemical bonding between the coating and the shaped body through photothermal synergistic curing; A hydrophobic base layer (such as fluorocarbon resin) and an antibacterial top layer (such as silver nanoparticle-doped polyurethane) are deposited along a three-dimensional gradient. The spray system's multi-axis robotic arm dynamically adjusts the spray speed (0.5-2 m / s) and atomization pressure (0.2-0.5 MPa), enabling the coating thickness to adapt to the curvature of the surface (e.g., 50 μm in flat areas and 80 μm in angular areas). Synergistic photothermal curing triggers crosslinking and hot melt penetration of the photoinitiator within the coating, forming chemical bonds (such as COC covalent bonds) and mechanical anchoring complexes with the TPU matrix, increasing the peel strength to >15 N / cm.

[0065] S53 uses multi-band nondestructive testing technology to scan the coating surface and interface area, fuse the reflection signal with the optical imaging data, collect surface microcracks and coating thickness deviation data, and generate a surface defect distribution map; Using multi-band nondestructive testing technologies (such as terahertz waves for detecting internal microcracks, near-infrared spectroscopy for analyzing coating thickness, and visible light imaging for identifying surface defects), signal fusion algorithms correlate reflectivity, transmittance, and topographic data to construct a three-dimensional defect distribution map. For example, terahertz waves have a sensitivity to microcracks down to 10μm, near-infrared spectroscopy can resolve coating thickness deviations of ±2μm, and optical imaging can identify surface depressions or protrusions greater than 5μm. By quantifying defect density and spatial distribution characteristics, the defect map provides positioning and priority criteria for precise repair.

[0066] S54, based on the surface defect distribution map, drives the laser repair system to selectively clad or etch the defective area. After the functional parameters are verified to meet the standards by the machine learning model, the output is a functional foamed product.

[0067] Based on the defect map, a laser repair system (such as a fiber laser with a wavelength of 1064 nm and a power of 20-50 W) is driven to selectively process the defect area: Cladding repair: For micro cracks (width < 20μm), laser remelting coating material fills the gaps and reconstructs the crystal structure; Etching correction: For areas where the coating is too thick (deviation > +10%), laser ablation is performed to the target thickness and the edges are smoothed.

[0068] Machine learning models (such as random forest classifiers) monitor the surface roughness and antibacterial properties of the repaired surface in real time, verify that the functional parameters meet the standards, and then output the finished product.

[0069] Example 2: Please combine Figure 4 FIG. 1 is a simplified schematic diagram of the system layout of a TPU particle foaming device. The present invention further provides a TPU particle foaming device, which is characterized in that it is used to implement the TPU particle foaming method of Example 1. The foaming device specifically includes: The raw material pretreatment module 10 includes an ultrasonic mixing unit 11 (with an integrated inert gas protection function) and a twin-screw extruder 12, and is used to generate a preform containing a uniform microporous embryo body.

[0070] The multi-zone gradient foaming module 20 includes a supercritical fluid rotating nozzle in the first zone, a dual-frequency dynamic pressure generator in the second zone, and a nano-groove rapid cooling mold in the third zone, to achieve dynamic regulation of the directional foam structure.

[0071] The multi-axial stretching shaping module 30 integrates an axial stretching mechanism driven by a servo motor, a hydraulic annular expansion die and a multi-modal sensor array for synchronously applying asymmetric stretching.

[0072] The digital twin optimization module 40 includes an embedded fiber optic sensor network, an edge computing node (running thermal-mechanical coupled field simulation and ACNN prediction algorithm) and an actuator dynamic control interface to form a closed-loop optimization chain for process parameters.

[0073] The surface functionalization module 50 is equipped with a plasma treatment chamber, a multi-axis linkage spraying robot and a multi-spectral fusion detector to complete gradient coating deposition and defect repair.

[0074] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for foaming TPU particles, characterized in that: The following steps are involved: S1, the TPU pellets are mixed with a nucleating agent and fed into a twin-screw extruder, where they are plasticized and extruded at a preset temperature to form a preform containing a microporous embryo. The extrusion parameters are controlled in real time by a closed-loop control system; S2, introducing the preform into a multi-zone gradient foaming device, and sequentially performing supercritical fluid injection, dynamic pressure field regulation, and rapid cooling and shaping treatment to form a foam with a directional cell structure; S3, placing the foam body in a multi-axial stretching device to simultaneously apply axial stretching and radial expansion, maintaining the stretched state at a set temperature to complete the shaping of the foam structure, and obtaining an anisotropically arranged shaped body; S4, based on the thermodynamic parameters and cell morphology data collected in real time during the foaming process, dynamically optimizes the foaming pressure field parameters and the quenching triggering timing through the digital twin model; S5, performing plasma activation treatment on the surface of the shaped body and coating a functional coating, and then constructing a surface defect distribution map through non-destructive testing technology to complete the preparation of the functional foamed product.

2. The foaming method of TPU particles according to claim 1, characterized in that: The step S1 comprises the following steps: S11, placing the TPU pellets in a vacuum drying oven and dehydrating them at 80-90° C. for 2-3 hours, while simultaneously performing surface hydroxylation modification on the nucleating agent under inert gas protection; S12, adding the dried TPU particles and the modified nucleating agent in a mass ratio of 10:1 into a high-speed mixer, and mixing them for 8-10 minutes under the synergistic effect of ultrasonic vibration and mechanical stirring to form uniformly dispersed composite particles; S13, the composite particles are fed into the segmented temperature control zone of the twin-screw extruder and sequentially undergo: The temperature of the feeding section is 150-155℃ for initial melting. The plasticizing temperature is 160-165℃ and the applied shear rate is 120-150 s -1 The strong shear flow field forms a molten mixture containing bubble nuclei; S14, injecting supercritical CO2 fluid at the end of the plasticizing section, allowing CO2 to evenly penetrate into the melt through the honeycomb microchannel array of the micropore distribution control module, and generating a microporous embryo with a first diameter in the preform.

3. The foaming method of TPU particles according to claim 2, characterized in that: After step S14, the following steps are further included: S15 uses a laser diameter gauge to monitor the extrudate diameter in real time. When the diameter fluctuation exceeds the allowable threshold range, the PID controller synchronously adjusts the screw speed and the temperature at the end of the plasticizing section to maintain the stability of the preform diameter. S16, introducing the extruded preform into a water-cooled setting sleeve, and solidifying the microporous structure at a cooling rate of 30-50°C / s to obtain a preform with a smooth surface and a target microporous distribution density.

4. The foaming method of TPU particles according to claim 1, characterized in that: The step S2 specifically includes the following steps: S21, introducing the preform into the preheating zone of the gradient foaming device, and heating it to 175-180°C at a rate of 10°C / min under a nitrogen atmosphere to form an activation layer on the surface of the microporous embryo; S22, injecting a CO2 / N2 mixed supercritical fluid into the foaming initiation zone through a rotating supercritical fluid nozzle, and utilizing the centrifugal force field of the fluid nozzle to cause the mixed supercritical fluid to spirally penetrate along the axial direction of the preform to a penetration depth of 80-90% of the cross-sectional thickness of the preform; S23, after the preform enters the cell growth zone, a dual-frequency dynamic pressure field is applied, specifically: axial oscillating pressure and radial pulse pressure, to guide the cells to grow in a directional manner along an inclination angle of 45-60 degrees through the pressure wave interference effect; S24, rapid cooling using liquid nitrogen spray and copper cooling mold in the structural stability area; S25, collecting cell aspect ratio distribution data in real time through an embedded optical fiber array, and triggering a dynamic pressure field frequency compensation module when detecting that the aspect ratio deviation in a local area exceeds a preset value; S26, introducing the rapidly cooled foamed body into a vacuum degassing chamber to remove residual foaming gas, thereby obtaining a foamed body with an oriented cell structure having consistent cell inclination angles and pore size distribution CV values.

5. The foaming method of TPU particles according to claim 4, characterized in that: The step S24 specifically includes: S241, setting the operating parameters of the liquid nitrogen injection: liquid nitrogen flow rate 0.5-1.2 L / min, injection angle 30-45°; S242, a copper cooling groove array is pre-set on the inner wall of the mold; S243, forming a lattice reinforcement structure on the cell wall at the moment of cooling when contacting the inner wall of the mold.

6. The foaming method of TPU particles according to claim 1, characterized in that: The step S3 comprises the following steps: S31, introducing the foam into a preheating chamber of a multi-axial stretching device, and heating the foam to 130-135° C. at a rate of 20-25° C. / min under argon protection to soften the cell walls to a preset storage modulus; S32, the servo motor group drives the axial stretching fixture and the hydraulic ring die radial expansion mechanism to apply force synchronously to implement the asymmetric stretching strategy; S33, transferring the stretched foam to a shaping mold, maintaining a biaxial prestressed state at 120-125°C for 90-120 seconds, and then curing the anisotropic arrangement structure by gradient cooling to obtain a shaped body with a preset rebound rate and density.

7. The foaming method of TPU particles according to claim 6, characterized in that: The asymmetric stretching strategy is specifically as follows: In the main stretching direction, the axial stretching ratio is 2.5:1; In the auxiliary stretching direction, the radial expansion ratio is 1.8:1; A transitional structure with a cell aspect ratio of 3.8-4.2 is formed.

8. The foaming method of TPU particles according to claim 1, characterized in that: The step S4 comprises the following steps: S41, deploying multimodal sensor arrays at key locations of the foaming equipment to simultaneously collect thermodynamic parameters and cell morphology data, and constructing a foaming process dataset containing four-dimensional spatiotemporal features; S42, inputting the foaming process data set into the core computing module of the digital twin model. The physical field simulation layer of the digital twin model reconstructs the thermal-mechanical coupling field inside and outside the foam body based on the finite element method; the deep learning prediction layer uses an adaptive convolutional neural network to predict the cell merging trend and the critical point of rapid cooling; S43, based on the pressure field optimization instructions output by the digital twin model, dynamically controls the actuators of the foaming equipment, specifically including: Axial pressure oscillation frequency, PID adjustment based on cell extension rate feedback; The radial pulse pressure peak value is matched with the pressure value according to the hole wall stress concentration factor; Generate dynamic pressure field parameters that match the cellular growth dynamics; S44: When the confidence level of the rapid cooling trigger predicted by the digital twin model reaches the warning value, the multi-level rapid cooling decision system is activated, including: Rapid cooling: The liquid nitrogen injection flow rate is adaptively adjusted according to the current cell density; Secondary rapid cooling: cooling mold contact pressure is dynamically compensated according to the shrinkage rate of the foam; S45, compare the digital twin prediction value with the actual production data through the virtual reality verification interface. If the deviation exceeds the standard, the model parameter self-correction is triggered. The self-correction is specifically as follows: Update of thermodynamic field reconstruction weight coefficients; The cell growth kinetics equation is modified based on the real-time collected cell wall deformation rate data; Complete closed-loop optimization of process parameters and store the optimized process parameters.

9. The foaming method of TPU particles according to claim 1, characterized in that: The step S5 comprises the following steps: S51, placing the shaped body in a plasma treatment device, introducing a mixed gas of an inert gas and an active gas, and exciting the plasma by dual-frequency radio frequency to form an activated surface on the surface; S52, using a spraying system to deposit a functional coating along the three-dimensional contour of the shaped body, forming a hydrophobic base layer and an antibacterial surface layer in sequence, and achieving chemical bonding between the coating and the shaped body through photothermal synergistic curing; S53 uses multi-band nondestructive testing technology to scan the coating surface and interface area, fuse the reflection signal with the optical imaging data, collect surface microcracks and coating thickness deviation data, and generate a surface defect distribution map; S54, based on the surface defect distribution map, drives the laser repair system to selectively clad or etch the defective area. After the functional parameters are verified to meet the standards by the machine learning model, the output is a functional foamed product.

10. A TPU particle foaming device, characterized in that: The foaming method for TPU particles according to any one of claims 1 to 9 is implemented, wherein the foaming equipment specifically comprises: A raw material pretreatment module, including an ultrasonic mixing unit and a twin-screw extruder, is used to produce a preform containing a uniform microporous embryo; The multi-zone gradient foaming module includes a supercritical fluid rotating nozzle in the first zone, a dual-frequency dynamic pressure generator in the second zone, and a nano-groove quenching mold in the third zone, enabling dynamic control of the directional cell structure. Multi-axial stretching and shaping module, integrating a servo motor-driven axial stretching mechanism, a hydraulic annular expansion die and a multi-modal sensor array for synchronous asymmetric stretching; The digital twin optimization module includes an embedded fiber optic sensor network, edge computing nodes, and an actuator dynamic control interface to form a closed-loop optimization chain for process parameters; The surface functionalization module is equipped with a plasma treatment chamber, a multi-axis linkage spraying robot and a multi-spectral fusion detector to complete gradient coating deposition and defect repair.

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