PVC-based corrosion-resistant cable protection pipe and preparation process thereof

Abstract

The present application relates to chlorinated polyvinyl chloride plastic technical field, specifically to a kind of PVC system corrosion-resistant cable protection pipe and preparation process thereof.The present application aims to solve the problem that the mechanical properties and corrosion resistance of existing PVC system cable protection pipe cannot be considered simultaneously.The present application obtains matrix resin by mixing chlorinated polyvinyl chloride and polyvinyl chloride, adds corrosion-resistant additives, composite flame retardant, toughening agent and other additives to obtain cable protection pipe;Corrosion-resistant additives are obtained by grafting modified nano-silica with epoxy resin, and are premixed with ethylene-vinyl alcohol copolymer;Composite flame retardant includes core layer of nitrogen, phosphorus and inorganic hydroxide, and shell layer of acrylate polymer, and is obtained by core-shell reaction;Through multi-step mixing process, cable protection pipe is prepared;Through the introduction of core-shell structure and corrosion-resistant additives, efficient flame retardation and corrosion resistance are realized at the same time, and through flexible shell layer stress buffering, the mechanical properties of the material are maintained.

Description

Technical Field

[0001] This invention relates to the field of chlorinated polyvinyl chloride plastics technology, specifically to a PVC-based corrosion-resistant cable protection pipe and its preparation process. Background Technology

[0002] Cable protection pipes are an indispensable infrastructure in power and communication engineering, used to protect cables from mechanical damage and chemical corrosion from the external environment. In the current technology, polyvinyl chloride (PVC) is widely used to manufacture such pipes due to its low cost, easy processing and inherent flame retardancy. However, as the application environment becomes increasingly harsh, the performance defects of traditional PVC pipes are becoming more and more prominent.

[0003] Insufficient mechanical properties are the main problem limiting the application of PVC in pipes. Ordinary PVC materials themselves have shortcomings such as insufficient toughness and poor impact resistance. In addition, in order to meet fire safety requirements, a large amount of flame retardant is usually added to PVC. However, these inorganic or organic small molecule flame retardants have poor compatibility with the PVC matrix and are prone to agglomeration during the blending process, forming stress concentration points, which seriously damages the continuity of the matrix and leads to a significant decrease in the mechanical properties of the composite material.

[0004] Since cable protection pipes are often buried in soil or exposed to industrial environments, they inevitably come into contact with corrosive media such as acids, alkalis, and salts, and the demand for corrosion resistance is increasing. Although PVC itself is chemically resistant, the ordinary fillers added are usually hydrophilic on the surface and have a weak interface with the hydrophobic PVC matrix, which can easily become a channel for the penetration of corrosive media. Corrosive media invade along this weak interface, causing the filler to detach from the matrix, accelerating the swelling, degradation and failure of the material, and resulting in the loss of its protective function.

[0005] In summary, existing technologies improve the mechanical and corrosion resistance of PVC pipes through modification. However, simple physical blending or single modification methods cannot improve the overall performance of the material. Often, methods that enhance mechanical properties compromise compatibility, thereby reducing other material properties. In practical applications, the challenge of simultaneously achieving both mechanical and corrosion resistance remains, leading to insufficient overall performance and a reduced material lifespan.

[0006] To address this, a PVC-based corrosion-resistant cable protection pipe and its manufacturing process are proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a PVC-based corrosion-resistant cable protection pipe and its manufacturing process. This invention involves thermally mixing chlorinated polyvinyl chloride (PVC) and polyvinyl chloride (PVC) to obtain a base resin, then adding corrosion-resistant additives, composite flame retardants, toughening agents, and other additives to obtain the cable protection pipe. The corrosion-resistant additives are obtained by grafting epoxy resin onto nano-silica and premixing it with an ethylene-vinyl alcohol copolymer. The composite flame retardant comprises a core layer of nitrogen-based, phosphorus-based, and inorganic hydroxides and a shell layer of acrylate polymers, obtained through a core-shell reaction. The cable protection pipe is prepared through a multi-step mixing process. This invention achieves high-efficiency flame retardancy and corrosion resistance through the core-shell structure and the introduction of corrosion-resistant additives, while maintaining the material's mechanical properties by buffering stress through a flexible shell layer.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] This invention provides a PVC-based corrosion-resistant cable protection pipe, comprising a base material, corrosion-resistant additives, composite flame retardants, and other additives;

[0010] The matrix materials include chlorinated polyethylene, polyvinyl chloride and calcium zinc composite stabilizer;

[0011] Corrosion-resistant additives include grafted nanoparticles and ethylene-vinyl alcohol copolymers;

[0012] Grafted nanoparticles include nano-silica, epoxy resin, and glycidyl etheroxypropyltrimethoxysilane.

[0013] Composite flame retardants include melamine cyanurate, triphenyl phosphate, nano magnesium hydroxide, butyl acrylate, styrene, and methyl methacrylate;

[0014] The additives include MBS, stearic acid, polyethylene wax, antimony trioxide, and antioxidant 1010.

[0015] This invention also provides a manufacturing process for PVC-based corrosion-resistant cable protection pipes, comprising the following manufacturing steps:

[0016] By weight, the matrix material and corrosion-resistant additives are fed into a cooling mixer and cooled to 60-70℃. The mixture is stirred for 20 minutes. Then, 20-30 parts of composite flame retardant, 6-10 parts of MBS, 0.3-0.8 parts of stearic acid, 1-2 parts of polyethylene wax, 1-1.5 parts of antimony trioxide, and 0.3-0.5 parts of antioxidant 1010 are added and stirred to obtain a mixture. The mixture is then added to a twin-screw extruder for melt extrusion. The mixture is shaped using a vacuum sizing sleeve and cooled and shaped using a spray water tank at a controlled water temperature of 15-20℃ for 30-60 seconds. The mixture is then pulled at a constant speed by a crawler-type traction machine and cut to the set length by a planetary cutter to obtain a cable protection pipe. The obtained cable protection pipe is a PVC solid-wall pipe with a diameter range of 50-100mm and a wall thickness of 2-5mm depending on the diameter. It is cut to the required length.

[0017] The temperatures in each zone of the melt extrusion process are as follows: feeding zone 170-180℃, compression zone 180-190℃, metering zone 190-195℃, die head 180-190℃, main screw speed 20-35rpm, and vacuum exhaust pressure -0.06 to -0.08MPa.

[0018] Preferably, the preparation of the matrix material and corrosion-resistant additives includes the following steps:

[0019] By mass, 50-60 parts of chlorinated polyvinyl chloride, 40-50 parts of polyvinyl chloride and 5 parts of calcium-zinc composite stabilizer are put into a high-speed mixer and the matrix material is obtained by hot mixing at 110-120℃ for 20-30 minutes.

[0020] By mass, 3-8 parts of grafted nanoparticles and 5-10 parts of ethylene-vinyl alcohol copolymer are added to a high-speed mixer and premixed at 80-90℃ for 30-40 minutes to obtain a corrosion-resistant additive.

[0021] Preferably, the preparation of grafted nanoparticles includes the following steps:

[0022] 15 parts of epoxy resin E518-15 parts and 2 ml of triethylamine were added to the modified nano-silica. The temperature was raised to 50-60℃ and the grafting reaction was carried out for 5-6 hours to obtain the reactant. The reactant was separated, washed three times with anhydrous ethanol, and dried under vacuum at 80℃ for 12 hours to obtain grafted nanoparticles.

[0023] Preferably, the preparation of modified nano-silica includes the following steps:

[0024] By mass, nano-silica was placed in a vacuum drying oven and dried at 100℃ for 5 hours to obtain dried raw material; 5-10 parts of glycidyl etheroxypropyltrimethoxysilane were added to 10 ml of 95% ethanol aqueous solution, acetic acid was added to adjust the pH to 4-5, and the mixture was stirred for 40 minutes to obtain silane solution; 100 parts of dried raw material were ultrasonically dispersed in 95% ethanol aqueous solution to prepare a dispersion with a mass concentration of 10%, the ultrasonic dispersion time was 30 minutes, the ultrasonic power was 200W, the silane solution was slowly added under stirring, the temperature was raised to 60-70℃, the modification reaction was carried out for 2-4 hours, the mixture was separated by centrifugation, washed 3 times with deionized water, and vacuum dried at 80℃ for 10 hours to obtain modified nano-silica.

[0025] Preferably, the preparation of the composite flame retardant includes the following steps:

[0026] Under nitrogen protection, the monomer pre-emulsion was added dropwise to the core layer solution over a period of 2 hours, with the temperature controlled at 70-80℃ and the stirring speed at 500-600 rpm. After the addition was complete, the core-shell reaction was allowed to proceed for 4-6 hours to obtain the reaction product. The reaction product was then cooled to room temperature, demulsified, filtered, and washed alternately with deionized water and anhydrous ethanol 5-8 times. Finally, it was vacuum dried at 70℃ for 10 hours to obtain the composite flame retardant. The composite flame retardant had a particle size of 5-10 μm and a shell coating rate of 12-18%.

[0027] Preferably, the preparation of the monomer preemulsion and the core layer solution includes the following steps:

[0028] Melamine cyanurate, triphenyl phosphate, and nano magnesium hydroxide were mixed, deionized water was added, and the mixture was placed in a high-speed mixer and stirred at 1000 rpm for 30 min to obtain a suspension. Ammonium persulfate was added to the suspension, and the temperature was raised to 50-60℃. The activation reaction was carried out for 1-2 h to obtain a core layer solution. Butyl acrylate, styrene, and methyl methacrylate were mixed, deionized water and sodium dodecyl sulfate were added, and the mixture was stirred at 200 rpm for 30 min to obtain a monomer preemulsion.

[0029] The mass ratio of melamine cyanurate, triphenyl phosphate and nano magnesium hydroxide is 1-2:1:1; the mass ratio of butyl acrylate, styrene and methyl methacrylate is 2-3:5-6:2-3.

[0030] Preferably, the chlorinated polyvinyl chloride has a chlorine content of 65-69% and a number-average molecular weight of 80,000-100,000; the polyvinyl chloride is selected from high-density polyvinyl chloride with a melt index of 0.5-2 g / 10 min; the ethylene-vinyl alcohol copolymer has an ethylene content of 32-38 mol% and a melt index of 1-5 g / 10 min; the nano-silica has a particle size of 20-30 nm and an epoxy group grafting rate of 10-15%; the polyethylene wax has a number-average molecular weight of 2000-4000 and a melting point of 100-110℃; the epoxy resin is E-51; and the nano-magnesium hydroxide has a particle size of 40-80 nm.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] 1. This solution increases the chlorine content of the matrix by introducing chlorinated polyvinyl chloride, thereby enhancing intermolecular forces and rigid support; the core-shell structure of the composite flame retardant avoids agglomeration, with the rubber-state core absorbing impact energy and the glass-state shell improving compatibility, achieving a balance between rigidity and toughness; nanoparticles enhance the material through size effect, and their surface epoxy groups form chemical bonds with the matrix, optimizing stress transmission; hot mixing and premixing processes ensure uniform dispersion of additives and avoid stress concentration. Through the synergistic effect of multiple components, the protective tube has both high tensile, bending and impact strength, improving mechanical properties.

[0033] 2. This invention utilizes the decomposition of melamine cyanurate to generate non-flammable gas that dilutes oxygen, and the generation of phosphorus-containing free radicals from triphenyl phosphate to break the combustion chain reaction. Both work synergistically to inhibit combustion in the gas phase. Nano-sized magnesium hydroxide undergoes endothermic decomposition to cool down and release water vapor, which, together with the carbonization promoted by triphenyl phosphate, forms a heat-insulating and oxygen-barrier barrier, achieving gas-solid two-phase flame retardancy. By utilizing the multi-mechanism flame retardant effect, an in-situ polymerized acrylate shell is introduced to disperse the flame retardant at the submicron level, reducing the negative impact on mechanical properties while improving flame retardant performance.

[0034] 3. This invention constructs dual protection through matrix modification and synergistic additives: Chlorinated polyvinyl chloride enhances the intermolecular forces of the matrix by increasing its high chlorine content, thereby improving its resistance to chemical corrosion; grafted nanoparticles are premixed and uniformly dispersed, and their epoxy groups strengthen the interfacial bonding, extending the penetration path of corrosive media; ethylene-vinyl alcohol copolymer forms a polar barrier layer, which, together with the nanoparticles, forms a composite network of chemical barrier and physical barrier, blocking the intrusion of media such as acids and alkalis, and significantly improving the corrosion resistance stability of the protective tube in different environments. Attached Figure Description

[0035] Figure 1 The changes in acid strength retention rate of the cable protection tubes obtained in Embodiment 10, Comparative Examples 1-3, and Comparative Examples 14-16 of the present invention are shown. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] In this invention, KH560 is glycidyl etheroxypropyltrimethoxysilane; MBS is a terpolymer of methyl methacrylate, butadiene, and styrene; MCA is melamine cyanurate; TPP is triphenyl phosphate; BA is butyl acrylate; St is styrene; and MMA is methyl methacrylate.

[0038] Please see Figure 1 This invention provides a PVC-based corrosion-resistant cable protection pipe and its manufacturing process, the technical solution of which is as follows:

[0039] Example 1

[0040] By mass, nano-silica was placed in a vacuum drying oven and dried at 100℃ for 5 hours to obtain dried raw material; 8 parts of KH560 were added to 10 ml of 95% ethanol aqueous solution, acetic acid was added to adjust the pH to 4, and the mixture was stirred for 40 minutes to obtain silane solution; 100 parts of the dried raw material were ultrasonically dispersed in 95% ethanol aqueous solution to prepare a 10% mass concentration dispersion, the ultrasonic dispersion time was 30 minutes, the ultrasonic power was 200W, the silane solution was slowly added under stirring, the temperature was raised to 70℃, the modification reaction was carried out for 3 hours, the mixture was separated and centrifuged, washed three times with deionized water, and vacuum dried at 80℃ for 10 hours to obtain modified nano-silica; 10 parts of epoxy resin E5110 and 2 ml of triethylamine were added to the modified nano-silica, the temperature was raised to 60℃, and the grafting reaction was carried out for 5 hours to obtain reactant; the reactant was separated, washed three times with anhydrous ethanol, and vacuum dried at 80℃ for 12 hours to obtain grafted nanoparticles;

[0041] 60 parts of melamine cyanurate, 30 parts of triphenyl phosphate, and 30 parts of nano-magnesium hydroxide were mixed and 500 parts of deionized water were added. The mixture was placed in a high-speed mixer and stirred at 1000 rpm for 30 min to obtain a suspension. 0.5 parts of ammonium persulfate were added to the suspension, and the temperature was raised to 50℃. The activation reaction was carried out for 2 h to obtain a core layer solution. 6 parts of butyl acrylate, 10 parts of styrene, and 4 parts of methyl methacrylate were mixed and 100 parts of deionized water and 0.2 parts of sodium dodecyl sulfate were added. The mixture was stirred at 200 rpm for 30 min to obtain a monomer pre-emulsion. Under nitrogen protection, the monomer pre-emulsion was slowly added dropwise to the core layer solution. The addition time was kept within 2 h, the temperature was controlled at 70℃, and the stirring speed was 600 rpm. After the addition was completed, the core-shell reaction was carried out for 5 h to obtain the reaction product. The reaction product was cooled to room temperature, demulsified and filtered. It was washed 5 times alternately with deionized water and anhydrous ethanol and then vacuum dried at 70℃ for 10 h to obtain a composite flame retardant.

[0042] 60 parts of chlorinated polyvinyl chloride, 40 parts of polyvinyl chloride, and 5 parts of calcium-zinc composite stabilizer were added to a high-speed mixer and hot-mixed at 110°C for 25 minutes to obtain the matrix material. 5 parts of grafted nanoparticles and 8 parts of ethylene-vinyl alcohol copolymer were added to the high-speed mixer and premixed at 90°C for 40 minutes to obtain a corrosion-resistant additive. The matrix material and corrosion-resistant additive were then transferred to a cooling mixer, cooled to 60°C, and stirred for 20 minutes. 25 parts of composite flame retardant, 8 parts of MBS, 0.5 parts of stearic acid, 1.5 parts of polyethylene wax, 1.2 parts of antimony trioxide, and 0.3 parts of antioxidant 1010 were added, and stirred at 500 rpm for 30 minutes to obtain a mixture. The mixture was then added to a twin-screw extruder for melt extrusion. The mixture was shaped using a vacuum sizing sleeve and cooled and shaped using a spray water tank at a controlled water temperature of 15°C for 40 seconds. Finally, the mixture was pulled at a constant speed by a crawler-type traction machine and cut to a set length by a planetary cutter to obtain a cable protection pipe.

[0043] Examples 2-5 follow the same preparation method and parameter conditions as Example 1, with differences shown in Table 1.

[0044] Table 1. Parameter variations in Examples 1-5

[0045]

[0046] Comparative Example 1 is the same as Example 1, except that chlorinated polyvinyl chloride is not added, and an equal amount of polyvinyl chloride is used.

[0047] Comparative Example 2 is the same as Example 1, except that no grafted nanoparticles are added.

[0048] Comparative Example 3 is the same as Example 1, except that it does not undergo epoxy resin grafting modification of nano-silica.

[0049] Comparative Example 4 is the same as Example 1, except that no composite flame retardant is added.

[0050] Comparative Example 5 is the same as Example 1, except that the composite flame retardant is added by melt blending without a core-shell structure.

[0051] Comparative Example 6 is the same as Example 1, except that MBS is not added.

[0052] Comparative Example 7 is the same as Example 1, except that the matrix material is not prepared by a hot mixing process, but is directly melted and added.

[0053] Comparative Example 8 is the same as Example 1, except that the grafted nanoparticles and ethylene-vinyl alcohol copolymer are added directly by melting without premixing.

[0054] Comparative Example 9 is the same as Example 1, except that it does not undergo hot mixing and blending processes, but is directly melt extruded.

[0055] Experimental Example 1: Mechanical Strength Test

[0056] The cable protection pipes prepared in Examples 1-5 and Comparative Examples 1-9 were subjected to mechanical strength tests. The tensile strength was tested according to GB / T1040.2-2006; the bending strength was tested according to GB / T 9341-2008; and the impact strength was tested according to GB / T 1843-2008. The test results are shown in Table 2.

[0057] Table 2 Test results of Examples 1-5 and Comparative Examples 1-9

[0058] Example Tensile strength / MPa Bending strength / MPa <![CDATA[Impact strength / kJ / m 2 > Example 1 45 65 22 Example 2 42 62 21 Example 3 43 64 20 Example 4 42 63 20 Example 5 46 60 21 Comparative Example 1 35 48 16 Comparative Example 2 32 45 18 Comparative Example 3 36 45 15 Comparative Example 4 42 56 17 Comparative Example 5 35 50 15 Comparative Example 6 42 58 12 Comparative Example 7 36 48 13 Comparative Example 8 37 51 14 Comparative Example 9 30 40 10

[0059] As shown in Table 2, the mechanical properties of the cable protection pipes obtained in the comparative examples, through adjustments to the components and processes, were significantly reduced compared to the examples. In Comparative Example 1, the lack of chlorinated polyvinyl chloride (PVC) led to a decrease in the rigidity and crosslinking density of the matrix resin, increased intermolecular slippage between molecular chains, and a significant reduction in strength and toughness. PVC, being a chlorinated modified product of PVC, has a higher chlorine content and stronger intermolecular forces; the matrix material formed by blending the two significantly improves mechanical strength. The results of Comparative Examples 2-3 show that the lack of physical reinforcement from nanoparticles resulted in significant stress concentration. Furthermore, the nanoparticles... The lack of interfacial cross-linking effect of the particles reduces the overall strength of the material. The unmodified nano-silica surface is hydrophilic, resulting in poor compatibility with the hydrophobic polyvinyl chloride matrix interface, easily forming stress concentration points. KH560 provides initial dispersion to prevent nanoparticle aggregation. Epoxy resin grafting and ethylene-vinyl alcohol copolymer blending can further strengthen the filler-matrix interface through chemical bonding. The absence of these features leads to particle detachment and a sharp drop in strength. In Comparative Examples 4-5, the absence of the composite flame retardant has little impact on the overall mechanical strength of the material. Although it reduces the disruption of the matrix continuity caused by the flame-retardant filler, the toughening effect of the core-shell structure disappears. The strength decreased slightly; however, without introducing flame retardants through a core-shell structure, nanoscale dispersion of the flame retardants could not be achieved. Direct melt blending led to severe agglomeration of flame retardant particles, forming rigid filler defects, causing stress concentration, and significantly reducing strength. The core-shell structure can buffer stress through a flexible shell layer, improve the compatibility between the filler and the matrix, and then form an interpenetrating network with polyvinyl chloride matrix, enhancing interfacial bonding and further improving mechanical strength. In Comparative Example 6, MBS, as an impact modifier, has a rubber phase that can absorb impact energy and inhibit crack propagation. Its absence leads to brittle fracture of the material and a significant reduction in impact strength. In addition, MBS... The dispersed phase can enhance the continuity of the matrix, and its absence leads to a decrease in overall strength. The results of Comparative Examples 7-9 show that by adjusting the process, the mechanical strength of the material can be greatly improved. The hot mixing process can make the calcium-zinc stabilizer uniformly dispersed and react with the polyvinyl chloride molecular chain, inhibit the release of hydrochloric acid during processing, and avoid degradation. The premixing process can improve the compatibility of blending by mechanically shearing the polar resin and the grafted nanoparticles to form hydrogen bonds or physical entanglement in advance. Direct blending and extrusion leads to severe component segregation, nanoparticle agglomeration, uneven distribution of flame retardant, and insufficient reaction of stabilizer. The matrix exhibits a "sea-island structure" defect, and the mechanical strength is significantly reduced.

[0060] In summary, by introducing chlorinated polyvinyl chloride (PVC), the chlorine content in the matrix is ​​increased, resulting in stronger intermolecular forces and a rigid molecular chain structure, providing sufficient support and compressive strength for the protective tube. Simultaneously, the core-shell structure in the composite flame retardant prevents agglomeration while achieving a balance between rigidity and toughness. Its rubbery core structure acts as a stress concentration point, effectively absorbing energy upon impact and inducing numerous crazing and shear bands in the matrix, thus dissipating the impact energy. Its glassy shell structure ensures compatibility with the matrix. Finally, the size effect of nanoparticles has a reinforcing effect; the epoxy groups on their surface form strong chemical bonds with the matrix, allowing stress to be effectively transferred from the flexible matrix to the rigid nanoparticles. The introduction of hot mixing and premixing processes ensures that the additives achieve a highly uniform dispersion before melting, avoiding stress concentration points. Through the synergistic effect of multiple components and processes, the overall mechanical strength of the material is improved.

[0061] Example 6 is the same as Example 1;

[0062] Examples 7-9 follow the same preparation method and parameter conditions as Example 1, with differences shown in Table 3.

[0063] Table 3. Parameter changes in Examples 6-9

[0064]

[0065] Comparative Example 4 is the same as Example 1, except that no composite flame retardant is added.

[0066] Comparative Example 5 is the same as Example 1, except that the composite flame retardant is added by melt blending without a core-shell structure.

[0067] Comparative Example 10 is the same as Example 1, except that only an equal amount of melamine cyanurate is used in the composite flame retardant.

[0068] Comparative Example 11 is the same as Example 1, except that only an equal amount of triphenyl phosphate is used in the composite flame retardant.

[0069] Comparative Example 12 is the same as Example 1, except that only an equal amount of nano magnesium hydroxide is used in the composite flame retardant.

[0070] Comparative Example 13 is the same as Example 1, except that no shell material is introduced into the composite flame retardant, and the flame retardant is directly melted and added.

[0071] Experiment Example 2 Flame Retardant Performance Test

[0072] The cable protection pipes prepared in Examples 6-9, Comparative Examples 4-5, and Comparative Examples 10-13 were subjected to flame retardant performance tests. The limiting oxygen index was tested according to GB / T 2406.2-2009, and the self-extinguishing time and vertical burning rating were tested according to GB / T 2408-2021. The test results are shown in Table 4.

[0073] Table 4. Test results of Examples 6-9, Comparative Examples 4-5, and Comparative Examples 10-13

[0074] Example Limiting oxygen index / % Vertical flammability rating Self-extinguishing time / s Example 6 36 V-0 ≤10 Example 7 35 V-0 ≤10 Example 8 34 V-0 ≤10 Example 9 35 V-0 ≤10 Comparative Example 4 20 Burning dripping No self-extinguishing Comparative Example 5 26 V-2 30 Comparative Example 10 24 V-1 16 Comparative Example 11 23 V-1 18 Comparative Example 12 22 V-2 20 Comparative Example 13 25 V-2 25

[0075] As shown in Table 4, the comparative examples, by adjusting the dosage of the composite flame retardant components and the process, exhibited significantly reduced flame retardant performance compared to the examples. In Comparative Examples 4-5, the absence of flame retardant resulted in the cable protection pipe material lacking the multi-component effects of melamine cyanurate inhibiting free radicals, triphenyl phosphate forming carbon to isolate oxygen, and nano-magnesium hydroxide absorbing heat, leading to intense combustion. The core-shell structure achieves nanoscale dispersion of the flame retardant through emulsion polymerization, while the shell layer forms an interpenetrating network with the polyvinyl chloride matrix, enhancing interfacial bonding and uniformly distributing the flame retardant components, thus improving flame retardant performance. Conversely, direct melt blending leads to flame retardant particle agglomeration, preventing effective contact with the flame, and numerous interfacial defects allow heat to easily conduct to the matrix, weakening flame retardancy. Efficiency; combined with Comparative Example 13, the lack of a shell layer leads to uneven dispersion of the flame retardant and a loose char layer. The gas generated by the decomposition of melamine cyanurate easily breaks through the char layer, and the cooling effect of nano-magnesium hydroxide cannot effectively cover the combustion area due to poor dispersion, ultimately resulting in a significant reduction in the flame retardant performance of the material. The introduction of the shell material is not only a dispersion carrier, but its polymer chains can also synergistically form an expanded char layer with triphenyl phosphate during combustion, enhancing the barrier effect. The results of Comparative Examples 10-12 show that the use of a single flame retardant, lacking the gas-phase flame retardant mechanism of melamine cyanurate, the condensed phase char formation of triphenyl phosphate, and the synergistic effect of multiple mechanisms such as heat absorption and physical cooling by nano-magnesium hydroxide, significantly reduces the flame retardant performance of the prepared cable protection pipe material.

[0076] In summary, the decomposition of melamine cyanurate during heating generates non-flammable gases such as NH3 and N2, diluting oxygen. Simultaneously, the decomposition of triphenyl phosphate produces phosphorus-containing free radicals that can capture highly reactive free radicals in the combustion chain reaction. Through this synergistic effect, combustible gases are diluted in the gas phase, and the combustion chain reaction is interrupted, achieving dual inhibition of dilution and capture. Furthermore, nano-magnesium hydroxide, through endothermic decomposition, releases water vapor to dilute oxygen and lower the material surface temperature. This, combined with the thermal decomposition of triphenyl phosphate, promotes the dehydration and carbonization of the matrix, forming a dense carbon layer that constructs a heat- and oxygen-barrier barrier on the material surface. This simultaneous gas-solid interaction and multi-mechanism complementary flame-retardant mechanism further enhances the material's flame-retardant performance. Additionally, the in-situ polymerization method introduces an acrylate shell, ensuring that the flame-retardant core is uniformly dispersed in the matrix in a submicron form, avoiding performance shortcomings caused by agglomeration. It also minimizes the negative impact of the flame-retardant on the material's mechanical properties, improving the overall performance of the protective tube.

[0077] Example 10 is the same as Example 1;

[0078] Examples 11-14 follow the preparation method and parameter conditions of Example 1, with differences shown in Table 5.

[0079] Table 5. Parameter variations in Examples 10-14

[0080]

[0081] Comparative Example 1 is the same as Example 1, except that chlorinated polyvinyl chloride is not added, and an equal amount of polyvinyl chloride is used.

[0082] Comparative Example 2 is the same as Example 1, except that no grafted nanoparticles are added.

[0083] Comparative Example 3 is the same as Example 1, except that it does not undergo epoxy resin grafting modification of nano-silica.

[0084] Comparative Example 8 is the same as Example 1, except that the grafted nanoparticles and ethylene-vinyl alcohol copolymer are added directly by melting without premixing.

[0085] Comparative Example 14 was prepared in accordance with Example 1, except that no ethylene-vinyl alcohol copolymer was added to obtain the corrosion-resistant additive.

[0086] Comparative Example 15 is the same as Example 1, except that the nano-silica is not modified or grafted and is directly added in the blend.

[0087] Comparative Example 16 is the same as Example 1, except that the nano-silica is not modified and is directly ring-grafted with epoxy resin.

[0088] Experiment Example 3 Corrosion Resistance Test

[0089] The cable protection pipes prepared in Examples 10-14, Comparative Examples 1-3, Comparative Example 8, and Comparative Examples 14-16 were subjected to corrosion resistance tests. A 3cm test sample was taken from each of the prepared protection pipes, and the tensile strength of the initial test sample was determined according to GB / T 1040.2-2006. The samples were then placed in 10% hydrochloric acid solution, 10% sodium hydroxide solution, and 5% sodium chloride solution, respectively, and allowed to stand at 25°C for 72 hours. After standing, the samples were removed, washed with deionized water, and dried at 50°C for 10 hours to obtain treated samples. The tensile strength of these treated samples was determined according to GB / T1040.2-2006, and the tensile strength retention rate was calculated. The test results are shown in Table 6. The changes in the acid strength retention rate of Examples 10, Comparative Examples 1-3, and Comparative Examples 14-16 are shown in Table 6. Figure 1 As shown.

[0090] Table 6. Test results of Examples 10-14, Comparative Examples 1-3, Comparative Example 8, and Comparative Examples 14-16

[0091] Example Acid strength retention rate / % Alkali strength retention rate / % Neutral strength retention rate / % Example 10 95.2 98.3 99.5 Example 11 94.9 97.8 99.4 Example 12 95.1 97.8 99.2 Example 13 94.8 98.2 99.5 Example 14 94.8 98.1 99.3 Comparative Example 1 82.6 86.4 93.2 Comparative Example 2 88.5 90.6 95.4 Comparative Example 3 80.6 80.5 90.8 Comparative Example 8 85.4 88.6 93.6 Comparative Example 14 87.3 89.5 94.6 Comparative Example 15 75.6 78.4 88.2 Comparative Example 16 83.5 84.2 91.5

[0092] As shown in Table 2, the cable protection pipes obtained in the comparative examples, through changes in components and processes, exhibited significantly reduced corrosion resistance compared to the examples. In Comparative Example 1, without the addition of chlorinated polyvinyl chloride (PVC), the density of polar groups in the molecular chain decreased, making it easier for acidic and alkaline media to penetrate into the gaps between the molecular chains, leading to swelling and chain breakage, thus reducing corrosion resistance. However, the addition of chlorinated PVC, due to the increased chlorine content, resulted in stronger intermolecular forces, and the electronegativity of chlorine atoms could inhibit the attack of acidic and alkaline media on the C-C bonds, improving chemical corrosion resistance. Comparative Examples 2-3 show that the epoxy groups on the surface of grafted nanoparticles can form hydrogen bonds or physical entanglement with the matrix, filling micro-defects in the matrix and forming a barrier effect, preventing corrosive media from easily penetrating through pores. Furthermore, epoxy resin grafting can chemically bond epoxy segments to the surface of nano-silica, improving interfacial compatibility, blocking media penetration, and preventing nanoparticle aggregation. Defects become the entry point for corrosion. In addition, the corrosion resistance of epoxy resin itself can work synergistically with the nanoparticles. In Comparative Example 8, direct melt addition leads to uneven dispersion of ethylene-vinyl alcohol copolymer and grafted particles. The high barrier properties of ethylene-vinyl alcohol copolymer and the filling effect of nanoparticles cannot work synergistically, and local areas are easily damaged by corrosive media. In Comparative Example 14, ethylene-vinyl alcohol copolymer molecules form hydrogen bonds with grafted nanoparticles through mechanical shearing during premixing, promoting uniform dispersion of both in the matrix and forming a nano-polymer composite barrier layer, further improving corrosion resistance. In Comparative Examples 15-16, unmodified nano-silica has high surface energy and is prone to agglomeration to form micron-sized defects. At the same time, the interface between it and the matrix is ​​weak, and corrosive media can quickly penetrate into the material through the gaps between the agglomerates. In addition, the lack of modification and grafting steps makes it impossible to improve compatibility through interface modification, causing nanoparticles to become corrosion channels and accelerating material corrosion.

[0093] In summary, this invention introduces chlorinated polyvinyl chloride (PVC) and polyvinyl chloride (PVC) as matrix materials. Utilizing the high chlorine content of PVC, the intermolecular forces within the matrix are stronger, improving corrosion resistance. The premixing process ensures uniform dispersion of the grafted nanoparticles within the matrix, extending the penetration path of corrosive media. The epoxy groups on the surface enhance the interfacial bonding with the matrix, preventing penetration channels caused by the detachment of the filler from the matrix. Furthermore, the micro-dispersed ethylene-vinyl alcohol copolymer phase forms a discontinuous barrier layer within the matrix. The synergistic effect of the two additives forms a nano-filler-polar barrier composite network, providing dual protection through both chemical and physical barriers, effectively preventing the intrusion of corrosive media and further improving corrosion resistance.

[0094] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A PVC-based corrosion-resistant cable protection pipe, characterized in that, The cable protection pipe comprises a base material, corrosion-resistant additives, a composite flame retardant, and other additives; wherein, the base material comprises chlorinated polyethylene, polyvinyl chloride, and a calcium-zinc composite stabilizer; the corrosion-resistant additives comprise grafted nanoparticles and ethylene-vinyl alcohol copolymers; the grafted nanoparticles comprise nano-silica, epoxy resin, and glycidyl etheroxypropyltrimethoxysilane; the composite flame retardant comprises melamine cyanurate, triphenyl phosphate, nano-magnesium hydroxide, butyl acrylate, styrene, and methyl methacrylate; and the additives comprise MBS, stearic acid, polyethylene wax, antimony trioxide, and antioxidant 1010. The preparation of the cable protection pipe includes the following steps: The matrix material and the corrosion-resistant additive are fed into a cooling mixer, cooled, and stirred; the composite flame retardant, MBS, stearic acid, polyethylene wax, antimony trioxide, and antioxidant 1010 are added and stirred to obtain a mixture; the mixture is added to a twin-screw extruder and melt-extruded; it is shaped using a vacuum sizing sleeve and cooled and shaped using a spray water tank; then it is pulled at a constant speed by a crawler-type traction machine and cut to a set length by a planetary cutter to obtain the cable protection pipe. The preparation of the matrix material and the corrosion-resistant additive includes the following steps: adding the chlorinated polyvinyl chloride, the polyvinyl chloride and the calcium-zinc composite stabilizer into a high-speed mixer and obtaining the matrix material by hot mixing; adding the grafted nanoparticles and the ethylene-vinyl alcohol copolymer into a high-speed mixer and premixing to obtain the corrosion-resistant additive; The preparation of the grafted nanoparticles includes the following steps: adding epoxy resin E51 and triethylamine to modified nano-silica, and performing a grafting reaction to obtain a reactant; separating the reactant, washing it with anhydrous ethanol, and vacuum drying to obtain the grafted nanoparticles. The preparation of the modified nano-silica includes the following steps: The nano-silica is placed in a vacuum drying oven and vacuum dried to obtain a dried raw material; the glycidyl etheroxypropyltrimethoxysilane is added to a 95% ethanol aqueous solution, acetic acid is added to adjust the pH to acidic, and the mixture is stirred to obtain a silane solution; the dried raw material is ultrasonically dispersed in a 95% ethanol aqueous solution to prepare a 10% (w / w) dispersion, the silane solution is added under stirring, the modification reaction is separated by centrifugation, washed with deionized water, and vacuum dried to obtain the modified nano-silica; The preparation of the composite flame retardant includes the following steps: under nitrogen protection, a monomer pre-emulsion is added dropwise to a core layer solution. After the addition is complete, a core-shell reaction is performed to obtain a reaction product. The reaction product is cooled to room temperature, demulsified and filtered, washed alternately with deionized water and anhydrous ethanol, and then vacuum dried to obtain the composite flame retardant. The preparation of the monomer preemulsion and the core layer solution includes the following steps: mixing the melamine cyanurate, the triphenyl phosphate and the nano magnesium hydroxide, adding deionized water, placing in a high-speed mixer, and stirring to obtain a suspension; adding ammonium persulfate to the suspension to activate the reaction and obtain the core layer solution; mixing the butyl acrylate, the styrene and the methyl methacrylate, adding deionized water and sodium dodecyl sulfate, and stirring to obtain the monomer preemulsion.

Images