High-toughness modified polypropylene power cable protection pipe and preparation method thereof
By modifying magnesium aluminum hydrotalcite with stearic acid intercalation and silane grafting, and combining it with dopamine-coated aramid fibers, the problems of brittle cracking and poor wear resistance of polypropylene cable protection pipes in underground laying were solved, and the high toughness and corrosion resistance were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANHUI ETE ELECTRIC POWER CO LTD
- Filing Date
- 2026-05-12
- Publication Date
- 2026-06-09
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of cable protection pipe technology, specifically relating to a high-toughness modified polypropylene power cable protection pipe and its preparation method. Background Technology
[0002] Power cable protection pipes are protective devices used in the laying of power and communication cables. They are mainly used to protect cables from external influences such as mechanical damage and chemical corrosion, assist in the smooth laying of cables, extend their service life, ensure safe and stable power transmission, and are suitable for various engineering scenarios.
[0003] Based on the unique advantages of polypropylene, it has become the preferred raw material for manufacturing power cable protection pipes. Polypropylene has a high specific modulus and low density, high extrusion efficiency, and is suitable for lightweight and large-scale production. It also possesses good insulation, chemical corrosion resistance, and a wide long-term operating temperature range. Furthermore, the raw material is environmentally friendly and recyclable, aligning with the green building requirements under the "dual carbon" goal. Compared to materials such as PVC-U and PE, it has advantages in rigidity and processing efficiency, better meeting the basic performance requirements of cable protection pipes. While choosing polypropylene for power cable protection pipes offers basic properties such as light weight, convenient construction, good insulation, and aging resistance, it also has drawbacks such as high low-temperature brittleness, poor flame retardancy, and easy accumulation of static electricity. Inconsistent crystallization may also occur during processing, making it difficult to adapt to special working conditions.
[0004] Chinese invention patent application CN116376163A discloses a deformation-resistant power cable protection pipe and its manufacturing process. It uses PP resin as a base material and adds nano-calcium carbonate, modified zirconium phosphate, modified carbon nanotubes, compatibilizers, and other additives as raw materials. The modified zirconium phosphate is obtained by grafting trimethoxysilane onto cashew phenol after phosphorylation and zirconization. The modified carbon nanotubes are obtained by the condensation reaction of carboxylated multi-walled carbon nanotubes with aminopropyl double-terminated polydimethylsiloxane. After mixing the raw materials, the mixture is granulated by twin-screw extrusion at 180-220℃, and then extruded into a pipe extruder to obtain the power cable protection pipe.
[0005] The above-mentioned scheme, which physically entangles the long chains grafted onto the surface with the PP matrix, fails to regulate the interlayer structure of zirconium phosphate. During the laying process without excavation, the interlayer forces of zirconium phosphate are strong, making it difficult to achieve sufficient peeling and uniform dispersion in PP, and it is easy to form agglomerates. In addition, the lack of chemical bonding sites between the zirconium phosphate and the matrix leads to low stress transfer efficiency, the toughening potential of the layered filler cannot be realized, the impact resistance of the pipe is insufficient, and it is prone to brittle cracking under buried service conditions. Summary of the Invention
[0006] The purpose of this invention is to provide a high-toughness modified polypropylene power cable protection pipe and its preparation method. By first intercalating magnesium aluminum hydrotalcite with stearic acid to expand the interlayer spacing and promote its uniform peeling in PP, and then grafting with KH-550 to introduce amino groups that chemically bond with PP-g-MAH, the problems of poor dispersion and weak interface are further solved, significantly improving stress transmission efficiency and impact resistance, and effectively reducing the occurrence of brittle cracking in buried applications.
[0007] The objective of this invention can be achieved through the following technical solutions: A method for preparing a high-toughness modified polypropylene power cable protection pipe includes the following steps: Step 1: Magnesium aluminum hydrotalcite is prepared by double-drop co-precipitation method, and then toughened hydrotalcite is obtained by sodium stearate intercalation and silane coupling agent surface grafting.
[0008] The specific preparation method of toughened hydrotalcite is as follows: Deionized water and anhydrous ethanol were mixed evenly, and silane coupling agent KH-550 was added and stirred evenly to obtain a silane solution. Modified hydrotalcite was added to ethanol and stirred at 80-90℃ for 1-2 hours. The silane solution was added dropwise, and stirring was continued for 4-5 hours. The mixture was centrifuged, washed, vacuum dried to constant weight, and ground to obtain toughened hydrotalcite.
[0009] Specifically, the ratio of deionized water, anhydrous ethanol, and silane coupling agent KH-550 is 50-80 mL: 50-70 mL: 5-8 g.
[0010] Specifically, the ratio of modified hydrotalcite, ethanol, and silane solution is 20-24g: 500-600mL: 100-200mL.
[0011] The specific preparation method of modified hydrotalcite is as follows: Sodium stearate was dissolved in deionized water to obtain a sodium stearate solution. Deionized water and anhydrous ethanol were stirred and mixed evenly. Magnesium aluminum hydrotalcite was added while stirring and stirred for 1-2 hours. Then, sodium stearate solution was added dropwise to adjust the pH to 4. The mixture was stirred at 70-80℃ for 6-7 hours. After centrifugation, washing, vacuum drying to constant weight, grinding and sieving, modified hydrotalcite was obtained.
[0012] Specifically, the sodium stearate solution is prepared by mixing sodium stearate and deionized water in a ratio of 30-38g: 500-600mL.
[0013] Specifically, the ratio of deionized water, anhydrous ethanol, magnesium aluminum hydrotalcite, and sodium stearate solution is 500-620mL: 500-680mL: 20-26g: 500-600mL.
[0014] The specific preparation method of magnesium aluminum hydrotalcite is as follows: Magnesium chloride hexahydrate and aluminum nitrate nonahydrate were dissolved in deionized water to obtain solution A; sodium hydroxide and anhydrous sodium carbonate were dissolved in deionized water to obtain solution B; under vigorous stirring, solutions A and B were simultaneously added dropwise to the reaction flask at a rate of about 0.1 mL / s, and the mixture was kept at 60-70℃ for 18-24 h for crystallization. After centrifugation, the supernatant was discarded, and the mixture was repeatedly washed with deionized water until the filtrate was neutral. The solid was collected, dried under vacuum to constant weight, ground, and sieved to obtain magnesium aluminum hydrotalcite.
[0015] Specifically, the ratio of magnesium chloride hexahydrate, aluminum nitrate nonahydrate, and deionized water is 60.96-68.92: 37.48-41.24: 400-600 mL.
[0016] Specifically, the ratio of sodium hydroxide, anhydrous sodium carbonate, and deionized water is 24-28g: 63.6-69.3g: 400-600mL.
[0017] Specifically, the volume ratio of solution A to solution B is 400-600 mL : 400-500 mL.
[0018] Step 2: Surface coating of aramid fibers is performed using dopamine self-polymerization to obtain dopamine-coated aramid fibers.
[0019] The specific preparation method of dopamine-coated aramid fibers is as follows: Dopamine hydrochloride was dissolved in Tris buffer to obtain a dopamine solution. Aramid fibers were then added and the solution was magnetically stirred at 300-400 rpm for 4-5 hours in a water bath at 30-40℃. The fibers were then removed and washed with deionized water 3-5 times. Finally, the fibers were vacuum dried at 60-70℃ for 12-14 hours to obtain dopamine-coated aramid fibers.
[0020] Specifically, the ratio of dopamine hydrochloride, Tris buffer, and aramid fiber is 2-3.2g: 1000-1200mL: 10-14g.
[0021] Step 3: Polypropylene, toughening hydrotalcite, dopamine-coated aramid fiber, maleic anhydride-grafted polypropylene, polypropylene wax, antioxidant 1010 and antioxidant 168 are blended, granulated by twin-screw extrusion, dried, and then extruded into pipes to obtain high-toughness modified polypropylene power cable protection pipes.
[0022] Specifically, the mass ratio of polypropylene, toughening hydrotalcite, dopamine-coated aramid fiber, maleic anhydride-grafted polypropylene, polypropylene wax, antioxidant 1010 and antioxidant 168 is 100-120:15-18:8-10:8-10:0.5-0.8:0.4-0.6:0.2-0.3.
[0023] The beneficial effects of this invention are: 1. This invention utilizes a dual modification process of "intercalation followed by grafting" of magnesium-aluminum hydrotalcite (TLT) and the synergistic effect of dopamine-coated aramid fibers to prepare a high-toughness modified polypropylene power cable protection pipe suitable for underground installation. Specifically, stearic acid intercalation expands the interlayer spacing of the TTL and imparts hydrophobicity to the surface, providing a good substrate for subsequent silane grafting. The grafted silane introduces reactive amino groups, forming chemical bonds with the compatibilizer and dopamine-coated fibers, constructing a strong interfacial connection from inorganic filler to organic matrix. The exfoliated TTL layers and fibers form a rigid-flexible energy dissipation network, improving impact toughness while the lubricating effect of the layered TTL and the reinforcing effect of the fibers jointly reduce surface wear of the pipe. The hydrophobic modification and dense interfacial bonding delay the penetration of moisture and corrosive media in the soil, enabling the pipe to maintain high performance stability in humid and acidic / alkaline environments.
[0024] 2. The toughened hydrotalcite in this invention achieves synergistic effects at the structural, interfacial, and performance levels through a dual modification process involving stearic acid intercalation and silane grafting. Stearic acid intercalation significantly expands the interlayer spacing and imparts surface hydrophobicity, facilitating the hydrotalcite's exfoliation and dispersion within the polypropylene matrix while improving its compatibility with the matrix. Silane grafting introduces reactive amino groups, enabling chemical bonding with maleic anhydride-grafted polypropylene and constructing a strong interfacial connection from the inorganic filler to the polymer matrix. The specific order of intercalation followed by grafting ensures sufficient intercalation and high grafting efficiency; reversing the order significantly weakens the effect. Benefiting from its hydrophobic layered structure and chemically sealed interface, the toughened hydrotalcite helps form a physical barrier network within the matrix, extending the diffusion path of corrosive media. Simultaneously, the layered slip mechanism reduces surface friction and improves wear resistance. Under stress, the exfoliated nanosheets induce crazing and shear banding to dissipate impact energy, forming a multi-level energy absorption system in synergy with aramid fibers. This provides an important foundation for polypropylene pipes to achieve good toughness, wear resistance and corrosion resistance in underground environments.
[0025] 3. The dopamine-coated aramid fiber of this invention forms a polydopamine coating rich in catechol and amino groups through self-polymerization on the fiber surface. This coating adheres firmly to the inert aramid surface, improving the wettability between the fiber and the polypropylene matrix. The active amino groups in the coating undergo an amidation reaction with maleic anhydride-grafted polypropylene, achieving chemical bond anchoring between the fiber and the matrix and significantly enhancing the interfacial bonding strength. During impact, the fiber undergoes a complete energy dissipation process of debonding, slippage, and fracture, effectively improving the elongation at break and impact toughness. The strong interfacial bonding also helps resist surface peeling during friction, further enhancing wear resistance. Simultaneously, the density and antioxidant capacity of the polydopamine layer can seal interfacial micro-pores, hindering the penetration of moisture and corrosive media, and extending the service life of the pipe in moist, acidic, or alkaline soils. Detailed Implementation
[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments in the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0027] Example 1: A method for preparing a high-toughness modified polypropylene power cable protection pipe, comprising the following steps: S1: Dissolve 60.96g magnesium chloride hexahydrate and 37.48g aluminum nitrate nonahydrate in 400mL of deionized water to obtain solution A; dissolve 24g sodium hydroxide and 63.6g anhydrous sodium carbonate in 400mL of deionized water to obtain solution B; transfer solutions A and B to constant pressure dropping funnels respectively, and simultaneously add 400mL of solution A and 400mL of solution B at a rate of about 0.1mL / s in a water bath at 60℃ with vigorous stirring. During the addition, monitor the pH value in real time with a pH meter, and maintain the pH value of the reaction solution at 10 by adjusting the dropping rate of solution B. After the addition is completed, keep it at 60℃ for crystallization for 18h, centrifuge at 4000rpm for 10min, discard the supernatant, wash repeatedly with deionized water until the filtrate is neutral, collect the solid, vacuum dry the solid at 70℃ to constant weight, grind, and pass through a 200-mesh sieve to obtain magnesium aluminum hydrotalcite.
[0028] Mg was obtained by a two-drop coprecipitation method under alkaline conditions at pH=10. 2+ And Al 3+ With OH - Co-precipitation forms a positively charged hydroxide layer, while carbonate ions are inserted into the interlayer to balance the charge. After crystallization, magnesium aluminum hydrotalcite is obtained.
[0029] S2: Dissolve 30g of sodium stearate in 500mL of deionized water to obtain a sodium stearate solution; mix 500mL of deionized water and 500mL of anhydrous ethanol evenly, add 20g of magnesium aluminum hydrotalcite while stirring, stir in a 70℃ water bath for 1h, then add 500mL of sodium stearate solution dropwise at a rate of 0.5mL / min, adjust the pH to 4 with 0.1mol / L dilute hydrochloric acid, stir at 70℃ for 6h, centrifuge at 4000rpm for 10min, discard the supernatant, wash the precipitate with deionized water and centrifuge, repeat 3 times, vacuum dry at 60℃ to constant weight, grind, and pass through a 200-mesh sieve to obtain modified hydrotalcite.
[0030] By adjusting the pH to protonate sodium stearate to generate stearic acid, magnesium aluminum hydrotalcite is intercalated and coated in an ethanol / water medium, achieving dual modification of interlayer spacing expansion and surface hydrophobicity.
[0031] S3: Mix 50 mL of deionized water and 50 mL of anhydrous ethanol evenly, add 5 g of silane coupling agent KH-550 and stir evenly to obtain a silane solution; add 20 g of modified hydrotalcite to 500 mL of ethanol, stir at 300 rpm for 1 h in an 80 °C water bath, add 100 mL of silane solution dropwise at a rate of 0.5 mL / min, stir at 80 °C for 4 h, centrifuge at 4000 rpm for 10 min, collect the precipitate, wash the precipitate 3 times with deionized water, wash it once with anhydrous ethanol, vacuum dry it at 60 °C to constant weight, grind it, and pass it through a 200 mesh sieve to obtain toughened hydrotalcite.
[0032] KH-550 hydrolyzes in an alcohol / water medium to generate silanol groups, which then form Si-OM bonds with the hydroxyl groups on the surface of intercalated hydrotalcite through a dehydration condensation reaction. This achieves surface grafting modification of LDH by silane coupling agent, thereby introducing organic hydrophobic segments and reactive amino groups onto the surface of LDH inorganic particles.
[0033] S4: Add 2g of dopamine hydrochloride to 1000mL of Tris buffer solution and stir to dissolve to obtain a dopamine solution. Then add 10g of aramid fiber and stir magnetically at 300rpm for 4h in a 30℃ water bath. Take out the fiber, soak and wash the fiber with deionized water 3 times, and vacuum dry at 60℃ for 12h to obtain dopamine-coated aramid fiber.
[0034] Dopamine self-polymerizes into polydopamine under alkaline aerobic conditions, which adheres to the surface of aramid fibers through non-covalent interactions such as π-π stacking and hydrogen bonding.
[0035] S5: Add 100g polypropylene, 15g toughening hydrotalcite, 8g dopamine-coated aramid fiber, 8g maleic anhydride-grafted polypropylene, 0.5g polypropylene wax, 0.4g antioxidant 1010 and 0.2g antioxidant 168 to a premixer and stir at 150rpm for 30min. Transfer to a twin-screw extruder, set the temperatures of zones one to five to 100, 150, 190, 180 and 160℃ respectively, the die temperature to 130℃, the feeding speed to 100rpm, and the screw speed to 250rpm. Extrude and granulate, and after hot air drying at 90℃ for 5h, form through a pipe extrusion production line to obtain a high-toughness modified polypropylene power cable protection pipe.
[0036] Example 2: A method for preparing a high-toughness modified polypropylene power cable protection pipe, comprising the following steps: S1: Dissolve 64.94g magnesium chloride hexahydrate and 39.36g aluminum nitrate nonahydrate in 500mL of deionized water to obtain solution A; dissolve 26g sodium hydroxide and 66.45g anhydrous sodium carbonate in 500mL of deionized water to obtain solution B; transfer solutions A and B to constant pressure dropping funnels respectively, and simultaneously add 500mL of solution A and 450mL of solution B at a rate of about 0.1mL / s in a water bath at 60℃ with vigorous stirring. During the addition, monitor the pH in real time with a pH meter, and maintain the pH of the reaction solution at 10.5 by adjusting the dropping rate of solution B. After the addition is complete, crystallize at 65℃ for 21h, centrifuge at 4500rpm for 15min, discard the supernatant, wash repeatedly with deionized water until the filtrate is neutral, collect the solid, vacuum dry the solid at 75℃ to constant weight, grind, and pass through a 200-mesh sieve to obtain magnesium aluminum hydrotalcite.
[0037] S2: Dissolve 34g of sodium stearate in 550mL of deionized water to obtain a sodium stearate solution; mix 560mL of deionized water and 590mL of anhydrous ethanol evenly, add 23g of magnesium aluminum hydrotalcite while stirring, stir in a 75℃ water bath for 1.5h, then add 550mL of sodium stearate solution dropwise at a rate of 0.5mL / min, adjust the pH to 4 with 0.1mol / L dilute hydrochloric acid, stir at 75℃ for 6.5h, centrifuge at 4500rpm for 15min, discard the supernatant, wash the precipitate with deionized water and centrifuge, repeat 4 times, vacuum dry at 65℃ to constant weight, grind, and pass through a 200-mesh sieve to obtain modified hydrotalcite.
[0038] S3: Mix 65 mL of deionized water and 60 mL of anhydrous ethanol evenly, add 6.5 g of silane coupling agent KH-550 and stir evenly to obtain a silane solution; add 22 g of modified hydrotalcite to 550 mL of ethanol, stir at 350 rpm for 1.5 h in an 85 °C water bath, add 150 mL of silane solution dropwise at a rate of 0.5 mL / min, stir at 85 °C for 4.5 h, centrifuge at 4500 rpm for 15 min, collect the precipitate, wash the precipitate 4 times with deionized water, wash it 2 times with anhydrous ethanol, vacuum dry it at 65 °C to constant weight, grind it, and pass it through a 200 mesh sieve to obtain toughened hydrotalcite.
[0039] S4: Add 2.6g of dopamine hydrochloride to 1100mL of Tris buffer solution and stir to dissolve to obtain a dopamine solution. Then add 12g of aramid fiber and stir magnetically at 350rpm for 4.5h in a 35℃ water bath. Take out the fiber, soak and wash the fiber with deionized water 4 times, and vacuum dry at 65℃ for 13h to obtain dopamine-coated aramid fiber.
[0040] S5: Add 110g polypropylene, 16.5g toughening hydrotalcite, 9g dopamine-coated aramid fiber, 9g maleic anhydride-grafted polypropylene, 0.65g polypropylene wax, 0.5g antioxidant 1010 and 0.25g antioxidant 168 to a premixer and stir at 175 rpm for 35 min. Transfer to a twin-screw extruder, set the temperatures of zones one to five to be 115, 170, 205, 195 and 180℃ respectively, the die temperature to be 145℃, the feeding speed to be 125 rpm and the screw speed to be 275 rpm. Extrude and granulate, dry with hot air at 95℃ for 5.5 h, and then form into a high-toughness modified polypropylene power cable protection pipe through a pipe extrusion production line.
[0041] Example 3: A method for preparing a high-toughness modified polypropylene power cable protection pipe, comprising the following steps: S1: Dissolve 68.92g magnesium chloride hexahydrate and 41.24g aluminum nitrate nonahydrate in 600mL of deionized water to obtain solution A; dissolve 28g sodium hydroxide and 69.3g anhydrous sodium carbonate in 600mL of deionized water to obtain solution B; transfer solutions A and B to constant pressure dropping funnels, and simultaneously add 600mL of solution A and 500mL of solution B at a rate of approximately 0.1mL / s in a water bath at 60℃ with vigorous stirring. Monitor the pH value of the reaction solution in real time with a pH meter during the addition process, and maintain the pH value of the reaction solution at 11 by adjusting the dropping rate of solution B. After the addition is completed, crystallize at 70℃ for 24h, centrifuge at 5000rpm for 20min, discard the supernatant, wash repeatedly with deionized water until the filtrate is neutral, collect the solid, vacuum dry the solid at 80℃ to constant weight, grind, and pass through a 200-mesh sieve to obtain magnesium aluminum hydrotalcite.
[0042] S2: Dissolve 38g of sodium stearate in 600mL of deionized water to obtain a sodium stearate solution; mix 620mL of deionized water and 680mL of anhydrous ethanol evenly, add 26g of magnesium aluminum hydrotalcite while stirring, stir in an 80℃ water bath for 2h, then add 600mL of sodium stearate solution dropwise at a rate of 0.5mL / min, adjust the pH to 4 with 0.1mol / L dilute hydrochloric acid, stir at 80℃ for 7h, centrifuge at 5000rpm for 20min, discard the supernatant, wash the precipitate with deionized water and centrifuge, repeat 5 times, vacuum dry at 70℃ to constant weight, grind, and pass through a 200-mesh sieve to obtain modified hydrotalcite.
[0043] S3: Mix 80 mL of deionized water and 70 mL of anhydrous ethanol evenly, add 8 g of silane coupling agent KH-550 and stir evenly to obtain a silane solution; add 24 g of modified hydrotalcite to 600 mL of ethanol, stir at 400 rpm for 2 h in a 90 °C water bath, add 200 mL of silane solution dropwise at a rate of 0.5 mL / min, stir at 90 °C for 5 h, centrifuge at 5000 rpm for 20 min, collect the precipitate, wash the precipitate 5 times with deionized water, then wash it 3 times with anhydrous ethanol, vacuum dry at 70 °C to constant weight, grind, and pass through a 200 mesh sieve to obtain toughened hydrotalcite.
[0044] S4: Add 3.2g of dopamine hydrochloride to 1200mL of Tris buffer solution and stir to dissolve to obtain a dopamine solution. Then add 14g of aramid fiber and magnetically stir at 400rpm for 5h in a 40℃ water bath. Take out the fiber, soak and wash the fiber with deionized water 5 times, and vacuum dry at 70℃ for 14h to obtain dopamine-coated aramid fiber.
[0045] S5: Add 120g polypropylene, 18g toughening hydrotalcite, 10g dopamine-coated aramid fiber, 10g maleic anhydride-grafted polypropylene, 0.8g polypropylene wax, 0.6g antioxidant 1010 and 0.3g antioxidant 168 to a premixer and stir at 200rpm for 40min. Transfer to a twin-screw extruder, set the temperatures of zones one to five to 130, 190, 220, 210 and 200℃ respectively, the die temperature to 160℃, the feeding speed to 150rpm and the screw speed to 300rpm. Extrude and granulate, dry with hot air at 100℃ for 6h, and then form into a high-toughness modified polypropylene power cable protection pipe through a pipe extrusion production line.
[0046] In Examples 1-3, magnesium chloride hexahydrate was selected from Guangdong Fangxin Biotechnology Co., Ltd., CAS No. 7791-18-6; aluminum nitrate nonahydrate was selected from Jiangsu Leien Environmental Protection Technology Co., Ltd., CAS No. 7784-27-2; sodium hydroxide was selected from Qidi Chemical Co., Ltd., CAS No. 1310-73-2; anhydrous sodium carbonate was selected from Shandong Zhijia Chemical Technology Co., Ltd., CAS No. 497-19-8; and sodium stearate was selected from Jinan Yuanyang Chemical Co., Ltd., with a molecular weight of 306.46 and a C AS number 822-16-2; silane coupling agent KH-550 is selected from Hunan Jinyu Fine Chemical Co., Ltd., with a molecular weight of 221.369 and CAS number 919-30-2; dopamine hydrochloride is selected from Xi'an Pinjian Biotechnology Co., Ltd.; Tris buffer is prepared by Tris buffer salt, i.e., tris(hydroxymethyl)aminomethane, and the pH value is adjusted to 8.5 with hydrochloric acid. The tris(hydroxymethyl)aminomethane is selected from Jiangsu Runfeng Synthetic Technology Co., Ltd., with a molecular weight of 121.14 and CAS number 77-86-1; The aramid fiber was selected from Nantong Runfeng Petrochemical Co., Ltd., CAS No. 308069-56-9; the polypropylene was selected from Suzhou Huying Plastics Co., Ltd., grade J340X; the maleic anhydride-grafted polypropylene was selected from Guangdong Jingcheng Plastics Technology Co., Ltd., grade QF541E; the polypropylene wax was selected from Jiangsu Faer Wax Industry Co., Ltd., model 1000, CAS No. 9002-88-4; antioxidant 1010 was selected from Jinan Juyang Chemical Technology Co., Ltd., CAS No. 6683-19-8; antioxidant 168 was selected from Jinan Haiyuan Chemical Co., Ltd., CAS No. 31570-04-4; the remaining raw materials were all commercially available products.
[0047] Comparative Example 1: The difference from Example 1 is that step S2 is omitted, and the modified hydrotalcite in step S3 is replaced with magnesium aluminum hydrotalcite in step S1, while the other steps remain unchanged, resulting in a high-toughness modified polypropylene power cable protection pipe.
[0048] Comparative Example 2: The difference from Example 1 is that step S3 is omitted, and the toughening hydrotalcite in step S5 is replaced with the modified hydrotalcite in step S2, while the other steps remain unchanged, resulting in a high-toughness modified polypropylene power cable protection pipe.
[0049] Comparative Example 3: The difference from Example 1 is that the order of steps S2 and S3 is reversed. First, silane coupling agent is used for grafting, and then sodium stearate is used for intercalation treatment. The remaining steps remain unchanged to obtain a high-toughness modified polypropylene power cable protection pipe.
[0050] Comparative Example 4: The difference from Example 1 is that step S4 is omitted, and the dopamine-coated aramid fiber in step S5 is replaced with commercially available aramid fiber. The remaining steps remain unchanged, resulting in a high-toughness modified polypropylene power cable protection pipe.
[0051] The following performance tests were conducted on the high-toughness modified polypropylene power cable protection pipes prepared in Examples 1-3 and Comparative Examples 1-4: Notched impact strength: Refer to GB / T 1843-2008 "Determination of impact strength of plastic cantilever beams" to determine the notched impact strength of the specimen at 23℃. The higher the value, the better the impact toughness of the material.
[0052] Wear amount: Refer to GB / T 3960-2016 "Plastics Sliding Friction and Wear Test Method" to determine the wear amount of the sample under the specified load and speed conditions. The lower the value, the better the wear resistance of the material.
[0053] Ring stiffness: Refer to GB / T 9647-2015 "Determination of ring stiffness of thermoplastic pipes" to measure the ring stiffness of the pipe. The higher the value, the stronger the resistance of the pipe to external pressure deformation.
[0054] Corrosion resistance: According to GB / T 11547-2008 "Determination of resistance of plastics to liquid chemical reagents", the samples were immersed in 10% sulfuric acid solution and 10% sodium hydroxide solution respectively for 7 days at room temperature (23±2℃). After immersion, the notched impact strength was measured according to GB / T1843-2008. The impact strength retention rate was calculated. The higher the retention rate, the better the acid and alkali corrosion resistance of the material.
[0055] The results are shown in Table 1: Table 1 Performance Test Results of High-Toughness Modified Polypropylene Power Cable Protection Pipe As can be seen from Table 1, Examples 1-3 are superior to the comparative examples in terms of notched impact strength, wear resistance, ring stiffness and corrosion resistance. This indicates that the present invention, through the dual modification of hydrotalcite (stearic acid intercalation combined with silane grafting), a specific modification sequence and the synergistic effect of dopamine-coated aramid fibers, helps to simultaneously improve the toughness, wear resistance and corrosion resistance of the material.
[0056] Comparative Example 1 skipped step S2, directly treating the unintercalated raw hydrotalcite with silane, thus missing the stearic acid intercalation step. This resulted in insufficient expansion of the interlayer spacing and inadequate surface hydrophobicity, making it more prone to agglomeration within the polypropylene matrix, forming stress concentration points. Simultaneously, the untreated hydrophobic hydrotalcite exhibited weak resistance to corrosive media. Therefore, Comparative Example 1 showed low impact toughness, wear resistance, and corrosion resistance, indicating that stearic acid intercalation is a crucial step in improving the dispersibility and hydrophobicity of hydrotalcite.
[0057] Comparative Example 2, lacking step S3 and using only stearic acid-intercalated hydrotalcite, omits the silane grafting step. The hydrotalcite surface lacks amino groups that can react with the polypropylene matrix, resulting in limited interfacial bonding strength. Under stress, the interface is prone to debonding, affecting the toughening effect. Simultaneously, the interfacial micropores may become channels for corrosive media penetration, leading to a decrease in corrosion resistance. However, since stearic acid intercalation still improves dispersibility to some extent, Comparative Example 2 outperforms the completely unmodified Comparative Example 1, but is inferior to the Example 1, indicating that silane grafting has a supplementary role in strengthening interfacial bonding and improving overall performance.
[0058] Comparative Example 3 altered the order of steps S2 and S3, performing silane grafting first followed by stearic acid intercalation. The pre-grafted silane molecules may occupy active sites on the edges and surface of the hydrotalcite layers, creating steric hindrance for subsequent stearate anion entry into the interlayer, leading to reduced intercalation efficiency and difficulty in fully expanding the interlayer spacing. Simultaneously, silane may undergo partial hydrolysis and failure under subsequent acidic intercalation conditions. This prevents the full realization of the synergistic effect of the hydrotalcite's dual modification, increases the tendency for filler agglomeration, and results in a lower overall performance compared to the comparative example. This demonstrates that the "intercalation before grafting" process sequence has a significant impact on achieving the desired modification effect.
[0059] Comparative Example 4 skipped step S4 and used untreated aramid fibers directly. The fiber surface was relatively smooth and chemically inert, resulting in weak interfacial bonding with the polypropylene matrix. During impact, the fibers were easily pulled out, making it difficult to effectively absorb energy. The pores remaining after fiber pull-out could also exacerbate wear and promote the penetration of corrosive media. However, due to the retained dual modification with hydrotalcite, Comparative Example 4 showed slightly better performance in some aspects than Comparative Examples 1-3, which lacked hydrotalcite modification, but overall it was still inferior to the examples. This indicates that dopamine coating treatment is beneficial for fully utilizing the toughening effect of aramid fibers and assisting in improving wear resistance and corrosion resistance.
[0060] 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 variations can be made to these embodiments without departing from the principles and spirit of the invention.
Claims
1. A method for preparing a high-toughness modified polypropylene power cable protection pipe, characterized in that, Includes the following steps: Step 1: Magnesium aluminum hydrotalcite was prepared by double-drop coprecipitation method, and then toughened hydrotalcite was obtained by sodium stearate intercalation and silane coupling agent surface grafting. Step 2: Surface coating of aramid fibers is performed using dopamine self-polymerization to obtain dopamine-coated aramid fibers; Step 3: Polypropylene, toughening hydrotalcite, dopamine-coated aramid fiber, maleic anhydride-grafted polypropylene, polypropylene wax, antioxidant 1010 and antioxidant 168 are blended, granulated by twin-screw extrusion, dried and then extruded into pipes to obtain high-toughness modified polypropylene power cable protection pipe. The mass ratio of the polypropylene, toughening hydrotalcite, dopamine-coated aramid fiber, maleic anhydride-grafted polypropylene, polypropylene wax, antioxidant 1010, and antioxidant 168 is 100-120:15-18:8-10:8-10:0.5-0.8:0.4-0.6:0.2-0.
3.
2. The method for preparing a high-toughness modified polypropylene power cable protection pipe according to claim 1, characterized in that, The specific preparation method of the toughened hydrotalcite is as follows: Deionized water and anhydrous ethanol were mixed evenly, and silane coupling agent KH-550 was added and stirred evenly to obtain a silane solution. Modified hydrotalcite was added to ethanol and stirred at 80-90℃ for 1-2 hours. The silane solution was added dropwise, and stirring was continued for 4-5 hours. The mixture was centrifuged, washed, vacuum dried to constant weight, and ground to obtain toughened hydrotalcite.
3. The method for preparing a high-toughness modified polypropylene power cable protection pipe according to claim 2, characterized in that, The ratio of deionized water, anhydrous ethanol, and silane coupling agent KH-550 is 50-80 mL: 50-70 mL: 5-8 g; the ratio of modified hydrotalcite, ethanol, and silane solution is 20-24 g: 500-600 mL: 100-200 mL.
4. The method for preparing a high-toughness modified polypropylene power cable protection pipe according to claim 3, characterized in that, The specific preparation method of the modified hydrotalcite is as follows: Sodium stearate was dissolved in deionized water to obtain a sodium stearate solution. Deionized water and anhydrous ethanol were stirred and mixed evenly. Magnesium aluminum hydrotalcite was added while stirring and stirred for 1-2 hours. Then, sodium stearate solution was added dropwise to adjust the pH to 4. The mixture was stirred at 70-80℃ for 6-7 hours. After centrifugation, washing, vacuum drying to constant weight, grinding and sieving, modified hydrotalcite was obtained.
5. The method for preparing a high-toughness modified polypropylene power cable protection pipe according to claim 4, characterized in that, The sodium stearate solution is prepared by using sodium stearate and deionized water at a ratio of 30-38g: 500-600mL; the ratio of deionized water, anhydrous ethanol, magnesium aluminum hydrotalcite and sodium stearate solution is 500-620mL: 500-680mL: 20-26g: 500-600mL.
6. The method for preparing a high-toughness modified polypropylene power cable protection pipe according to claim 5, characterized in that, The specific preparation method of the magnesium aluminum hydrotalcite is as follows: Magnesium chloride hexahydrate and aluminum nitrate nonahydrate were dissolved in deionized water to obtain solution A; sodium hydroxide and anhydrous sodium carbonate were dissolved in deionized water to obtain solution B; under vigorous stirring, solutions A and B were simultaneously added dropwise to the reaction flask at a rate of about 0.1 mL / s, and the mixture was kept at 60-70℃ for 18-24 h for crystallization. After centrifugation, the supernatant was discarded, and the mixture was repeatedly washed with deionized water until the filtrate was neutral. The solid was collected, dried under vacuum to constant weight, ground, and sieved to obtain magnesium aluminum hydrotalcite.
7. The method for preparing a high-toughness modified polypropylene power cable protection pipe according to claim 6, characterized in that, The ratio of magnesium chloride hexahydrate, aluminum nitrate nonahydrate, and deionized water is 60.96-68.92:37.48-41.24:400-600mL; the ratio of sodium hydroxide, anhydrous sodium carbonate, and deionized water is 24-28g:63.6-69.3g:400-600mL; and the volume ratio of solution A to solution B is 400-600mL:400-500mL.
8. The method for preparing a high-toughness modified polypropylene power cable protection pipe according to claim 1, characterized in that, The specific preparation method of the dopamine-coated aramid fiber is as follows: Dopamine hydrochloride was dissolved in Tris buffer to obtain a dopamine solution. Aramid fibers were then added and the solution was magnetically stirred at 300-400 rpm for 4-5 hours in a water bath at 30-40℃. The fibers were then removed and washed with deionized water 3-5 times. Finally, the fibers were vacuum dried at 60-70℃ for 12-14 hours to obtain dopamine-coated aramid fibers.
9. The method for preparing a high-toughness modified polypropylene power cable protection pipe according to claim 8, characterized in that, The ratio of dopamine hydrochloride, Tris buffer, and aramid fiber is 2-3.2g: 1000-1200mL: 10-14g.
10. A high-toughness modified polypropylene power cable protection pipe, prepared according to any one of claims 1-9.