PP-T / CMF-based composite phase change material with electromagnetic wave absorption performance as well as preparation method and application of PP-T / CMF-based composite phase change material

Abstract

The invention discloses a PP-T / CMF-based composite phase change material with electromagnetic wave absorption performance, and the PP-T / CMF-based composite phase change material is prepared from the following raw materials: polyethylene glycol PEG 6000, poly-3, 4-ethylenedioxythiophene: polystyrene sulfonate PP, tetrabutyl titanate TBT and melamine foam MF; mF is used as a framework, and a T / MF foam matrix is obtained through hydrothermal reaction; calcining and carbonizing to obtain a T / CMF matrix; then, PP is subjected to vacuum impregnation and freeze drying, and a PP-T / CMF foam matrix is obtained; and finally, adsorbing PEG 6000 through vacuum. PEG 6000 is used as a heat storage medium; mF is a phase change material carrier and a supporting framework; pP is a conducting medium; tBT is used as a precursor; and ammonia water is used as a pH value regulator. The PP-T / CMF is of a three-dimensional network structure, and TiO2 nanoparticles are loaded on the surface of the PP-T / The preparation method comprises the following steps: 1, preparing T / CMF; 2, preparation of the PP-T / CMF; and 3, preparation of the PP-T / CMF / PEG. The material can be used as a phase-change material and a wave-absorbing material at the same time.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic wave absorption and phase change energy storage materials, specifically to a PP-T / CMF-based composite phase change material with electromagnetic wave absorption properties, its preparation method, and its applications. Background Technology

[0002] Phase change materials (PCMs) exhibit isothermal phase transitions during endothermic-exothermic processes, which can address thermal management issues arising from transient overheating in chips. Among PCMs, polyethylene glycol (PEG) possesses advantages such as high energy density, adjustable phase transition temperature, stable physicochemical properties, non-toxicity, and low cost. However, it also suffers from drawbacks including easy leakage in its liquid state, insufficient thermal conductivity, poor flame retardancy, and limited functionality. To address these issues, a hollow structure can be created by physically adsorbing and fixing the composite material using a high specific surface area porous matrix. This technical solution not only solves the leakage problem but also imparts additional properties to the composite material through matrix functionalization. Specifically, by improving the conductivity of the porous matrix, the composite material can simultaneously achieve dual functions of thermal management and electromagnetic wave absorption—the conductive network promotes electromagnetic wave energy conversion, and the porous structure enhances electromagnetic wave scattering loss, thereby significantly improving the overall protection performance of electronic devices.

[0003] In porous matrices, melamine foam (MF) possesses a continuous network structure, thus exhibiting advantages such as low density and high specific surface area. Simultaneously, MF also possesses a nitrogen-rich skeleton, which can form hydrogen bonding sites, enhancing the bonding stability of the composite material. Furthermore, poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT):PSS) is a novel conductive polymer material with excellent conductivity and water dispersibility, and can be assembled with MF to form a stable foam structure. For example, existing literature 1 (Gu W, Ong SJH, Shen Y, et al. A Lightweight, Elastic, and Thermally Insulating Stealth Foam With High Infrared-Radar Compatibility[J]. 2022, 9(35): 2204165.) successfully improved the material conductivity from 0 S / cm by modifying the MF skeleton with DMSO-modified PEDOT:PSS. -1 up to 2.16 Scm -1 The composite foam material exhibits significant improvements in performance; simultaneously, it possesses excellent electromagnetic wave absorption properties, with a minimum reflection loss of -57.57 dB and an ultra-wide effective absorption bandwidth of 10.52 GHz; furthermore, the material also demonstrates good radar wave scattering characteristics, with simulation results showing a radar cross-section reduction of up to 17.68 dB·m. 2Although the composite material obtained by this technical solution achieves excellent electromagnetic wave absorption performance by modifying the surface of the MF skeleton with PEDOT:PSS, the large-scale through-pore structure of the MF leads to leakage problems in the phase change material.

[0004] Furthermore, both PEDOT:PSS and MF suffer from poor thermal conductivity, meaning the resulting composite foam requires modification to improve its thermal conductivity. In existing technologies, TiO2 can be used as a thermally conductive material. Utilizing the characteristic of TiO2's easy hydrogen bonding with polymers, the dispersion of the thermally conductive material within the polymer material can be improved, thereby forming a continuous thermal transport network. For example, existing literature 2 (Kim J, Jang E, Cho J, et al. Porous TiO2 microspheres containing MgO nanoparticles / epoxy composite with superior thermal conductivity, EMI shielding, and electrical insulation[J]. Chemical Engineering Journal, 2024, 500: 156789.) uses epoxy resin as the matrix material to composite TiO2 and MgO to obtain a composite material with high thermal conductivity and EMI interference shielding effect. Specifically, the TiO2 / MgO / epoxy resin composite material has a maximum thermal conductivity of 7.52 W / (m·K), an EMI SE of 64.92 dB, and a tensile strength of 79.10 MPa. This technical solution effectively improves the thermal conductivity of the composite material by modifying the MF skeleton with TiO2 and carbonizing the skeleton. However, because this technical solution uses metal particles for composite formation, there is a problem that the TiO2 / MgO particles cannot be effectively dispersed in the epoxy resin. Summary of the Invention

[0005] The purpose of this invention is to provide a PP-T / CMF-based composite phase change material with electromagnetic wave absorption properties, its preparation method, and its applications. To address the aforementioned technical problems, this invention utilizes the water-dispersible nature of PEDOT:PSS and employs an ice-template method to treat the MF regulating pore structure, thereby solving the leakage problem of the phase change material.

[0006] Specifically,

[0007] 1. The porous structure of MF is used as a carrier and supporting framework for phase change materials; carbonization provides a conductive network framework for the material; hydrogen bonds can be formed between MF and TiO2 and PEDOT:PSS, making the composite material structure more robust;

[0008] 2. PEDOT: PSS is used as a conductive filler in composite materials to aggregate conductive networks that induce charge transport and introduce heterogeneous interfaces with multiple relaxations into the material.

[0009] 3. TiO2 modification of the MF foam surface increases the reflective surface of the foam and improves the material's wave absorption performance.

[0010] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0011] A PP-T / CMF-based composite phase change material with electromagnetic wave absorption properties is disclosed, using polyethylene glycol (PEG) 6000, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PP), tetrabutyl titanate (TBT), and melamine foam (MF) as raw materials. Using MF as the framework, a T / MF foam matrix is ​​obtained through a hydrothermal reaction. The T / MF matrix is ​​then calcined and carbonized to obtain a T / CMF matrix. The T / CMF matrix is ​​then vacuum-impregnated with PP and freeze-dried to obtain a PP-T / CMF foam matrix. Finally, PEG 6000 is vacuum-adsorbed onto the PP-T / CMF matrix to obtain the PP-T / CMF-based composite phase change material.

[0012] The function of PEG 6000 is to provide thermal storage performance as a thermal storage medium;

[0013] The role of MF is to serve as a carrier and supporting framework for phase change materials, providing hydrogen bonding sites for TiO2 and PEDOT:PSS, and providing a conductive network framework for the material after carbonization.

[0014] The role of PP is to serve as a conductive medium, to construct a conductive network that induces charge transport through aggregation, and to introduce a heterogeneous interface for multiple relaxations.

[0015] The role of TBT is to serve as a precursor for TiO2, enabling the preparation of TiO2 nanoparticles via a hydrothermal reaction; the prepared TiO2 modifies the surface of MF foam, increasing the reflective surface and improving the material's wave absorption performance.

[0016] The role of ammonia is to act as a pH adjuster for the hydrothermal reaction of TiO2.

[0017] The PP-T / CMF-based composite phase change material with electromagnetic wave absorption properties has a PP-T / CMF matrix exhibiting a three-dimensional network structure, and its surface is loaded with TiO2 nanoparticles. Due to the PP loading, a small number of pores are covered by a PP-constructed thin film. The PP-T / CMF / PEG composite phase change material exhibits that PEG is completely filled inside the three-dimensional network structure of PP-T / CMF and is not covered on the surface of PP-T / CMF.

[0018] A method for preparing a PP-T / CMF-based composite phase change material with electromagnetic wave absorption properties includes the following steps:

[0019] Step 1, Preparation of T / CMF: First, tetrabutyl titanate (TBT) and anhydrous ethanol are mixed to obtain a TBT solution. Then, melamine foam (MF) is impregnated in the TBT solution under certain conditions. After impregnation, 3 mL of ammonia water is added, and a hydrothermal reaction is carried out under certain conditions. After the reaction is completed, the mixture is dried to obtain the TiO2 / MF matrix, abbreviated as T / MF. Finally, the TiO2 / MF matrix is ​​calcined under certain conditions to achieve carbonization, thereby obtaining the TiO2 / C-MF matrix, abbreviated as T / CMF.

[0020] In step 1, the MF is cleaned before use. The cleaning conditions are as follows: ultrasonic cleaning is performed with an ultrasonic time of 6 hours and anhydrous ethanol and deionized water as ultrasonic media.

[0021] In step 1, the hydrothermal reaction conditions are: hydrothermal temperature of 180℃ and hydrothermal time of 10h.

[0022] In step 1, the calcination conditions are: under nitrogen atmosphere, the calcination temperature is 400℃, and the calcination time is 1 hour.

[0023] In step 1, TBT and MF satisfy the ratio of 1.5-2.5 mL: 8 cm. 3 The soaking time is 12 hours;

[0024] Step 2, Preparation of PP-T / CMF: First, (3,4-ethylenedioxythiophene monomer): polystyrene sulfonate PEDOT:PSS aqueous solution, abbreviated as PP, dimethyl sulfoxide DMSO and sodium dodecylbenzene sulfonate SDBS are mixed to obtain a modified solution. Then, the TiO2 / C-MF matrix obtained in Step 1 is placed in the modified solution for vacuum impregnation and adsorption. After the vacuum impregnation and adsorption are completed, freeze drying is performed to obtain the PEDOT:PSS / TiO2 / C-MF foam matrix, abbreviated as PP-T / CMF.

[0025] In step 2, PP, DMSO and SDBS meet the following ratios: 8-12 mL: 0.3-0.6 mL: 0.05-0.15 g, and the concentration of PP is 0.25-0.75 wt.%.

[0026] Step 3, Preparation of PP-T / CMF / PEG: The PP-T / CMF obtained in Step 2 and PEG6000 are mixed in a certain mass ratio. Under certain conditions, PP-T / CMF-50 is impregnated in molten PEG6000 to obtain a PP-T / CMF-based composite phase change material with electromagnetic wave absorption properties, abbreviated as PP-T / CMF / PEG. The material obtained in Example 1 is named PP-T / CMF / PEG-97.

[0027] In step 3, the mass ratio of PP-T / CMF to PEG6000 is 96-98 wt.%; the vacuum impregnation conditions are an impregnation temperature of 60-100℃ and an impregnation time of 7-9h.

[0028] The PP-T / CMF-based composite phase change material with electromagnetic wave absorption properties, when used as a phase change material, has a melting temperature of 58.77-59.65℃ and a melting enthalpy of 158.64-162.05 J / g; a crystallization temperature of 34.66-36.15℃ and a crystallization enthalpy of 157.08-159.62 J / g.

[0029] As a microwave absorbing material, PP-T / CMF / PEG exhibits a return loss of less than -5dB across the entire wavelength range.

[0030] It exhibits a return loss of less than -10dB in the S-band 2-4GHz.

[0031] It exhibits a return loss of -10 to 29.54 dB in the Ku band 12-18 GHz.

[0032] Electromagnetic signal attenuation reaches 90-96.8%.

[0033] This invention, tested using FTIR, XRD, SEM, TEM, DSC, vector network analyzer, and leak resistance testing, has the following characteristics:

[0034] FTIR spectroscopy revealed that the PP-T / CMF prepared by this invention contains all the infrared characteristic peaks of carbonized CMF, TiO2, and PP. Furthermore, no other characteristic peaks were observed, indicating that the interaction between CMF, TiO2, and PP is purely physical and not chemical. The PP-T / CMF / PEG prepared by this invention contains all the infrared characteristic peaks of both PP-T / CMF and PEG, indicating that the impregnation process is a physical adsorption process.

[0035] XRD analysis showed that the PP-T / CMF prepared by this invention contained all the characteristic diffraction peaks of MF, TiO2, and PP, and the diffraction peaks did not change significantly, indicating that the interaction between MF, TiO2, and PP was purely physical. The PP-T / CMF / PEG prepared by this invention contained all the characteristic diffraction peaks of PP-T / CMF and PEG, indicating that the impregnation process was a physical adsorption process.

[0036] Scanning electron microscopy (SEM) tests showed that the PP-T / CMF framework prepared in this invention has TiO2 nanoparticles loaded on its surface, and a small number of pores are covered by the PP-constructed film without affecting the loaded TiO2; in the PP-T / CMF / PEG prepared in this invention, PEG is completely filled inside the three-dimensional network structure of PP-T / CMF.

[0037] Differential scanning calorimetry (DSC) testing revealed that the PP-T / CMF / PEG prepared in this invention has a melting temperature of 58.77-59.65℃ and a melting enthalpy of 158.64-162.05 J / g; a crystallization temperature of 34.66-36.15℃ and a crystallization enthalpy of 157.08-159.62 J / g; furthermore, the PP-T / CMF / PEG exhibits high cycling stability and thermal stability, with no significant changes in the cycling curve after 100 cycles.

[0038] Leakage resistance tests show that the PP-T / CMF / PEG prepared in this invention has good leak-proof performance. Under the condition of heating time of 30 min, PP-T / CMF / PEG-97 still maintains the initial solid form, that is, there is no leakage.

[0039] Absorption tests show that the PP-T / CMF / PEG prepared in this invention exhibits a return loss of less than -5dB across the entire frequency band; a return loss of less than -10dB in the S-band (2-4GHz); and a return loss of -10-29.54dB in the Ku-band (12-18GHz). The electromagnetic signal attenuation reaches 90-96.8%, indicating that PP-T / CMF / PEG has excellent absorption performance.

[0040] Therefore, the present invention has the following advantages over the prior art:

[0041] 1. The carbonized MF foam skeleton loaded with TiO2 nanoparticles modified by PP significantly enhances the material's electrical conductivity and wave absorption ability;

[0042] 2. By using the MF skeleton as a phase change material carrier, the phase change leakage problem of PEG6000 was solved by utilizing the capillary effect of foam, thus improving the thermal stability of the material.

[0043] 3. The PP-T / CMF-based composite phase change material prepared by this invention is self-assembled through physical action, effectively maintaining the high latent heat of phase change of the phase change material;

[0044] 4. The PP-T / CMF-based composite phase change material prepared by this invention has excellent shape stability, thermal stability and cycle stability. Attached Figure Description

[0045] Figure 1 FTIR plots of MF, PP, T / MF, CMF, T / CMF, PP-T / CMF, and TiO2;

[0046] Figure 2 FTIR spectra of PEG 6000, PP-T / CMF / PEG-96, PP-T / CMF / PEG-97 and PP-T / CMF / PEG-98;

[0047] Figure 3 XRD patterns of PP-T / CMF / PEG-97, PEG 6000, PP-T / CMF, T / CMF, T / MF, MF, PP, and TiO2;

[0048] Figure 4 SEM images of MF and T / MF;

[0049] Figure 4 SEM images of PP-T / CMF-25, PP-T / CMF-50, and PP-T / CMF-75;

[0050] Figure 5 SEM images of PP-T / CMF / PEG-96, PP-T / CMF / PEG-97, and PP-T / CMF / PEG-98;

[0051] Figure 6 DSC plots for PEG 6000, PP-T / CMF / PEG-96, PP-T / CMF / PEG-97, and PP-T / CMF / PEG-98;

[0052] Figure 7 DSC cycle diagram for PP-T / CMF / PEG-97;

[0053] Figure 8 Leakage prevention diagrams for PEG 6000, PP-T / CMF / PEG-96, PP-T / CMF / PEG-97 and PP-T / CMF / PEG-98;

[0054] Figure 9 SEt, SEa, and SEr curves for PP-T / CMF / PEG-97;

[0055] Figure 10 Return loss diagrams for 1-5mm PP-T / CMF / PEG-97 and PEG 6000;

[0056] Figure 11 Diagrams showing practical applications of PP-T / CMF / PEG-97 and PEG 6000;

[0057] Figure 12 Absorption tests for PP-T / CMF / PEG-97 and PEG 6000. Detailed Implementation

[0058] The present invention will be further described in detail through embodiments and with reference to the accompanying drawings, but this is not intended to limit the scope of the invention.

[0059] Example 1

[0060] A method for preparing a PP-T / CMF-based composite phase change material with electromagnetic wave absorption properties, comprising the following steps: (PP content: 0.5 wt.%)

[0061] Step 1, Preparation of T / CMF: First, 2 mL of tetrabutyl titanate (TBT) and 40 mL of anhydrous ethanol are mixed to obtain a TBT solution. Then, melamine foam (MF) is impregnated in the TBT solution for 12 hours. After impregnation, 3 mL of ammonia is added, and a hydrothermal reaction is carried out at 180°C for 10 hours. After the reaction is complete, the substrate is dried to obtain the TiO2 / MF matrix, abbreviated as T / MF. Finally, the TiO2 / MF matrix is ​​calcined under nitrogen at 400°C for 1 hour to achieve carbonization, thus obtaining the TiO2 / C-MF matrix, abbreviated as T / CMF.

[0062] The MF has dimensions of 2cm×2cm×2cm and is cleaned before use. The cleaning conditions for the MF are as follows: ultrasonic cleaning is performed with an ultrasonic time of 6 hours and anhydrous ethanol and deionized water as the ultrasonic media.

[0063] To demonstrate the microstructure of T / CMF, i.e. the successful introduction of TiO2, SEM testing was performed; at the same time, for comparison, SEM testing was performed on MF and T / CMF.

[0064] The microstructure of MF is as follows Figure 3 a and Figure 3 As shown in b, MF has a three-dimensional network structure formed by the interconnection of melamine resins.

[0065] The micromorphology of T / MF is as follows Figure 3 c and Figure 3 As shown in d, the basic microstructure of T / MF is the same as that of MF, namely a three-dimensional network structure. However, the surface of T / MF is loaded with TiO2 nanoparticles, and there is no covering inside the foam pores.

[0066] The microstructure of T / CMF is as follows Figure 3 e and Figure 3 As shown in f, the basic microstructure of T / CMF is the same as that of T / MF, namely a three-dimensional network structure. Furthermore, TiO2 nanoparticles are loaded on the surface. However, the framework of the three-dimensional network structure exhibits shrinkage.

[0067] Test results show that TiO2 was successfully introduced into the form of nanoparticles by first hydrothermal treatment and then calcination. At the same time, the calcination process had no substantial impact on the microstructure of TiO2.

[0068] Step 2, Preparation of PP-T / CMF: First, 10 mL of a 0.50 wt% aqueous solution of (3,4-ethylenedioxythiophene monomer): polystyrene sulfonate PEDOT:PSS (abbreviated as PP), 0.5 mL of dimethyl sulfoxide (DMSO), and 0.1 g of sodium dodecylbenzene sulfonate (SDBS) are mixed to obtain a modified solution. Then, the TiO2 / C-MF matrix obtained in Step 1 is placed in the modified solution for vacuum impregnation and adsorption. After vacuum impregnation and adsorption are completed, freeze-drying is performed to obtain the PEDOT:PSS / TiO2 / C-MF foam matrix, abbreviated as PP-T / CMF. Specifically, the PP-T / CMF obtained in Example 1 is abbreviated as PP-T / CMF-50 because the concentration of PP is 0.50 wt%.

[0069] To confirm the composition of PP-T / CMF-50, i.e., successful preparation, FTIR testing was performed. Simultaneously, for comparison, FTIR tests were performed on MF, TiO2, T / MF, and PP. The test results are as follows: Figure 1 As shown, PP-T / CMF-50 contains all the infrared characteristic peaks of carbonized CMF, TiO2, and PP, while no other characteristic peaks appear. The test results indicate that there is only a physical interaction between CMF, TiO2, and PP, and no chemical reaction occurs.

[0070] To further confirm the composition of PP-T / CMF-50, XRD tests were performed. Simultaneously, for comparison, XRD tests were performed on MF, TiO2, T / MF, and PP. The test results are as follows: Figure 2 As shown, PP-T / CMF-50 contains all the characteristic diffraction peaks of MF, TiO2, and PP, and the characteristic diffraction peaks of MF, TiO2, and PP show no significant changes.

[0071] To demonstrate the microstructure of PP-T / CMF-50, i.e., successful PP loading, SEM testing was performed. The test results are as follows: Figure 4 c and Figure 4 As shown in d, the basic microstructure of PP-T / CMF-50 is the same as that of T / CMF, namely a three-dimensional network structure. Furthermore, TiO2 nanoparticles are loaded on the surface. However, due to the loading of PP, a small number of pores are covered by the PP-constructed film, while the loaded TiO2 is not affected.

[0072] To demonstrate the electromagnetic shielding performance of PP-T / CMF-50, an electromagnetic shielding test was conducted. The specific test method involved blending the sample with 20 wt.% paraffin wax to a thickness of 3.8 mm. The test results are as follows: Figure 9 As shown, the electromagnetic shielding performance of PP-T / CMF-50 is as follows:

[0073] SEr exhibits a maximum reflection loss of 4dB in the S-band 2-4GHz, generally showing a trend of first increasing and then decreasing.

[0074] SEa exhibits the highest absorption loss of 14dB in the Ku band 12-18GHz, and generally shows a trend of continuous increase with increasing frequency.

[0075] The total electromagnetic shielding effectiveness of SEt exceeds 10dB in the C, X, and Ku bands from 4 to 18 GHz, and reaches a peak of 16.5dB in the Ku band. Overall, it shows a trend of continuous increase with increasing frequency.

[0076] Therefore, the electromagnetic signal attenuation of PP-T / CMF-50 reaches 77.6-85%. Test results show that PP-T / CMF-50 has electromagnetic shielding performance.

[0077] Step 3, Preparation of PP-T / CMF / PEG: With a mass ratio of PP-T / CMF-50 obtained in Step 2 to PEG6000 of 97 wt.%, PP-T / CMF-50 is placed in molten PEG6000 for vacuum impregnation at an impregnation temperature of 80°C and an impregnation time of 8 h to obtain a PP-T / CMF-based composite phase change material with electromagnetic wave absorption properties, abbreviated as PP-T / CMF / PEG. The material obtained in Example 1 is named PP-T / CMF / PEG-97.

[0078] To demonstrate the adsorption capacity of PP-T / CMF / PEG-97, the mass of the material before and after adsorption was compared. The test results are as follows:

[0079] The adsorption amount was 0.0506 g before adsorption and 1.6192 g after adsorption. The calculated adsorption rate reached 96.87%, which is close to 97 wt.%, indicating that the adsorption amount of the material was not excessive, and the composite phase change material was successfully prepared.

[0080] To confirm the composition of PP-T / CMF / PEG-97 and thus its successful preparation, FTIR testing was performed; simultaneously, for comparison, FTIR testing was conducted on PEG. The test results are as follows... Figure 1 As shown, PP-T / CMF / PEG-97 contains all the infrared characteristic peaks of PP-T / CMF and PEG. The test results indicate that the impregnation process is a physical adsorption process.

[0081] To further confirm the composition of PP-T / CMF / PEG-97, XRD testing was performed; simultaneously, for comparison, XRD testing was performed on PEG. The test results are as follows: Figure 2 As shown, PP-T / CMF / PEG-97 contains all the characteristic diffraction peaks of PP-T / CMF and PEG. The XRD test results are consistent with the FTIR test results, indicating that the impregnation process is a physical adsorption, meaning that PP-T / CMF does not affect the crystallization state of PEG.

[0082] To demonstrate the microstructure of PP-T / CMF / PEG-97, SEM testing was performed. The test results are as follows: Figure 5 c and Figure 5 As shown in Figure d, PEG completely fills the three-dimensional network structure of PP-T / CMF-50 and does not cover the surface of PP-T / CMF-50. The test results show that at a mass ratio of 97 wt.%, no supersaturation occurred when PP-T / CMF adsorbed PEG.

[0083] To demonstrate the phase transition properties of PP-T / CMF / PEG-97, DSC testing was performed. The test results are as follows: Figure 4 As shown in Table 1, within the test temperature range of -10 to 100℃, an endothermic peak exists at 58.77℃ during the melting process, with a latent heat value of 160.45 J / g; and an exothermic peak exists at 34.66℃ during the crystallization process, with a latent heat value of 158.81 J / g. The test results indicate that PCM-2 exhibits good phase change behavior and heat storage capacity.

[0084] Table 1. Phase transition enthalpy and temperature of composite phase change materials with different PEG 6000 addition contents.

[0085]

[0086] To demonstrate the cycling stability of PP-T / CMF / PEG-97, cycling tests were conducted. The test results are as follows: Figure 5As shown, the thermal cycling curve of PP-T / CMF / PEG-97 remained essentially unchanged after 100 cycles. The test results indicate that the phase transition properties of PP-T / CMF / PEG-97 did not change before and after cycling. The test results also demonstrate that PCM-2 exhibits good cycling stability.

[0087] To demonstrate the thermal conductivity of PP-T / CMF / PEG-97, thermal conductivity tests were conducted. Simultaneously, for comparison, thermal conductivity tests were performed on PEG 6000.

[0088] The test results for PEG 6000 are as follows: Figure 8 As shown in Table 2, the thermal conductivity of PEG 6000 is 0.2185 W / (m·K);

[0089] The test results for PP-T / CMF / PEG-97 are as follows: Figure 8 As shown in Table 2, the thermal conductivity of PP-T / CMF / PEG-97 is 0.3629 W / (m·K);

[0090] Test results show that the thermal conductivity of PP-T / CMF / PEG-97 is 66.08% higher than that of PEG 6000. This is because the TiO2 and MF skeleton form a continuous thermally conductive network, which improves the thermal conductivity of the composite material.

[0091] Table 2 Thermal conductivity of composite phase change materials with different PEG 6000 addition contents

[0092] Sample Name PEG 6000 Comparative Example 4 Example 1 Comparative Example 3 Thermal conductivity W / (m·K) 0.2185 0.3537 0.3629 0.3813

[0093] To demonstrate the leak-resistance of PP-T / CMF / PEG-97, a leak-resistance test was conducted; simultaneously, for comparison, PEG was also subjected to a leak-resistance test. The leak-resistance test temperature was 80℃.

[0094] The test results for PEG are as follows: Figure 9 As shown, under a heating time of 10 minutes, PEG completely dissolved, i.e., leakage occurred;

[0095] The test results for PP-T / CMF / PEG-97 are as follows: Figure 9 As shown, under a heating time of 30 minutes, PP-T / CMF / PEG-97 still maintained its initial solid state, i.e., there was no leakage.

[0096] Test results show that PP-T / CMF / PEG-97 has anti-leakage properties.

[0097] To demonstrate the electromagnetic shielding performance of PP-T / CMF-50, an electromagnetic shielding test was conducted. The specific test method involved blending the sample with 20 wt.% paraffin wax to a thickness of 3.8 mm. The test results are as follows: Figure 10 As shown, the electromagnetic shielding performance of PP-T / CMF-50 is as follows:

[0098] SEr exhibits a maximum reflection loss of 4dB in the S-band 2-4GHz, generally showing a trend of first increasing and then decreasing.

[0099] SEa exhibits the highest absorption loss of 14dB in the Ku band 12-18GHz, and generally shows a trend of continuous increase with increasing frequency.

[0100] The total electromagnetic shielding effectiveness of SEt exceeds 10dB in the C, X, and Ku bands from 4 to 18 GHz, and reaches a peak of 16.5dB in the Ku band. Overall, it shows a trend of continuous increase with increasing frequency.

[0101] Therefore, the electromagnetic signal attenuation of PP-T / CMF-50 reaches 77.6-85%. Test results show that PP-T / CMF-50 has electromagnetic shielding performance.

[0102] To demonstrate the microwave absorption performance of PP-T / CMF / PEG-97, return loss tests were conducted; simultaneously, for comparison, return loss tests were performed on PEG. The test results are as follows: Figure 11 As shown, PP-T / CMF / PEG-97

[0103] It exhibits a return loss of less than -5dB across the entire frequency band;

[0104] It exhibits a return loss of less than -10dB in the S-band 2-4GHz.

[0105] It exhibits a return loss of -10 to 29.54 dB in the Ku band 12-18 GHz.

[0106] Therefore, the electromagnetic signal attenuation of PP-T / CMF / PEG-97 reaches 90-96.8%. Test results show that PP-T / CMF / PEG-97 has excellent microwave absorption performance.

[0107] To demonstrate the application value of the microwave absorption performance of PP-T / CMF / PEG-97, microwave absorption tests were conducted; simultaneously, for comparison, microwave absorption tests were performed on PEG. The test results are as follows: Figure 12 As shown. The test results indicate that,

[0108] When there is no interval, the neon bulb will be lit by the electromagnetic waves of the electromagnetic coil;

[0109] The neon bulb went out instantly when the PP-T / CMF / PEG-97 interval was reached;

[0110] The neon bulb dimmed when the PEG was applied. Test results show that PP-T / CMF / PEG-97 exhibits excellent microwave absorption performance.

[0111] To demonstrate the effect of PP addition on PP-T / CMF, Comparative Example 1 and Comparative Example 2 are provided, with PP-T / CMF prepared by adding 0.25 wt.% and 0.75 wt.% of PP, respectively.

[0112] Comparative Example 1

[0113] A method for preparing PP-T / CMF with an addition of 0.25 wt.% PP is described below. Unless otherwise specified, the steps are the same as in Example 1, except that in step 2, the concentration of PP is 0.25 wt.% and the resulting PP-T / CMF is referred to as PP-T / CMF-25.

[0114] SEM test results of PP-T / CMF-25 are as follows Figure 4 a and Figure 4 As shown in b, the basic microstructure of PP-T / CMF-25 is the same as that of PP-T / CMF-50 obtained in step 2 of Example 1, namely, a three-dimensional network structure, and the surface is loaded with TiO2 nanoparticles. However, a large number of through-pores exist. Compared with PP-T / CMF-50 obtained in Example 1, it can be seen that because PP-T / CMF-25 contains less PP, the constructed film has less coverage and cannot encapsulate T / CMF, ultimately resulting in a large number of through-pores, which cannot meet the requirements of subsequent applications.

[0115] Comparative Example 2

[0116] A method for preparing PP-T / CMF with an addition of 0.75 wt.% PP is described below. Unless otherwise specified, the steps are the same as in Example 1, except that in step 2, the concentration of PP is 0.75 wt.% and the resulting PP-T / CMF is referred to as PP-T / CMF-75.

[0117] To demonstrate the adsorption capacity of PP-T / CMF-75, the mass of the material before and after adsorption was compared. The test results showed that the mass before adsorption was 0.0702 g, and the mass after adsorption was 1.7082 g. Calculations showed that the adsorption rate reached 95.89 wt.%, which is much lower than that of PP-T / CMF-50, meaning it cannot meet the requirements for subsequent applications.

[0118] SEM test results of PP-T / CMF-75 are as follows Figure 4 e and Figure 4As shown in f, the basic microstructure of PP-T / CMF-75 is the same as that of PP-T / CMF-50 obtained in step 2 of Example 1, which is a three-dimensional network structure. Comparing it with PP-T / CMF-50 obtained in Example 1, it can be seen that due to the excessive addition of PP in PP-T / CMF-75, the constructed film has excessive coverage, resulting in excessive coating of T / CMF. Ultimately, this leads to the coverage of the pores, failing to meet the requirements of subsequent applications.

[0119] As can be seen from Examples 1, 1, and 2, as the PP content increases, the porous structure of the material gradually decreases. Due to the excessive PP content, it cannot meet the requirements of subsequent applications.

[0120] To demonstrate the effect of PEG addition on PP-T / CMF / PEG, Comparative Examples 3 and 4 are provided, with PP-T / CMF / PEG prepared with PEG additions of 96 wt.% and 98 wt.%, respectively.

[0121] Comparative Example 3

[0122] A method for preparing a PP-T / CMF-based composite phase change material with a PEG addition of 96 wt.% is disclosed. Unless otherwise specified, the steps are the same as in Example 1, except that in step 3, the PEG addition is 96 wt.% and the resulting PP-T / CMF-based composite phase change material is referred to as PP-T / CMF / PEG-96.

[0123] To verify the adsorption capacity of PP-T / CMF / PEG-96, the mass of the material before and after adsorption was compared. The test results showed that the mass before adsorption was 0.0605 g and the mass after adsorption was 1.4792 g. The calculated adsorption rate was 95.91 wt.%, which is close to 96 wt.%, indicating that PEG was not in excess.

[0124] To demonstrate the phase transition properties of PP-T / CMF / PEG-96, DSC testing was performed. The test results are as follows: Figure 6 As shown in Table 1, within the test temperature range of -10 to 100℃, an endothermic peak exists at 59.04℃ during the melting process, with a latent heat value of 158.64 J / g; during the crystallization process, an exothermic peak exists at 35.01℃, with a latent heat value of 157.08 J / g. The test results indicate that PP-T / CMF / PEG-96 exhibits good phase change behavior and heat storage capacity.

[0125] To demonstrate the thermal conductivity of PP-T / CMF / PEG-96, thermal conductivity tests were conducted. The test results are as follows: Figure 8 As shown in Table 2, the thermal conductivity of PP-T / CMF / PEG-96 is 0.3813 W / (m·K);

[0126] To demonstrate the anti-leakage performance of PP-T / CMF / PEG-96, an anti-leakage test was conducted. The test results are as follows: Figure 9 As shown, PP-T / CMF / PEG-96 maintained its initial solid state for 30 minutes, indicating no leakage.

[0127] Comparative Example 4

[0128] A method for preparing a PP-T / CMF-based composite phase change material with a PEG addition of 98 wt.% is provided. The steps not specifically described are the same as those in Example 1, except that in step 3, the PEG addition is 98 wt.% and the resulting PP-T / CMF-based composite phase change material is referred to as PP-T / CMF / PEG-98.

[0129] To demonstrate the adsorption capacity of PP-T / CMF / PEG-98, the mass of the material before and after adsorption was compared. The test results showed that the mass before adsorption was 0.0525g and the mass after adsorption was 1.8394g. The calculated adsorption rate reached 97.14wt.%, which was significantly lower than 98wt.%, indicating that PEG was in excess.

[0130] To demonstrate the phase transition properties of PP-T / CMF / PEG-98, DSC testing was performed. The test results are as follows: Figure 6 As shown in Table 1, within the test temperature range of -10 to 100℃, an endothermic peak exists at 59.65℃ during the melting process, with a latent heat value of 162.05 J / g; and an exothermic peak exists at 36.15℃ during the crystallization process, with a latent heat value of 159.62 J / g. The test results indicate that PP-T / CMF / PEG-98 exhibits good phase change behavior and heat storage capacity.

[0131] To demonstrate the thermal conductivity of PP-T / CMF / PEG-98, thermal conductivity tests were conducted. The test results are as follows: Figure 8 As shown in Table 2, the thermal conductivity of PP-T / CMF / PEG-98 is 0.3537 W / (m·K);

[0132] To demonstrate the anti-leakage performance of PP-T / CMF / PEG-98, an anti-leakage test was conducted, and the test results are as follows: Figure 9 As shown, PP-T / CMF / PEG-98 leaked after 10 minutes, indicating that an excessive amount of PEG was adsorbed.

[0133] As can be seen from Examples 1, 3, and 4, PP-T / CMF / PEG-97 possesses both excellent leak resistance and heat storage capacity, specifically in the following two aspects:

[0134] 1. By utilizing the hydrogen bonding between PEG and PP-T / CMF, a composite phase change material with excellent thermal stability was obtained;

[0135] 2. By utilizing the porous structure of MF, the electromagnetic shielding performance of composite phase change materials can be improved by doping with PP and TiO2.

Claims

1. A PP-T / CMF-based composite phase change material with electromagnetic wave absorption properties, characterized in that: Using polyethylene glycol (PEG6000), poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PP), tetrabutyl titanate (TBT), and melamine foam (MF) as raw materials; MF serves as the skeleton, a T / MF foam matrix is ​​obtained through hydrothermal reaction; the T / MF matrix is ​​then calcined and carbonized to obtain a T / CMF matrix; the T / CMF matrix is ​​then vacuum-impregnated with PP and freeze-dried to obtain a PP-T / CMF foam matrix; finally, PEG 6000 is vacuum-adsorbed onto the PP-T / CMF matrix to obtain a PP-T / CMF-based composite phase change material. The function of PEG 6000 is to serve as a thermal storage medium, providing thermal storage performance; The role of MF is to serve as a carrier and supporting framework for phase change materials, providing hydrogen bonding sites for TiO2 and PEDOT:PSS, and providing a conductive network framework for the material after carbonization. The role of PP is to serve as a conductive medium, to construct a conductive network that induces charge transport through aggregation, and to introduce a heterogeneous interface for multiple relaxations. The role of TBT is to serve as a precursor for TiO2, enabling the preparation of TiO2 nanoparticles via a hydrothermal reaction; the prepared TiO2 modifies the surface of MF foam, increasing the reflective surface and improving the material's wave absorption performance. The role of ammonia is to act as a pH adjuster for the hydrothermal reaction of TiO2.

2. The PP-T / CMF-based composite phase change material with electromagnetic wave absorption properties according to claim 1, characterized in that: The PP-T / CMF matrix exhibits a three-dimensional network structure, and the surface is loaded with TiO2 nanoparticles. Due to the PP loading, a small number of pores are covered by the PP-constructed film. The PP-T / CMF / PEG composite phase change material shows that PEG is completely filled inside the three-dimensional network structure of PP-T / CMF and does not cover the surface of PP-T / CMF.

3. A method for preparing a PP-T / CMF-based composite phase change material with electromagnetic wave absorption properties, characterized by the following steps: Step 1, Preparation of T / CMF: First, tetrabutyl titanate (TBT) and anhydrous ethanol are mixed to obtain a TBT solution. Then, melamine foam (MF) is impregnated in the TBT solution under certain conditions. After impregnation, 3 mL of ammonia water is added, and a hydrothermal reaction is carried out under certain conditions. After the reaction is completed, the mixture is dried to obtain the TiO2 / MF matrix, abbreviated as T / MF. Finally, the TiO2 / MF matrix is ​​calcined under certain conditions to achieve carbonization, thereby obtaining the TiO2 / C-MF matrix, abbreviated as T / CMF. Step 2, Preparation of PP-T / CMF: First, (3,4-ethylenedioxythiophene monomer): polystyrene sulfonate PEDOT:PSS aqueous solution, abbreviated as PP, dimethyl sulfoxide DMSO and sodium dodecylbenzene sulfonate SDBS are mixed to obtain a modified solution. Then, the TiO2 / C-MF matrix obtained in Step 1 is placed in the modified solution for vacuum impregnation and adsorption. After the vacuum impregnation and adsorption are completed, freeze drying is performed to obtain the PEDOT:PSS / TiO2 / C-MF foam matrix, abbreviated as PP-T / CMF. Step 3, Preparation of PP-T / CMF / PEG: Using the PP-T / CMF obtained in Step 2 and PEG6000 at a certain mass ratio, PP-T / CMF-50 is impregnated in molten PEG6000 under specific conditions to obtain a PP-T / CMF-based composite phase change material with electromagnetic wave absorption properties, abbreviated as PP-T / CMF / PEG. The material obtained in Example 1 was named PP-T / CMF / PEG-97.

4. The preparation method according to claim 3, characterized in that: In step 1, the MF is cleaned before use. The cleaning conditions are as follows: ultrasonic cleaning is performed with an ultrasonic time of 6 hours and anhydrous ethanol and deionized water as ultrasonic media. In step 1, the hydrothermal reaction conditions are: hydrothermal temperature of 180℃ and hydrothermal time of 10h. In step 1, the calcination conditions are: under nitrogen atmosphere, the calcination temperature is 400℃, and the calcination time is 1 hour.

5. The preparation method according to claim 3, characterized in that: In step 1, TBT and MF satisfy the ratio of 1.5-2.5 mL: 8 cm. 3 The soaking time is 12 hours.

6. The preparation method according to claim 3, characterized in that: In step 2, PP, DMSO, and SDBS are present in a ratio of 8-12 mL: 0.3-0.6 mL: 0.05-0.15 g, and the concentration of PP is 0.25-0.75 wt.%.

7. The preparation method according to claim 3, characterized in that: In step 3, the mass ratio of PP-T / CMF to PEG6000 is 96-98 wt.%; the vacuum impregnation conditions are an impregnation temperature of 60-100℃ and an impregnation time of 7-9h.

8. The PP-T / CMF-based composite phase change material with electromagnetic wave absorption properties according to claim 1, characterized in that: As a phase change material, PP-T / CMF / PEG has a melting temperature of 58.77-59.65℃ and a melting enthalpy of 158.64-162.05 J / g; a crystallization temperature of 34.66-36.15℃ and a crystallization enthalpy of 157.08-159.62 J / g.

9. The PP-T / CMF-based composite phase change material with electromagnetic wave absorption properties according to claim 1, characterized in that: As a microwave absorbing material, PP-T / CMF / PEG exhibits a return loss of less than -5dB across the entire wavelength range. It exhibits a return loss of less than -10dB in the S-band 2-4GHz. It exhibits a return loss of -10 to 29.54 dB in the Ku band 12-18 GHz. Electromagnetic signal attenuation reaches 90-96.8%.

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