Multi-effect synergistic hydrogel composite film and preparation method thereof

Abstract

The invention discloses a hydrogel-based composite film integrating efficient phase change cooling, high thermal conductivity, electromagnetic shielding and leakage prevention and a preparation method of the hydrogel-based composite film. The thin film is of a double-layer composite structure, wherein the lower layer is a high-thermal-conductivity electromagnetic shielding layer composed of polyacrylamide (PAM) hydrogel, Si3N4 and electromagnetic shielding filler, and the upper layer is a phase-change leakage-proof layer composed of PAM hydrogel and polyethylene glycol (PEG); the upper layer and the lower layer form a stable integrated structure through the synergistic effect of interface hydrogen bonds and physical entanglement, and finally integration of thermal management and electromagnetic protection functions is achieved. The phase change latent heat of the prepared film is larger than or equal to 120 J / g, the X-band electromagnetic shielding effectiveness (SE) is larger than or equal to 32 dB, and leakage is avoided at the high temperature of 80 DEG C. The preparation process is simple, and the product can be applied to various scenes such as power chips, LED equipment and wearable electronic devices.

Description

Technical Field

[0001] This application relates to the field of electronic functional composite materials technology, specifically to a multi-effect synergistic hydrogel composite film and its preparation method. Background Technology

[0002] With the rapid development of the digital age and the continuous advancement of materials technology, multifunctional electronic devices are evolving towards higher power density and higher integration. However, thermal management and electromagnetic compatibility protection of electronic devices have become key factors restricting their development. The generation and accumulation of a large amount of heat inside the device during operation will lead to performance degradation, decreased reliability, and even permanent damage. At the same time, electromagnetic radiation interference generated by high-frequency circuits not only affects the normal operation of the device itself and surrounding equipment but also poses a potential risk to human health.

[0003] Currently, phase change materials for thermal management of electronic devices can absorb / release a large amount of latent heat near the phase change temperature, but they have problems such as easy leakage during the phase change process and generally low thermal conductivity. In the field of electromagnetic shielding, commonly used materials such as metal foil and conductive coatings have excellent shielding effectiveness, but they have defects such as large weight and poor flexibility.

[0004] Existing technologies attempting to combine thermal conductivity and electromagnetic shielding suffer from problems such as high filler density, material brittleness, and poor interfacial compatibility. Furthermore, functional materials combining phase change cooling and leak prevention cannot simultaneously meet the thermal management and electromagnetic protection requirements of electronic devices. Therefore, developing a multifunctional material with simple processing, capable of simultaneously addressing heat dissipation and electromagnetic interference issues, and possessing good flexibility, is of significant practical importance and market demand. Summary of the Invention

[0005] The purpose of this invention is to overcome the technical problems of existing electronic device materials, such as easy leakage during phase transition, low thermal conductivity, separation of electromagnetic shielding and heat dissipation functions, and complex processes, and to develop a multi-effect synergistic hydrogel composite film.

[0006] This application discloses a multi-effect synergistic hydrogel composite film, wherein the composite film is a stable integrated composite structure formed by two layers through interfacial hydrogen bonds;

[0007] The lower layer is a high thermal conductivity electromagnetic shielding layer, which is composed of polyacrylamide (PAM) hydrogel, high thermal conductivity filler silicon nitride (Si3N4), and electromagnetic shielding functional filler.

[0008] The upper layer is a phase change leak-proof layer, which is composed of (PAM) hydrogel and phase change material polyethylene glycol (PEG).

[0009] The hydrogen bonds primarily originate from the incompletely cross-linked amide and hydroxyl groups of the lower PAM layer, as well as the amide groups of the upper PAM layer and the ether bonds of PEG. This hydrogen bond network forms densely at the interface between the two layers, providing significant interfacial bonding energy and chemical compatibility. Meanwhile, physical entanglement stems from the dense network structure formed by the interpenetration and entanglement between the upper prepolymer liquid and the lower PAM molecular chains during polymerization, ensuring a stable interfacial bond.

[0010] Preferably, the electromagnetic shielding filler is selected from one or more of graphene, conductive carbon black, and multi-walled carbon nanotubes, and its content is 0.5% to 2.5% of the total mass of the lower layer.

[0011] Preferably, the Si3N4 content is 1.5% to 3% of the total mass of the lower layer; the PEG content is 15% to 20% of the total mass of the upper layer, and its molecular weight is 1000 to 20000.

[0012] This application also provides a method for preparing the above-mentioned composite film, including the following steps:

[0013] S1: Preparation of lower layer prepolymer solution: Acrylamide (AM) is dissolved in deionized water, Si3N4 and electromagnetic shielding functional filler are added, and the mixture is stirred evenly; crosslinking agent N,N'-methylenebisacrylamide (MBA), crosslinking accelerator N,N,N',N'-tetramethylethylenediamine (TEMED), and thermal initiator potassium persulfate (KPS) are added sequentially and stirred evenly to obtain a lower layer prepolymer solution with a viscosity of 50~80 mPa·s;

[0014] S2: Curing the lower layer: The prepolymer liquid obtained in S1 is poured into a mold and dried at 75~85℃ for 25~35min. After cooling to room temperature, the surface moisture content is maintained at 5~8% to obtain a high thermal conductivity electromagnetic shielding base film. The surface of the base film retains some unreacted active groups, which facilitates the formation of chemical bonds with the upper layer.

[0015] S3: Preparation of upper prepolymer solution: Dissolve AM in deionized water, stir until evenly dispersed, then add MBA, TEMED and KPS in sequence, stir evenly, then add PEG, stir in a water bath at 50°C until completely dissolved, to obtain an upper prepolymer solution with a viscosity of 80~120 mPa·s.

[0016] S4: Composite Curing Upper Layer: The prepolymer liquid obtained in S3 is uniformly cast onto the surface of the lower layer substrate film obtained in S2. After standing for 10-15 minutes, the prepolymer liquid is allowed to fully wet the interface. Then, a gradient curing process is used for curing. After natural cooling and demolding, an integrated composite film is obtained.

[0017] Preferably, in steps S1 and S3, the content of AM is 6% to 10% of the total mass of the prepolymer liquid.

[0018] Preferably, in step S1, the electromagnetic shielding functional filler needs to be ultrasonically dispersed at 150~200w for 30min before being added. The particle size of the electromagnetic shielding functional filler after ultrasonic dispersion is ≤5μm to ensure that it is uniformly distributed in the prepolymer liquid and avoids agglomeration.

[0019] Preferably, the gradient curing process in step S4 is as follows: first, drying at 75°C for 30 minutes to promote the molecular reaction of hydrogen bond formation at the interface; then heating to 85°C for 75~105 minutes to ensure that PEG is fully embedded and encapsulated in the PAM network, and crosslinked with the active groups on the surface of the lower layer to further achieve strong interfacial bonding between the upper and lower layers.

[0020] Compared with the prior art, the advantages of the present invention are as follows:

[0021] 1. This application utilizes a dual-layer functional partitioning design, consisting of a lower layer of thermally conductive shielding and an upper layer of phase change leakage prevention, to synergistically integrate four major functions: phase change cooling, high thermal conductivity, electromagnetic shielding, and leakage prevention. This addresses the limitation of existing materials having only one function. Furthermore, the dual-layer functional partitioning design structurally avoids interference from functional fillers on the phase change material, allowing each layer to focus on its core function, thereby achieving a synergistic enhancement of multiple functions simultaneously as a whole.

[0022] 2. This application utilizes the three-dimensional cross-linked network of PAM hydrogel to physically encapsulate the phase change material. Combined with the physical support of the underlying substrate, this effectively suppresses leakage during the PEG phase change process, thereby improving the safety and reliability of the device.

[0023] 3. The high thermal conductivity filler Si3N4 constructs a vertically efficient thermal conduction pathway, significantly improving heat transfer efficiency and increasing the thermal conductivity of the film by more than three times compared to pure PEG. The electromagnetic shielding filler forms a continuous transverse conductive network, achieving efficient shielding through reflection, absorption, and multiple attenuation of incident electromagnetic waves. Both are uniformly dispersed and synergistically compatible in the PAM hydrogel matrix, jointly constructing a highly efficient functional transport system without obvious interface defects.

[0024] 4. This application precisely controls key process parameters—the upper and lower prepolymer liquids of different viscosities, the interface wetting time after casting the upper layer, and the gradient curing process—to ensure stable product performance. The lower layer, lacking high-viscosity molten PEG, exhibits good system fluidity and rapid heat transfer, allowing for rapid PAM crosslinking and the formation of a substrate that combines support and interfacial activity. The upper layer, however, requires simultaneous PEG encapsulation and PAM network crosslinking. The PEG it contains increases in viscosity after melting at 50°C, delaying the diffusion and crosslinking of monomers and initiators. Therefore, extending the curing time is necessary to achieve PEG encapsulation, which is crucial for achieving high-temperature leak-proof functionality. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 The diagram shown is a flowchart of the composite film preparation process of the present invention;

[0027] Figure 2 The figure shown is a diagram of the cooling effect when the product of Example 1 of the present invention is in contact with a PI film heating element with a power of 5W.

[0028] Figure 3 The image shows the cooling effect of the product of Example 1 of the present invention in contact with a PI film heating element with a power of 10W. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] Preparation of S1 lower layer prepolymer: Dissolve 0.8g of AM in 8ml of deionized water, add 0.2g of Si3N4 and 0.01g of graphene that has been ultrasonically dispersed for 30min, and stir for 5min; add 5.2mg of MBA, 6μL of TEMED and 10.8mg of KPS in sequence, and stir for 1min each to obtain a lower layer prepolymer with a viscosity of 65mPa·s;

[0032] S2 Lower Layer Curing: The prepolymer liquid obtained in S1 is cast into a polytetrafluoroethylene mold, dried at 80°C for 30 min, cooled to room temperature, and the surface moisture content is kept at 6% to obtain a PAM-Si3N4-graphene substrate film (thickness 0.15 mm).

[0033] Preparation of S3 upper prepolymer solution: Dissolve 0.8g of AM in 8ml of deionized water, then add 5.2mg of MBA, 6μL of TEMED, and 10.8mg of KPS in sequence, and stir for 1min each; then add 1.86g of PEG (molecular weight 4000), and stir in a 50℃ water bath for 10min until dissolved to obtain an upper prepolymer solution with a viscosity of 100mPa·s;

[0034] S4 Composite Curing: The upper prepolymer liquid obtained in S3 is cast onto the surface of the lower film and left to stand for 10 minutes; it is first dried at 75°C for 30 minutes, then heated to 85°C and dried for 90 minutes. After natural cooling, it is demolded to obtain a composite film with a total thickness of 0.8 mm.

[0035] Example 2

[0036] In Example 1, the 0.01g graphene in step 1 was replaced with 0.1g conductive carbon black, while the remaining steps remained the same as in Example 1.

[0037] Example 3

[0038] In Example 1, the 0.01g graphene in step 1 was replaced with 0.05g multi-walled carbon nanotubes, while the remaining steps remained the same as in Example 1.

[0039] Example 4

[0040] The amount of Si3N4 in step 1 of Example 1 was adjusted to 0.25g, while the remaining steps remained the same as in Example 1.

[0041] Example 5

[0042] In Example 1, the "0.01g graphene" in step 1 is changed to "0.005g graphene + 0.05g conductive carbon black", and the remaining steps are the same as in Example 1.

[0043] Comparative Example 1

[0044] The graphene in step 1 of Example 1 was removed, and the remaining steps were kept the same as in Example 1 to obtain a PAM-Si3N4 / PAM / PEG bilayer film.

[0045] To verify the practical application performance of the present invention, tests were conducted on the composite films prepared in Examples 1-5 and Comparative Example 1, including tests on leak prevention, thermal performance, electromagnetic shielding, cooling effect, and cycle stability. The results are as follows:

[0046] sample Phase transition temperature (°C) Latent heat of phase transition (J / g) Thermal conductivity (W / (m・K)) X-band SE_T (dB) Leakage prevention at 80℃ 5W chip cooling temperature difference (°C) Weight retention rate after 500 cycles (%) Example 1 38.2 135.6 0.92 35.6 No leakage 30.2 96.3 Example 2 38.5 136.1 0.95 32.5 No leakage 29.8 96.7 Example 3 38.1 134.8 1.15 42.8 No leakage 31.5 95.7 Example 4 38.3 135.2 1.08 34.9 No leakage 32.1 95.2 Example 5 38.4 135.8 0.94 36.8 No leakage 30.5 97.1 Comparative Example 1 38.2 135.4 0.89 <5.0 No leakage 27.3 96.1

[0047] Based on the above test results, the following conclusions can be drawn: Regarding leakage prevention, all samples remained intact and showed no PEG leakage after drying at 80℃ for 1 hour. This is because the synergistic effect of the cross-linked network of the PAM hydrogel and the underlying film, as well as the enhanced structural integrity due to the chemical cross-linking between the two layers, are significant. In terms of thermal properties, the thermal conductivity of Examples 1-5 is higher than that of Comparative Example 1 due to the thermal pathway synergistically constructed between the shielding filler and Si3N4. Furthermore, the phase change core performance of all samples remained highly stable, indicating that adjustments to the type and amount of shielding filler and the amount of Si3N4 do not affect the phase change nature of PEG.

[0048] Regarding electromagnetic shielding performance: Comparative Example 1 has almost no electromagnetic protection capability, while Examples 1-5, thanks to different shielding filler systems, achieve a shielding performance SE_T of no less than 32.5 dB, with Example 3 reaching 42.8 dB, meeting the standard for high-efficiency shielding. This is because the conductive filler forms a continuous conductive network in the PAM network, thereby achieving the reflection and absorption of electromagnetic waves. In terms of cooling efficiency, Examples 1-5 show better temperature differences on the 5W chip than Comparative Example 1; combined with… Figure 2-3 It can be seen that as the power increases, the heat dissipation advantage of the composite film becomes more prominent, which indicates that the synergistic effect of the high thermal conductivity filler and the phase change material can better cope with high power heating scenarios.

[0049] After 500 cycles of heating and cooling at 80°C for 1 hour followed by cooling at room temperature for 1 hour, all samples maintained a weight retention rate of ≥95.2%. In Example 5, the weight retention rate was as high as 97.1% due to the synergistic dispersion effect of the mixed fillers. Furthermore, after pre-ultrasonic dispersion, the shielding filler can form a tighter bond with the PAM network, thereby further enhancing the structural compactness of the film and reducing performance degradation after long-term cycling.

[0050] In summary, this composite film maintains the stable properties and leakage prevention of phase change materials, while simultaneously improving thermal conductivity and electromagnetic shielding performance through the addition of shielding filler. It also exhibits excellent cycle stability and is suitable for multi-power heating scenarios.

[0051] This embodiment is merely an illustrative description of the present patent and does not limit its scope of protection. Those skilled in the art may make partial modifications to it. As long as they do not exceed the spirit and essence of the present patent, they shall be regarded as equivalent substitutions to the present patent and shall be within the scope of protection of the present patent.

Claims

1. A multi-effect synergistic hydrogel composite film, characterized in that, The composite film is a stable integrated composite structure formed by two layers at the interface through hydrogen bonds. The lower layer is a high thermal conductivity electromagnetic shielding layer, which is composed of polyacrylamide hydrogel, high thermal conductivity filler silicon nitride, and electromagnetic shielding functional filler. The upper layer is a phase change leak-proof layer, which is composed of polyacrylamide hydrogel and polyethylene glycol, a phase change material.

2. The composite film according to claim 1, characterized in that, The electromagnetic shielding filler is selected from one or more of graphene, conductive carbon black, and multi-walled carbon nanotubes, and its content is 0.5% to 2.5% of the total mass of the lower layer.

3. The composite film according to claim 1, characterized in that, The content of silicon nitride is 1.5% to 3% of the total mass of the lower layer; the content of polyethylene glycol is 15% to 20% of the total mass of the upper layer, and its molecular weight is 1000 to 20000.

4. The method for preparing the composite thin film according to claims 1-3, characterized in that, Includes the following steps: S1: Preparation of lower layer prepolymer solution: Dissolve acrylamide in deionized water, add silicon nitride and electromagnetic shielding filler, and stir evenly; add crosslinking agent N,N'-methylenebisacrylamide, crosslinking accelerator N,N,N',N'-tetramethylethylenediamine, and thermal initiator potassium persulfate in sequence, and stir evenly to obtain a lower layer prepolymer solution with a viscosity of 50~80 mPa·s; S2: Curing the lower layer: The prepolymer liquid obtained in S1 is poured into a mold, dried at 75~85℃ for 25~35min, and cooled to room temperature while maintaining a surface moisture content of 5~8% to obtain a high thermal conductivity electromagnetic shielding base film. S3: Preparation of upper prepolymer solution: Dissolve acrylamide in deionized water, stir until evenly dispersed, then add N,N'-methylenebisacrylamide, N,N,N',N'-tetramethylethylenediamine and potassium persulfate in sequence, stir evenly, then add polyethylene glycol, and stir in a water bath at 50°C until completely dissolved to obtain an upper prepolymer solution with a viscosity of 80~120 mPa·s; S4: Composite Curing Upper Layer: The prepolymer liquid obtained in S3 is uniformly cast onto the surface of the lower base film obtained in S2. After standing for 10-15 minutes, it is cured using a gradient curing process. After natural cooling, it is demolded to obtain an integrated composite film.

5. The method for preparing the composite film according to claim 4, characterized in that, In steps S1 and S3, the content of acrylamide is 6% to 10% of the total mass of the prepolymer liquid.

6. The method for preparing the composite thin film according to claim 4, characterized in that, In step S1, the electromagnetic shielding functional filler needs to be ultrasonically dispersed at 150~200w for 30 minutes before being added. The particle size of the electromagnetic shielding functional filler after ultrasonic dispersion is ≤5μm.

7. The method for preparing the composite thin film according to claim 4, characterized in that, The gradient curing process in step S4 is as follows: first, dry at 75°C for 30 minutes, then raise the temperature to 85°C and continue the treatment for 75~105 minutes.

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