Preparation method of PVA-based foam with hydrophobic ternary synergistic surface and high interfacial compatibility

Abstract

The invention provides a preparation method of PVA-based foam with a hydrophobic ternary synergistic surface and high interfacial compatibility, and the preparation method comprises the following steps: firstly, modifying to prepare modified nano silicon dioxide, and then mixing the modified nano silicon dioxide with polydimethylsiloxane and titanium dioxide to prepare a functional coating; the preparation method comprises the following steps: modifying a PVA-based foam material with a silane coupling agent to prepare modified PVA-based foam, finally coating the modified PVA-based foam with a functional coating, and curing to obtain the multifunctional PVA-based foam. According to the invention, a polymethylsiloxane / titanium dioxide system is taken as a substrate, modified nano silicon dioxide is combined to form a soft organic-inorganic hybrid multifunctional coating, and the PVA-based foam subjected to surface modification by a silane coupling agent is cooperated, so that excellent hydrophobic performance and high interfacial compatibility are shown; meanwhile, excellent flame-retardant, antibacterial and anti-aging properties are shown.

Description

Technical Field

[0001] The present invention belongs to the technical field of multifunctional PVA-based foam materials, and relates to a preparation method of a PVA-based foam with ternary synergistic surface hydrophobicity and high interfacial compatibility. Specifically, it relates to a preparation method of a multifunctional PVA-based foam with ternary synergistic surface modification based on modified nano-silica, PDMS / TiO2 system and silane coupling agent. Background Art

[0002] With the implementation and promotion of environmental protection policies, polymer foam packaging materials are rapidly developing towards green and high-performance. PVA-based foam materials show broad prospects in the fields of packaging and medical treatment due to their environmentally friendly characteristics, good biocompatibility and excellent comprehensive mechanical properties. To achieve large-scale replacement of traditional petroleum-based foam materials, PVA-based foam materials still face severe challenges and need to conduct in-depth research on structural optimization and functional composite.

[0003] In the prior patent technology application of the present invention, "A green and environmentally friendly flame-retardant PVA composite material based on bio-based raw materials and its preparation method" (CN119039724A), the problem of difficult thermoplastic processing of PVA was successfully solved by introducing a bio-based flame-retardant system. In subsequent research, further combined with supercritical carbon dioxide foaming technology and adjusted the foaming process, the optimization of the cell structure was achieved, and an environmentally friendly flame-retardant PVA composite foam material with excellent comprehensive properties was successfully prepared, with breakthroughs in structural optimization and flame-retardant modification.

[0004] However, single-functional PVA composite materials are difficult to meet the increasingly complex packaging requirements. For example, the high hydrophilicity of PVA-based foam materials leads to serious water absorption in high-humidity environments, resulting in a decline in various performances and restricting their applications in cold-chain packaging, marine transportation packaging, etc. In addition, some food packaging also puts forward requirements for antibacterial performance. Therefore, it is still necessary to conduct multifunctional modification of PVA foam materials to expand their application fields.

[0005] The traditional functional modification method is to directly add functional fillers. This method is convenient to operate and has a simple process, but often requires a large amount of filler addition, has poor compatibility with the PVA matrix, affects the plasticization effect and foaming performance of PVA, and is difficult to effectively balance its cell structure and functionalization.

[0006] The method of constructing a functional coating on the surface of PVA by using coating technology can effectively solve the problem of poor compatibility between the PVA matrix and the filler, and does not damage its cell structure while endowing it with multifunctionality, achieving both structural optimization and functional composite at the same time. However, the interfacial compatibility between the hydrophobic coating formed by conventional hydrophobic coatings and the PVA material is poor, which easily leads to defects such as physical delamination and coating peeling. Summary of the Invention

[0007] In order to solve the problems in the above-mentioned prior art, the present invention provides a method for preparing a PVA-based foam with a ternary synergistic surface hydrophobicity and high interface compatibility. The method is based on a polymethylsiloxane (PDMS) / titanium dioxide (TiO2) system, combined with modified nano-silica to form a soft organic-inorganic hybrid multifunctional coating, and the PVA-based foam surface-modified by a silane coupling agent exhibits excellent hydrophobicity and high interface compatibility, and at the same time exhibits excellent flame retardant, antibacterial and anti-aging properties, which proposes a new idea for taking into account the functional composite and structural optimization of PVA-based foam materials.

[0008] To achieve the above objectives, the present invention is implemented by adopting a technical solution consisting of the following technical measures.

[0009] The present invention provides a method for preparing a ternary synergistic surface hydrophobic PVA-based foam with high interfacial compatibility, which mainly comprises the following steps:

[0010] (1) Based on The modified nano-silicon dioxide is prepared by the method of modification:

[0011] 8-10 mL of tetraethoxysilane is added to 100 mL of ethanol and mixed, and then 6-8 mL of ammonia water with a concentration of 28-30% is added as a catalyst, and the mixture is stirred at room temperature for at least 12 hours; after the time is up, 4-6 mL of trimethylethoxysilane is added and mixed evenly, and the mixture is stirred and reacted for at least 12 hours. After the time is up, the mixture is separated, washed, and dried in sequence to obtain modified nano-silica;

[0012] (2) Prepare the following raw materials by weight:

[0013] 10 parts of polydimethylsiloxane,

[0014] 0.5 to 1.5 parts of titanium dioxide,

[0015] 0.5-1.5 parts of modified nano silicon dioxide;

[0016] Mix the prepared raw materials, add the curing agent and mix evenly, and then use it as a functional coating;

[0017] (3) The PVA-based foam material is modified by coating with a silane coupling agent KH570 to prepare a PVA-based foam with surface methacryloyloxy functionalization modification;

[0018] (4) coating the functional coating obtained in step (2) on the PVA-based foam with surface methacryloyloxy functionalization modified obtained in step (3), and obtaining a multifunctional PVA-based foam with ternary synergistic surface hydrophobicity and high interface compatibility after curing.

[0019] In this text, in step (3), the PVA-based foam material is coated and modified with the silane coupling agent KH570 to prepare a PVA-based foam with surface methacryloxy-functionalized modification. Among them, using the silane coupling agent KH570 to modify PVA is a conventional modification method in the art, and the specific modification conditions and operations can all refer to the instructions of the silane coupling agent or the records in the existing technical literature.

[0020] To better illustrate the present invention and provide a technical solution for reference, in step (3), the method for preparing a PVA-based foam with surface methacryloxy-functionalized modification by coating and modifying the PVA-based foam material with the silane coupling agent KH570 is as follows:

[0021] Prepare an aqueous solution of KH570 with a mass percentage of 10%, spray it onto the surface of the PVA-based foam material after sufficient dispersion, and then let it stand for 3 to 5 minutes at a temperature of 60 to 80 °C, thus preparing a PVA-based foam with surface methacryloxy-functionalized modification.

[0022] In this text, the PVA-based foam material described in step (3) can be a commercially available foam material or can be obtained by self-preparation.

[0023] In one technical solution, in order to finally obtain a multifunctional PVA-based foam with better flame retardancy, the PVA-based foam material described in step (3) is a PVA-based foam material obtained by supercritical CO2 foaming of the green and environmentally friendly flame retardant PVA composite material provided in the inventor's previously published patent application "A Green and Environmentally Friendly Flame Retardant PVA Composite Material Based on Biomass as Raw Material and Its Preparation Method" (CN119039724A).

[0024] The preparation method of the above green and environmentally friendly flame retardant PVA composite material includes the following steps:

[0025] ① Weigh the following raw material components according to parts by weight:

[0026] 100 parts of PVA,

[0027] 20 - 30 parts of water,

[0028] 5 - 10 parts of phytic acid;

[0029] ② After mixing the raw material components in step ① evenly, perform sealed plasticization treatment at a temperature of 50 - 70 °C for at least 72 h to obtain plasticized PVA;

[0030] ③ Mix the plasticized PVA obtained in step ② evenly with 5 - 10 parts of lignin, and then prepare a green and environmentally friendly flame retardant PVA composite material through thermoplastic processing.

[0031] In this article, the curing agent in step (2) is a curing agent commonly used in conjunction with polydimethylsiloxane (PDMS) in the art, and a person skilled in the art can select a suitable initiator according to actual needs. For example, the curing agent includes any one or more compound mixtures of dimethyl methyl hydrogen (siloxane and polysiloxane) (CAS: 68037-59-2), monovinyl-terminated dimethyl (siloxane and polysiloxane) (CAS: 68083-19-2), and vinyl MQ resin mixture (CAS: 68988-89-6); the amount of the curing agent added is 5 to 15% of the mass of polydimethylsiloxane.

[0032] Herein, the coating follows the conventional coating method of coating in the chemical industry, such as spraying, brushing, or dipping, and the specific coating rate follows the use of conventional hydrophobic coatings.

[0033] Herein, the uniform mixing is a conventional process in the art, for example, the components are dispersed and mixed uniformly by mechanical stirring such as a high-speed rotating mixer.

[0034] In this article, the separation, washing and drying all follow the conventional principles in chemical processes, and those skilled in the art can perform specific operations based on common knowledge.

[0035] The present invention has the following beneficial effects:

[0036] (1) The present invention provides a method for preparing a ternary synergistic surface hydrophobic PVA-based foam with high interface compatibility, which is based on a polymethylsiloxane (PDMS) / titanium dioxide (TiO2) system, combined with modified nano-silica to form a soft organic-inorganic hybrid multifunctional coating, and synergistically with the PVA-based foam whose surface is modified by a silane coupling agent, showing excellent hydrophobic properties and high interface compatibility.

[0037] (2) In one of the technical solutions, the green and environmentally friendly flame-retardant PVA composite material provided by the inventor in the prior patent application "A green and environmentally friendly flame-retardant PVA composite material with bio-based raw materials and its preparation method" (CN119039724A) is prepared by supercritical CO2 foaming to obtain a PVA-based foam material as a raw material, so that the multifunctional PVA-based foam finally prepared exhibits excellent flame retardant, antibacterial and anti-aging properties, which proposes a new idea for taking into account the functional composite and structural optimization of PVA-based foam materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1Infrared spectra (a) and XRD spectra (b) of the modified nano-silica obtained in the embodiments of the present invention and the nano-silica obtained in Comparative Example 1.

[0039] Figure 2 XPS spectra of the modified nano-silica obtained in the embodiments of the present invention and the nano-silica obtained in Comparative Example 1. Among them, Figure (a) is the full XPS spectrum, Figure (b) is the XPS sub-spectrum of Si 2p, and Figure (c) is the XPS sub-spectrum of C1s.

[0040] Figure 3 TEM images of the modified nano-silica (b) obtained in the embodiments of the present invention and the nano-silica (a) obtained in Comparative Example 1.

[0041] Figure 4 SEM images and X-ray energy spectrum surface distribution analysis diagrams at the interface between the coating and the substrate in the samples prepared in Example 3 of the present invention and Comparative Example 2. Among them, Figure (a) is the SEM image at the interface between the coating and the substrate in the sample of Example 3; Figure (a1) is the X-ray energy spectrum surface distribution analysis diagram of Si element at the interface in the sample of Example 3; Figure (a2) is the X-ray energy spectrum surface distribution analysis diagram of O element at the interface in the sample of Example 3; Figure (b) is the SEM image at the interface between the coating and the substrate in the sample of Comparative Example 2.

[0042] Figure 5 Diagram of the water contact angle test results of the samples prepared in Examples 1-3 and Comparative Example 1 of the present invention.

[0043] Among them, Figure (a) is the diagram of the water contact angle test results of the PVA-based foam material before surface modification in step (3) of the example; Figure (b) is the diagram of the water contact angle test results of the comparative sample prepared in Comparative Example 1; Figure (c) is the diagram of the water contact angle test results of the sample prepared in Example 1; Figure (d) is the diagram of the water contact angle test results of the sample prepared in Example 2; Figure (e) is the diagram of the water contact angle test results of the sample prepared in Example 3.

[0044] Figure 6 Dot-line diagram of the comparison of the peak area intensity of CO2 released during the in-situ aging experiment of the intermediate PVA-based foam material and the final multi-functional PVA-based foam in Example 3 of the present invention. Detailed implementation manners

[0045] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the invention. Those skilled in the art can draw on the content of this article and appropriately modify the process parameters to achieve. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The methods and applications of the present invention have been described through preferred embodiments, and those related can obviously make changes or appropriate alterations and combinations to the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention. Although it is believed that those of ordinary skill in the art are fully aware of the following terms, the following definitions are still stated to help illustrate the subject matter disclosed by the present invention.

[0046] The present invention provides a method for preparing a PVA-based foam with ternary synergistic surface hydrophobicity and high interfacial compatibility, mainly including the following steps:

[0047] (1) Modify the nano-silica prepared by the method to obtain modified nano-silica:

[0048] Add 8-10 mL of tetraethoxysilane to 100 mL of ethanol and mix, then add 6-8 mL of ammonia water with a concentration of 28-30% as a catalyst, and stir and react at room temperature for at least 12 h; after the time reaches, add 4-6 mL of trimethylethoxysilane and mix evenly, then continue to stir and react for at least 12 h. After the time reaches, obtain the modified nano-silica through separation, washing, and drying in sequence;

[0049] (2) Prepare the following raw materials by mass parts:

[0050] Polydimethylsiloxane 10 parts,

[0051] Titanium dioxide 0.5-1.5 parts,

[0052] Modified nano-silica 0.5-1.5 parts;

[0053] Mix the prepared raw materials, add a curing agent and mix evenly, and reserve as a functional coating;

[0054] (3) Coating and modifying the PVA-based foam material with the silane coupling agent KH570 to obtain a surface methacryloyloxy-functionalized modified PVA-based foam;

[0055] (4) Coating the functional coating obtained in step (2) onto the surface methacryloyloxy-functionalized modified PVA-based foam obtained in step (3), and after curing, a ternary synergistic surface-hydrophobic and highly interfacially compatible multifunctional PVA-based foam can be obtained.

[0056] In this article, the surface methacryloyloxy-functionalized modified PVA-based foam is prepared by coating and modifying the PVA-based foam material with the silane coupling agent KH570 in step (3). Among them, using the silane coupling agent KH570 to modify PVA is a conventional modification method in the field, and its specific modification conditions and operations can all refer to the instructions of the silane coupling agent or the records in the existing technical literature.

[0057] To better illustrate the present invention and provide a reference implementation method, the specific method for preparing the surface methacryloyloxy-functionalized modified PVA-based foam by coating and modifying the PVA-based foam material with the silane coupling agent KH570 in step (3) is as follows:

[0058] Prepare an aqueous solution of KH570 with a mass percentage of 10%, spray it onto the surface of the PVA-based foam material after sufficient dispersion, and then let it stand at a temperature of 60 - 80 °C for 3 - 5 minutes to prepare the surface methacryloyloxy-functionalized modified PVA-based foam.

[0059] In this article, the PVA-based foam material described in step (3) can be a commercially available foam material or can be self-made.

[0060] In one of the implementation methods, in order to finally obtain a multifunctional PVA-based foam with better flame retardant performance, the PVA-based foam material described in step (3) is the PVA-based foam material obtained by supercritical CO2 foaming of the green and environmentally friendly flame retardant PVA composite material provided in the inventor's previously published patent application "A Green and Environmentally Friendly Flame Retardant PVA Composite Material Based on Biomass and Its Preparation Method" (CN119039724A).

[0061] The preparation method of the above green and environmentally friendly flame retardant PVA composite material includes the following steps:

[0062] ① Prepare the following raw material components by weight:

[0063] 100 parts of PVA,

[0064] 20 - 30 parts of water,

[0065] 5 - 10 parts of phytic acid;

[0066] ② After mixing the raw material components in step ① evenly, perform a sealing and plasticizing treatment at a temperature of 50 - 70 °C for at least 72 h to obtain the plasticized PVA;

[0067] ③ Mix the plasticized PVA obtained in step ② with 5 - 10 parts of lignin evenly, and then prepare the green and environmentally friendly flame-retardant PVA composite through thermoplastic processing.

[0068] In this article, the curing agent described in step (2) is the curing agent commonly used in this technical field in combination with polydimethylsiloxane (PDMS). Those skilled in the art of this technical field can select a suitable initiator according to actual needs. For example, the selected curing agent includes any one or a compound mixture of dimethylmethylhydrogen (siloxane and polysiloxane) (CAS: 68037 - 59 - 2), dimethyl (siloxane and polysiloxane) capped with monovinyl (CAS: 68083 - 19 - 2), vinyl MQ resin mixture (CAS: 68988 - 89 - 6); the addition amount of the curing agent is 5 - 15% of the mass of polydimethylsiloxane.

[0069] In this article, the coating follows the conventional coating methods of coatings in the chemical industry field. In one of the embodiments, for example, one of spraying, brushing, and dipping methods, and its specific coating rate follows the use of conventional hydrophobic coatings.

[0070] In this article, the term "mix evenly" refers to a conventional process method in this field. In one of the embodiments, for example, mechanical stirring methods such as through a high-speed rotating mixer are used to disperse and mix each component evenly.

[0071] In this article, the separation, washing, and drying all follow the conventional principles in chemical engineering processes, and those skilled in the art can perform specific operations according to common knowledge.

[0072] The following will further explain this application with reference to the embodiments. However, those skilled in the art should understand that these embodiments are provided only for the purpose of illustration and are not intended to limit this application.

[0073] Embodiments

[0074] The following will describe the implementation schemes of this application in detail in combination with the embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate this application and should not be regarded as limiting the scope of this application. For those embodiments where specific conditions are not indicated, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase. This application should not be construed as being limited by the specific embodiments described.

[0075] 1. Raw materials

[0076]

[0077] 2. Preparation method

[0078] (1) Modify the nano-silica prepared by method to obtain modified nano-silica:

[0079] Add 8 mL of tetraethoxysilane to 100 mL of ethanol and mix. Then add 6 mL of ammonia water as a catalyst and stir at room temperature for 12 h with a stirring speed of 300 rpm. After the time is up, add 4 mL of trimethylethoxysilane and mix evenly, then continue to stir for 12 h. After the time is up, centrifuge to obtain a precipitate. The precipitate is washed with ethanol and centrifuged again. After repeating three times, it is dried to obtain modified nano-silica, denoted as mNano-SiO2;

[0080] (2) Prepare the following raw materials:

[0081] 10 g of polydimethylsiloxane,

[0082] 1 g of titanium dioxide,

[0083] 0.5 - 1.5 g of modified nano-silica;

[0084] Mix the prepared raw materials by ultrasonic stirring, and add the supporting curing agent when purchasing polydimethylsiloxane and mix evenly, then reserve it as a functional coating;

[0085] The supporting curing agent when purchasing polydimethylsiloxane is a compound mixture composed of dimethylmethylhydrogen (siloxane and polysiloxane) (CAS: 68037 - 59 - 2), dimethyl (siloxane and polysiloxane) capped with monovinyl (CAS: 68083 - 19 - 2), and vinyl MQ resin mixture (CAS: 68988 - 89 - 6); the addition amount of the curing agent is 10% of the mass of polydimethylsiloxane.

[0086] (3) Prepare 10 mL of KH570 aqueous solution with a mass percentage of 10%. After sufficient dispersion, spray it onto the surface of a 10×10 cm PVA-based foam material, and then let it stand at 60 - 80 °C for 3 - 5 minutes to obtain a PVA-based foam with surface methacryloyloxy-functionalized modification;

[0087] The PVA-based foam material is the PVA-based foam material obtained by supercritical CO2 foaming of the green and environmentally friendly flame-retardant PVA composite material provided in the inventor's prior publicly disclosed patent application "A Green and Environmentally Friendly Flame-Retardant PVA Composite Material Based on Biomass as Raw Material and Its Preparation Method" (CN119039724A), and its preparation method is as follows:

[0088] ① By weight, prepare the following raw material components:

[0089] 100 parts of PVA,

[0090] 20 parts of water,

[0091] 10 parts of phytic acid;

[0092] ② After mixing the raw material components in step ① evenly, perform sealed plasticization treatment at 60 °C for 72 h to obtain plasticized PVA;

[0093] ③ Mix the plasticized PVA obtained in step ② with 5 parts of lignin evenly as a mixture, and perform thermoplastic processing using a flat vulcanizing instrument. The specific process parameters are: add the mixture to the mold frame, first pre-press at 165 °C and 5 Mpa for 3 - 5 minutes, increase the pressure to 10 Mpa, stop heat preservation after holding the pressure for 3 minutes, keep the pressure and let it cool naturally. After cooling, obtain a green environmental protection flame-retardant PVA composite material;

[0094] ④ Prepare the PVA-based foam material, denoted as Foam, from the green environmental protection flame-retardant PVA composite material obtained in step ③ by supercritical CO2 foaming;

[0095] Among them, the process parameters of the supercritical CO2 foaming are: impregnation temperature is 45 °C, impregnation pressure is 10 MPa, impregnation time is 2 h, and foaming temperature is 185 °C; finally, prepare a PVA-based foam material with an average cell size of 37.8 μm and a cell density of 2.21×10 7 cells / cm 3 , and the specific compressive strength of the foam is 8.1×10 3 Nm / kg;

[0096] (4) Spray the functional coating obtained in step (2) on the surface of the PVA-based foam with surface methacryloyloxy functionalization modification obtained in step (3) with a size of 10×10 cm, and cure at 60 °C for 24 h to obtain a ternary synergistic surface-hydrophobic and highly interfacially compatible multifunctional PVA-based foam.

[0097] 3. Test methods

[0098] X-ray diffraction test (XRD): Use an Ultima IV type X-ray powder diffractometer (Rigaku, Japan) to test the modified nano-silica. The test uses a CuKα target, the scanning angle 2θ range is 2 - 90°, and the scanning speed is 5° / Min.

[0099] Fourier transform infrared spectroscopy analysis: Use a Thermo Fisher Scientific FT-IR spectrometer (FT-IS10 type, USA) to test the modified nano-silica in the wavenumber range of 400 - 4000, scanning times: 32 times, scanning accuracy: 4 cm -1 .

[0100] Scanning electron microscopy (SEM): The morphology of the modified nano-silica and the adhesion of the coating to the foam groups were observed using a JSM-5900LV scanning electron microscope from JEOL, Japan. The samples were treated by liquid nitrogen embrittlement and surface sputtering before testing.

[0101] Transmission electron microscopy (TEM): The morphology and surface element distribution of the nano-silica microspheres before and after modification were observed using a JEM-1400Flash transmission electron microscope (Japan).

[0102] Elemental content analysis (EDS): The elemental distribution of the modified nano-silica was analyzed using an Octane Elect Super energy spectrometer from EDAX, USA.

[0103] X-ray photoelectron spectroscopy (XPS): The chemical structure of the modified nano-silica was analyzed using an XSAM800 electron spectrometer from Kratos, UK. The X-ray source was Al, the scanning atomic energy (Binding energy) range was 1100.00 eV - 0.00 eV, and the scanning speed was 150 ms / 0.65 eV.

[0104] Ultraviolet absorption test: The ultraviolet absorbance of the samples was measured using a UV-3600 ultraviolet-visible-near-infrared spectrophotometer from Shimadzu, Japan. The test wavelength range was 240 nm - 400 nm.

[0105] Water contact angle test: The water contact angle of the samples was measured using a DSA25 optical contact angle measuring instrument from Kruss Instrument, Germany.

[0106] Example 1

[0107] Example 1 was prepared according to the above "2. Preparation method", where 0.5 g of the modified nano-silica was used in step (2), and finally a ternary synergistic surface-hydrophobic and highly interfacially compatible multifunctional PVA-based foam was prepared as a sample, denoted as Foam@mFC1.

[0108] Example 2

[0109] Example 2 was prepared according to the above "2. Preparation method", where 1 g of the modified nano-silica was used in step (2), and finally a ternary synergistic surface-hydrophobic and highly interfacially compatible multifunctional PVA-based foam was prepared as a sample, denoted as Foam@mFC2.

[0110] Example 3

[0111] Example 3 was prepared according to the above "2. Preparation method", where 1.5 g of modified nano-silica was used in step (2), and finally a ternary synergistic surface-hydrophobic and highly interfacially compatible multifunctional PVA-based foam was prepared as a sample, denoted as Foam@mFC3.

[0112] Comparative Example 1

[0113] Comparative Example 1 was prepared by referring to the above "2. Preparation method", but directly used the nano-silica prepared by the method without modification, that is, trimethylethoxysilane was not added in step (1). The prepared nano-silica was denoted as Nano-SiO2, and this nano-silica was used to replace the modified nano-silica in the subsequent steps; 1.5 g of nano-silica was used in step (2), and finally a PVA-based foam was prepared as a comparative sample, denoted as Foam@FC.

[0114] Comparative Example 2

[0115] Comparative Example 2 was prepared by referring to the above "2. Preparation method", where 1.5 g of modified nano-silica was used in step (2), but in step (3), the PVA-based foam material was not coated and modified with the silane coupling agent KH570, that is, the un-surface-modified PVA-based foam material was directly used in step (4), and finally a PVA-based foam was prepared as a comparative sample.

[0116] 4. Test Results

[0117] Through infrared and XRD tests, Nano-SiO2 and mNano-SiO2 were characterized and analyzed, as Figure 1 shown. The infrared spectra of Nano-SiO2 and mNano-SiO2 both showed obvious SiO2 characteristic peaks. At 1092 cm -1 and 795 cm -1 corresponded to the asymmetric stretching vibration and symmetric stretching vibration of Si-O-Si respectively, and at 960 cm -1 corresponded to the stretching vibration peak of Si-OH, which confirmed the synthesis of nano-silica particles. In addition, the peak intensity of -CH3 in mNano-SiO2 was significantly higher than that in Nano-SiO2, and the peak intensity of -OH at 3400 cm -1 and the peak intensity of Si-OH at 960 cm -1 in mNano-SiO2 were significantly lower than those in Nano-SiO2, indicating that the introduction of TMES reduced the hydroxyl groups on the surface of SiO2 and increased the methyl groups, which confirmed the successful modification of SiO2. In the XRD spectra, the 2θ angles of Nano-SiO2 and mNano-SiO2 did not shift, but their peak intensities changed.

[0118] XPS tests were further carried out on Nano-SiO2 and mNano-SiO2 to analyze and compare the modification of mNano-SiO2, such as Figure 2 shown. In the XPS full spectrum, the peak intensity of C1s in mNano-SiO2 is significantly higher than that in Nano-SiO2, confirming the introduction of methyl groups after modification. In addition, peak fitting was performed on Si 2p and C1s. New Si-C peaks appeared in both Si 2p and C1s of the modified silica, further confirming the methylation of hydroxyl groups and indicating the synthesis of modified nano-silica.

[0119] The morphology and surface elements of the nano-silica particles before and after modification were analyzed by TEM. The modified nano-silica particles were more evenly dispersed, with a wider particle size distribution. The EDS test results showed that the Si element on the surface was less dense than that of the unmodified one, and the C element could not form a particulate morphology distribution, confirming that its surface was covered by C-containing methyl groups, which was difficult to identify due to its compatibility with the C element content in the background. Since there was no C element on the surface of the unmodified nano-silica, a clear C element difference was shown, further confirming the successful modification of TMES.

[0120] In Example 3 and Comparative Example 2, the functional coating was sprayed onto the KH570-pretreated and untreated PVA-based foam materials, and SEM tests were performed on the interface to analyze the compatibility and adhesion at the interface, such as Figure 4 shown. The coating pretreated with KH570 was closely adhered to the foam phase interface, and the Si element distribution also showed an obvious boundary. However, there were obvious gaps at the interface without KH570 treatment, indicating that KH570 pretreatment could effectively improve the interface compatibility and adhesion.

[0121] The hydrophobic properties of the coating were analyzed by water contact angle (WCA) tests, such as Figure 5 shown. Figure 5 (a) shows the water contact angle test results of the PVA-based foam material before surface modification in step (3) of the example, showing high hydrophilicity and water absorption. The WCA when just dropped onto the foam surface was 47.8°, and it was completely spread and absorbed after 5 s. Figure 5(b) shows the WCA test results of the comparative sample prepared in Comparative Example 1. Its WCA increased to 81.1°. This may be because although Nano-SiO2 has hydrophilicity, it has a nano-size effect, which increases the roughness, and PDMS has a certain hydrophobic effect. Therefore, the WCA increased, but it was still lower than 90°. The samples prepared in Examples 1 to 3 showed high hydrophobic performance, which increased with the increase in the content of mNano-SiO2. The WCAs of Foam@mFC1 (c), Foam@mFC2 (d), and Foam@mFC3 (e) were 105.8°, 115.1°, and 123.2°, respectively. The sample of Example 3 showed excellent hydrophobic performance.

[0122] The aging performance of the intermediate PVA-based foam material and the final obtained multifunctional PVA-based foam in Example 3 was analyzed by in-situ aging experiments, as Figure 6 shown. The peak area intensity of CO2 released during the aging test can reflect the aging progress of the matrix. The CO2 intensity of the sample coated with the multifunctional coating decreased significantly, indicating that the coating can effectively isolate water vapor, absorb and shield ultraviolet light, protect the internal matrix from ultraviolet light irradiation, and improve the aging performance.

[0123] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A preparation method of a PVA-based foam with ternary synergistic surface hydrophobicity and high interfacial compatibility, characterized in that The main steps include: (1) Modify the preparation of nano-silica based on method to obtain modified nano-silica: 8-10 mL of tetraethoxysilane is added to 100 mL of ethanol and mixed, and then 6-8 mL of ammonia water with a concentration of 28-30% is added as a catalyst, and the mixture is stirred at room temperature for at least 12 hours; after the time is up, 4-6 mL of trimethylethoxysilane is added and mixed evenly, and the mixture is stirred and reacted for at least 12 hours. After the time is up, the mixture is separated, washed, and dried in sequence to obtain modified nano-silica; (2) Prepare the following raw materials by weight: 10 parts of polydimethylsiloxane, 0.5 to 1.5 parts of titanium dioxide, 0.5-1.5 parts of modified nano silicon dioxide; Mix the prepared raw materials, add the curing agent and mix evenly, and then use it as a functional coating; (3) The PVA-based foam material is modified by coating with a silane coupling agent KH570 to prepare a PVA-based foam with surface methacryloyloxy functionalization modification; (4) coating the functional coating obtained in step (2) on the PVA-based foam with surface methacryloyloxy functionalization modified obtained in step (3), and obtaining a multifunctional PVA-based foam with ternary synergistic surface hydrophobicity and high interface compatibility after curing.

2. The preparation method according to claim 1, wherein: In step (3), the PVA-based foam material is coated with a silane coupling agent KH570 to prepare a surface methacryloyloxy-functionalized PVA-based foam, and the specific method is as follows: A 10% by mass KH570 aqueous solution is prepared, sprayed onto the surface of the PVA-based foam material after being fully dispersed, and then allowed to stand at 60-80° C. for 3-5 minutes to prepare a surface methacryloyloxy functionalized PVA-based foam.

3. The preparation method according to claim 1, characterized in that: The PVA-based foam material in step (3) is a PVA-based foam material prepared by supercritical CO2 foaming of a green, environmentally friendly, flame-retardant PVA composite material; The preparation method of the green, environmentally friendly, flame-retardant PVA composite material comprises the following steps: ① Prepare the following raw materials by weight: PVA 100 parts, 20-30 parts water, Phytic acid 5-10 parts; ② After uniformly mixing the raw material components in step ①, seal and plasticize them at a temperature of 50-70° C. for at least 72 hours to obtain plasticized PVA; ③ The plasticized PVA obtained in step ② is uniformly mixed with 5 to 10 parts of lignin, and then subjected to thermoplastic processing to obtain a green, environmentally friendly, flame-retardant PVA composite material.

4. The preparation method according to claim 1, wherein: The curing agent in step (2) includes any one or more of dimethyl methyl hydrogen (siloxane and polysiloxane), monovinyl-terminated dimethyl (siloxane and polysiloxane), and vinyl MQ resin mixture; the added amount of the curing agent is 5-15% of the mass of the polydimethylsiloxane.

5. The multifunctional PVA-based foam prepared by the method for preparing a PVA-based foam with ternary synergistic surface hydrophobicity and high interface compatibility as claimed in claim 1.

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