A pva-based composite material and a method for preparing the same

Abstract

This invention discloses a PVA-based composite material and its preparation method, belonging to the field of materials technology. The product of this invention introduces specific hyperbranched polymer grafted modified nano-silica as a functional compound filler into the PVA resin matrix, which can effectively improve the overall thermal stability and corrosion resistance of the product without introducing additional chemical additives, so that it has high environmental adaptability and long service life when used as a cable insulation sheath material.

Description

Technical Field

[0001] This invention relates to the field of materials technology, specifically to a PVA-based composite material and its preparation method. Background Technology

[0002] In addition to basic electrical insulation, cable insulation sheaths also need to be stable and protective against the external environment. This requires that the materials used to manufacture cable insulation sheaths have thermal stability and corrosion resistance.

[0003] PVA (polyvinyl alcohol) is a high-volume, cold-resistant, and well-sealing plastic polymer, theoretically making it an excellent material for cable insulation sheaths. However, PVA resin itself has poor thermal stability and weak corrosion resistance. In harsh environments, its intrinsic properties will significantly deteriorate after a period of use, resulting in a short lifespan. To address this, researchers have attempted to introduce heat stabilizers, corrosion inhibitors, and other chemical additives into PVA resin to improve its performance, but this approach significantly increases production costs. Summary of the Invention

[0004] Based on the deficiencies of existing technologies, the purpose of this invention is to provide a PVA-based composite material. By introducing specific hyperbranched polymer-grafted modified nano-silica into the PVA resin matrix as a functional compound filler, the thermal stability and corrosion resistance of the overall product can be effectively improved without introducing additional chemical additives, making it more environmentally adaptable and longer in service life when used as a cable insulation sheath material.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A PVA-based composite material comprising 75-95 parts of PVA and 5-30 parts of filler;

[0007] The filler comprises hyperbranched polymerized grafted nano-silica of N,N-dihydroxyethyl-3-aminomethylpropionate.

[0008] The modified nano-silica is a surface-modified nano-silica coupled with γ-aminopropyltriethoxysilane and methyl methacrylate.

[0009] Silica is a common filler used in plastic-based materials. It is not uncommon for those skilled in the art to introduce fillers such as silica into compound formulations to adjust the rigidity and toughness balance of organic materials. In the technical solution of this invention, the inventors discovered through research and development that in PVA-based composite materials, the commonly added silica filler is specially modified. This involves pre-treating the component with special surface modification and hyperbranched polymer grafting. Firstly, the methyl ester group formed by coupling modification with the small molecule coupling agent γ-aminopropyltriethoxysilane (KH-550) and methyl methacrylate (MMA) provides the reaction initiation core for the hyperbranched monomer N,N-dihydroxyethyl-3-aminomethylpropionate. Subsequently, the N,N-dihydroxyethyl-3-aminomethylpropionate is further modified... Hyperbranched polymer grafting modification of methyl propionate (MPA) results in high compatibility between the graft and PVA resin. Therefore, the intrinsic properties of PVA resin are not degraded after the introduction of this filler. The high compatibility based on polymer modification leads to the dispersion of silica particles around the resin molecules, providing them with inorganic heat resistance. At the same time, these particles significantly inhibit the free chain movement of PVA resin molecules, achieving "surface pore closure" when corrosive media erode the surface. This also prevents excessive reduction in the overall crystallinity of the molecules, ultimately greatly improving the corrosion resistance of the product.

[0010] However, the initial silica modification is crucial in this process and must be carried out using γ-aminopropyltriethoxysilane. If other types of silane coupling agents are used, not only may they fail to effectively graft the subsequent hyperbranched polymers, but they may also cause the subsequent hyperbranched polymers to agglomerate, requiring specific selection.

[0011] Preferably, the N,N-dihydroxyethyl-3-aminomethylpropionate methyl ester is prepared by an addition reaction of methyl methacrylate and diethanolamine (DEA).

[0012] More preferably, the mass ratio of methyl methacrylate to diethanolamine is (0.8–1.2):(0.8–1.2), and the addition reaction is carried out at a temperature of 35–45°C for 6–10 days.

[0013] The AB2-type hyperbranched monomer N,N-dihydroxyethyl-3-aminomethylpropionate can be directly prepared by Michael addition reaction using MMA and DEA. However, it should be noted that, depending on the actual situation, those skilled in the art can also prepare N,N-dihydroxyethyl-3-aminomethylpropionate by other means. Based on the clear structure of the synthesized product, it is not limited to a certain preparation method under specific conditions.

[0014] Preferably, when the nano-silica undergoes coupling surface modification, the molar ratio of γ-aminopropyltriethoxysilane to methyl methacrylate is 1:(1.8-2.2).

[0015] More preferably, the mass ratio of the nano-silica to γ-aminopropyltriethoxysilane is 1:(1.8-2.2).

[0016] By introducing an appropriate amount of small molecule coupling agent for modification, in the modification stage, γ-aminopropyltriethoxysilane first acts on the surface of nano silica and introduces amino groups, which are then linked to methyl methacrylate through the amino groups, providing group sites for the subsequent formation of hyperbranched polyamine esters. If too much or too little is introduced, the subsequent hyperbranched monomer polymerization effect will be reduced, and the performance improvement and synergistic effect of the grafted modified nano silica after introduction into the product will not be ideal.

[0017] Preferably, the average particle size of the nano-silica is 10–100 nm.

[0018] More preferably, the nano-silica is hydrophobic nano-silica, such as the hydrophobic nano-silica product with a particle size of 50nm produced by Qinghe County Ruijiang Metal Materials Co., Ltd.

[0019] More preferably, the method for preparing the modified nano-silica is as follows:

[0020] Nano-silica and γ-aminopropyltriethoxysilane are dispersed in a solvent, then mixed and reacted at 90–110 °C for 10–15 h. Methyl methacrylate is then added and mixed, and the mixture is reacted at 35–45 °C for 6–10 days. After filtration, drying, and impurity removal, the modified nano-silica is obtained.

[0021] Preferably, the preparation method of the N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymer graft-modified nano-silica is as follows:

[0022] Methyl N,N-dihydroxyethyl-3-aminomethylpropionate, modified nano-silica, and p-toluenesulfonic acid were mixed and then reacted under vacuum at 55–65 °C for 0.5–1.5 h. The resulting mixture was then heated to 75–85 °C for a second reaction for 1.5–2.5 h, then heated to 95–105 °C for a third reaction for 1.5–2.5 h, and finally heated to 115–125 °C for a fourth reaction for 3.5–4.5 h. The resulting product was washed, purified, dried, and sieved to obtain the hyperbranched polymerized grafted modified nano-silica of methyl N,N-dihydroxyethyl-3-aminomethylpropionate.

[0023] More preferably, in the preparation of the hyperbranched polymer grafted modified nano-silica of N,N-dihydroxyethyl-3-aminomethylpropionate, the mass percentage of p-toluenesulfonic acid in the N,N-dihydroxyethyl-3-aminomethylpropionate, modified nano-silica, and p-toluenesulfonic acid is 0.4-0.6%.

[0024] Preferably, the mass ratio of N,N-dihydroxyethyl-3-aminomethylpropionate to modified nano-silica is (5:95) to (25:75).

[0025] More preferably, the mass ratio of N,N-dihydroxyethyl-3-aminomethylpropionate to modified nano-silica is (10:90) to (20:80).

[0026] Different amounts of grafting material and grafted material will affect the grafting efficiency, grafting amount, and product dispersion uniformity of the prepared modified inorganic components. In the hyperbranched polymerization grafting process, when the content of modified nano-silica is low, the reactant monomer will form a polymer by itself, resulting in a low molecular weight of the polymer and failing to achieve the ideal heat resistance and corrosion resistance improvement effect. As the content of nano-silica increases, the probability of heterogeneous nucleation increases, the molecular weight of the reactant increases, and the degree of performance improvement of the product also improves. However, further increasing the content of nano-silica will lead to excessively long polymer chains and excessive steric hindrance, which will affect the uniformity of the grafted polymer. Therefore, the grafting ratio within the above-mentioned preferred range is optimal.

[0027] Preferably, the PVA-based composite material comprises 75-90 parts of PVA and 10-25 parts of filler.

[0028] In addition to altering the mechanical properties of the product, the introduction of filler described in this invention, as mentioned above, also affects the crystallinity of PVA resin. The inventors have found that when the filler content is low, its introduction reduces the crystallinity of PVA resin to some extent. This is likely because the modified nano-silica contains numerous hydroxyl and quaternary ammonium groups on its surface. With high particle dispersion, these groups inhibit hydrogen bonding between PVA molecular chains, thus suppressing PVA crystallization. As the filler content increases, the overall crystallinity of the material improves. However, further increases reduce the dispersibility of inorganic particles in the material. Although the overall crystallinity further improves, the product performance may decrease. Therefore, the above-mentioned preferred ratio yields the best results.

[0029] Another object of the present invention is to provide a method for preparing the PVA-based composite material, comprising the following steps:

[0030] The components are mixed in a solution, ultrasonically dispersed, and then placed in a mold for vacuum drying to obtain the PVA-based composite material.

[0031] The preparation method of the PVA-based composite material described in this invention has simple steps, low equipment requirements, and can achieve industrial-scale production.

[0032] Preferably, the solution comprises at least one of dimethyl sulfoxide, N,N-dimethylamide, acetone, and tetrahydrofuran.

[0033] Another object of the present invention is to provide a cable insulation protective sleeve comprising the PVA-based composite material described in the present invention.

[0034] PVA-based composite materials, with their excellent insulation, cold resistance, and plasticity, have been used in various supporting components for cable production. The PVA-based composite material described in this invention, based on the introduction of special modified fillers, has significantly improved thermal stability and corrosion resistance. Therefore, it can completely replace existing PVA composite materials for the preparation of cable insulation protective sleeves. At the same time, this product does not require the introduction of additional chemical additives, resulting in low application costs and high overall benefits.

[0035] The beneficial effects of this invention are that it provides a PVA-based composite material. By introducing specific hyperbranched polymer-grafted modified nano-silica into the PVA resin matrix as a functional compound filler, the thermal stability and corrosion resistance of the overall product can be effectively improved without introducing additional chemical additives, making it more environmentally adaptable and longer in service life when used as a cable insulation sheath material. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the preparation process of N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymer grafting modified nano-silica according to the present invention.

[0037] Figure 2 The infrared comparison diagrams are of SiO2-g-HBPAE and precursor materials KH-550 and SiO2-KH550 obtained in step (1) of Example 1 of the present invention.

[0038] Figure 3 This is a scanning electron microscope image of the PVA-based composite material prepared in Example 1.

[0039] Figure 4 The thermogravimetric analysis charts for each product in Example 1 are shown, where "KH550" is the product of Example 1, "KH570" is the product of Comparative Example 1, and "IPDI" is the product of Comparative Example 2.

[0040] Figure 5The images shown are XRD test results for each product in Example 2. "15%" corresponds to the product in Example 1, "5%" corresponds to the product in Example 2, "10%" corresponds to the product in Example 3, "20%" corresponds to the product in Example 4, and "25%" corresponds to the product in Example 5.

[0041] Figure 6 The following are fluorescence test images of each product in Example 3, where "5%" corresponds to the product of Example 1, "10%" corresponds to the product of Example 6, "15%" corresponds to the product of Example 7, "20%" corresponds to the product of Example 8, "25%" corresponds to the product of Example 9, and "30%" corresponds to the product of Example 10.

[0042] Figure 7 The TGA test charts for each product in Example 5 are shown. "5wt%SiO2-g-HBPAE" corresponds to the product in Example 1, and "5wt%SiO2" corresponds to the product in Example 3. Detailed Implementation

[0043] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and comparative examples. The purpose of this description is to provide a detailed understanding of the invention, not to limit its scope. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention. Unless otherwise specified, the experimental reagents and instruments involved in the implementation of this invention are commonly used reagents and instruments.

[0044] Example 1

[0045] An embodiment of the PVA-based composite material and its preparation method according to the present invention includes the following steps:

[0046] (1) Preparation of nano-silica modified by hyperbranched polymerization of N,N-dihydroxyethyl-3-aminomethylpropionate, such as Figure 1 As shown:

[0047] (1.1) Preparation of hyperbranched polymer monomer: Weigh 20g MMA and 20g DEA and add them to a four-necked flask equipped with a thermometer, stirrer and condenser. Add 0.5wt% sodium ethoxide and keep the temperature at 40℃ for 7 days. Then remove the unreacted material by rotary evaporation in a water bath at 60℃ to obtain the hyperbranched monomer N,N-dihydroxyethyl-3-aminomethylpropionate methyl ester.

[0048] (1.2) Preparation of modified nano silica: Commercially available hydrophobic nano silica with an average particle size of 50 nm and commercially available KH-550 were placed in 95% ethanol at a mass ratio of 1:2 and ultrasonically dispersed for 30 min. Then, the mixture was stirred and reacted at 100 °C in an oil bath for 12 h. The resulting mixture was denoted as SiO2-KH550. MMA and 0.05 wt% sodium ethoxide were added, and the mixture was cooled to 40 °C and reacted for 7 days. The mixture was filtered, dried, and extracted with ethanol at 100 °C for 48 h in a Soxhlet extractor to remove impurities. The mixture was then dried at 45 °C to obtain the modified nano silica.

[0049] (1.3) Preparation of N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymer graft modified nano silica: The modified nano silica was placed in a four-necked flask equipped with a thermometer, stirrer and condenser. Hyperbranched monomer and 0.5 wt% p-toluenesulfonic acid were added. The mixture was stirred rapidly under vacuum and reacted at 60°C for 1 h to further remove unreacted substances remaining in the monomer. Then the reaction temperature was gradually increased to 80°C and reacted for 2 h. The temperature was then increased to 100°C and reacted for 2 h. Finally, the temperature was increased to 120°C and reacted for 4 h. Finally, the mixture was dried in acetone as a solvent in a Soxhlet drawer at 80°C for 48 hours to remove ungrafted homopolymer, then vacuum dried, ground and sieved to obtain the hyperbranched polymerized grafted modified nano-silica of N,N-dihydroxyethyl-3-aminomethylpropionate, denoted as SiO2-g-HBPAE; the mass ratio of N,N-dihydroxyethyl-3-aminomethylpropionate to modified nano-silica was (15:85).

[0050] Among them, KH-550, SiO2-KH550, and SiO2-g-HBPAE were subjected to infrared testing, and the results are as follows: Figure 2 As shown, it can be seen that SiO2-KH550 at 3440 cm⁻¹ -1 and 1558cm -1 The presence of stretching and shear vibration absorption peaks of NH bonds at 3388 cm⁻¹ confirms that KH-550 has been attached to the surface of nano-silica; while SiO₂-g-HBPAE shows an absorption peak at 3388 cm⁻¹. -1 The stretching vibration of the associated OH group of the primary hydroxyl group appeared at 1725 cm⁻¹. -1 The presence of stretching vibration absorption of esters indicates that hyperbranched polymers were successfully grafted onto the surface of modified nano-silica.

[0051] (2) Preparation of PVA-based composite material: 5 parts (100 parts) of hyperbranched polymerized grafted modified nano-silica and 95 parts of polymer matrix PVA (PVA117 produced by Kuraray Co., Ltd., Japan) were mixed in a 10% wt% dimethyl sulfoxide solution. The resulting mixture was ultrasonically dispersed for 0.5 h, then stirred at 1000 rpm for 2 h at 80 °C. Finally, the mixture was poured into a 20×80×5 mm silicone rubber mold and dried under forced air at 60 °C for 24 h, followed by vacuum drying at 100 °C for 48 h to obtain the PVA-based composite material. The product was observed under a scanning electron microscope. Figure 3 As shown, the material does not exhibit obvious agglomeration, and the compatibility and dispersion uniformity of the PVA resin and filler are high.

[0052] Example 2

[0053] An embodiment of the PVA-based composite material and its preparation method described in this invention differs from Example 1 only in that, in step (1.3), the mass ratio of N,N-dihydroxyethyl-3-aminomethylpropionate to modified nano-silica is (5:95).

[0054] Example 3

[0055] An embodiment of the PVA-based composite material and its preparation method described in this invention differs from Example 1 only in that, in step (1.3), the mass ratio of N,N-dihydroxyethyl-3-aminomethylpropionate to modified nano-silica is (10:90).

[0056] Example 4

[0057] An embodiment of the PVA-based composite material and its preparation method described in this invention differs from Example 1 only in that, in step (1.3), the mass ratio of N,N-dihydroxyethyl-3-aminomethylpropionate to modified nano-silica is (20:80).

[0058] Example 5

[0059] An embodiment of the PVA-based composite material and its preparation method described in this invention differs from Example 1 only in that, in step (1.3), the mass ratio of N,N-dihydroxyethyl-3-aminomethylpropionate to modified nano-silica is (25:75).

[0060] Example 6

[0061] An embodiment of the PVA-based composite material and its preparation method described in this invention differs from Example 1 only in that, in step (2), 10 parts of N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymerized grafted modified nano-silica are used, and 90 parts of the polymer matrix PVA are used.

[0062] Example 7

[0063] An embodiment of the PVA-based composite material and its preparation method described in this invention differs from Example 1 only in that, in step (2), 15 parts of N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymerized grafted modified nano-silica are used, and 85 parts of the polymer matrix PVA are used.

[0064] Example 8

[0065] An embodiment of the PVA-based composite material and its preparation method described in this invention differs from Example 1 only in that, in step (2), 20 parts of N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymerized grafted modified nano-silica are used, and 80 parts of the polymer matrix PVA are used.

[0066] Example 9

[0067] An embodiment of the PVA-based composite material and its preparation method described in this invention differs from Example 1 only in that, in step (2), 25 parts of N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymerized grafted modified nano-silica are used, and 75 parts of the polymer matrix PVA are used.

[0068] Example 10

[0069] An embodiment of the PVA-based composite material and its preparation method described in this invention differs from Example 1 only in that, in step (2), 30 parts of N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymerized grafted modified nano-silica are used, and 70 parts of the polymer matrix PVA are used.

[0070] Comparative Example 1

[0071] A PVA-based composite material and its preparation method differ from Example 1 only in that the commercially available KH-550 is replaced with commercially available KH-570 (γ-(isobutyryloxy)propyltrimethoxysilane).

[0072] Comparative Example 2

[0073] A PVA-based composite material and its preparation method are disclosed, differing from Example 1 only in that the commercially available KH-550 is replaced with commercially available isophorone diisocyanate (IPDI).

[0074] Comparative Example 3

[0075] A PVA-based composite material and its preparation method, the preparation method comprising the following steps:

[0076] Five parts of commercially available hydrophobic nano-silica with an average particle size of 50 nm and 85 parts of polymer matrix PVA (PVA 117 produced by Kuraray Co., Ltd., Japan) were mixed in a 10% wt% dimethyl sulfoxide solution of the polymer matrix. The resulting mixture was ultrasonically dispersed for 0.5 h, stirred at 1000 rpm at 80 °C for 2 h, and finally poured into a 20×80×5 mm silicone rubber mold. The mixture was then dried in a forced-air dryer at 60 °C for 24 h and in a vacuum dryer at 100 °C for 48 h to obtain the PVA-based composite material.

[0077] Comparative Example 4

[0078] A PVA-based composite material and its preparation method differ from Example 1 only in that the nano-silica is not modified and is directly prepared by hyperbranched polymerization grafting of N,N-dihydroxyethyl-3-aminomethylpropionate according to step (1.3).

[0079] Example 1

[0080] To verify the specificity of the silane coupling agent used in the preparation of the hyperbranched polymerization grafted modified nano-silica of N,N-dihydroxyethyl-3-aminomethylpropionate described in this invention, thermogravimetric analysis was performed on the N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymerization grafted modified nano-silica obtained in Example 1, Comparative Example 1, and Comparative Example 2. The results are as follows: Figure 4 As shown, compared to KH-550 used in Example 1, the product prepared by the commonly used silane coupling agent KH-570 in Comparative Example 1 exhibits extremely low thermal weight loss under the 800℃ test conditions. This indicates that the actual content of hyperbranched polymer in this product is relatively low, and the monomer reaction polymerization grafting rate is low during the reaction process. This fully demonstrates that different silane coupling agents have different activities for the subsequent hyperbranched polymer grafting reaction. In contrast, the product of Comparative Example 2 has a higher thermal weight loss, indicating that this coupling agent has the highest activity for the subsequent grafting polymerization reaction. The main reason may be that its isocyanate group has high activity.

[0081] Example 2

[0082] To verify the effect of the amount of monomer added during the preparation of the hyperbranched polymer grafted modified nano-silica of N,N-dihydroxyethyl-3-aminomethylpropionate described in this invention on the grafting effect, fluorescence tests were performed on the N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymer grafted modified nano-silica obtained in Examples 1-5. The results are as follows: Figure 5 As shown, when the relative content of modified nano-silica is low, the fluorescence intensity of the product is weak. This is mainly because when the inorganic phase content is low, the monomer undergoes self-nucleation polymerization, resulting in a low molecular weight of the hyperbranched polymer. As the proportion increases, the probability of heterogeneous nucleation in the reaction system increases, and the hyperbranched polymer formed at this time has the highest quality. As the relative proportion of monomer further decreases, a large number of inorganic particles cause steric hindrance to the product, and the quality of the hyperbranched polymer in the product begins to decline again.

[0083] Example 3

[0084] To verify the effect of the proportion of N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymer grafted modified nano-silica in the PVA-based composite material on the overall crystallinity of the material, XRD tests were performed on the products obtained in Examples 1 and 6-10, as well as the pure PVA reference standard from the raw materials used in the examples. The results are as follows: Figure 6 As shown, it can be seen that, overall, compared with pure PVA resin, the crystallinity of the material decreases after the introduction of fillers, especially when the amount of N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymer grafted modified nano-silica is low, the product has a high degree of amorphous phase; as the amount of N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymer grafted modified nano-silica increases, the crystallinity of the product improves to a certain extent.

[0085] Example of effect 4

[0086] To verify the corrosion resistance of the PVA-based composite material described in this invention, products were prepared in advance according to GB / T12683-2009 according to the methods of each embodiment and comparative example, and the tensile strength was tested using a tensile testing machine. Subsequently, the products were immersed in commercially available industrial-grade lubricating oil for 30 minutes, the surface impregnation oil was cleaned off, and the products were left to stand for 10 days. The tensile strength was then tested using the same method, and the tensile strength retention rate after immersion was calculated. The results are shown in Table 1.

[0087] Table 1

[0088] product Tensile strength retention rate (%) Example 1 95 Example 2 92 Example 3 93 Example 4 95 Example 5 92 Example 6 96 Example 7 98 Example 8 98 Example 9 95 Example 10 93 Comparative Example 1 85 Comparative Example 2 88 Comparative Example 3 83 Comparative Example 4 84

[0089] The test results show that the product of this invention has good corrosion resistance when dealing with some common external corrosive media in cable insulation protection materials. After corrosion, the mechanical properties can be maintained at more than 90%. According to the products in Examples 1 to 5 and Examples 6 to 10, it can be seen that in the product, both the graft loading of methyl N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymer grafted modified nano-silica during preparation and the proportion of methyl N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymer grafted modified nano-silica in the product are optimal when the amount is moderate, so that the product can maintain better corrosion resistance. In contrast, as described above, Comparative Examples 1 and 2 showed different results. Comparative Example 1 exhibited a low grafting rate and low corrosion resistance due to the hyperbranched polymerization of N,N-dihydroxyethyl-3-aminomethylpropionate grafted onto nano-silica. While Comparative Example 2 had a high grafting rate, the uniformity of the N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched onto nano-silica prepared by this reaction was not good, resulting in a final product performance retention rate of less than 90%. Comparative Example 3, a common nano-silica composite PVA material, performed significantly worse than the product in Example 1 with the same amount of inorganic filler. Comparative Example 4, which was not modified with a silane coupling agent before grafting the hyperbranched polymer, also showed poor grafting results with excessive self-nucleation polymerization of monomers, resulting in a final product corrosion resistance comparable to Comparative Example 3.

[0090] Example 5

[0091] To verify the thermal stability of the PVA-based composite material described in this invention, TGA analysis was performed on Example 1, Comparative Example 3, and pure PVA. Figure 7 As shown, compared to pure PVA products and Comparative Example 3 products which only conventionally introduce the same amount of unmodified nano-silica, the product of Example 1 has less thermal weight loss, and the weight loss peak appears later in the order of the peak. This fully demonstrates that the thermal stability of the product is significantly improved after the introduction of N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymer graft-modified nano-silica as described in this invention.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the present invention.

Claims

1. A corrosion-resistant cable insulation protective sleeve, characterized in that, The invention includes a PVA-based composite material, wherein the PVA-based composite material comprises 80-90 parts of PVA and 10-20 parts of filler; The filler includes hyperbranched polymerized grafted modified nano-silica of N,N-dihydroxyethyl-3-aminomethylpropionate; the mass ratio of N,N-dihydroxyethyl-3-aminomethylpropionate to modified nano-silica is (10:90) to (20:80). The N,N-dihydroxyethyl-3-aminomethylpropionate methyl methacrylate is prepared by an addition reaction of methyl methacrylate and diethanolamine; the mass ratio of methyl methacrylate to diethanolamine is (0.8~1.2):(0.8~1.2), and the addition reaction is carried out at a temperature of 35~45℃ for 6~10 days. The modified nano-silica is a surface-modified nano-silica coupled with γ-aminopropyltriethoxysilane and methyl methacrylate; when the nano-silica is subjected to coupling surface modification, the molar ratio of γ-aminopropyltriethoxysilane and methyl methacrylate is 1:(1.8~2.2). The method for preparing the modified nano-silica is as follows: Nano-silica and γ-aminopropyltriethoxysilane are dispersed in a solvent, then mixed and reacted at 90-110℃ for 10-15h, methyl methacrylate is added and mixed, and reacted at 35-45℃ for 6-10d. After filtration, drying and impurity removal, the modified nano-silica is obtained. The preparation method of the N,N-dihydroxyethyl-3-aminomethylpropionate hyperbranched polymer graft modified nano-silica is as follows: Methyl N,N-dihydroxyethyl-3-aminomethylpropionate, modified nano-silica, and p-toluenesulfonic acid were mixed and then reacted under vacuum at 55-65°C for 0.5-1.5 h. The resulting mixture was then heated to 75-85°C for a second reaction for 1.5-2.5 h, then heated to 95-105°C for a third reaction for 1.5-2.5 h, and finally heated to 115-125°C for a fourth reaction for 3.5-4.5 h. The resulting product was washed, purified, dried, and sieved to obtain the hyperbranched polymerized grafted modified nano-silica of methyl N,N-dihydroxyethyl-3-aminomethylpropionate. The mass percentage of p-toluenesulfonic acid in the methyl N,N-dihydroxyethyl-3-aminomethylpropionate, modified nano-silica, and p-toluenesulfonic acid was 0.4-0.6%.

2. The corrosion-resistant cable insulation protective sleeve as described in claim 1, characterized in that, The preparation method of the PVA-based composite material includes the following steps: The components are mixed in a solution, ultrasonically dispersed, and then placed in a mold for vacuum drying to obtain the PVA-based composite material.

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