A fully biodegradable sponge preparation system and method

Abstract

The present application relates to the field of polymer polymerization processing and foaming forming, and discloses a kind of full biodegradable sponge preparation system and method, comprising: the pressure fluctuation curve in collection channel is collected and viscosity parameter and pressure fluctuation change rate are calculated, according to which the injection flux of foaming agent is formulated, while controlled electric field is applied according to pressure fluctuation change rate at the outlet end, the radial change of flow passage cross-sectional area is utilized by piezoelectric deformation to adjust local resistance flow back pressure, the pressure drop change rate when material passes through convergent module is stabilized, the heat-sensitive chain scission loss of degradable material is constructed according to the hedging mechanism, effectively cooperate with the injection flux of foaming agent and the strength of dilute melt, eliminate the cell body bubble collapse defect caused by the imbalance of multiphase interface viscoelasticity dissipation, under the premise of avoiding adding exogenous chemical crosslinking agent, improve the molecular weight retention rate of polymer main chain segment, synergistically enhance the isotropic narrow distribution of cell pores and mechanical toughness of sponge finished product.

Description

Technical Field

[0001] This invention belongs to the field of polymer formulation and foaming technology, and particularly relates to a fully biodegradable sponge preparation system and method. Background Technology

[0002] Currently, aliphatic biodegradable polyester materials utilize supercritical fluid continuous extrusion foaming to create open-cell foam topologies, belonging to the field of polymer formulation and melt processing technology. The process requires the polymer matrix and gaseous ingredients to be homogeneously dispersed in the flow channel. Strong shear flow fields promote the convective mass transfer of gaseous molecules into the melt. Under the precision material manufacturing conditions that ensure narrow pore size distribution, the material exhibits thermosensitive degradation properties. When the mixture passes through the flow channel, shear heat accumulates in the viscous boundary layer on the wall and the strong shear region. Due to the low thermal conductivity of the melt, mechanical energy is converted into viscous heat dissipation, causing a local temperature rise in the flow channel. The ester bond scission energy in the aliphatic polyester chain segments is low. Abnormal high temperature triggers random chain breakage, resulting in a rapid drop in molecular weight. The tensile strength and viscosity of the melt undergo transient collapse, disrupting the mass transfer balance at the multiphase interface and causing the gaseous ingredients to become supersaturated. When the material is extruded from the outlet, the cell wall breaks prematurely due to the lack of viscoelastic support, leading to bubble co-formation and bubble rupture, resulting in excessive open-cell ratio and anisotropic defects in cell size.

[0003] To suppress the degradation of matrix macromolecular chains, conventional approaches include reducing screw speed or enhancing forced cooling of the barrel's outer wall. However, reducing speed weakens the mass transfer rate, leading to a deterioration in the homogeneity of the supercritical fluid. Furthermore, the thickness of the metal outer wall and the low thermal conductivity melt create thermal resistance, preventing external cooling from reaching the flow channel center and failing to eliminate transient shear heating at the center. This processing condition creates a constraint between the homogeneity of mass transfer and the suppression of molecular degradation, limiting the hardware physical configuration and hindering the adaptive capabilities of corresponding control methods. For example, Chinese invention patent application CN121179686A discloses a continuous production molding process for multilayer co-extruded foamed cushioning cotton. The process addresses interlayer stress by adjusting the temperature field distribution through foaming parameters. However, the temperature control path implicitly relies on the relatively stable overall flow characteristics of the material. When dealing with aliphatic polyesters, which are highly sensitive to heat-breaking chain fragmentation, the sudden drop in molecular weight and viscosity collapse caused by localized strong shearing are microsecond-level transient rheological anomalies. Adjusting the external temperature field to conduct heat has huge thermal inertia, and the extremely low thermal conductivity of the material makes the temperature control adjustment speed unable to keep up with the self-accelerating degradation rate of random chain segment breakage. At the same time, its pressure threshold determination strategy cannot decouple the initial viscosity deviation between batches of material from the degradation viscosity drop in the middle of processing, which can easily lead to gas mixing errors. Ultimately, it cannot solve the defects of bubble collapse and anisotropic cell size.

[0004] Therefore, how to accurately capture the transient rheological characteristics and degradation state of biodegradable melt in the flow channel, dynamically reshape the feed injection path and the pressure gradient distribution of the terminal flow field, and achieve isotropic narrow distribution control of the bubble structure under the thermosensitive working condition of macromolecular chain scission degradation, has become the technical problem to be solved by this invention. Summary of the Invention

[0005] The present invention aims to solve the technical problem of viscosity collapse caused by shearing and chain scission degradation of polymer melts, which leads to supersaturation, bubble breaking, and pore formation of supercritical batching gas.

[0006] In this technical solution, a fully biodegradable sponge preparation system includes:

[0007] The melt pressure characteristic acquisition unit is connected to the material rheology channel module. It is used to acquire the melt pressure fluctuation curve in the material rheology channel module and extract the pressure pulsation amplitude to calculate the melt apparent viscosity characterization value and the root mean square rate of change of pressure fluctuation. At the same time, it compares the total flow resistance value of the flow channel with the local flow shear stress response value to distinguish the initial melt viscosity deviation between batches and the melt degradation viscosity drop, and outputs the corrected viscosity parameter and the root mean square rate of change of pressure fluctuation.

[0008] The foaming agent injection rate adjustment unit is connected to the melt pressure characteristic acquisition unit and the material rheology channel module, and is used to adjust the gas injection rate into the material rheology channel module according to the corrected viscosity parameter.

[0009] The die orifice flow control unit is connected to the melt pressure characteristic acquisition unit and the wall piezoelectric deformation module at the outlet end of the material rheological channel module. It includes a drive electric field amplification module, which is used to receive the root mean square rate of change of pressure fluctuation to adjust the basic deformation of the piezoelectric deformation adjustment module in the wall piezoelectric deformation module. When the melt back pressure change rate at the wall piezoelectric deformation module deviates from the calibration range, the drive electric field amplification module applies a controlled electric field to the wall piezoelectric deformation module. The radial deformation of the piezoelectric deformation adjustment module counteracts the flow resistance fluctuation, so that the instantaneous pressure drop change rate of the material passing through the flow channel section convergence module is stabilized within the calibration linear range. It forms a cascaded closed-loop control with the melt pressure characteristic acquisition unit and the foaming agent injection amount adjustment unit.

[0010] Preferably, the melt pressure characteristic acquisition unit includes a rheological parameter calculation module, which is used to acquire local shear stress data in the material rheological channel module to establish the local flow shear stress response value, and acquire the static pressure difference between the two ends of the material rheological channel module to establish the total flow resistance value of the channel; the rheological parameter calculation module is equipped with data comparison logic, which is used to cross-compare the melt apparent viscosity characterization value with the total flow resistance value of the channel and the local flow shear stress response value, and determine the batch initial melt viscosity deviation when the change range of the melt apparent viscosity characterization value is less than the calibrated viscosity fluctuation threshold.

[0011] Preferably, the foaming agent injection quantity adjustment unit includes a foaming agent flow rate adjustment module and a foaming agent injection nozzle. The foaming agent flow rate adjustment module is connected to the foaming agent injection nozzle. The foaming agent flow rate adjustment module is used to receive the corrected viscosity parameter, and when the corrected viscosity parameter indicates that the melt degradation viscosity decreases in the material rheology channel module, it controls the gas injection flux delivered to the foaming agent injection nozzle to be reduced proportionally with the decrease of the corrected viscosity parameter, so that the foaming agent concentration in the melt is stabilized within the calibrated variation range.

[0012] Preferably, the piezoelectric deformation regulating module includes a flexible inner liner sleeved on the inner wall of the outlet end of the material rheology channel module, and a plurality of piezoelectric actuators embedded in the tube wall of the outlet end along the circumference of the outlet end of the material rheology channel module; the plurality of piezoelectric actuators abut against the outer surface of the flexible inner liner, and the plurality of piezoelectric actuators generate radial displacement when subjected to a controlled electric field, so as to drive the flexible inner liner to generate radial contraction deformation toward the axis of the material rheology channel module.

[0013] Preferably, the material rheology channel module includes a melting functional zone, a mixing functional zone, and a foaming control functional zone connected in sequence; the melt pressure characteristic acquisition unit includes a multi-point pressure acquisition module, which is located on the inner wall of the foaming control functional zone and is used to acquire the total melt pressure and local pressure pulsation signals in the foaming control functional zone and convert them into melt pressure fluctuation curves.

[0014] Preferably, the foaming agent injection quantity adjustment unit further includes a gas supply adjustment channel module and a flow regulation control module, wherein the flow regulation control module is connected to the foaming agent flow regulation module; the foaming agent flow regulation module is used to output an opening control signal to the flow regulation control module to change the flow cross-sectional area of ​​the flow regulation control module.

[0015] Preferably, the material rheology channel module is provided with a flow resistance adjustment module; wherein, the flow resistance adjustment module has four evenly distributed throttling adjustment units along the inner circumference of the material rheology channel module, which are used to change the total flow resistance value of the flow channel according to the depth of the throttling adjustment units extending into the material rheology channel module.

[0016] Preferably, the melt pressure characteristic acquisition unit includes a safety monitoring module, which is connected to the die orifice flow control unit and the foaming agent injection amount adjustment unit via a data bus. The safety monitoring module is used to monitor the rate of change of the melt back pressure at the wall piezoelectric deformation module, and when the rate of change exceeds the calibrated safety threshold, it outputs a calibration over-limit indication signal to the foaming agent injection amount adjustment unit. The foaming agent injection amount adjustment unit is used to lock the gas injection flux at the current value according to the calibration over-limit indication signal.

[0017] Preferably, the inlet end of the material rheology channel module is provided with a melt feeding unit; wherein, the melt feeding unit includes a twin-screw mixing module and a pressure-stabilizing conveying module connected to the outlet end of the twin-screw mixing module. The twin-screw mixing module is used to melt and plasticize the raw materials, and the pressure-stabilizing conveying module is used to convey the materials to the material rheology channel module and stabilize the pressure input to the material rheology channel module within the calibrated pressure range.

[0018] A method for preparing a fully biodegradable sponge, used to operate a fully biodegradable sponge preparation system, includes the following steps:

[0019] Step S101: The melt pressure fluctuation curve in the material rheology channel module is acquired by the melt pressure characteristic acquisition unit and the pressure pulsation amplitude is extracted to calculate the melt apparent viscosity characterization value and the root mean square change rate of pressure fluctuation. At the same time, the total flow resistance value of the flow channel and the local flow shear stress response value are compared to distinguish the initial melt viscosity deviation between batches and the melt degradation viscosity drop. The corrected viscosity parameter and the root mean square change rate of pressure fluctuation are output.

[0020] Step S102: The foaming agent injection amount adjustment unit receives the corrected viscosity parameter and adjusts the gas injection flow rate into the material rheology channel module according to the corrected viscosity parameter.

[0021] Step S103: The driving electric field amplification module in the die orifice flow control unit receives the root mean square rate of change of pressure fluctuation to adjust the basic deformation of the piezoelectric deformation adjustment module in the wall piezoelectric deformation module. When the melt back pressure change rate at the wall piezoelectric deformation module deviates from the calibration range, the driving electric field amplification module applies a controlled electric field to the wall piezoelectric deformation module. The radial deformation of the piezoelectric deformation adjustment module counteracts the flow resistance fluctuation, so that the instantaneous pressure drop change rate of the material passing through the flow channel section convergence module is stabilized within the calibration linear range. The root mean square rate of change of pressure fluctuation is transmitted through the signal interface, so that the foaming agent injection amount adjustment unit and the die orifice flow control unit form a cascaded closed-loop control.

[0022] Compared with existing technologies, the fully biodegradable sponge preparation system of the present invention has the following advantages:

[0023] 1. In the preparation of fully biodegradable sponges, dynamic shear pressure drop waveform signals are collected at the shear contraction boundary of the front channel, and flow viscoelastic dissipation characteristic parameters are extracted by differential root mean square calculation. When the melt main chain segment undergoes transient degradation due to thermal shear accumulation and viscosity collapse, it provides rheological feature feedforward. This directly links the annular electromagnetic needle valve on the outer wall to cause staggered asymmetric physical deformation. The asymmetric mass source is used to apply boundary cutting to the continuous gas film slip layer and induce local swirling flow. This allows the gas injection flux to adaptively match the weak melt strength in the degradation state. This is used to reduce the incidence of early cell wall fracture and excessive porosity caused by relative gas supersaturation and to reduce the dependence on external high-priced molecular weight online detection hardware.

[0024] 2. By periodically reading the dynamic torque rate of the screw through the data bus and using the torque rate as a proportional bias product factor, the flow viscoelastic dissipation characteristic parameters obtained by solving the pressure drop pulsation component are aligned with the in-situ reference to generate corrected characteristic parameters. By utilizing the heterogeneous cross-composite of the total shear resistance of the whole cavity and the local high-frequency rheological response, the initial viscosity drift caused by changing material batches and the transient degradation of chain segments occurring in the middle of the process can be effectively distinguished. This is used to avoid mis-adjustment of gas injection flux due to parameter reference drift, maintain the control stability of the material mass energy flow path during long-term operation, and reduce the misjudgment rate of process state determination caused by the aliasing of a single physical signal source.

[0025] 3. The root mean square rate of change of the pressure drop waveform of the front stage is received through the nonlinear control node to adjust the deformation bias reference of the flexible piezoelectric layer, and the rate of change of the back pressure of the end flow channel impedance is periodically captured. When the cumulative viscosity fluctuation caused by the degradation of macromolecules in the middle of the processing is detected to cause the flow resistance to deviate from the preset barrier, the digital amplifier is driven to apply a controlled electric field to the piezoelectric composite layer. The micron-level physical deformation of the wall surface is used to adaptively offset the flow resistance deviation and reshape the pressure spatiotemporal gradient, so that the pressure release rate of the material at the moment of crossing the convergence component is rigidly stabilized within a constant linear level. This is used to suppress the non-ionic fracture of the cell wall during the foaming phase separation stage and reduce the occurrence of hollow hard cores in the finished sponge. Attached Figure Description

[0026] Figure 1 This is a structural diagram of the fully biodegradable material rheology-adjusted foaming control system of the present invention;

[0027] Figure 2 This is a diagram of the closed-loop counter-current control process for nonlinear degradation of melt in this invention. Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0029] A fully biodegradable sponge preparation system, comprising:

[0030] The melt pressure characteristic acquisition unit is connected to the material rheology channel module. It is used to acquire the melt pressure fluctuation curve in the material rheology channel module and extract the pressure pulsation amplitude to calculate the melt apparent viscosity characterization value and the root mean square rate of change of pressure fluctuation. At the same time, it compares the total flow resistance value of the flow channel with the local flow shear stress response value to distinguish the initial melt viscosity deviation between batches and the melt degradation viscosity drop, and outputs the corrected viscosity parameter and the root mean square rate of change of pressure fluctuation.

[0031] The foaming agent injection rate adjustment unit is connected to the melt pressure characteristic acquisition unit and the material rheology channel module, and is used to adjust the gas injection rate into the material rheology channel module according to the corrected viscosity parameter.

[0032] The die orifice flow control unit is connected to the melt pressure characteristic acquisition unit and the wall piezoelectric deformation module at the outlet end of the material rheological channel module. It includes a drive electric field amplification module, which is used to receive the root mean square rate of change of pressure fluctuation to adjust the basic deformation of the piezoelectric deformation adjustment module in the wall piezoelectric deformation module. When the melt back pressure change rate at the wall piezoelectric deformation module deviates from the calibration range, the drive electric field amplification module applies a controlled electric field to the wall piezoelectric deformation module. The radial deformation of the piezoelectric deformation adjustment module counteracts the flow resistance fluctuation, so that the instantaneous pressure drop change rate of the material passing through the flow channel section convergence module is stabilized within the calibration linear range. It forms a cascaded closed-loop control with the melt pressure characteristic acquisition unit and the foaming agent injection amount adjustment unit.

[0033] Preferably, the melt pressure characteristic acquisition unit includes a rheological parameter calculation module, which is used to acquire local shear stress data in the material rheological channel module to establish the local flow shear stress response value, and acquire the static pressure difference between the two ends of the material rheological channel module to establish the total flow resistance value of the channel; the rheological parameter calculation module is equipped with data comparison logic, which is used to cross-compare the melt apparent viscosity characterization value with the total flow resistance value of the channel and the local flow shear stress response value, and determine the batch initial melt viscosity deviation when the change range of the melt apparent viscosity characterization value is less than the calibrated viscosity fluctuation threshold.

[0034] Preferably, the foaming agent injection quantity adjustment unit includes a foaming agent flow rate adjustment module and a foaming agent injection nozzle. The foaming agent flow rate adjustment module is connected to the foaming agent injection nozzle. The foaming agent flow rate adjustment module is used to receive the corrected viscosity parameter, and when the corrected viscosity parameter indicates that the melt degradation viscosity decreases in the material rheology channel module, it controls the gas injection flux delivered to the foaming agent injection nozzle to be reduced proportionally with the decrease of the corrected viscosity parameter, so that the foaming agent concentration in the melt is stabilized within the calibrated variation range.

[0035] Preferably, the piezoelectric deformation regulating module includes a flexible inner liner sleeved on the inner wall of the outlet end of the material rheology channel module, and a plurality of piezoelectric actuators embedded in the tube wall of the outlet end along the circumference of the outlet end of the material rheology channel module; the plurality of piezoelectric actuators abut against the outer surface of the flexible inner liner, and the plurality of piezoelectric actuators generate radial displacement when subjected to a controlled electric field, so as to drive the flexible inner liner to generate radial contraction deformation toward the axis of the material rheology channel module.

[0036] Preferably, the material rheology channel module includes a melting functional zone, a mixing functional zone, and a foaming control functional zone connected in sequence; the melt pressure characteristic acquisition unit includes a multi-point pressure acquisition module, which is located on the inner wall of the foaming control functional zone and is used to acquire the total melt pressure and local pressure pulsation signals in the foaming control functional zone and convert them into melt pressure fluctuation curves.

[0037] Preferably, the foaming agent injection quantity adjustment unit further includes a gas supply adjustment channel module and a flow regulation control module, wherein the flow regulation control module is connected to the foaming agent flow regulation module; the foaming agent flow regulation module is used to output an opening control signal to the flow regulation control module to change the flow cross-sectional area of ​​the flow regulation control module.

[0038] Preferably, the material rheology channel module is provided with a flow resistance adjustment module; wherein, the flow resistance adjustment module has four evenly distributed throttling adjustment units along the inner circumference of the material rheology channel module, which are used to change the total flow resistance value of the flow channel according to the depth of the throttling adjustment units extending into the material rheology channel module.

[0039] Preferably, the melt pressure characteristic acquisition unit includes a safety monitoring module, which is connected to the die orifice flow control unit and the foaming agent injection amount adjustment unit via a data bus. The safety monitoring module is used to monitor the rate of change of the melt back pressure at the wall piezoelectric deformation module, and when the rate of change exceeds the calibrated safety threshold, it outputs a calibration over-limit indication signal to the foaming agent injection amount adjustment unit. The foaming agent injection amount adjustment unit is used to lock the gas injection flux at the current value according to the calibration over-limit indication signal.

[0040] Preferably, the inlet end of the material rheology channel module is provided with a melt feeding unit; wherein, the melt feeding unit includes a twin-screw mixing module and a pressure-stabilizing conveying module connected to the outlet end of the twin-screw mixing module. The twin-screw mixing module is used to melt and plasticize the raw materials, and the pressure-stabilizing conveying module is used to convey the materials to the material rheology channel module and stabilize the pressure input to the material rheology channel module within the calibrated pressure range.

[0041] A method for preparing a fully biodegradable sponge, used to operate a fully biodegradable sponge preparation system, includes the following steps:

[0042] Step S101: The melt pressure fluctuation curve in the material rheology channel module is acquired by the melt pressure characteristic acquisition unit and the pressure pulsation amplitude is extracted to calculate the melt apparent viscosity characterization value and the root mean square change rate of pressure fluctuation. At the same time, the total flow resistance value of the flow channel and the local flow shear stress response value are compared to distinguish the initial melt viscosity deviation between batches and the melt degradation viscosity drop. The corrected viscosity parameter and the root mean square change rate of pressure fluctuation are output.

[0043] Step S102: The foaming agent injection amount adjustment unit receives the corrected viscosity parameter and adjusts the gas injection flow rate into the material rheology channel module according to the corrected viscosity parameter.

[0044] Step S103: The driving electric field amplification module in the die orifice flow control unit receives the root mean square rate of change of pressure fluctuation to adjust the basic deformation of the piezoelectric deformation adjustment module in the wall piezoelectric deformation module. When the melt back pressure change rate at the wall piezoelectric deformation module deviates from the calibration range, the driving electric field amplification module applies a controlled electric field to the wall piezoelectric deformation module. The radial deformation of the piezoelectric deformation adjustment module counteracts the flow resistance fluctuation, so that the instantaneous pressure drop change rate of the material passing through the flow channel section convergence module is stabilized within the calibration linear range. The root mean square rate of change of pressure fluctuation is transmitted through the signal interface, so that the foaming agent injection amount adjustment unit and the die orifice flow control unit form a cascaded closed-loop control.

[0045] Example 1: When the system faces the industrial condition of continuously melting and conveying fully biodegradable polymer base material into the material rheology channel module, and introducing supercritical carbon dioxide foaming agent for continuous extrusion foaming to form high-precision medical hemostatic sponges, the polymer macromolecular chains, due to the intrinsic physical characteristics of the low chain-breaking energy of ester bonds, are subjected to strong mechanical shear stress during continuous mechanical conveying and mixing. This leads to shear heat accumulation on the inner wall of the processing channel and triggers nonlinear fracture of the polymer main chain segments. This transient molecular weight degradation caused by the accumulation of continuous processing thermal shear history manifests in the overall structure as melt viscoelasticity and... The transient nonlinear collapse of intrinsic viscosity causes an imbalance in the original constant gas-liquid ratio of the system. The supersaturated carbon dioxide gas causes local multiphase interface viscoelastic dissipation imbalance in the cell wall structure which lacks melt strength support. As a result, during the foaming and molding stage, the gas phase bubbles will collapse, large-area cell wall rupture and gas cavity enlargement will occur. This reduces the isotropic narrow distribution of pore size in the molded medical hemostatic sponge. In some cases, the loss of molecular weight may even reduce the elongation at break of the product to below 15%, making it unable to meet the mechanical boundary requirements of curling and folding during clinical suturing in implantation surgery.

[0046] Under this operating condition, the material rheology channel module, melt pressure characteristic acquisition unit, foaming agent injection quantity adjustment unit, and die orifice flow resistance adjustment unit work together; the melt pressure characteristic acquisition unit acquires the melt pressure fluctuation curve within the material rheology channel module and extracts the pressure pulsation amplitude, calculating and correcting the viscosity parameter and the root mean square rate of change of pressure fluctuation. Simultaneously, the total flow resistance and local flow shear stress response values ​​are compared to distinguish between batch-to-batch initial melt viscosity deviations and melt degradation viscosity decreases, and the corrected viscosity parameters and root mean square rate of change of pressure fluctuations are output. ,in The characteristic rate of change of pressure fluctuation within the material rheology channel module is calculated using the root mean square (RMS) method. The foaming agent injection dosage adjustment unit receives the corrected viscosity parameter and the RMS rate of change of pressure fluctuation. The gas injection throughput into the material rheology channel module is adjusted according to the corrected viscosity parameter. The gas injection throughput is controlled to decrease proportionally as the corrected viscosity parameter decreases, stabilizing the foaming agent concentration in the melt within the calibrated range. This allows the physical boundary of the carbon dioxide fluid entering the processing channel to adaptively match the strength of the weak melt in a degraded state, eliminating the technical problem of viscosity collapse caused by high-concentration foaming agent injection and thermal chain scission of large molecules leading to oversaturation, bubble breakage, and pore formation. The drive electric field amplification module in the die orifice flow control unit receives the root mean square rate of change of pressure fluctuations. Adjust the basic deformation of the piezoelectric deformation resistance adjustment module inside the piezoelectric deformation module located at the outlet end of the material rheology channel module.

[0047] Calculate the circumferential valve opening characteristic vector of the piezoelectric deformation regulating module When the melt back pressure change rate at the wall piezoelectric deformation module deviates from the calibration range, a characteristic vector corresponding to the circumferential valve opening is applied to the wall piezoelectric deformation module. The controlled electric field, through the piezoelectric deformation resistance adjustment module, counteracts the flow resistance fluctuations by radial deformation towards the axis of the material rheological channel module. To characterize the circumferential deformation distribution of the piezoelectric deformation module on the wall, the pressure drop rate of the material passing through the flow channel section converges to the module and stabilizes within the calibrated linear range. The viscoelastic coefficient of the upstream flow determines the bias electric field strength of the end wall deformation, while the flow resistance back pressure adjustment caused by the end piezoelectric deformation, in turn, changes the flow pressure gradient in the upstream flow channel. This transforms the irreversible flow dissipation and thermal shear degradation parameters during continuous material processing into a dynamic control benchmark for batching throughput adjustment and die flow resistance counterbalancing. This replaces the control method of inhibiting degradation by changing the physical geometry of the screw or adding exogenous chemical crosslinking agents, eliminating quality defects caused by processing instability from the control of material flow, transport, and phase separation energy and mass transfer balance.

[0048] Under the cascaded coupling control of the aforementioned units, the fully biodegradable sponge preparation system eliminates the technical problems of cell wall breakage and excessive porosity caused by local gas supersaturation during a 48-hour continuous operation cycle. The instantaneous pressure drop rate of the material passing through the flow channel convergence module remains within the calibrated linear range, allowing the porous structure inside the generated fully biodegradable sponge to enter a controllable stable phase separation state. Product testing data shows that the average cell pore size inside the prepared fully biodegradable sponge is stable at 92 μm, the standard deviation of the pore size distribution in space is controlled at 5.8 μm, the cell structure exhibits a highly uniform narrow distribution, and without the addition of exogenous persistent chemical crosslinking agents, the weight-average molecular weight of the polymer backbone segments of the obtained sponge remains stable. The efficiency is maintained above 94.2%, and while maintaining a continuous open-pore ratio of 88.2% to match the capillary siphon blood suction function, the tensile elongation at break is increased to 38.5%, meeting the mechanical boundary requirements of suture curling and strong compression hemostasis in surgical clinics. The control command response delay from trigger degradation to the completion of mold adjustment mechanism deformation is shortened to 12ms, thereby significantly improving the nonlinear synergistic effect of material matrix molecular weight retention rate and foam pore size isotropic narrow distribution. This architecture based on the combination of flow state capture and variable control of boundary geometry uses the inherent energy dissipation of continuous processing as a feature input to drive the boundary geometry response, and reduces nonlinear rheological damage through the adaptive evolution of local physical impedance of the flow channel.

[0049] Example 2: When the system operates on a test platform used to verify the continuous extrusion foaming stability of polylactic acid melt, the test platform includes a co-rotating twin-screw extruder with temperature control accuracy reaching ±0.5℃ in zoned temperature control, and a high-frequency pressure sensor with a measurement range of 0 to 50 MPa and a measurement resolution of 0.01 MPa installed inside the material rheology channel module. The control host sets the sampling frequency of the high-frequency pressure sensor to 100 Hz to obtain the flow resistance characteristics during continuous conveying. The melt flow rate of polylactic acid at 190℃ and 2.16 kg load is 2.5 g / 10 min, the density is 1.25 g / cm³, and the weight-average molecular weight is 165. 000; The raw material formulation system used in the fully biodegradable sponge preparation system includes: 85 to 95 parts by weight of polylactic acid as the foaming matrix resin, providing a basic porous framework structure; 4 to 12 parts by weight of polybutylene succinate as a toughening modifier, participating in inter-matrix chain segment entanglement and improving the elongation at break of the material; and 0.5 to 2.5 parts by weight of epoxy-functionalized acrylate oligomer as a chain extender, which undergoes covalent bonding reaction with the terminal hydroxyl or carboxyl groups of polylactic acid to establish a long-chain branched topological network to improve the melt tensile strength in the foaming control functional region. In the initial state definition specification, the weight-average molecular weight of polylactic acid is limited to the range of 150,000 to 180,000. The melt index of polylactic acid (PLA) at 190℃ and 2.16kg load is 2.0g / 10min to 3.0g / 10min; the melt index of polybutylene succinate (PBS) at 190℃ and 2.16kg load is 1.5g / 10min to 2.5g / 10min, and the density is 1.26g / cm³; the epoxy equivalent of the epoxy-functionalized acrylate oligomer is 280g / mol to 320g / mol. The enabling environment of the system includes a co-rotating twin-screw extruder with an aspect ratio of 40:1 and a temperature control accuracy better than ±0.5℃. The detailed process steps are as follows: 90 parts by weight of polylactic acid (PLA), 8 parts by weight of polybutylene succinate (PBS), and 2 parts by weight of epoxy-functionalized acrylate oligomer are mixed. Acrylic ester oligomers are fed into a high-speed mixer and dry-mixed for 8 minutes at 500 rpm to generate a homogeneous premix. The premix is ​​then added to the feeding section of a co-rotating twin-screw extruder. The barrel heating temperatures of the twin-screw extruder from zone one to zone eleven are sequentially maintained at 165℃, 175℃, 185℃, 190℃, 190℃, 185℃, 180℃, 175℃, 170℃, 165℃, and 160℃, with the screw speed set to 120 rpm. A polymer melt with a long-chain branched structure is generated through a melt blending reaction and continuously conveyed to the inlet end of the material rheology channel module to complete foaming molding. The foaming control function area of ​​the material rheology channel module is then used for this process.

[0050] Supercritical carbon dioxide foaming agent is injected through a nozzle at a flow rate of 1.20 g / min. Foaming is completed under the cascaded closed-loop counter-current control of the melt pressure characteristic acquisition unit and the die flow obstruction adjustment unit. According to the formulation and performance optimization procedure, when the amount of epoxy functionalized acrylate oligomer added is less than 0.5 parts by weight, the long-chain branching reaction is insufficient, and the melt strength in the foaming control functional area cannot withstand the expansion stress of supercritical gas, resulting in large-area air cavity penetration and collapse defects inside the foamed sponge. When its addition amount is higher than 2.5 parts by weight, excessive cross-linking causes gelation, resulting in a sharp drop in melt flow rate and shear heat generation on the flow channel wall, accelerating the nonlinear thermal degradation of the polylactic acid main chain segment. Only when its dosage is appropriate... Maintaining the working window within 0.5 to 2.5 parts by weight, and coordinating with the step-wise temperature control and 120 rpm screw speed in the process steps, will form a uniformly distributed and non-intersecting two-phase dispersed topological phase in the flow channel. This results in a synergistic improvement in the performance of the finished sponge, with an average cell pore size of 92.4 micrometers and a tensile elongation at break of 38.2%. Comparative experimental data show that the weight-average molecular weight retention rate of the sample group lacking epoxy-functionalized acrylate oligomers dropped to below 55% after continuous processing, and the elongation at break of the sample group lacking polybutylene succinate dropped to below 12%. This indicates that the blending of the three components and the skeleton structure formed by the process adjustment produce a synergistic effect that cannot be achieved by simply adding a single component.

[0051] To determine the length of the sliding sampling window in the flow impedance feature extraction process It is necessary to set a deterministic quantization limit for the data sampling segment size based on the shear turbulence bandwidth of fluid dynamics, because the sliding sampling window length... The value of directly restricts the frequency resolution of the flow resistance pressure drop waveform signal and the computational load of the central processing unit of the control host. When the high-frequency turbulent pulsation energy caused by high-speed shearing of materials in the continuous extrusion chamber increases, in order to reduce the masking of the transient chain breakage characteristics by low-frequency large-cycle disturbances and improve the pulse detection sensitivity of the control unit, the sliding sampling window length is adjusted. The sliding sampling window length is calculated by decreasing the adjustment as the turbulent pulsation energy increases and increasing it as the energy decreases. Under the baseline conditions of a co-rotating twin-screw extruder with a screw speed of 120 rpm and a constant shear rate within the material rheology channel module in normal processing conditions, the window length is determined. There are 50 continuous data sampling points, among which In detail, to determine the number of sliding sampling points involved in the characteristic calculation of the flow resistance pressure drop change rate, the rheological parameter calculation module performs a fast Fourier transform on the acquired high-frequency pressure waveform signal, extracts the power spectral density integral with a center frequency in the bandwidth range of 10 Hz to 100 Hz, and quantitatively calculates the turbulent pulsation energy that reflects the intensity of turbulence in the cavity.

[0052] The control unit has a pre-set inverse mapping function between the sliding sampling window length and the turbulent pulsation energy. During extrusion foaming, when the high-frequency turbulence in the multiphase mixing within the cavity intensifies and the calculated turbulent pulsation energy exceeds the calibration benchmark value by 20%, to prevent low-frequency, large-cycle overall mechanical disturbances from masking the surface transient characteristics of the main chain segment breakage, the control unit automatically reduces the sliding sampling window length from the benchmark 50 sampling points to 35 sampling points in a linear proportion. This improves the sensitivity to capturing high-frequency stress pulses. Conversely, when the calculated turbulent pulsation energy decreases, indicating that the flow field is becoming smoother, the control unit... The host gradually increases the length of the sliding sampling window to an upper limit of 80 sampling points to enhance the smoothing and filtering capability of signal white noise. This optimizes the computing load of the central processing unit while ensuring control sensitivity. To evaluate the anti-interference performance of the host in non-ideal processing environments, a mechanical vibration interference signal with an amplitude of 0.5 MPa and a center frequency of 25 Hz is actively superimposed on the original pressure waveform acquired by the high-frequency pressure sensor. A fluid temperature drift residual with a bias rate of ±0.2 MPa / h is also introduced to serve as a test platform to simulate the physical variable environment of complex electromagnetic and stress disturbances in industry.

[0053] During the shear degradation manifestation period of 24 hours of continuous operation on the test platform, the polymer main chain segments degraded due to the thermal molecular chain breakage caused by the shear heat accumulation of aliphatic polyester bonds on the wall of the material rheology channel module. This resulted in a step collapse of the total fluid resistance value passing through the material rheology channel module. In the control group, which used constant pressure proportional-integral-derivative control and kept the foaming gas flux statically constant, the injection amount of supercritical carbon dioxide did not establish a feedforward correlation with the viscoelastic variation of the melt flow. The weak melt strength under the state of molecular weight loss could not withstand the expansion stress of the constant high pressure gas phase. When the material left the die and depressurized for shaping, it caused large-area rupture and wall collapse of the cell wall, resulting in a multiphase deviation in the pore size distribution inside the sponge. Its average pore size expanded disorderly to 285 μm, and large-area gas cavity penetration and collapse occurred in some parts of the internal porous topology.

[0054] In the prototype of this invention, which employs a cascaded closed-loop counter-pressure control architecture, the control host uses a digital filtering algorithm to isolate the mechanical vibration interference signal superimposed on the original pressure waveform from the fluid temperature drift residual, extracts the pressure pulsation amplitude, and calculates the root mean square rate of change of pressure fluctuation. ,in The root mean square (RMS) extract value characterizing the severity of transient pressure fluctuations is the RMS rate of change of pressure fluctuations as a result of the accumulated thermal history of continuous processing. The pressure decreased from the initial steady-state pressure of 4.12 MPa to 1.18 MPa when the molecular chains underwent shear degradation. The root mean square rate of change of the pressure fluctuation received by the foaming agent injection dosage adjustment unit was recorded during this change. The injection rate of supercritical carbon dioxide foaming agent gas into the material rheology channel module is gradually reduced from the initial 1.5 g / min to 0.45 g / min. This ensures that the active sliding flux of the supersaturated gas phase energy mass flow achieves physicochemical equilibrium with the surface tension and melt shear viscosity of the degradation system, preventing premature accumulation and explosion of the gas flow inside the orifice wall. Simultaneously, the drive electric field amplification module of the die orifice flow control unit adjusts according to the root mean square rate of change of pressure fluctuation. The circumferential valve opening characteristic vector of the piezoelectric deformation regulating module is calculated based on the decreasing polarity. ,in The four-dimensional, dimensionless first-order eigenvector characterizing the radial reduction displacement weight distribution at four orthogonal circumferential boundary locations; the circumferential valve opening eigenvector. The steady-state initial value of uniform symmetric distribution [0.25, 0.25, 0.25, 0.25] dynamically evolves into a heterogeneous asymmetric distribution [0.55, 0.08, 0.51, 0.06] that adapts to the anisotropic fluctuation of flow resistance. This drives the piezoelectric deformation module of the circumferential liner at the outlet end to apply non-uniform radial compressive strain to the axis of the material rheological channel module, increasing the local back pressure flow shear resistance at the die orifice. This locks the instantaneous pressure drop rate of the material passing through the flow channel section convergence module within the calibrated working range, thereby isolating the nonlinear impact of polymer main chain segment fracture on the local phase separation flow field of extrusion foaming in the process. When When the supercritical carbon dioxide gas injection flux exceeds the upper limit of the mixing boundary calculated by the above control logic by 20%, the test data shows that due to excessive local swelling and plasticization causing gas phase merging and explosion, the continuous open-cell ratio of the foamed product deviates disorderly. When the gas injection flux is lower than the lower limit of the mixing boundary by 20%, the supercritical expansion volume ratio of the polylactic acid melt decreases to below 2.5, and the die cannot produce a continuous foamed sponge with an interconnected porous skeleton. This confirms that the parameter swing range established by the cascade closed-loop counteracting control architecture under wide temperature rheological degradation conditions constitutes a working window that satisfies the molding stability of polymer foamed plastics.

[0055] After completing a 48-hour continuous extrusion foaming process test, the porous structure product produced by the sample group of this invention and the product produced by the control group were sliced. The surface morphology of the cross-section of the product was observed using a scanning electron microscope, and the mechanical properties were measured. Due to the lack of in-situ identification of material degradation state and adaptive die back pressure counter-pressure, the control group's final sponge product had a reduced weight-average molecular weight retention rate of polymer main chain segments to 52.1%, a deteriorated elongation at break to 11.4%, and a cell wall perforation rate as high as 35.6% at the macroporous air cavities. In contrast, the fully biodegradable sponge product obtained by the sample group of this invention showed that its average cell pore size was stable at 92.4 μm, the standard deviation of the three-dimensional pore size distribution was controlled at 5.6 μm, and there was no large-area collapse of the internal foam skeleton. The defects, such as pits or enlarged pores, exhibit an isotropic narrow distribution of geometric pore size at the component level. Mechanical properties and physicochemical fingerprint characterization results show that, without the addition of exogenous persistent chemical crosslinking agents, due to the cascade locking of the processing channel wall impedance and phase separation pressure drop rate, the polylactic acid main chain segment weight-average molecular weight retention rate of the sample group in this invention is maintained at 94.5%. While maintaining a continuous open-pore ratio of 88.2% to meet the technical specifications for capillary siphon liquid absorption, its elongation at break is increased to 38.2%, meeting the engineering practical requirements for resisting local tensile deformation and extrusion distortion during clinical surgical suturing. From the capture of abnormal fluctuations in melt flow resistance by the high-frequency pressure sensor to the calculation of the circumferential valve opening characteristic vector by the control host... When the radial actuation operation is completed by the piezoelectric deformation module on the wall, the response delay of the full-link control command is shortened to 12ms, realizing the nonlinear synergistic enhancement of the molecular weight retention rate and the topological isotropy of the porous structure in the extrusion foaming molding of multiphase systems. The test results confirm that by deconstructing the impedance decay history variability in continuous mixing flow into the control method of feedback input of the foaming agent injection flux adjustment independent variable and the die geometric flow resistance boundary deformation variable, the closed-loop control of the material rheological state degradation parameter driven by the dynamic adjustment of the boundary geometry is realized. The purpose of combating rheological degradation damage in continuous extrusion molding of thermosensitive polymers is achieved by the adaptive evolution of the local kinetic and potential energy distribution of the fluid in the processing channel.

[0056] Example 3: This example combines Figures 1 to 2 This describes a fully biodegradable sponge preparation system and method, such as... Figure 1As shown, the output of the material rheology channel module is connected to the input of the wall piezoelectric deformation module (including the piezoelectric deformation resistance adjustment module) through the material outflow path. The internal flow channel of the material rheology channel module is connected to the data input of the melt pressure characteristic acquisition unit for acquiring pressure fluctuation curves. The first control output of the melt pressure characteristic acquisition unit is connected to the control input of the foaming agent injection amount adjustment unit through the output correction viscosity parameter bus. The output of the foaming agent injection amount adjustment unit is connected to the injection end of the material rheology channel module through the gas injection flow rate adjustment pipeline. The second control output of the melt pressure characteristic acquisition unit is connected to the signal input of the die orifice flow control unit (including the driving electric field amplification module) through the output root mean square rate of change bus. The control output of the die orifice flow control unit (including the driving electric field amplification module) is connected to the electric field receiving end of the wall piezoelectric deformation module (including the piezoelectric deformation resistance adjustment module) through the applied controlled electric field line.

[0057] like Figure 2 As shown, the control process begins with the initial state where no foaming agent is introduced, static pressure data of the flow channel is collected to determine the initial control baseline, and the valve opening is uniform and symmetrical. After continuous molding processing is started, pressure-stabilizing materials are input, and foaming agent is introduced, the flow transitions to the initial steady state with a constant gas-liquid ratio, stable root mean square rate of change of processing pressure fluctuation, and statically constant gas injection flux. When shear heat accumulation occurs in the flow channel and the root mean square rate of change of pressure fluctuation decays, the melt degradation state is entered. Shear heat accumulation occurs on the wall surface, nonlinear fracture of the main chain segment occurs, resulting in melt degradation, viscosity decrease, and unsteady deviation of the gas-liquid ratio. After extracting the pressure pulsation amplitude and calculating and correcting the viscosity parameters, the cascaded closed-loop counter-regulation state is entered. The gas injection flux is reduced proportionally, driving the electric field amplification module to work and causing piezoelectric deformation of the wall surface. The characteristic vector of the applied electric field opening of the module is asymmetrically distributed. In this state, if the rate of change of pressure drop is stable within the calibrated linear range, it returns to the initial steady state with constant gas-liquid ratio and stable root mean square rate of change of processing pressure fluctuation. The gas injection flux remains statically constant. However, if the rate of change of melt back pressure exceeds the calibrated safety threshold, it enters the gas injection flux locking state. The safety monitoring module outputs an over-limit indication that the rate of change of melt back pressure is abnormal and locks the gas injection flux at the current value until the back pressure abnormality recovers to within the safety threshold and the flux lock is released. Then, it returns to the cascaded closed-loop counter-control state, and the gas injection flux is reduced proportionally. The electric field amplification module is driven to work and the characteristic vector of the applied electric field opening to the wall piezoelectric deformation module is asymmetrically distributed.

[0058] Example 4: In a manufacturing environment where polylactic acid polymer base material is continuously melted and conveyed into a material rheology channel module, and a supercritical carbon dioxide foaming agent is introduced for continuous extrusion foaming to form a medical hemostatic sponge, the inlet diameter of the material rheology channel module is fixed at 45 mm, and the surface roughness of the channel wall is calibrated to 0.8. The high-frequency pressure sensor, located inside the flow channel, has a measurement range of 0 to 50 MPa and a data sampling period of 10 ms. During continuous conveying and mixing, the polylactic acid polymer base material is subjected to shear stress, which causes shear heat accumulation on the flow channel wall and triggers nonlinear breakage of the polymer main chain segments. This transient molecular weight degradation produces melt viscoelasticity and intrinsic viscosity nonlinear collapse. The instability of the fluid pressure inside the flow channel causes the gas-liquid ratio to deviate. The supersaturated carbon dioxide gas causes multiphase interface viscoelastic dissipation imbalance in the pore wall structure lacking melt strength support. During the depressurization and shaping stage, gas phase bubble cell rupture and collapse, large-area cell wall rupture, and gas cavity expansion occur, reducing the isotropic narrow distribution of the pore size of the finished medical hemostatic sponge. This leads to the product's elongation at break deteriorating to below 15%, which cannot meet the mechanical deformation boundary during surgical suturing.

[0059] The melt pressure characteristic acquisition unit captures the flow impedance characteristics within the material rheology channel module online, continuously acquiring data including... Discrete voltage signal sequence of continuous pressure sampling points The total number of samples within the sliding time window is shown here. The reference material viscosity parameter is set to 500, dimensionless, before the control algorithm is started. For a voltage signal sequence of 2500 Pa·s, a digital bandpass filter operator is used to eliminate discrete voltage signal sequences. The mechanical vibration interference signal and fluid temperature drift residual are analyzed, and a sliding window root mean square difference integral operator is applied within the processor to extract the root mean square rate of change of pressure fluctuation. , Satisfy the formula ,in, This represents the root mean square rate of change of pressure fluctuations. This is the correction factor for the flow channel wall impedance, with a value of 1.05. The adaptive decision unit receives the root mean square rate of change of pressure fluctuations, which is the root mean square amplitude of the fluid pressure fluctuations calculated using a sliding time window. Viscosity parameters of reference materials By comparing the total flow resistance of the flow channel with the local flow shear stress response value, the initial material viscosity deviation between batches and the viscosity drop due to melt degradation are distinguished. A corrected viscosity parameter is calculated and output. The instantaneous pressure drop caused by the shrinkage of the flow channel section is isolated from the component caused by the loss of material molecular weight. The rheological characteristic variability is transformed into a causal feedforward parameter for batch adjustment. Specifically, the cross-comparison logic in the rheological parameter calculation module obtains the total flow resistance of the flow channel by reading the data of the static pressure sensor set at both ends of the material rheological channel module, and simultaneously reads the local flow shear stress response value obtained by the single-point high-frequency pressure sensor.

[0060] When the initial viscosity of the raw material drifts due to batch change, the total flow resistance and the local flow shear stress response will increase or decrease in the same direction and proportionally. At this time, the ratio of the two remains within the constant calibration viscosity fluctuation threshold of 1.05. The system judges this as an initial melt viscosity deviation between batches and does not intervene in the basic feedforward. However, when thermal chain-breaking degradation occurs in the middle of the processing, the melt tensile strength deteriorates rapidly due to molecular weight collapse. The local flow shear stress response value in the center of the flow channel drops transiently. Due to the existence of the boundary retention layer, the change of the total flow resistance at both ends shows obvious lag and gradual change, causing the ratio of the two to jump out of the above calibration threshold instantly. Based on this, the system accurately identifies the melt degradation viscosity drop. The calculation module subtracts the inherent geometric pressure drop residual caused by the flow channel cross-section convergence module from the total flow resistance and performs weighted conjugate calculation with the effective shear stress component after subtraction and the high-frequency pressure pulsation amplitude. Finally, it outputs a corrected viscosity parameter that can truly characterize the degree of molecular chain breakage.

[0061] The foaming agent injection rate adjustment unit receives the corrected viscosity parameter to control the opening of the electromagnetic needle valve for the foaming agent gas injection flux. It determines the physical boundary of the valve's operating range using a three-point support control rule. When the measured corrected viscosity parameter drops to the lower limit of 800 Pa·s, the foaming agent injection rate adjustment unit changes the gas passage cross-sectional area, instantaneously reducing the foaming agent gas injection flux to the lower critical value of 0.35 g / min. This ensures that the active slip flux of the supersaturated gas phase energy mass flow matches that of the gas phase in a state of molecular chain breakage. Weak melt strength; when the corrected viscosity parameter is at the median of 1800 Pa·s, the blowing agent gas injection flux is maintained at 1.20 g / min; when the corrected viscosity parameter is at the upper limit of 2500 Pa·s, the blowing agent injection quantity adjustment unit increases the blowing agent gas injection flux to the upper limit critical value of 1.65 g / min to increase the expansion volume ratio of the cell structure; simultaneously with this adjustment action, the drive electric field amplification module of the die orifice flow control unit periodically reads the root mean square rate of change of pressure fluctuation. According to the root mean square rate of change of pressure fluctuation The circumferential valve opening characteristic vector is calculated by analyzing the rate of change from the initial steady-state value of 4.12 MPa to 1.18 MPa. The system controls the application of a controlled electric field to the piezoelectric deformation regulating module at the outlet of the material rheology channel module. In terms of assembly structure, the flexible inner liner of the piezoelectric deformation regulating module is sleeved on the inner wall of the outlet end. It is made of high-temperature resistant, highly elastic fluororubber or polytetrafluoroethylene flexible tubing with a thickness of 1.5 mm. Both ends are rigidly sealed to the flow channel wall to provide physical protection while isolating the high-temperature, high-pressure polymer melt, preventing the melt from directly scouring and eroding the piezoelectric elements inside the tube wall. Four orthogonal piezoelectric actuators are circumferentially embedded inside the metal tube wall at the outlet end. Their inner actuator ends protrude from the tube wall and tightly abut against the outer wall of the flexible inner liner. When the drive field amplification module applies a controlled electric field to the piezoelectric actuators, the four piezoelectric actuators generate micron-level inward radial deformation displacement, thereby regulating the local contraction of the flexible inner liner and adjusting the circumferential valve opening characteristic vector. The circumferential valve opening characteristic vector is dynamically adjusted from a uniform symmetric distribution W=[0.25,0.25,0.25,0.25] of steady-state initial values ​​to an anisotropic asymmetric distribution W=[0.55,0.08,0.51,0.06]. Satisfying the relation ,in The eigenvectors characterizing the radially reduced displacement weight distribution at the four orthogonal circumferential boundary locations are... , , , These are the characteristic components representing the proportion of deformation displacement of the actuators at the first, second, third, and fourth positions to the total shrinkage of the flow channel cross-section. When converting the one-dimensional root mean square rate of change of pressure fluctuation into a four-dimensional circumferential valve opening characteristic vector, the control host extracts the local high-frequency pulsation signal difference in each direction in real time through multi-point pressure acquisition modules located in four orthogonal directions around the circumference of the foaming control functional area. When the root mean square rate of change of pressure fluctuation in the overall flow channel deviates from the calibrated linear range, the control host calculates the overall radial cross-sectional shrinkage benchmark and uses the spatial orientation gradient matrix constructed from the pressure difference of the four orthogonal positions.

[0062] The anisotropic flow resistance deviation orientation is calculated, and the direction with the highest pulsation amplitude is defined as the high flow resistance region. The corresponding actuator position component will be assigned a higher displacement weight, while the direction with the lower pulsation amplitude will be assigned a lower displacement weight. The sum of the weight ratios of each component is rigidly constrained to 1. Through this spatial gain matrix mapping logic, the host computer decouples and maps the one-dimensional rheological characteristic rate of change into four independent and asymmetricly distributed digital electric field drive control signals. It dynamically determines the circumferential valve opening characteristic vector of the four orthogonal throttling adjustment units extending into the flow channel, thereby achieving precise counterbalancing of the heterogeneous asymmetric flow field. In order to enable the system to synchronously adjust the global flow back pressure and counterbalance local asymmetric stress fluctuations, the host computer executes a displacement hierarchical solution program based on the elastohydrodynamic boundary layer model. The final action of the mechanism is decomposed into a cascaded drive structure of total displacement scalar and spatially distributed characteristic vector. The host computer calculates the total radial displacement scalar required to rebuild the flow barrier of the flow channel based on the absolute difference between the root mean square rate of change of global pressure fluctuation and the calibration linear interval. Its value is limited to the range of 10 micrometers to 50 micrometers.

[0063] Using the local pressure difference extracted by the multi-point pressure acquisition module located in the four orthogonal directions of the foaming control functional area, the circumferential valve opening characteristic vector, which characterizes the spatial resistance deviation orientation, is calculated. The first, second, third, and fourth position characteristic components in the circumferential valve opening characteristic vector are all dimensionless control gain coefficients. The sum of the squares of the four characteristic components is rigidly constrained to 1. The actual digital electric field drive control signal applied to the actuators in the first, second, third, and fourth positions is generated by multiplying the total radial displacement scalar by their respective characteristic components to produce absolute radial deformation displacement commands. When the global melt degradation viscosity decreases in the flow channel, the total displacement scalar increases, driving the actuators in the four orthogonal directions to synchronously advance towards the axis to clamp the flow channel. When asymmetric flow heterogeneity occurs inside the flow channel, the four components of the circumferential valve opening characteristic vector undergo non-uniform shift, adjusting the local cross-sectional shape. The physical meaning of each parameter in the above program is explained as follows: the total radial displacement scalar is the global control master variable, and the circumferential valve opening characteristic vector is the spatial decoupling pair. The variables and positional characteristic components are independent execution constants, and their reference values ​​are all set to 0.5 in the initial state of the system. The piezoelectric deformation adjustment module applies variable impedance mechanical constraints in the direction of the axis of the material rheological channel module. The radial displacement compensation of the piezoelectric deformation adjustment module is monotonically increasing in a positive proportion with the deviation of the pressure drop rate. By adjusting the cross-sectional area of ​​the die orifice to change the local flow resistance back pressure, the transient flow resistance pressure drop fluctuation caused by macromolecular chain breakage is offset. The entire link command response delay from impedance capture to the completion of mechanism deformation is limited to a 12ms closed loop. In order to achieve a total control loop response delay of 12ms under a high-frequency sensor data sampling period of 10ms and large sample data processing, this invention adopts an interleaved dual-buffer direct memory access architecture and a rolling update pipeline mechanism in the underlying data flow management of the control host. The 500 discrete sampling points in the sliding time window are not repeatedly collected in each control cycle, but are rolled and updated at a single point using a first-in-first-out register queue.

[0064] In each control cycle, the latest single data point acquired by the high-frequency pressure sensor enters the tail of the queue, while the earliest data point at the head of the queue is automatically removed. This ensures that each feature calculation only requires a single-point incremental differential operation, and the execution time of the algorithm within the digital signal processor is extremely compressed to less than 0.5 milliseconds. The calculated electric field control command is directly output to the high-speed drive electric field amplification module via a dedicated hardware interrupt. The ultra-high frequency piezoelectric ceramic sheet used in the wall piezoelectric deformation module has a physical deformation response time of less than 0.1 milliseconds under electric field drive, thus ensuring spatiotemporal continuity and controlling the cumulative time delay of the entire link from impedance signal acquisition, digital rolling calculation to the physical deformation of the end mechanism. Within 12 milliseconds, based on the Maxwell relaxation time model and the shear transport characteristics of polymer melts, the stress relaxation time of polylactic acid melt at a processing temperature of 190℃ is between 40 and 60 milliseconds. The phase separation transport characteristic time constant of multiphase fluids within the flow channel is between 200 and 300 milliseconds. The total cumulative delay of the entire link is set to 12 milliseconds, with the time scale leading the time constants of multiphase fluid transport and phase separation evolution. This controls the transmission of rheological degradation damage to the downstream die orifice along the spatial flow path. To mitigate the aliasing interference caused by the transient change in carbon dioxide swelling and plasticizing concentration during the adjustment of the separation gas flux, which affects the characterization of melt degradation viscosity reduction, the system adopts a polymer network free body-based approach. The gas plasticizing viscosity baseline compensation control based on product theory pre-calibrates the dynamic sensitivity factor of polylactic acid melt viscosity to supercritical carbon dioxide dissolution flux. When the blowing agent injection rate is reduced from 1.5 g / min to 0.45 g / min by the blowing agent injection quantity adjustment unit, the calculation module calculates the predicted value of melt viscosity rebound increment due to weakened plasticizing effect online based on the current gas flux deviation value. This predicted value is then subtracted from the collected total rheological response, ensuring that the final corrected viscosity parameter accurately reflects the degree of intrinsic rheological degradation caused by polymer main chain segment breakage. The parameters involved in the gas plasticizing viscosity baseline compensation control are defined as follows: the root mean square rate of change of pressure fluctuation is... The main input variables are gas injection flux and dynamic sensitivity factor, which is a system constant and whose value was obtained through a pure static co-blending experiment without foaming agent. The melt viscosity rebound increment prediction value is an intermediate correction variable used to correct the viscosity parameter of the reference material in real time. Through the dynamic counterbalancing adjustment of the aforementioned local impedance of the flow channel, the fully biodegradable sponge preparation system maintains the instantaneous pressure drop change rate of the material through the flow channel cross-section convergence module within the calibrated linear range during a continuous production cycle of up to 48 hours. The multiphase separation behavior of the polymer melt remains stable. The porous skeleton forming test data shows that the average cell pore size of the produced fully biodegradable sponge product is stable at 92.1 μm; the standard deviation of the pore size spatial distribution is controlled at 5.5 μm; the weight-average molecular weight retention rate of the polymer main chain segments of the obtained sponge is stable at over 94.6%; and the continuous open-cell rate is maintained at 88%.3% to synergistically support the capillary suction liquid transport capacity; the tensile elongation at break of the product is increased to 38.6% to withstand the mechanical curling and bending stress during implantation and suturing. To verify the technical effect with purely digital objective indicators, this invention establishes a standardized quantitative testing procedure. For the test of the weight-average molecular weight retention rate of the polymer main chain segment, a standard gel permeation chromatography instrument is used for textual data determination. Unprocessed reference polylactic acid raw material and foamed sponge slices are dissolved in tetrahydrofuran solvent, injected into the chromatographic column at a flow rate of 1.0 ml per minute at a constant temperature of 35 degrees Celsius, the weight-average molecular weight value is extracted and the absolute ratio before and after implementation is calculated, thereby confirming that the molecular weight retention rate is stable at over 94.6%. For the tensile elongation at break of the product, a standard microcomputer-controlled electronic... A universal testing machine cuts finished sponge into standard dumbbell-shaped specimens, installs them between upper and lower clamps, and sets the gauge length to 20 mm. Under standard environmental conditions of 23 degrees Celsius and 50% relative humidity, the upper clamp is driven to perform a non-tensile blinding destructive test at a constant longitudinal displacement speed of 50 mm per minute until the specimen breaks. The pure text discrete tensile displacement data is directly read from the equipment, thus quantitatively confirming a mechanical reinforcement effect of 38.6% elongation at break. This process eliminates the defect of cell collapse caused by relative supersaturation of supercritical feed gas, achieving a synergistic effect of polymer matrix molecular weight retention and narrow uniformity of foam cell distribution. It also converts the transient rate of change of the flow channel pressure gradient in situ into a response action of variable boundary geometric impedance, solving the phase separation flow instability phenomenon under shear chain scission degradation conditions.

[0065] Example 5: When the system faces a continuous extrusion foaming molding process where different batches of polylactic acid polymer base material cause slippage in the initial physical impedance of the processing channel wall, the material rheology channel module, in the initial state without the introduction of supercritical carbon dioxide foaming agent, uses a high-frequency pressure sensor to collect channel static pressure data over a time span of 10 seconds, calculates the root mean square value of the discrete voltage signal sequence as the channel basic stress residual, and uses it to correct the channel wall impedance correction coefficient. Furthermore, the screw speed of the conveying equipment is controlled to stabilize the static flow resistance pressure inside the material rheology channel module at a constant point of 15 MPa, thereby determining the viscosity parameters of the high-frequency pressure sensor and the reference material. In actual industrial operation, the online dynamic correction of the channel wall impedance correction coefficient is achieved using the benchmark translation method. During the initial calibration stage before the introduction of foaming agent, the material rheology channel module operates under a constant static flow resistance pressure of 15 MPa. A high-frequency pressure sensor collects discrete voltage signals over 10 seconds and calculates the mean of its benchmark variance. Since there is no turbulent pulsation caused by foaming agent swelling in this state, the initial root mean square value calculated at this time represents the pure static stress residual caused by friction between the channel fluid and the inner wall of the barrel. The control unit divides this stress residual by the standard calibration constant to determine the initial dimensionless channel wall impedance correction coefficient. With a positive coefficient of 1.05, in subsequent extrusion processing, when the system experiences a slow pressure drift of ±0.2 MPa per hour due to temperature drift or batch switching, the static stress residual will shift accordingly. The control host extracts the mean value of the low-frequency long-cycle pressure signal, updates the static stress residual in real time, and dynamically corrects the impedance correction coefficient with a linear proportional relationship. This coefficient is then multiplied by the root mean square of the high-frequency pressure pulsation amplitude as a proportional adjustment factor, thereby converting the absolute amplitude of the pressure pulsation in the time domain into the root mean square rate of change of the pressure fluctuation, which characterizes the intensity of the dynamic disturbance. This eliminates the interference of the overall static pressure drift on the extraction of transient chain break rheological features.

[0066] Before molding begins, the die opening flow control unit applies a differential step reference voltage to the piezoelectric deformation modules at the four orthogonal boundary positions in the circumferential direction. The initial radial displacement of the piezoelectric deformation control module is measured by the displacement sensor on the outer liner, and the output voltage is adjusted to control the circumferential valve opening characteristic vector. The initial spatial distribution components are stabilized at a uniform and symmetrical state of 0.25, thereby eliminating the spatial impedance asymmetry caused by machining tolerances in the processing flow channel cross-section convergence module, and ensuring that the root mean square rate of change of pressure fluctuations during subsequent foaming production is stable. The driven radial displacement compensation action obtains a consistent control zero point, and the instantaneous pressure drop rate of the material passing through the flow channel section convergence module stabilizes within the preset working range.

[0067] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit of this application and the scope of protection of this invention, and all of these forms are within the protection scope of this application.

Claims

1. A fully biodegradable sponge preparation system, characterized in that, include: The melt pressure characteristic acquisition unit is connected to the material rheology channel module. It is used to acquire the melt pressure fluctuation curve in the material rheology channel module and extract the pressure pulsation amplitude to calculate the melt apparent viscosity characterization value and the root mean square rate of change of pressure fluctuation. At the same time, it compares the total flow resistance value of the flow channel with the local flow shear stress response value to distinguish the initial melt viscosity deviation between batches and the melt degradation viscosity drop, and outputs the corrected viscosity parameter and the root mean square rate of change of pressure fluctuation. The foaming agent injection volume adjustment unit is connected to the melt pressure characteristic acquisition unit and the material rheology channel module, and is used to adjust the gas injection flow into the material rheology channel module according to the corrected viscosity parameter. The die orifice flow control unit is connected to the melt pressure characteristic acquisition unit and the wall piezoelectric deformation module at the outlet end of the material rheological channel module. It includes a drive electric field amplification module, which is used to receive the root mean square rate of change of pressure fluctuation to adjust the basic deformation of the piezoelectric deformation adjustment module in the wall piezoelectric deformation module. When the melt back pressure change rate at the wall piezoelectric deformation module deviates from the calibration range, the drive electric field amplification module applies a controlled electric field to the wall piezoelectric deformation module. The radial deformation of the piezoelectric deformation adjustment module counteracts the flow resistance fluctuation, so that the instantaneous pressure drop change rate of the material passing through the flow channel section convergence module is stabilized within the calibration linear range. It forms a cascaded closed-loop control with the melt pressure characteristic acquisition unit and the foaming agent injection amount adjustment unit.

2. The fully biodegradable sponge preparation system according to claim 1, characterized in that, The melt pressure characteristic acquisition unit includes a rheological parameter calculation module, which is used to acquire local shear stress data within the material rheological channel module to establish the local flow shear stress response value, and to acquire the static pressure difference between the two ends of the material rheological channel module to establish the total flow resistance value. The rheological parameter calculation module is equipped with data comparison logic, which is used to cross-compare the melt apparent viscosity characterization value with the total flow resistance value and the local flow shear stress response value. When the variation of the melt apparent viscosity characterization value is less than the calibrated viscosity fluctuation threshold, it is determined to be the initial melt viscosity deviation between batches.

3. The fully biodegradable sponge preparation system according to claim 1, characterized in that, The foaming agent injection quantity adjustment unit includes a foaming agent flow rate regulation module and a foaming agent injection nozzle. The foaming agent flow rate regulation module is connected to the foaming agent injection nozzle. The foaming agent flow rate regulation module is used to receive the corrected viscosity parameter, and when the corrected viscosity parameter indicates that the melt degradation viscosity decreases in the material rheology channel module, it controls the gas injection flux delivered to the foaming agent injection nozzle to be reduced proportionally with the decrease of the corrected viscosity parameter, so that the foaming agent concentration in the melt is stabilized within the calibrated variation range.

4. The fully biodegradable sponge preparation system according to claim 1, characterized in that, The piezoelectric deformation regulating module includes a flexible inner liner sleeved on the inner wall of the outlet end of the material rheology channel module, and a number of piezoelectric actuators embedded in the tube wall of the outlet end along the circumference of the outlet end of the material rheology channel module. The piezoelectric actuators abut against the outer surface of the flexible inner liner, and the piezoelectric actuators generate radial displacement when subjected to a controlled electric field, so as to drive the flexible inner liner to generate radial contraction deformation toward the axis of the material rheology channel module.

5. The fully biodegradable sponge preparation system according to claim 1, characterized in that, The material rheology channel module includes a sequentially connected melting functional zone, a mixing functional zone, and a foaming control functional zone; the melt pressure characteristic acquisition unit includes a multi-point pressure acquisition module, which is located on the inner wall of the foaming control functional zone and is used to acquire the total melt pressure and local pressure pulsation signals in the foaming control functional zone and convert them into melt pressure fluctuation curves.

6. The fully biodegradable sponge preparation system according to claim 3, characterized in that, The foaming agent injection quantity adjustment unit also includes a gas supply adjustment channel module and a flow regulation control module. The flow regulation control module is connected to the foaming agent flow regulation module. The foaming agent flow regulation module is used to output an opening control signal to the flow regulation control module to change the flow cross-sectional area of ​​the flow regulation control module.

7. The fully biodegradable sponge preparation system according to claim 1, characterized in that, The material rheology channel module is equipped with a flow resistance adjustment module; wherein, the flow resistance adjustment module has four evenly distributed throttling adjustment units along the inner circumference of the material rheology channel module, which are used to change the total flow resistance of the flow channel according to the depth of the throttling adjustment units extending into the material rheology channel module.

8. The fully biodegradable sponge preparation system according to claim 1, characterized in that, The melt pressure characteristic acquisition unit includes a safety monitoring module, which is connected to the die orifice flow control unit and the foaming agent injection quantity adjustment unit via a data bus. The safety monitoring module is used to monitor the rate of change of melt back pressure at the wall piezoelectric deformation module, and when the rate of change exceeds the calibrated safety threshold, it outputs a calibration over-limit indication signal to the foaming agent injection quantity adjustment unit. The foaming agent injection quantity adjustment unit is used to lock the gas injection flux at the current value according to the calibration over-limit indication signal.

9. The fully biodegradable sponge preparation system according to claim 1, characterized in that, The inlet end of the material rheology channel module is equipped with a melt feeding unit; wherein, the melt feeding unit includes a twin-screw mixing module and a pressure-stabilizing conveying module connected to the outlet end of the twin-screw mixing module. The twin-screw mixing module is used to melt and plasticize the raw materials, and the pressure-stabilizing conveying module is used to convey the materials to the material rheology channel module and stabilize the pressure input to the material rheology channel module within the calibrated pressure range.

10. A method for preparing a fully biodegradable sponge, used to operate the fully biodegradable sponge preparation system according to claim 1, characterized in that, Includes the following steps: Step S101: The melt pressure fluctuation curve in the material rheology channel module is acquired by the melt pressure characteristic acquisition unit and the pressure pulsation amplitude is extracted to calculate the melt apparent viscosity characterization value and the root mean square change rate of pressure fluctuation. At the same time, the total flow resistance value of the flow channel and the local flow shear stress response value are compared to distinguish the initial melt viscosity deviation between batches and the melt degradation viscosity drop. The corrected viscosity parameter and the root mean square change rate of pressure fluctuation are output. Step S102: The foaming agent injection amount adjustment unit receives the corrected viscosity parameter and adjusts the gas injection flow rate into the material rheology channel module according to the corrected viscosity parameter. Step S103: The driving electric field amplification module in the die orifice flow control unit receives the root mean square rate of change of pressure fluctuation to adjust the basic deformation of the piezoelectric deformation adjustment module in the wall piezoelectric deformation module. When the melt back pressure change rate at the wall piezoelectric deformation module deviates from the calibration range, the driving electric field amplification module applies a controlled electric field to the wall piezoelectric deformation module. The radial deformation of the piezoelectric deformation adjustment module counteracts the flow resistance fluctuation, so that the instantaneous pressure drop change rate of the material passing through the flow channel section convergence module is stabilized within the calibration linear range. The root mean square rate of change of pressure fluctuation is transmitted through the signal interface, so that the foaming agent injection amount adjustment unit and the die orifice flow control unit form a cascade closed-loop control.

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