Preparation and application of high-temperature-resistant polypropylene cable insulation material

Abstract

The application discloses a kind of preparation and application of high-temperature-resistant polypropylene cable insulation material, and the application belongs to electrical insulating material and its preparation technical field;In view of the problem that the mechanical strength and insulation performance of existing polypropylene cable insulation material deteriorate sharply at high temperature, 1,6-hexanediol diacrylate is grafted in polypropylene, and tetra (3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) pentaerythritol ester is doped to realize modification;Using the double grafting site of 1,6-hexanediol diacrylate to connect multiple molecular chains, the interchain force is enhanced, and the high-temperature mechanical properties are improved by synergistic antioxidant;At the same time, the C=O polar bond of 1,6-hexanediol diacrylate is used to introduce electron traps, the free volume is reduced by antioxidant, the high-energy electron transport is inhibited, the bulk conductive current is reduced, and the high-temperature insulation strength is improved;The application is a fully organic system, which has strong adaptability to cable production process and is suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of electrical insulation materials and their preparation technology, specifically to the preparation and application of a high-temperature resistant polypropylene cable insulation material. Background Technology

[0002] High-voltage direct current (HVDC) transmission boasts advantages such as large transmission capacity, low loss, high reliability, and high stability, making it a key area for power system development. In HVDC transmission systems, plastic-insulated cables are widely used due to their high operating temperature, high strength, and light weight. Currently, most plastic-insulated cables use cross-linked polyethylene (XLPE) as the main insulation material. However, with the large-scale application of XLPE cables, problems in manufacturing, production, and recycling after decommissioning have become increasingly prominent. Specifically, on the one hand, the production process of XLPE cables is time-consuming and energy-intensive; on the other hand, as a thermosetting polymer, XLPE has a unique cross-linked network structure, making it difficult to degrade the insulation layer of XLPE cables after decommissioning, thus preventing processing and reuse. Developing recyclable and environmentally friendly cable materials has become a research hotspot in the field of electrical materials.

[0003] The production process of polypropylene cables is energy-efficient, produces no harmful byproducts, and polypropylene is recyclable, effectively reducing carbon emissions. However, as a linear semi-crystalline polymer, polypropylene is prone to insulation breakdown and cable eccentricity under high-temperature conditions, significantly reducing the operational stability of polypropylene cables. Therefore, developing a polypropylene insulation material with excellent high-temperature insulation and mechanical properties is crucial to ensuring the safe operation of polypropylene cables. Summary of the Invention

[0004] The purpose of this invention is to solve the bottleneck problems of poor high-temperature insulation and mechanical properties of existing polypropylene cable insulation materials, which are prone to insulation breakdown and cable eccentricity. The invention provides a method for preparing polypropylene cable insulation materials that combine high breakdown strength and good mechanical properties at high temperatures, as well as their applications.

[0005] To achieve the above objectives, the present invention provides the following solution: This invention provides a method for preparing high-temperature resistant polypropylene cable insulation material, the method comprising the following steps: 1. Weigh an appropriate amount of polypropylene and place it in a vacuum oven. Place it under vacuum and 80°C conditions for 24 hours to obtain dried polypropylene for later use. 2. Place the dried polypropylene into a mixer, add 1,6-hexanediol diacrylate and the initiator dicumyl peroxide into the mixer, set the mixer speed to 60 r / min and the temperature to 180℃, mix for 10 min to complete the grafting of 1,6-hexanediol diacrylate. 3. Add pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid), set the speed of the internal mixer to 60 r / min and the temperature to 180℃, and mix for 3 min to ensure that the grafted polypropylene and pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) are evenly mixed. 4. Remove the grafted polypropylene from the internal mixer in a molten state, cut it with scissors, and allow the cut polypropylene to cool naturally in the air to obtain high-temperature resistant polypropylene cable insulation material.

[0006] Preferably, the mass ratio of 1,6-hexanediol diacrylate to polypropylene in the polypropylene molecular linker is (0.002~0.016):1, and the mass ratio of pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) doped to polypropylene is 0.003:1.

[0007] Preferably, in step two, the mass ratio of the initiator dicumyl peroxide to polypropylene is 0.001:1.

[0008] This invention also provides a high-temperature resistant polypropylene cable insulation material, wherein 1,6-hexanediol diacrylate is grafted onto the polypropylene molecular chain. The polypropylene molecular chain is bridged by two grafting sites and the structure of the polypropylene molecular chain is changed by introducing polar C=O groups on the molecular chain. On the other hand, pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) is doped into the grafted polypropylene to increase the intermolecular forces of the grafted polypropylene molecular chains.

[0009] Preferably, the high-temperature resistant polypropylene cable insulation material can achieve a breakdown field strength of 385.3 kV / mm and a strength of 1.59 × 10⁻⁶ kV / mm at 120°C. -6 A / m 2 It has an electrical conductivity current of 9.7 MPa, a tensile strength of 9.7 MPa, an elongation at break of 2181%, and a creep variation of 4%.

[0010] Finally, this invention provides an application of high-temperature resistant polypropylene cable insulation material, characterized in that the high-temperature resistant polypropylene cable insulation material serves as the main insulation material of the cable, wrapping around the cable conductor to isolate voltage, prevent leakage and short circuits, and ensure safe power transmission as a core insulation layer; its improved insulation and mechanical properties at high temperatures can effectively enhance the operational safety of polypropylene cables.

[0011] Compared with the prior art, the present invention has the following beneficial effects: I. In this invention, 1,6-hexanediol diacrylate is grafted onto polypropylene. From the perspective of molecular chain structure modification, 1,6-hexanediol diacrylate has dual grafting sites, which can connect two or more polypropylene molecular chains, increasing the interaction force between polypropylene molecular chains. At the same time, increasing the length of polypropylene molecular chains can increase the degree of entanglement between molecular chains.

[0012] The doping with pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) increases the intermolecular forces between the grafted polypropylene molecular chains. Increased intermolecular forces and the degree of chain entanglement improve the mechanical properties of polypropylene at high temperatures. Final examples show that the high-temperature resistant polypropylene cable insulation material prepared according to this invention exhibits improved high-temperature tensile strength by 28%, high-temperature elongation at break by 16.7%, and creep resistance by 64%.

[0013] II. This invention grafts 1,6-hexanediol diacrylate onto polypropylene. The grafted 1,6-hexanediol diacrylate introduces traps within the polypropylene, inhibiting the transport of high-energy electrons, reducing the damage of high-energy electrons to the polypropylene molecular chains, and significantly reducing the conductivity current of polypropylene at high temperatures, thus improving the insulation performance of polypropylene at high temperatures. The doped pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) reduces the free volume of the grafted polypropylene, inhibiting the transport of high-energy electrons and further improving the insulation performance of polypropylene at high temperatures. Final examples show that the high-temperature resistant polypropylene cable insulation material prepared by this invention can increase the high-temperature breakdown field strength by 24.4% and reduce the high-temperature conductivity current by 6 times at a field strength of 20 kV / mm.

[0014] Third, in this invention, 1,6-hexanediol diacrylate is grafted onto polypropylene. The grafted 1,6-hexanediol diacrylate has a high negative surface potential, which can scatter electrons inside the polypropylene, reduce the energy of electrons, and hinder electron transport.

[0015] Fourth, this invention belongs to a fully organic system, with low modification costs, making it suitable for large-scale production, and providing a new R&D approach for the large-scale production of high-temperature resistant polypropylene cable materials.

[0016] Fifth, this invention is highly compatible with cable manufacturing processes. The grafting process of 1,6-hexanediol diacrylate and the doping process of pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrogenated cinnamic acid) can be directly introduced into the three-layer co-extrusion process during cable production, providing a new R&D approach for the large-scale production of high-temperature resistant polypropylene cables. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope.

[0018] Figure 1 (a) is a surface electrostatic potential cloud diagram of polypropylene, and (b) is a surface electrostatic potential cloud diagram and potential statistics diagram of 1,6-hexanediol diacrylate grafted polypropylene. Figure 2 (a) is a simulation diagram of LUMO and HUMO energy levels of polypropylene grafted with 1,6-hexanediol diacrylate; (b) is a comparison diagram of LUMO and HUMO energy levels and trap types of polypropylene grafted with 1,6-hexanediol diacrylate. Figure 3 (a) Intermolecular forces of 1,6-hexanediol diacrylate grafted polypropylene; (b) Intermolecular forces of 1,6-hexanediol diacrylate grafted polypropylene and pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid); (c) Free volume of 1,6-hexanediol diacrylate grafted polypropylene; (d) Free volume of 1,6-hexanediol diacrylate grafted polypropylene after doping with pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid). Figure 4 (a) Infrared spectra of the materials obtained in Comparative Example 1 and Examples 1-4; (b) Torque-time curves of the materials obtained in Comparative Example 1 and Examples 1-4 in a mixer; (c) XRD patterns of the materials obtained in Comparative Example 1 and Examples 1-4. Figure 5 (a) is a scatter plot of the electrical conduction current of the materials obtained in Comparative Example 1 and Examples 1-4 at 30°C; (b) is a scatter plot of the electrical conduction current of the materials obtained in Comparative Example 1 and Examples 1-4 at 60°C; (c) is a scatter plot of the electrical conduction current of the materials obtained in Comparative Example 1 and Examples 1-4 at 90°C; and (d) is a scatter plot of the electrical conduction current of the materials obtained in Comparative Example 1 and Examples 1-4 at 120°C. Figure 6 (a) is the Weibull distribution diagram of the breakdown field strength of the material obtained in Comparative Example 1 and Examples 1-4 at 30°C; (b) is the Weibull distribution diagram of the breakdown field strength of the material obtained in Comparative Example 1 and Examples 1-4 at 60°C; (c) is the Weibull distribution diagram of the breakdown field strength of the material obtained in Comparative Example 1 and Examples 1-4 at 90°C; and (d) is the Weibull distribution diagram of the breakdown field strength of the material obtained in Comparative Example 1 and Examples 1-4 at 120°C. Figure 7(a) Creep curves and recovery curves of the materials obtained at 30°C for 30 min for Comparative Example 1 and Examples 1-4 are shown. (b) Creep curves and recovery curves of the materials obtained at 120°C for 30 min for Comparative Example 1 and Examples 1-4 are shown. Figure 8 (a) is the stress-strain curve of the material at 30°C obtained in Comparative Example 1 and Examples 1-4, and (b) is the stress-strain curve of the material at 120°C obtained in Comparative Example 1 and Examples 1-4. Figure 9 (a) is a curve showing the change of loss factor with temperature obtained from dynamic thermomechanical analysis of materials obtained in Comparative Example 1 and Examples 1-4; (b) is a curve showing the change of storage modulus with temperature obtained from dynamic thermomechanical analysis of materials obtained in Comparative Example 1 and Examples 1-4; (c) is an enlarged view of the curves showing the change of storage modulus with temperature obtained from dynamic thermomechanical analysis of materials obtained in Comparative Example 1 and Examples 1-4 from 100℃ to 140℃. Figure 10 (a) is the thermogravimetric curve of the materials obtained in Comparative Example 1 and Examples 1-4, and (b) is the scatter plot of the thermal decomposition temperature of the materials obtained in Comparative Example 1 and Examples 1-4. Detailed Implementation

[0019] Specific Implementation Method 1: This implementation method relates to a high-temperature resistant polypropylene cable insulation material, characterized by modification of polypropylene in two aspects: molecular chain structure and intermolecular interaction forces. On one hand, 1,6-hexanediol diacrylate is grafted onto the polypropylene molecular chain, bridging the polypropylene molecular chain through dual grafting sites and introducing polar C=O groups onto the molecular chain to alter the polypropylene molecular chain structure. On the other hand, pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) is doped into the grafted polypropylene, increasing the intermolecular interaction forces. The changes in molecular chain structure and the enhancement of intermolecular interaction forces improve the insulation and mechanical properties of polypropylene at high temperatures.

[0020] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the mass ratio of the grafted monomer 1,6-hexanediol diacrylate to polypropylene is (0.002~0.016):1, and the mass ratio of the doped pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrogenated cinnamic acid) to polypropylene is 0.003:1. Other steps are the same as in Specific Implementation Method One.

[0021] Specific Implementation Method 3: The 1,6-hexanediol diacrylate is grafted onto the molecular chain of polypropylene, and pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrogenated cinnamic acid) is incorporated into the grafted polypropylene. The preparation method is specifically carried out according to the following steps: 1. Weigh an appropriate amount of polypropylene and place it in a vacuum oven. Place it under vacuum and 80°C conditions for 24 hours to obtain dried polypropylene for later use.

[0022] 2. Place the dried polypropylene into a mixer, add 1,6-hexanediol diacrylate and the initiator dicumyl peroxide into the mixer, set the mixer speed to 60 r / min and the temperature to 180℃, mix for 10 min to complete the grafting of 1,6-hexanediol diacrylate.

[0023] 3. Add pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid), set the speed of the internal mixer to 60 r / min and the temperature to 180℃, and mix for 3 min to ensure that the grafted polypropylene and pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) are evenly mixed.

[0024] 4. Remove the modified polypropylene from the internal mixer in its molten state, cut it with scissors, and allow it to cool naturally in the air to obtain high-temperature resistant polypropylene cable insulation material.

[0025] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the mass ratio of the initiator dicumyl peroxide to polypropylene is 0.001:1. The other steps are the same as in Specific Implementation Methods One to Four.

[0026] Specific Implementation Method Five: A high-temperature resistant polypropylene cable insulation material is used as the main insulation material in polypropylene cables; the main cable insulation is a core insulation layer wrapped around the cable conductor to isolate voltage, prevent leakage and short circuits, and ensure safe power transmission. The high-temperature resistant polypropylene cable insulation material maintains a breakdown field strength of 385.3 kV / mm, a tensile strength of 9.7 MPa, an elongation at break of 2181%, and a creep variation of 4% at 120°C.

[0027] The beneficial effects of the present invention are verified using the following embodiments: Example 1: A high-temperature resistant polypropylene cable insulation material, wherein 1,6-hexanediol diacrylate is grafted onto the polypropylene molecular chain, and pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrogenated cinnamic acid) is incorporated into the grafted and modified polypropylene. The preparation method is specifically carried out according to the following steps: 1. Weigh an appropriate amount of polypropylene and place it in a vacuum oven. Place it under vacuum and 80°C conditions for 24 hours to obtain dried polypropylene for later use.

[0028] The mass of polypropylene weighed in step one is 40g.

[0029] 2. Add 1,6-hexanediol diacrylate and the initiator dicumyl peroxide to a mixer. Set the mixer speed to 60 r / min and the temperature to 180℃. Mix for 10 min to complete the grafting of 1,6-hexanediol diacrylate.

[0030] The mass ratio of 1,6-hexanediol diacrylate to polypropylene added in step two is 0.002:1.

[0031] In step two, 0.04 g of initiator dicumyl peroxide was added.

[0032] 3. Place the dried polypropylene into a mixer, add pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid), set the mixer speed to 60 r / min and the temperature to 180℃, and mix for 3 min to ensure that the polypropylene and pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) are mixed evenly.

[0033] In step three, 0.12 g of pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) was added.

[0034] 4. Remove the modified polypropylene from the internal mixer in its molten state, cut it with scissors, and allow it to cool naturally in the air to obtain high-temperature resistant polypropylene, which is called 0.2H-PP.

[0035] Example 2: The difference between this example and Example 1 is that the mass ratio of 1,6-hexanediol diacrylate to polypropylene in step three is 0.004:1; it is called 0.4H-PP. The other steps and parameters are the same as in Example 1.

[0036] Example 3: The difference between this example and Example 1 is that the mass ratio of 1,6-hexanediol diacrylate to polypropylene in step three is 0.008:1; it is called 0.8H-PP. The other steps and parameters are the same as in Example 1.

[0037] Example 4: The difference between this example and Example 1 is that the mass ratio of 1,6-hexanediol diacrylate to polypropylene in step three is 0.016:1; it is called 1.6H-PP. The other steps and parameters are the same as in Example 1.

[0038] Comparative Example 1: The preparation method of polypropylene material is specifically carried out according to the following steps: 1. Weigh an appropriate amount of polypropylene and place it in a vacuum oven. Place it under vacuum and 80°C conditions for 24 hours to obtain dried polypropylene for later use.

[0039] The mass of polypropylene weighed in step one is 40g.

[0040] 2. Place the dried polypropylene into a mixer, add pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid), set the mixer speed to 60 r / min and the temperature to 180℃, and mix for 13 min to ensure that the polypropylene and pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) are mixed evenly.

[0041] In step two, 0.12 g of pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) was added.

[0042] 3. Remove the molten polypropylene from the internal mixer, cut it with scissors, and let the cut polypropylene cool naturally in the air to obtain polypropylene, which is called PP.

[0043] The insulating materials obtained in Examples 1-4 and Comparative Example 1 were characterized in terms of structure and performance. The results are as follows: Figure 1 (a) is a surface electrostatic potential cloud diagram of polypropylene, and (b) is a surface electrostatic potential cloud diagram and potential statistics diagram of 1,6-hexanediol diacrylate grafted polypropylene. Depend on Figure 1 It is known that polypropylene has low surface electrostatic potentials, but grafting 1,6-hexanediol diacrylate can introduce a negative surface electrostatic potential of 0.8 eV.

[0044] Figure 2 (a) is a simulation diagram of LUMO and HUMO energy levels of polypropylene grafted with 1,6-hexanediol diacrylate; (b) is a comparison diagram of LUMO and HUMO energy levels and trap types of polypropylene grafted with 1,6-hexanediol diacrylate. Depend on Figure 2 It is known that the LUMO energy level of 1,6-hexanediol diacrylate-grafted polypropylene is lower than that of polypropylene, introducing a 1.9 eV electron trap between the polypropylene molecular chains. Simultaneously, the HUMO energy level of 1,6-hexanediol diacrylate-grafted polypropylene is higher than that of polypropylene, introducing a 0.68 eV hole trap between the polypropylene molecular chains. The introduction of electron and hole traps can effectively reduce the migration of high-energy charge carriers and improve the high-temperature insulation performance of polypropylene.

[0045] Figure 3 (a) Intermolecular forces of 1,6-hexanediol diacrylate grafted polypropylene; (b) Intermolecular forces of 1,6-hexanediol diacrylate grafted polypropylene and pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid); (c) Free volume of 1,6-hexanediol diacrylate grafted polypropylene; (d) Free volume of 1,6-hexanediol diacrylate grafted polypropylene after doping with pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid). Depend on Figure 3 It is known that doping pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) ester into polypropylene grafted with 1,6-hexanediol diacrylate can increase the intermolecular interaction forces of the system while reducing the free volume of the system.

[0046] Figure 4 (a) Infrared spectra of the materials obtained in Comparative Example 1 and Examples 1-4; (b) Torque-time curves of the materials obtained in Comparative Example 1 and Examples 1-4 in a mixer; (c) XRD patterns of the materials obtained in Comparative Example 1 and Examples 1-4. Depend on Figure 4 It can be seen that the characteristic peak at 1740 cm⁻¹ in the infrared spectra of Examples 1-4 is caused by the C=O stretching vibration of 1,6-hexanediol diacrylate, proving that 1,6-hexanediol diacrylate was successfully grafted onto polypropylene. In Examples 1-4, a torque peak appeared in the torque-time curves during the grafting process. This is because the dual grafting sites of 1,6-hexanediol diacrylate connect two or more polypropylene molecular chains, increasing the viscosity of polypropylene and ultimately leading to an increase in the internal mixer torque. This also proves that both grafting sites of 1,6-hexanediol diacrylate can participate in the grafting process. The XRD patterns of Examples 1-4 show that grafting 1,6-hexanediol diacrylate does not affect the crystallinity of polypropylene.

[0047] Figure 5 (a) is a scatter plot of the electrical conduction current of the materials obtained in Comparative Example 1 and Examples 1-4 at 30°C; (b) is a scatter plot of the electrical conduction current of the materials obtained in Comparative Example 1 and Examples 1-4 at 60°C; (c) is a scatter plot of the electrical conduction current of the materials obtained in Comparative Example 1 and Examples 1-4 at 90°C; and (d) is a scatter plot of the electrical conduction current of the materials obtained in Comparative Example 1 and Examples 1-4 at 120°C.

[0048] Depend on Figure 5 It can be seen that Examples 1-4 maintain low conductivity current over a wide temperature and electric field range. At 120℃ and 20kV / mm, the conductivity current of Examples 1-4 is 9.75×10⁻⁶ compared to Comparative Example 1. -6 A / m 2 They decreased to 6.26 × 10 - 6 A / m 2 2.93×10 -6 A / m 2 1.59×10 -6 A / m 2 3.93×10 -6 A / m 2The reduction in electrical conductivity current can effectively reduce cable loss, reduce heat generation, suppress space charge, and improve electric field distribution, thereby significantly improving the cable's transmission efficiency, operational reliability, thermal stability, and ultimately extending its service life.

[0049] Figure 6 (a) is the Weibull distribution diagram of the breakdown field strength of the material obtained in Comparative Example 1 and Examples 1-4 at 30°C; (b) is the Weibull distribution diagram of the breakdown field strength of the material obtained in Comparative Example 1 and Examples 1-4 at 60°C; (c) is the Weibull distribution diagram of the breakdown field strength of the material obtained in Comparative Example 1 and Examples 1-4 at 90°C; and (d) is the Weibull distribution diagram of the breakdown field strength of the material obtained in Comparative Example 1 and Examples 1-4 at 120°C.

[0050] Depend on Figure 6 It can be seen that Examples 1-4 maintain a high breakdown field strength over a wide temperature range. At 120℃, compared with Comparative Example 1, the breakdown strength of Examples 1-4 increased from 309.9 kV / mm to 341.9 kV / mm, 368.5 kV / mm, 385.3 kV / mm, and 358 kV / mm, respectively. The increase in breakdown field strength is beneficial for reducing cable insulation thickness, increasing cable voltage rating, and increasing cable safety margin, thereby ensuring the long-term operational reliability of the cable.

[0051] Figure 7 (a) Creep curves and recovery curves of the materials obtained at 30°C for 30 min for Comparative Example 1 and Examples 1-4 are shown. (b) Creep curves and recovery curves of the materials obtained at 120°C for 30 min for Comparative Example 1 and Examples 1-4 are shown.

[0052] Depend on Figure 7 It can be seen that Examples 1-4 maintain good creep resistance at both 30℃ and 120℃. At 30℃, compared with Comparative Example 1, the creep rate of Examples 1-4 decreased from 1.85% to 0.93%, 0.88%, 0.84%, and 0.87%, respectively. At 120℃, compared with Comparative Example 1, the creep rate of Examples 1-4 decreased from 7.06% to 5.55%, 4.88%, 4.75%, and 4.3%, respectively. The improved creep resistance can effectively reduce the eccentricity problem of the cable during operation and maintain the reliability of the cable's mechanical structure during long-term operation.

[0053] Figure 8 (a) is the stress-strain curve of the material at 30°C obtained in Comparative Example 1 and Examples 1-4, and (b) is the stress-strain curve of the material at 120°C obtained in Comparative Example 1 and Examples 1-4.

[0054] Depend on Figure 8It can be seen that Examples 1-4 maintain good mechanical properties at both 30℃ and 120℃. At 120℃, compared with Comparative Example 1, the elongation at break of Examples 1-4 increased from 1971.8% to 2079.6%, 2199.3%, 2157.5%, and 2191.1%, respectively; the tensile strength increased from 7.7MPa to 8.1MPa, 8.7MPa, 8.9MPa, and 9.6MPa, respectively. The improvement in tensile strength and elongation at break can significantly enhance the cable's resistance to mechanical damage.

[0055] Figure 9 (a) is a curve showing the change of loss factor with temperature obtained from dynamic thermomechanical analysis of materials obtained in Comparative Example 1 and Examples 1-4; (b) is a curve showing the change of storage modulus with temperature obtained from dynamic thermomechanical analysis of materials obtained in Comparative Example 1 and Examples 1-4; (c) is an enlarged view of the curves showing the change of storage modulus with temperature obtained from dynamic thermomechanical analysis of materials obtained in Comparative Example 1 and Examples 1-4 from 100℃ to 140℃.

[0056] Depend on Figure 9 It can be seen that Examples 1-4 have higher storage modulus at high temperatures. Compared with Comparative Example 1, the storage modulus of Examples 1-4 increased from 211.9 MPa to 214.5 MPa, 225.9 MPa, 234.9 MPa, and 250.3 MPa at 120°C, respectively. This also indicates that Examples 1-4 have superior mechanical properties at high temperatures.

[0057] Figure 10 (a) is the thermogravimetric curve of the materials obtained in Comparative Example 1 and Examples 1-4, and (b) is the scatter plot of the thermal decomposition temperature of the materials obtained in Comparative Example 1 and Examples 1-4.

[0058] Depend on Figure 10 It can be seen that the thermal decomposition temperatures of Examples 1-4 were increased to 323.8℃, 338.4℃, 339.1℃ and 349.1℃ respectively, which significantly improved the high-temperature stability of the material.

[0059] In summary, the high-temperature resistant polypropylene cable insulation material prepared by this invention is achieved by grafting 1,6-hexanediol diacrylate onto polypropylene and doping it with pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid). This regulates the molecular chain structure and intermolecular interactions of polypropylene, resulting in a final polypropylene insulation material with high insulation strength and good mechanical strength at high temperatures.

[0060] This invention illustrates the all-polymer receptor material, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials used in this invention, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.

Claims

1. A method for preparing a high-temperature resistant polypropylene cable insulation material, characterized in that, The preparation method includes the following steps:

1. Weigh an appropriate amount of polypropylene and place it in a vacuum oven. Place it under vacuum and 80°C conditions for 24 hours to obtain dried polypropylene for later use.

2. Place the dried polypropylene into a mixer, add 1,6-hexanediol diacrylate and the initiator dicumyl peroxide into the mixer, set the mixer speed to 60 r / min and the temperature to 180℃, mix for 10 min to complete the grafting of 1,6-hexanediol diacrylate.

3. Add pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid), set the speed of the internal mixer to 60 r / min and the temperature to 180℃, and mix for 3 min to ensure that the grafted polypropylene and pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) are evenly mixed.

4. Remove the grafted polypropylene from the internal mixer in a molten state, cut it with scissors, and allow the cut polypropylene to cool naturally in the air to obtain high-temperature resistant polypropylene cable insulation material.

2. The preparation method according to claim 1, characterized in that, The mass ratio of 1,6-hexanediol diacrylate to polypropylene in the polypropylene molecular linking branch is (0.002~0.016):1, and the mass ratio of pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) doped to polypropylene is 0.003:

1.

3. The preparation method according to claim 1, characterized in that, In step two, the mass ratio of the initiator dicumyl peroxide to polypropylene is 0.001:

1.

4. A high-temperature resistant polypropylene cable insulation material prepared by the method according to any one of claims 1-3, characterized in that, 1,6-hexanediol diacrylate of high-temperature resistant polypropylene cable insulation material is grafted onto the polypropylene molecular chain. The polypropylene molecular chain is bridged by two grafting sites and the structure of the polypropylene molecular chain is changed by introducing polar C=O groups on the molecular chain. On the other hand, pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) is doped into the grafted polypropylene to increase the intermolecular forces of the grafted polypropylene molecular chain.

5. The high-temperature resistant polypropylene cable insulation material according to claim 4, characterized in that, High-temperature resistant polypropylene cable insulation material can achieve a breakdown field strength of 385.3 kV / mm and a strength of 1.59 × 10⁻⁶ kV / mm at 120℃. -6 A / m 2 It has an electrical conductivity current of 9.7 MPa, a tensile strength of 9.7 MPa, an elongation at break of 2181%, and a creep variation of 4%.

6. The application of the high-temperature resistant polypropylene cable insulation material according to any one of claims 4-5, characterized in that, High-temperature resistant polypropylene cable insulation material is the main insulation material of the cable, wrapped around the cable conductor to isolate voltage, prevent leakage and short circuit, and ensure safe power transmission. The improved insulation and mechanical properties at high temperatures can effectively enhance the operational safety of polypropylene cables.

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