High-temperature melting and laminating process for PVDF (Polyvinylidene Fluoride) film and metal substrate

Abstract

The invention relates to the technical field of preparation of layered products, and discloses a PVDF (polyvinylidene fluoride) film and metal substrate high-temperature melting and laminating process which comprises the following steps: preheating a metal substrate to enable the surface temperature of the metal substrate to be above the melting point of a film material, guiding the normal-temperature film material to cut into a nip point of a pressing and laminating roller at a tiny offset included angle to form a transverse exhaust wave, a transverse shear field is introduced on an interface by adjusting the speed ratio of a pressing roller to the substrate, melt is driven to fill micropores in the surface of the substrate, and the speed ratio is adjusted according to motor current load deviation; keeping the complex at a constant temperature near the crystallization temperature to induce in-situ relaxation of an interface chain segment; according to the method, the apparent viscosity of the melt is reduced by utilizing an interface shear field, a microporous air plug is eliminated, and a crystallization buffer layer with modulus in gradient distribution is constructed between heterogeneous materials, so that essential transformation from discrete physical stacking to a continuous microscopic mutual embedding structure is realized, and the interface bonding strength consistency and the cold-bending-resistant processing performance are improved.

Description

Technical Field

[0001] This invention belongs to the field of layered product preparation technology, and particularly relates to a high-temperature fusion lamination process for PVDF film and metal substrate. Background Technology

[0002] The high-temperature melt lamination process of polyvinylidene fluoride (PVDF) film and metal substrate is the core technology for producing high weather-resistant layered products. It utilizes the chemical stability of PVDF and the mechanical strength of the metal substrate to achieve bonding by thermally stimulating interfacial melting. Conventional technology usually adopts a mode of global preheating and constant pressure rolling. However, the high thermal conductivity of the metal substrate and the high viscosity of the PVDF melt constitute a physical constraint at the interface. During high-speed lamination, the instantaneous cooling effect generated when the PVDF melt contacts the metal surface causes the interfacial layer to solidify rapidly and hinders the penetration of polymer chain segments into the metal micropores. At the same time, a small amount of air is trapped in the micron-sized pores on the surface of the metal substrate. When heated, the air expands and creates micro-cavitation shielding, reducing the effective wetting area of ​​the interface.

[0003] The linear improvement path of increasing preheating temperature or rolling pressure is limited by the thermal degradation limit of polyvinylidene fluoride (PVDF). Excessive heat input can cause polymer chain segment breakage, and static pressurization can only compress the volume of micro-cavities but cannot drive gas out, resulting in the interface being in a discrete point contact state. This kinetic contradiction caused by the thermal conduction lag and the interfacial fluid permeation resistance restricts the consistency of the interfacial bonding strength of the composite material. In addition to hardware improvements, the lack of dynamic rheological control and stress regulation logic in production is a key bottleneck restricting the composite quality. For example, the authorization announcement number CN1050 Chinese invention patent 34486B discloses a high-strength wear-resistant coated plate, which focuses on improving the bonding strength by chemically modifying the film material and statically adjusting the adhesive components. In high-speed continuous production, the static material matching approach is difficult to solve the dynamic contradictions in the melt pouring process. Without the intervention of the interfacial shear field, the high-viscosity PVDF melt cannot achieve the essential transformation from physical stacking to microscopic interlocking, resulting in insufficient anchoring depth. This technology does not consider the interfacial stress accumulated by the difference in shrinkage rate of heterogeneous materials during the cooling and crystallization stage. When the product is subjected to narrow radius cold bending, it is easy to induce brittle fracture or local peeling due to stress concentration.

[0004] Therefore, how to overcome the physical shielding of microscopic cavitation at the interface and construct a deep anchoring structure with a modulus gradient has become the technical problem to be solved by this invention. Summary of the Invention

[0005] This invention provides a high-temperature melt lamination process for PVDF film and metal substrate, comprising the following steps: Step S101: Preheat the metal substrate so that the surface temperature of the metal substrate when it enters the lamination site is within the range of the melting point temperature of the PVDF film plus 10°C to the melting point temperature plus 25°C. Step S102: Guide the PVDF film with a body temperature lower than the melting point temperature minus 40° to cut into the bite point formed by the pressing roller and the metal substrate at an angle of 1.0° to 3.0° relative to the surface of the metal substrate, and form a transverse exhaust surface at the bonding front edge of the PVDF film and the metal substrate. Step S103: Adjust the surface linear speed of the pressing roller and the running speed of the metal substrate so that the speed ratio between the pressing roller and the metal substrate is within the range of 0.2% to 1.0%; apply a pressure of 1.2MPa to 2.5MPa at the bite point to introduce a transverse shear force at the contact interface between the PVDF film and the metal substrate, driving the molten PVDF to fill the micropores on the surface of the metal substrate; at the same time, obtain the current load deviation value of the pressing roller drive motor, and adjust the speed ratio according to the current load deviation value. Step S104: The composite material is placed in a constant temperature environment and maintained in the temperature range of 3s to 8s between the crystallization temperature of the PVDF film minus 5°C and the crystallization temperature plus 5°C. Step S105: Perform gradient cooling on the composite, with the cooling rate controlled within the range of 10℃ / min to 20℃ / min.

[0006] Preferably, in step S103, the speed ratio R satisfies the following formula: R=(V2−V1) / V1, where V2 is the surface linear velocity of the pressing roller and V1 is the running speed of the metal substrate; the current load deviation value ΔI is preset with a steady-state threshold; when the current load deviation value ΔI is detected to be lower than the steady-state threshold, the value of the speed ratio R is increased.

[0007] Preferably, before step S101, the temperature drop slope of the metal substrate during the transfer to the bonding site is monitored, and the initial preheating temperature is adjusted according to the temperature drop slope so that the surface temperature of the metal substrate when it enters the bonding site falls within the range of Tm+10℃ to Tm+25℃, where Tm is the melting point temperature.

[0008] Preferably, in step S103, the pressure is asymmetrically distributed, including setting an initial pressure of 0.1 MPa to 0.3 MPa at the front end of the bite point and applying a pressure of 1.2 MPa to 2.5 MPa at the center of the bite point.

[0009] Preferably, before performing step S102, the lateral temperature difference of the metal substrate in the width direction is monitored, and the unwinding tension gradient distribution of the PVDF film in the width direction is adjusted synchronously according to the lateral temperature difference to compensate for the thermal deformation of the metal substrate.

[0010] Preferably, in step S103, the speed ratio is controlled to fluctuate periodically within the range of 0.2% to 1.2%, with a fluctuation frequency of 5Hz to 15Hz, thereby inducing an alternating shear field at the contact interface.

[0011] Preferably, after step S104 and before step S105, the composite is placed in a thermal environment for 2 to 5 seconds to release the interfacial stress between the PVDF film and the metal substrate.

[0012] Preferably, in step S101, the running speed V1 of the metal substrate and the thermal conductivity K of the metal substrate satisfy the following relationship: V1⋅K=Φ, where Φ is a preset proportional constant used to maintain the melting depth of the interface layer in the range of 5μm to 15μm.

[0013] Preferably, in step S102, the transverse exhaust surface is composed of a transverse sweeping wave with continuous displacement induced by the included angle, and the transverse sweeping wave is used to discharge the air in the micropores along the axial direction of the pressing roller.

[0014] Preferably, in step S104, the temperature stability of the constant temperature environment is controlled within ±1.0℃, and the composite is in a state of uniform motion within the constant temperature environment.

[0015] Compared with existing technologies, the high-temperature fusion lamination process of PVDF film and metal substrate of the present invention has the following advantages: 1. In the high-temperature melting of PVDF film and metal substrate, the difference between the preheating temperature of the metal substrate and the melting point temperature of the polymer is used to compensate for the difference, so that the metal substrate acts as an endogenous heat and momentum source to drive the interface melting. With the slight speed difference between the pressing roller and the metal substrate, a transverse shear field is introduced at the bonding interface. The shear thinning characteristics of non-Newtonian fluid are used to reduce the apparent viscosity of the interface layer melt, and the melt is driven to be poured into the fractal micropores of the metal surface before cooling, realizing the transformation from discrete physical stacking to continuous micro-interlocking structure.

[0016] 2. By setting a small offset angle between the film material and the pressing roller, a rolling wave effect is created at the bonding front. The super fluidity of the interface melt is used to continuously remove residual air in the micropores of the metal surface in the transverse direction. Combined with the segmented pressure distribution in the pre-pressing zone and the high-pressure zone, the micro-cavities formed by the thermal expansion of air at the interface are eliminated, the effective molecular contact area at the interface is increased, and stress concentration and local delamination of layered products are avoided in the service environment.

[0017] 3. During the composite cooling stage, an isothermal growth platform near the crystallization temperature is set up to induce the polymer chain segments to complete in-situ stress relaxation within the micropores. Utilizing the temperature field phase difference formed by the gradient temperature drop, a crystallization buffer layer with a continuous modulus transition is constructed at the interface. A flexible hinge structure is formed between the hard metal substrate and the semi-crystalline polymer body to absorb the interfacial shear stress generated by the difference in thermal shrinkage rate, enabling the layered product to have the physical property of withstanding narrow radius cold bending without interfacial microcrack failure. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the high-temperature fusion lamination process of the PVDF film and the metal substrate of the present invention and the control of key parameters; Figure 2 This is a diagram of the intelligent process control system architecture that integrates thermal rheology and stress regulation according to the present invention. Detailed Implementation

[0019] 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.

[0020] It should be noted that all directional and positional terms used in this invention, such as: up, down, left, right, front, back, vertical, horizontal, inner, outer, top, low, lateral, longitudinal, center, etc., are only used to explain the relative positional relationship and connection between components in a specific state (as shown in the accompanying drawings). They are only for the convenience of describing this invention and do not require that this invention be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention. In addition, the descriptions of "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly indicating the number of technical features indicated.

[0021] In the description of this invention, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal communication between two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0022] In the description of this specification, references to the terms "an embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0023] A high-temperature melt lamination process for PVDF film and metal substrate comprises a metal substrate preheating and activation module, a polyvinylidene fluoride (PVDF) film asymmetric lamination module, an interface shear strengthening and anchoring module, an isothermal stress relaxation module, and a gradient cooling crystallization module. By controlling the thermal conductivity momentum of the metal substrate and the rheological state of the PVDF film at the lamination site, a crystallization buffer layer with a modulus gradient distribution is constructed at the heterogeneous material interface. The metal substrate is preheated so that its surface temperature upon entering the lamination site is within the range of the PVDF film's melting point (Tm+10℃ to Tm+25℃). The temperature drop slope of the metal substrate during its transfer to the lamination site is monitored, and the initial preheating temperature is adjusted based on this slope to ensure that the surface temperature of the metal substrate upon entering the lamination site falls within the range of Tm+10℃ to Tm+25℃. The running speed V1 of the plate and the thermal conductivity K of the metal substrate satisfy the relationship V1⋅K=Φ, where Φ is a preset proportional constant used to maintain the interface layer melting depth within the range of 5μm to 15μm. The preset proportional constant Φ is determined through pre-calibration based on different substrate materials and thermal conductivity characteristics. Specifically, a substrate sample of the target material is selected, and trial bonding is performed at gradient running speeds of 10m / min, 30m / min, and 50m / min under a pressure of 1.2MPa to 2.5MPa. The interface layer melting depth D of each sample cross section is measured using a metallographic microscope. A linear regression equation for depth D is established by combining the substrate thermal conductivity K and the running speed V1. The preset proportional constant Φ corresponding to the current material is calculated backward based on the median of the target melting depth of 5μm to 15μm, and the value is input into the intelligent process control center to adjust the preheating power.

[0024] A polyvinylidene fluoride (PVDF) film with a body temperature lower than its melting point Tm−40°C is inserted into the bonding roller at an angle of 1.0° to 3.0° relative to the metal substrate surface. A transverse venting surface is formed at the bonding front edge of the PVDF film and the metal substrate. This surface consists of a transverse sweeping wave with continuous displacement induced by the angle, used to expel air from the micropores on the metal substrate surface along the axial direction of the bonding roller. Before performing this step, the transverse temperature difference of the metal substrate in the width direction is monitored, and the PVDF film is synchronously adjusted in the width direction based on this transverse temperature difference. The unwinding tension gradient distribution is adjusted to compensate for the thermal deformation of the metal substrate; the surface linear velocity V2 of the pressing roller and the running speed V1 of the metal substrate are adjusted so that the speed ratio R between the pressing roller and the metal substrate is within the range of 0.2% to 1.0%, and the speed ratio R satisfies the formula R=(V2−V1) / V1; a pressure of 1.2MPa to 2.5MPa is applied at the bite point to introduce a transverse shear force at the contact interface between the polyvinylidene fluoride film and the metal substrate, driving the molten polyvinylidene fluoride to fill the micropores on the surface of the metal substrate, while simultaneously obtaining the current load deviation of the pressing roller drive motor. The current load deviation value ΔI is used to adjust the speed ratio. When the current load deviation value ΔI is detected to be lower than the steady-state threshold, the speed ratio R is increased. The current load deviation value ΔI is obtained and the speed ratio is adjusted according to the following procedure: During the production line start-up phase, the control roll drive motor is run at the target linear speed V2 under no-load. The current sensor collects no less than 500 current sample points with a sampling period of 10ms. The arithmetic mean is calculated to set the steady-state physical reference Ibase. During the lamination process, the current load deviation is obtained by subtracting the steady-state physical reference Ibase from the motor feedback current Ireal. If the deviation value ΔI is detected to be lower than the preset steady-state threshold for 5 consecutive sampling cycles, it is determined that the micropore filling damping has increased. The control system increases the speed ratio R value according to the proportional feedback logic until the deviation value returns to the steady-state threshold range, maintaining the interface shear strength constant, and controlling the speed ratio to fluctuate periodically in the range of 0.2% to 1.2%, with a fluctuation frequency of 5Hz to 15Hz. The pressure adopts an asymmetric distribution, including setting an initial pressure of 0.1MPa to 0.3MPa at the front end of the bite point, and applying a pressure of 1.2MPa to 2.5MPa at the center of the bite point.

[0025] The transverse venting surface and asymmetric pressure are achieved by adjusting the vertical displacement of the feed guide roller, maintaining the included angle of the PVDF film cutting and biting point at 1.0∘ to 3.0∘. This angle induces a physical wave with a wavelength of 3mm to 5mm at the bonding front, forming a transverse sweeping air wave to expel air from the micropores. The elastic layer on the surface of the laminating roller undergoes radial deformation under pressure, forming a 10mm to 20mm pre-compression zone at the biting point, generating an initial pressure of 0.1MPa to 0.3MPa. Combined with a central positive load, this achieves a peak pressure of 1.2MPa to 2.5MPa, enabling a single laminating station to complete air removal and melt infusion. The composite is then placed in a constant temperature environment, with the temperature stability controlled within ±1.0℃. The composite is maintained within the temperature range of Tc−5℃ to Tc+5℃ of the polyvinylidene fluoride film for 3 to 8 seconds. The composite is in a state of uniform motion within the constant temperature environment. The composite is then placed in an insulated environment for 2 to 5 seconds to release the interfacial stress between the polyvinylidene fluoride film and the metal substrate. Gradient cooling is then performed on the composite, with the cooling rate controlled within the range of 10℃ / min to 20℃ / min, until the temperature of the composite drops below the crystallization temperature of polyvinylidene fluoride.

[0026] Example 1: In a continuous production scenario of 5052 aluminum-magnesium alloy composite sheet, the surface of the metal substrate has fractal micropores with an average pore size of 2μm to 10μm. The melting point temperature (Tm) of the polyvinylidene fluoride (PVDF) film is 170℃, and the crystallization temperature (Tc) is 145℃. When the production line speed is set to 30m / min, the temperature drop lag caused by the PVDF melt contacting the metal surface leads to a cooling effect at the interface layer. The increased melt viscosity hinders its penetration into the metal micropores, and the trapped air inside the micropores expands upon heating, creating microscopic cavitation barriers. This results in point contact at the interface, inducing peeling of the layered product during cold bending. Preheating the metal substrate involves monitoring the temperature drop slope of the metal substrate in the transport path and adjusting the heating power to ensure proper cooling of the metal substrate. The surface temperature of the board when it enters the lamination point is maintained at 188℃, which is Tm+18℃. The heat stored in the metal substrate is used to compensate for the interface melting energy, and the polyvinylidene fluoride film with a main body temperature of 25℃ is guided to cut into the bite point formed by the lamination roller and the metal substrate at an angle of 2.0°. A transverse sweeping wave with continuous displacement is generated at the lamination front edge of the polyvinylidene fluoride film and the metal substrate, which discharges the air in the micropores of the metal surface along the axial direction of the lamination roller, thereby increasing the effective molecular contact area of ​​the interface. An initial pressure of 0.2MPa is set at the front end of the lamination bite point to remove residual air, and a pressure of 2.0MPa is applied at the center of the bite point. At the same time, the surface linear velocity V2 of the lamination roller and the running speed V1 of the metal substrate are adjusted to keep the speed ratio R constant at 0.5%.

[0027] The speed ratio R satisfies the formula R=(V2−V1) / V1, where R is the speed ratio between the pressing roller and the metal substrate, V2 is the surface linear velocity of the pressing roller, and V1 is the running speed of the metal substrate. A slight speed difference at the interface introduces transverse shear force at the contact interface. Utilizing the shear-thinning properties of PVC melt, the apparent viscosity of the interface layer melt is reduced, driving the molten PVC to penetrate deep into the fractal micropores on the metal surface. The current load deviation value ΔI of the pressing roller drive motor is acquired in real time. When the current load deviation value ΔI is detected to be lower than the preset steady-state threshold, the speed ratio R is increased to enhance the shear strength. The speed ratio R is controlled to periodically fluctuate at a frequency of 5Hz, inducing an alternating shear field. Residual oxide particles at the driving interface migrate to the amorphous region and are embedded by the melt. The composite is then placed in a constant temperature environment, and the temperature is maintained at 148℃ for 6 seconds to allow the polymer chain segments to complete in-situ stress relaxation at Tc+3℃. The composite is then placed in a heat-insulating environment for 3 seconds to release the residual stress caused by the difference in thermal shrinkage rates between the metal substrate and the polyvinylidene fluoride film. Gradient cooling at a cooling rate of 15℃ / min is then performed until the composite temperature drops below Tc, forming a crystalline buffer layer with a modulus gradient distribution at the interface. This buffer structure absorbs the shear stress caused by the difference in thermal shrinkage. When the layered product is subjected to a narrow radius cold bending process of 0.5T, there are no microcracks or failures at the bonding interface.

[0028] Example 2: In a test platform simulating industrial mass production, test data were obtained from a multi-channel pressure monitoring system and a non-contact infrared temperature sensor array integrated on a continuous lamination line. The temperature sensor had a measurement accuracy better than ±0.5℃, and the pressure sensor's sampling frequency was set to 1000Hz. Real-time parameters of the 5052 aluminum alloy substrate and polyvinylidene fluoride film during the lamination process were collected to verify the correlation between the interface anchoring effect and process parameters. The test adopted the peel strength test procedure specified in ASTM D903 standard and a high-resolution scanning electron microscope. Microscopic interlocking structures were observed using a microscope to determine the melting depth and filling quality of the interface layer. To simulate the industrial environment, the raw pressure signal collected by the sensor was superimposed with Gaussian white noise with a signal-to-noise ratio of 20dB to verify the stability of the pressure compensation procedure based on the motor current load deviation value ΔI under dynamic disturbance. The polyvinylidene fluoride film involved in the experiment had a melting point temperature Tm of 170℃, a crystallization temperature Tc of 145℃, and a thermal conductivity K of 238W / m·K for the metal substrate. A preset proportional constant Φ was used to dynamically adjust the preheating power according to the running speed V1 of the metal substrate.

[0029] The setting of the speed ratio R is based on balancing the interfacial shear strength and the smoothness of the film operation. The main technical factors affecting the value of this parameter include the power law exponent of the polyvinylidene fluoride melt and the fractal dimension of the metal substrate surface. When the detected motor current load deviation value ΔI is lower than the steady-state threshold, it is determined that the micropore filling resistance has increased. At this time, the speed ratio R is adjusted to the upper limit of 1.0%, and vice versa, it is adjusted to the lower limit of 0.2%. When the operating speed V1 is set to 30 m / min and the pressure is 2.0 MPa, the speed ratio R is calibrated in the range of 0.5% to 0.8% through this logic, in conjunction with a periodic fluctuation of 10 Hz. Frequency was used to achieve in-situ rearrangement of micro-oxidation particles at the interface. To verify the synergistic effect of the process and the rationality of the parameter boundaries, a multi-dimensional comparison system was designed, including the sample group of this invention, a partially missing control group, and an out-of-range control group. The sample group of this invention adopted the complete high-temperature melt lamination process. Control group A removed the speed ratio bias, i.e., R=0. Control group B removed the isothermal growth platform stage. Control group C set the preheating temperature to Tm+35°C. Control group D set the pressure to 0.8MPa. The problem intensity gradient was set by changing the oxide layer thickness on the surface of the metal substrate during the experiment.

[0030] Table 1: Summary Table of Experimental Data

[0031] Referring to Table 1, when the preheating temperature of the present invention is between Tm+10℃ and Tm+25℃ and the speed ratio is between 0.2% and 1.0%, the interfacial anchoring depth of the sample group is stable at 12.3μm to 14.6μm, the average peel strength reaches 15.4N / mm, and no microcracks appear in the 0.5T narrow radius cold bending test. The control group A, due to the lack of shear thinning effect caused by the transverse shear field, has an anchoring depth of only 2.4μm and a peel strength that decreases to 5.2N / mm. Although the control group C achieves deeper penetration due to the high temperature, it is still affected by the polyvinylidene fluoride. Thermal degradation occurred near 205℃, resulting in a peel strength reduction to 6.5 N / mm accompanied by yellowing, indicating that the defined parameter range is a working window that balances melt flowability and material thermal stability. By synergistically controlling the preheating temperature of the metal substrate and the transverse shear field of the interface, the filling of metal micropores by polyvinylidene fluoride melt was achieved. The setting of the isothermal growth platform released the in-situ stress in the interface layer, and a crystalline buffer layer with a modulus gradient was constructed between the hard metal and the semi-crystalline polymer, solving the problem of bonding failure of layered products under processing deformation.

[0032] Example 3: This example combines Figures 1 to 2 This describes a high-temperature melt lamination process for a PVDF film onto a metal substrate, such as... Figure 1As shown, the metal substrate is preheated and the temperature drop slope is monitored to adjust the initial temperature so that the surface temperature of the substrate when it enters the lamination site is in the range of the PVDF film melting point Tm+10℃ to Tm+25℃. The product of the substrate speed and thermal conductivity is controlled to maintain a melting depth of 5μm to 15μm at the interface. The PVDF film with a body temperature lower than Tm-40℃ is guided to cut into the bite point at an angle of 1.0° to 3.0°, forming a transverse continuous displacement exhaust wave to discharge microporous air along the axial direction. The width unwinding tension gradient of the film material is adjusted synchronously according to the transverse temperature difference of the substrate to compensate for thermal deformation. Then, an asymmetric pressure of 1.2MPa to 2.5MPa is applied at the center of the bite point and the 0° is adjusted. A speed ratio of 0.2% to 1.0% is introduced to drive the melt to fill the micropores. The speed ratio is adjusted in real time according to the motor current load deviation, and a periodic fluctuation of 5Hz to 15Hz is applied to induce an alternating shear field. Then, the composite is sent into a constant temperature environment with a temperature control accuracy of ±1.0℃. It is maintained in the crystallization temperature range of Tc±5℃ for 3s to 8s, and the interfacial chain segments are induced to relax in situ and release interfacial stress during the holding period of 2s to 5s. Finally, the composite is subjected to gradient cooling at a rate of 10℃ / min to 20℃ / min to build a crystallization buffer layer with modulus gradient distribution between heterogeneous materials, completing the essential transformation from discrete physical stacking to continuous microscopic interlocking structure.

[0033] like Figure 2 As shown, the system is centered on an intelligent process control center integrating PLC and industrial control computer algorithms. It connects various sub-control domains via industrial Ethernet. In the thermal energy precision management domain, infrared temperature measurement arrays and transverse scanning thermometers collect temperature data and transmit it to the control center for temperature drop compensation calculation, thereby regulating the induction heating controller. In the rheology and shear control domain, current load monitors and laser gap rangefinders acquire status signals in real time, adjust the servo drive of the pressing roller through damping feedback, and interact with the control center for load data and speed ratio commands. In the crystallization and stress regulation domain, the control center sends temperature control commands to the constant temperature tunnel temperature controller, gradient cooling fan unit, and magnetic powder tension controller according to process requirements, thereby coordinating with each execution unit to complete the entire process.

[0034] Example 4: In a scenario where a 1500mm wide 304 stainless steel substrate is laminated with a polyvinylidene fluoride (PVDF) film, the thermal conductivity K of the metal substrate is 16.2 W / m·K. There is a thickness deviation of ±5.0 μm between the edge and center. This non-uniform heat capacity distribution makes it difficult to precisely control the interfacial melting energy at the lamination site, causing brittle peeling of the interfacial layer due to the chilling effect. To determine the preset proportional constant Φ for maintaining the interfacial layer melting depth within the range of 5 μm to 15 μm, stainless steel samples were selected before formal production. Trial lamination was performed at a gradient speed of 10 m / min to 50 m / min under a pressure of 1.0 MPa. Metallographic microscopy was used to analyze the results. The actual melt penetration depth of the interface layer is measured to establish a linear proportional relationship between the running speed V1 and the depth D. When the target depth D is set to 10 μm, the preset proportional constant Φ under the current material is determined to be 162 μm·W / m·K·s−1. Based on Φ, the temperature drop slope of the stainless steel substrate during the transfer to the bonding site is monitored in real time, and the output current of the induction heater is dynamically adjusted to ensure that the surface temperature of the substrate is stable at 185℃ when it enters the biting point. For the working condition of a transverse temperature difference ΔT of 8.5℃, the temperature gradient between the transverse center point and the edge point of the substrate is obtained, and the unwinding tension in the edge area is reduced accordingly to counteract the interface strain caused by the thermal deformation of the substrate.

[0035] During the interface shear strengthening anchoring stage, the system uses discrete sampling logic to process the load information of the pressing roller drive motor. The current load deviation value ΔI is obtained by a current sensor with a sampling period of 10ms. The steady-state threshold calibration method includes continuously collecting 500 current samples under no-load operation and calculating the arithmetic mean as the reference load. The instantaneous current during the lamination process is subtracted from the reference load to obtain ΔI. When the deviation value ΔI of 5 consecutive sampling points is detected to be lower than the preset steady-state threshold of 0.5A, it is determined that the filling damping has increased. The control system increases the speed ratio R from the initial 0.4% to 0.9% according to the proportional feedback logic. The speed ratio R satisfies the formula R=(V2−V1) / V1, where R is the speed ratio between the pressing roller and the metal substrate, V2 is the surface linear velocity of the pressing roller, and V1 is the running speed of the metal substrate. This action increases the transverse shear field strength of the interface and reduces the apparent viscosity by utilizing the shear thinning effect.

[0036] The composite material moves at a constant speed in a constant-temperature tunnel near the crystallization temperature Tc. The temperature stability of the constant-temperature environment is controlled within ±1.0℃. When the composite temperature drops to 148℃, it is maintained in this state for 5s. During this isothermal growth platform stage, the polyvinylidene fluoride layer adjacent to the stainless steel surface is affected by the residual heat conduction of the metal, and its polymer chain segments are in an in-situ stress relaxation state, which leads to a slowdown in the crystallization rate and the formation of a low-modulus region. As the main layer away from the interface crystallizes rapidly, a crystallization buffer layer with a continuous gradient distribution is induced in the thickness direction. This buffer layer absorbs the interfacial shear stress caused by the mismatch in thermal shrinkage rates between stainless steel and polyvinylidene fluoride through flexible deformation. Scanning electron microscopy shows that the polymer chain segments at the interface are embedded in the fractal micropores on the stainless steel surface in a root-like manner. After the layered product is subjected to a narrow radius cold bending process of 0.5T, the interfacial bonding strength remains above 15.5N / mm, and the peel strength does not show any decrease.

[0037] Example 5: Before starting each batch of continuous lamination operation of layered products, a pre-calibration process is performed. With the metal substrate in a stationary state and the induction heater in a turned-off state, the ambient background radiation data is collected using an infrared temperature sensor array and set as the reference zero point. Then, the lamination roller motor is started and runs at a linear speed of 30 m / min under no-load, and 1000 current sampling points are collected simultaneously to calculate their arithmetic mean, which is used as the steady-state physical reference for obtaining the current load deviation value ΔI. The induction heater is turned on and the metal substrate is adjusted to run at a running speed V1 to the predetermined temperature. The compensation weight of the preset proportional constant Φ is corrected according to the monitored sensor response deviation, so as to obtain a stable temperature drop slope feedback basis in the transmission path.

[0038] When fluctuations in the production environment cause a decrease in the output heat energy of the induction heater, the system activates a compensation response procedure by monitoring the real-time temperature of the metal substrate when it enters the bite point. If the real-time temperature drops to the melting point temperature Tm+10℃, the control unit adjusts the speed ratio R using proportional feedback logic, adding a 0.15% bias component to the original value. The speed ratio R satisfies the relationship R=(V2−V1) / V1, where V2 is the linear velocity of the pressing roller surface and V1 is the running speed of the metal substrate. This action uses the frictional heat generated by the transverse shear field of the interface to compensate for the interface melting energy, and combines it with adjusting the unwinding tension gradient distribution of the polyvinylidene fluoride film in the width direction to counteract the transverse displacement caused by the thermal shrinkage of the metal substrate. This allows the composite to still build a gradient-distributed crystalline buffer layer through the relaxation of the interface chain segments under fluctuating thermal conditions. Tests have shown that the peel strength of the layered products obtained under this condition remains consistent.

[0039] Example 6: In the system initialization deployment procedure for heterogeneous layered products, in order to adapt to polyvinylidene fluoride (PVDF) films with different viscosity characteristics and handle interfacial gas plug residue, a standardized pre-calibration step is performed. The cutting angle of the PVDF film entering the bite point is set by adjusting the vertical displacement of the feed guide roller. The geometric gap between the PVDF film and the metal substrate surface is monitored using a laser rangefinder with a measurement accuracy better than 0.1 mm. The cutting angle is locked at 2.2°. This angle is used to generate a transverse sweeping gas wave with a wavelength of 3 mm to 5 mm at the bonding front. The initial ratio of the linear velocity V2 of the laminating roller surface to the running speed V1 of the metal substrate is set according to the melt index of the PVDF film. The response function between the apparent viscosity of the melt and the periodic fluctuation frequency of the speed ratio is established using shear rheology testing. The fluctuation frequency under this condition is determined to be 12 Hz. This frequency is used to generate an alternating shear field at the bite point to break the interfacial micro gas film.

[0040] When adapting to a 1500mm wide metal substrate, the system initiates tension compensation parameter optimization. A transverse scanning thermometer is used to obtain the transverse temperature difference ΔT of the metal substrate in the width direction, establishing an unwinding tension gradient distribution model. Considering the rapid temperature rise at the edges of the metal substrate, the relationship between local thermal stress and thermal shrinkage rate is experimentally determined. The tension compensation coefficient for the edge region is set to 0.85 times that of the center region. The current output of the magnetic powder brake is adjusted so that the unit tension of the polyvinylidene fluoride film in the width direction is linearly inversely proportional to the local thermal expansion of the metal substrate, thus offsetting the transverse shear stress caused by the thermal deformation of the metal substrate. An initial pressure of 0.25MPa is applied at the front end of the bite point to guide air out. Combined with a peak pressure of 2.1MPa at the center of the bite point, the melt is driven to fill the micropores on the surface of the metal substrate. The resulting micro-interlocking structure ensures the interfacial bonding strength.

[0041] 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 high-temperature fusion lamination process for PVDF film and metal substrate, characterized in that, Includes the following steps: Step S101: Preheat the metal substrate so that the surface temperature of the metal substrate when it enters the lamination site is within the range of the melting point temperature of the PVDF film plus 10°C to the melting point temperature plus 25°C. Step S102: Guide the PVDF film with a body temperature lower than the melting point temperature minus 40° to cut into the bite point formed by the pressing roller and the metal substrate at an angle of 1.0° to 3.0° relative to the surface of the metal substrate, and form a transverse exhaust surface at the bonding front edge of the PVDF film and the metal substrate. Step S103: Adjust the surface linear speed of the pressing roller and the running speed of the metal substrate so that the speed ratio between the pressing roller and the metal substrate is within the range of 0.2% to 1.0%. A pressure of 1.2 MPa to 2.5 MPa is applied at the bite point to introduce a transverse shear force at the contact interface between the PVDF film and the metal substrate, driving the molten PVDF to fill the micropores on the surface of the metal substrate; at the same time, the current load deviation value of the pressing roller drive motor is obtained, and the speed ratio is adjusted according to the current load deviation value. Step S104: The composite material is placed in a constant temperature environment and maintained in the temperature range of 3s to 8s between the crystallization temperature of the PVDF film minus 5°C and the crystallization temperature plus 5°C. Step S105: Perform gradient cooling on the composite, with the cooling rate controlled within the range of 10℃ / min to 20℃ / min.

2. The high-temperature fusion lamination process for PVDF film and metal substrate according to claim 1, characterized in that, In step S103, the speed ratio R satisfies the following formula: R=(V2−V1) / V1, where V2 is the surface linear velocity of the pressing roller and V1 is the running speed of the metal substrate; the current load deviation value ΔI is preset with a steady-state threshold; when the current load deviation value ΔI is detected to be lower than the steady-state threshold, the value of the speed ratio R is increased.

3. The high-temperature fusion lamination process for PVDF film and metal substrate according to claim 1, characterized in that, Before step S101, the temperature drop slope of the metal substrate during the transfer to the bonding site is monitored, and the initial preheating temperature is adjusted according to the temperature drop slope so that the surface temperature of the metal substrate when it enters the bonding site falls within the range of Tm+10℃ to Tm+25℃, where Tm is the melting point temperature.

4. The high-temperature fusion lamination process for PVDF film and metal substrate according to claim 1, characterized in that, In step S103, the pressure is asymmetrically distributed, including setting an initial pressure of 0.1 MPa to 0.3 MPa at the front end of the bite point and applying a pressure of 1.2 MPa to 2.5 MPa at the center of the bite point.

5. The high-temperature fusion lamination process for PVDF film and metal substrate according to claim 1, characterized in that, Before performing step S102, the lateral temperature difference of the metal substrate in the width direction is monitored, and the unwinding tension gradient distribution of the PVDF film in the width direction is adjusted synchronously according to the lateral temperature difference to compensate for the thermal deformation of the metal substrate.

6. The high-temperature fusion lamination process for PVDF film and metal substrate according to claim 1, characterized in that, In step S103, the speed ratio is controlled to fluctuate periodically within the range of 0.2% to 1.2%, with a fluctuation frequency of 5Hz to 15Hz, thereby inducing an alternating shear field at the contact interface.

7. The high-temperature fusion lamination process for PVDF film and metal substrate according to claim 1, characterized in that, After step S104 and before step S105, the composite is placed in a thermal environment for 2 to 5 seconds to release the interfacial stress between the PVDF film and the metal substrate.

8. The high-temperature fusion lamination process for PVDF film and metal substrate according to claim 1, characterized in that, In step S101, the running speed V1 of the metal substrate and the thermal conductivity K of the metal substrate satisfy the following relationship: V1⋅K=Φ, where Φ is a preset proportional constant used to maintain the melting depth of the interface layer in the range of 5μm to 15μm.

9. The high-temperature fusion lamination process for PVDF film and metal substrate according to claim 1, characterized in that, In step S102, the transverse exhaust surface is composed of transverse sweeping waves with continuous displacement induced by the included angle. The transverse sweeping waves are used to discharge the air in the micropores along the axial direction of the pressing roller.

10. The high-temperature fusion lamination process for PVDF film and metal substrate according to claim 1, characterized in that, In step S104, the temperature stability of the constant temperature environment is controlled within ±1.0℃, and the composite is in a state of uniform motion within the constant temperature environment.

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