A trolley cable jacket material and method of making the same

Abstract

This application relates to a trolley cable sheath material and its preparation method, belonging to the field of cable technology. The trolley cable sheath material provided in this application, by weight, comprises the following components: 100 parts PVC, 20-40 parts aconitate, 0.5-1 part UV-absorbing additive, 5-10 parts flame retardant, 0.5-2 parts lubricant, and 1-5 parts heat stabilizer. This trolley cable sheath material has good cold resistance, high temperature resistance, and UV resistance, and is safe and environmentally friendly for direct user contact. It can meet the usage scenarios of trolley cables in cold or sunny weather and with high heat generation. Furthermore, it has suitable hardness, is easy to process, and has excellent wear resistance, making it suitable as a sheath material for trolley cables.

Description

A material for sheathing trolley cables and its preparation method Technical Field

[0001] This application relates to a sheath material for tram cables and its preparation method, belonging to the field of cable technology. Background Technology

[0002] With the rapid popularization of new energy electric vehicles, the performance improvement of cables inside electric vehicles and charging equipment has faced severe challenges. Compared with traditional cable sheaths, electric vehicle cable sheath materials have more stringent requirements for safety and durability in the field of new energy electric vehicles. For example, electric vehicle cables used for outdoor charging of new energy electric vehicles need to meet the following requirements.

[0003] First, there is the environmental friendliness of the materials. In the field of new energy electric vehicles, the chances of cables coming into contact with the human body have increased significantly. This means that the plasticizers in PVC composite sheaths are more likely to migrate into the human body. Traditional cable plasticizers use toxic phthalic plasticizers, which are extremely harmful to the human body, especially the reproductive system of adolescents.

[0004] Secondly, the environment in which trolley cables operate is more complex. They are not used stably in a single location for extended periods; most are exposed outdoors, facing extreme heat and cold, requiring a wider operating temperature range and good UV resistance. However, current environmentally friendly plasticizers replace benzene rings in their main structure. While ensuring safety and non-toxicity, this also weakens the material's UV resistance. Under prolonged exposure to sunlight, cable sheath materials struggle to maintain good long-term stability.

[0005] Finally, due to their structure, existing plasticizers are difficult to balance the plasticizing stability of materials at both high and low temperatures, resulting in a narrow operating temperature range and making them unsuitable for long-term stable use.

[0006] Based on the actual usage requirements of electric vehicle cables, there is an urgent need to provide a cable sheath material that has good cold resistance, high temperature resistance, UV resistance, and is safe, environmentally friendly, and suitable for direct user contact. This material can meet the charging performance requirements of new energy electric vehicles in cold or sunny weather and in scenarios with high heat generation. Summary of the Invention

[0007] To address the aforementioned issues, a trolley cable sheath material and its preparation method are provided. This trolley cable sheath material exhibits good cold resistance, high temperature resistance, and UV resistance, and is safe and environmentally friendly, suitable for direct user contact. It can meet the usage scenarios of trolley cables in cold or sunny weather and with high heat generation power. Furthermore, it has suitable hardness, is easy to process, and has excellent wear resistance, making it suitable as a sheath material for trolley cables.

[0008] This application provides a trolley cable sheath material, which, by weight, comprises the following components: 100 parts PVC, 20-40 parts aconitate, 0.5-1 part UV absorbent additive, 5-10 parts flame retardant, 0.5-2 parts lubricant, and 1-5 parts heat stabilizer.

[0009] Optionally, the aconitate is selected from one or more of tri-n-butyl aconitate, tri-n-pentyl aconitate, tri-n-hexyl aconitate, tri-n-heptyl aconitate, tri-n-octyl aconitate, or tri(2-ethylhexyl) aconitate.

[0010] Optionally, the absorbent UV-resistant additive is selected from one or more of UV-623 or UV3035.

[0011] Optionally, the flame retardant is selected from one or more of tri(2-chloropropyl) phosphate, aluminum hydroxide, or magnesium hydroxide.

[0012] Optionally, the lubricant is selected from one or more of butyl stearate or chlorinated polyethylene wax.

[0013] Optionally, the heat stabilizer is selected from one or more of calcium stearate, zinc stearate, or methyltin mercaptan.

[0014] Optionally, the trolley cable sheath material comprises the following components by weight: 100 parts PVC, 35 parts aconitate, 0.6 parts UV absorbent additive, 7 parts flame retardant, 1 part lubricant, and 3 parts heat stabilizer.

[0015] This application provides a method for preparing a tram cable comprising the above-mentioned tram cable sheath material, characterized in that the preparation method includes the following steps:

[0016] 1) Add the absorbent UV stabilizer, flame retardant, lubricant, and heat stabilizer to the mixer, set the speed to 450~550 rpm, and the mixing time to 5~15 min to obtain the additive mixture;

[0017] 2) Mix PVC, aconitate and the additive mixture obtained in step 1) and add it to a twin-screw extruder. Adjust the temperature of each zone of the twin screw to 120℃, 130℃, 150℃, 170℃, 170℃ and 160℃, the speed to 50~70 rpm, the extrusion mass flow rate to 30~40 kg / h, and after melt blending, extrude it onto the outside of the cable core.

[0018] 3) Pass the wrapped cable core through a thermoplastic box to form a protective layer, and finally cool and solidify to obtain a trolley cable containing the trolley cable sheath.

[0019] Optionally, the preparation method includes the following steps:

[0020] 1) Add the absorbent UV stabilizer, flame retardant, lubricant, and heat stabilizer to the mixer, set the speed to 500 rpm, and the mixing time to 10 min to obtain the additive mixture;

[0021] 2) Mix PVC, aconitate and the additive mixture obtained in step 1) and add them to a twin-screw extruder. Adjust the temperature of each zone of the twin screw to 120℃, 130℃, 150℃, 170℃, 170℃ and 160℃, the speed to 60 rpm, and the extrusion mass flow rate to 35 kg / h. After melt blending, extrude it onto the outside of the cable core.

[0022] 3) Pass the wrapped cable core through a thermoplastic box to form a protective layer, and finally cool and solidify to obtain a trolley cable containing the trolley cable sheath.

[0023] The beneficial effects of this application include, but are not limited to:

[0024] 1. The tram cable sheath material according to this application has good environmental protection and non-toxicity. Since tram cable sheaths are more likely to come into contact with the human body than traditional cables, and the aconitate ester plasticizer used in the tram cable sheath material of this application has good non-toxic and environmental protection properties compared with traditional phthalic plasticizers, it will not pose a threat to human safety and health.

[0025] 2. In the tram cable sheath material of this application, the added aconitate ester not only plays a plasticizing role, but the "conjugated double bond" structure of the aconitate ester itself can also effectively absorb ultraviolet light. At the same time, it forms a good synergistic effect with the absorbent anti-ultraviolet additives UV-623 or UV3050 in the material, further improving the anti-ultraviolet performance of the material.

[0026] 3. According to the trolley cable sheath material of this application, the aconitate is selected from tri-n-butyl aconitate, tri-n-pentyl aconitate, tri-n-hexyl aconitate, tri-n-heptyl aconitate, tri-n-octyl aconitate, or tri(2-ethylhexyl) aconitate, which has a wider operating temperature range. When the carbon number of the aconitate group is ≤8, its own trimer structure can be effectively compatible with PVC, improving the mobility of PVC molecular chains, thereby making the material exhibit good cold resistance. At the same time, when the carbon number of the ester group is ≥4, the aconitate has a large molecular weight, which is difficult to volatilize into the environment, thus enhancing the heat resistance of the material. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0028] Figure 1 shows the results of the changes in mechanical properties before and after aging in Embodiment 1 of this application. Detailed Implementation

[0029] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments. Unless otherwise specified, the raw materials and catalysts in the embodiments of the present application are all purchased through commercial channels.

[0030] UV-resistant additives are mainly divided into two categories: absorptive UV-resistant agents, which selectively absorb high-energy ultraviolet rays and convert them into other lower-energy forms (such as longer-wavelength light or heat) for release; and reflective UV-resistant additives, which reflect and shield ultraviolet rays to prevent them from reaching the PVC surface, thereby reducing photochemical reactions. This application uses absorptive UV-resistant additives, such as UV-623 and UV3035, but is not limited to these. The UV-resistant additives used in this application can synergistically complement the conjugated double bonds in aconitine esters. The combination of the two not only increases the ultraviolet absorption wavelength range but also enhances the material's ultraviolet absorption capacity, making it more resistant to ultraviolet rays. Experiments have shown that reflective UV-resistant additives have contradictory ultraviolet absorption properties with aconitine esters and do not have a good synergistic UV-resistant effect.

[0031] In this application, PVC was purchased from Ningxia Jinyuyuan Chemical Group Co., Ltd.; aconitate was purchased from Chengdu Kamaier Pharmaceutical Technology Co., Ltd.; UV-623 was purchased from Weihai Huaen Rubber & Plastic New Materials Co., Ltd.; UV3035 was purchased from Qingdao Jiedejia New Materials Technology Co., Ltd.; tris(2-chloropropyl) phosphate was purchased from Zhangjiagang Xinya Chemical Co., Ltd.; aluminum hydroxide was purchased from Guangzhou Jicheng Import & Export Trading Co., Ltd.; magnesium hydroxide was purchased from Nanjing Hengqiao Chemical Technology & Materials Co., Ltd.; butyl stearate was purchased from Shanghai Rongli Chemical Technology Co., Ltd.; chlorinated polyethylene wax was purchased from Dongguan Dinghai Plastic & Chemical Co., Ltd.; calcium stearate was purchased from Nanjing Jinling Chemical Plant Co., Ltd.; zinc stearate was purchased from Shandong Qiangsen Chemical Co., Ltd.; and methyl tin mercaptan was purchased from Hubei Nordina Biotechnology Co., Ltd.

[0032] It should be noted that since this application focuses on the sheath material of trolley cables, unless otherwise specified, the trolley cables will not be prepared with cable cores in the performance test. Therefore, the trolley cable sheath material does not contain cable cores during the test, and the test is not conducted on the trolley cable finally prepared in the embodiment. Those skilled in the art should understand that the test is specifically conducted using the test strips prepared according to GB / T1040.2-2006 for trolley cable sheath material.

[0033] Example 1

[0034] In this embodiment, the basic formula of the tram cable sheath material, by weight, consists of the following components: 100 parts PVC, 35 parts aconitate, 0.6 parts UV absorber, 7 parts flame retardant, 1 part lubricant, and 3 parts heat stabilizer. The aconitate is tributyl aconitate, the UV absorber is UV-623, the flame retardant is tri(2-chloropropyl) phosphate, the lubricant is butyl stearate, and the heat stabilizer is calcium stearate.

[0035] The manufacturing process of this tram cable includes the following steps:

[0036] 1) Add the absorbent UV stabilizer, flame retardant, lubricant, and heat stabilizer to the mixer, set the speed to 550 rpm, and the mixing time to 5 min to obtain the additive mixture;

[0037] 2) Mix PVC, tributyl aconitate and the additive mixture from step 1) and add them to a twin-screw extruder. Adjust the temperature of each zone of the twin screw to 120℃, 130℃, 150℃, 170℃, 170℃ and 160℃, the speed to 60 rpm, and the extrusion mass flow rate to 35 kg / h. After melt blending, extrude it onto the outside of the cable core. Then, pass the coated cable core through a thermoplastic box to obtain a protective layer. Finally, after cooling and curing, an environmentally friendly and non-toxic trolley cable is obtained.

[0038] Example 2

[0039] In this embodiment, the basic formula of the tram cable sheath material, by weight, consists of the following components: 100 parts PVC, 20 parts aconitate, 0.5 parts UV absorber additive, 5 parts flame retardant, 2 parts lubricant, and 5 parts heat stabilizer. The aconitate is tri-n-hexyl aconitate, the UV absorber additive is UV absorber UV3035, the flame retardant is aluminum hydroxide, the lubricant is chlorinated polyethylene wax, and the heat stabilizer is zinc stearate.

[0040] The manufacturing process of this tram cable includes the following steps:

[0041] 1) Add the absorbent UV stabilizer, flame retardant, lubricant, and heat stabilizer to the mixer, set the speed to 500 rpm, and the mixing time to 10 min to obtain the additive mixture;

[0042] 2) Mix PVC, tri-n-hexyl aconitate and the additive mixture from step 1) and add them to a twin-screw extruder. Adjust the temperature of each zone of the twin screw to 120℃, 130℃, 150℃, 170℃, 170℃ and 160℃, apply 50 rpm, and the extrusion mass flow rate is 30 kg / h. After melt blending, extrude it to the outside of the cable core. Then, pass the coated cable core through a thermoplastic box to obtain a protective layer. Finally, after cooling and curing, an environmentally friendly and non-toxic trolley cable is obtained.

[0043] Example 3

[0044] In this embodiment, the basic formula of the tram cable sheath material consists of the following components by weight: 100 parts PVC, 40 parts aconitate, 0.5 parts UV absorber additive, 10 parts flame retardant, 0.5 parts lubricant, and 1 part heat stabilizer. The aconitate is tri-n-octyl aconitate, the UV absorber additive is UV absorber UV3035, the flame retardant is magnesium hydroxide, the lubricant is butyl stearate, and the heat stabilizer is methyltin mercaptan.

[0045] The manufacturing process of this tram cable includes the following steps:

[0046] 1) Add the absorbent UV stabilizer, flame retardant, lubricant, and heat stabilizer to the mixer, set the speed to 450 rpm, and the mixing time to 15 min to obtain the additive mixture;

[0047] 2) Mix PVC, tri-n-octyl aconitate and the additive mixture from step 1) and add them to a twin-screw extruder. Adjust the temperature of each zone of the twin screw to 120℃, 130℃, 150℃, 170℃, 170℃ and 160℃, apply 70 rpm, and the extrusion mass flow rate is 40 kg / h. After melt blending, extrude it to the outside of the cable core. Then, pass the coated cable core through a thermoplastic box to obtain a protective layer. Finally, after cooling and curing, an environmentally friendly and non-toxic trolley cable is obtained.

[0048] Comparative Example 1

[0049] This comparative example is basically the same as Example 1, except that it does not contain aconitate, but is replaced with an equal amount of dibutyl phthalate as a plasticizer.

[0050] Comparative Example 2

[0051] This comparative example is basically the same as Example 1, except that it does not contain aconitate, but is replaced with an equal amount of di(2-ethylhexyl) phthalate as a plasticizer.

[0052] Comparative Example 3

[0053] This comparative example is basically the same as Example 1, except that it does not contain aconitine esters, but is replaced with an equal amount of epoxidized soybean oil as a plasticizer.

[0054] Test Example 1

[0055] Performance tests were conducted on the tram cable sheath materials prepared in the examples and comparative examples, including tests on cold resistance, high temperature resistance, and UV resistance. Among them, tensile strength, elongation at break, and UV aging resistance tests were conducted on the test strips of tram cable sheath materials prepared according to GB / T1040.2-2006. The hardness was tested according to GB / T531-2008 "Indentation Hardness Test Method, Shore Hardness Tester Method". Hardness indicates the plasticizing performance of the material; the lower the value, the better the plasticizing effect. Tensile strength was tested according to GB / T1040–2006 "Plastics - Tensile Properties Test", with a tensile speed of 50 mm / min and a temperature of 25℃. Tensile strength indicates the strength of the material; the higher the value, the higher the strength. Elongation at break was tested according to GB / T1040–2006 "Plastics - Tensile Properties Test", with a tensile speed of 50 mm / min and a temperature of 25℃. Elongation at break indicates the toughness of the material; the higher the elongation at break, the stronger the toughness. In the UV aging resistance test, the prepared sample was placed in a test chamber and irradiated with a 6KW xenon lamp for 2000 hours, followed by standing at room temperature for 24 hours. Tensile strength and elongation were then tested, and the retention rate was calculated. The test results are shown in Table 1 below.

[0056] Table 1

[0057]

[0058] According to the data in Table 1, the trolley cable sheath materials in Examples 1-3 have good heat resistance and UV resistance, and have lower tensile strength and hardness compared to the comparative example, indicating that aconitate has a good plasticizing effect on the sheath material. At the same time, the PVC products plasticized with aconitate have suitable strength and elongation at break, and have smaller hardness difference after aging, higher tensile strength retention rate after aging, and higher elongation at break retention rate after aging, indicating that the sheath material has better aging resistance. Therefore, it is suitable for manufacturing trolley cable products to meet the needs of high temperature and sun exposure.

[0059] Experimental Example 1

[0060] The researchers tested the effect of adding aconitate esters with different carbon numbers on the performance of tram cable sheath materials. The test samples differed from those in Example 1 in that they used different types of aconitate esters, as detailed in Table 2 below. The performance results of the prepared tram cable sheaths are shown in Table 3. The hardness test method was the same as that in Example 1. The low-temperature brittleness temperature was tested according to GB / T 15256-2014. The volatility test was conducted on the volatility of plasticizers such as aconitate esters involved in the examples and test cases in PVC, to reflect the varying volatility of different types of plasticizers. The test was conducted with reference to HG / T 4458–2012 "Determination of Plasticizer Loss in Plastics - Activated Carbon Method", with a test temperature of 70℃ and a test time of 24 h.

[0061] Table 2

[0062]

[0063] Table 3

[0064]

[0065] According to the data in Table 3, the addition of tributyl aconitate, tripentyl aconitate, trihexyl aconitate, triheptyl aconitate, and trioctyl aconitate to the sheathing material of electric vehicle cables can balance cold resistance, high temperature resistance, and plasticizing properties. This is because aconitate esters with ≤8 carbon atoms in the ester group have a wider operating temperature range, and the trimer structure of these aconitate esters is effectively compatible with PVC, improving the mobility of PVC molecular chains and thus giving the material good cold resistance. At the same time, when the carbon number of the ester group is ≥4, aconitine has a larger molecular weight and is less likely to volatilize into the environment, thereby enhancing the heat resistance of the material.

[0066] When the carbon number of the ester group of aconitine is less than 4, the molecular weight of aconitine is lower, making it easier to extract from PVC, which affects the plasticizing effect and high-temperature resistance of the material. When the carbon number of the ester group is greater than 8, the molecular weight of aconitine is higher. Although aconitine is difficult to extract from PVC at this time, its polarity will also increase due to the longer polar ester group molecular chain, resulting in poorer compatibility with PVC and a poorer plasticizing effect on PVC. It also has a poorer effect when combined with absorbent UV-resistant additives, affecting the UV resistance of PVC.

[0067] The trolley cable sheaths prepared using tri-n-butyl aconitate, tri-n-pentyl aconitate, tri-n-hexyl aconitate, tri-n-heptyl aconitate, and tri-n-octyl aconitate are more suitable for the use scenarios of trolley cables. While meeting certain cold resistance requirements and excellent high temperature resistance and UV resistance, they also have good plasticizing properties.

[0068] Experimental Example 2

[0069] The researchers tested the effects of adding aconitate plasticizer and reflective UV-resistant additives on UV absorption and UV protection performance. Samples 7 and 8 differed from Example 1 only in the type of UV-resistant additive; otherwise, the performance testing methods were the same as in Example 1. The specific selection of UV-resistant additives is shown in Table 4 below, and the test results are shown in Table 5 below.

[0070] Table 4

[0071]

[0072] Table 5

[0073]

[0074] As shown in Table 5, aconitate has a good synergistic effect with the absorbent UV additives UV3035 and UV-623. Compared with the reflective UV additives, it has a better synergistic UV absorption effect, thus making the UV resistance of the plasticized PVC material more excellent.

[0075] Test Example 2

[0076] The researchers tested the materials for genotoxicity according to GB 15193.5-2014, "National Food Safety Standard: Micronucleus Test for Mammalian Erythrocytes". A positive result indicated genotoxicity, while a negative result indicated no genotoxicity. The test results showed that among the plasticizers, tri-n-butyl aconitate, tri-n-hexyl aconitate, and tri-n-octyl aconitate were negative; dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DOP) were positive; and epoxidized soybean oil was negative.

[0077] The bioaccumulation of materials was characterized according to GB / T 21853-2008 "Partition Coefficient (n-Octanol-Water) Shake Flask Test". According to the standard "Borectomy of Benthic Oligochaeta Annelids in Chemical Sediments", a log Pow > 3 indicates a certain degree of bioaccumulation, while a log Pow < 3 indicates no bioaccumulation. The tests revealed that the log Pows for tri-n-butyl aconitate was 2.95, tri-n-hexyl aconitate was 2.96, tri-n-octyl aconitate was 2.97, dibutyl phthalate (DBP) was 4.45, di(2-ethylhexyl) phthalate (DOP) was 7.50, and epoxidized soybean oil was 2.97.

[0078] It is evident that the addition of aconitate to the sheathing material of tram cables not only has a good plasticizing effect, but also provides good cold resistance, high temperature resistance, and UV resistance. Moreover, compared with petroleum-based phthalate plasticizers, aconitate is environmentally friendly and non-toxic. The plasticized material obtained after adding it to PVC is safer and more environmentally friendly, suitable for human contact, and will not produce toxic side effects.

[0079] According to the experimental results of Examples 1-3 of the present invention, when aconitate esters with 4 ≤ carbon number ≤ 8 are used for PVC plasticizing, plasticized products with high tensile strength and suitable elongation at break can be obtained, which are more suitable for industrial molding and processing. At the same time, when the carbon number of the ester group is in this range, aconitate esters can exist stably in PVC materials, are not easy to migrate and volatilize, and can form a good synergistic effect with absorbent UV absorbers. The superposition of plasticizing and UV protection effects gives PVC plasticized products good UV resistance and cold resistance, high retention rate of tensile strength and elongation at break after aging, and low low-temperature brittleness temperature. Compared with petroleum-based plasticizers, aconitate ester plasticizers are environmentally friendly and non-toxic, with log Pow < 3, and the use of such plasticizers will not have any impact on human health. Due to the special nature of their use, trolley cables need to be exposed to the outdoor environment for extended periods and have prolonged contact with the human body. Therefore, the substrate used to prepare trolley cables must meet high requirements for cold resistance, high temperature resistance, UV resistance, and non-toxicity and environmental friendliness. The PVC plasticized product prepared by this invention meets the requirements of trolley cable substrates and is suitable for the production of trolley cables for outdoor charging of new energy trolley vehicles.

[0080] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. The application of tram cable sheath material in the preparation of tram cable sheaths with cold resistance, high temperature resistance, and UV resistance, characterized in that, The trolley cable sheath material, by weight, comprises the following components: 100 parts PVC, 20-40 parts aconitate, 0.5-1 part UV-absorbing additive, 5-10 parts flame retardant, 0.5-2 parts lubricant, and 1-5 parts heat stabilizer; the aconitate is selected from one or more of tri-n-butyl aconitate, tri-n-pentyl aconitate, tri-n-hexyl aconitate, tri-n-heptyl aconitate, tri-n-octyl aconitate, or tri(2-ethylhexyl) aconitate; the UV-absorbing additive is selected from one or more of UV-623 or UV3035.

2. The application according to claim 1, characterized in that, The flame retardant is selected from one or more of tri(2-chloropropyl) phosphate, aluminum hydroxide, or magnesium hydroxide.

3. The application according to claim 1, characterized in that, The lubricant is selected from one or more of butyl stearate or chlorinated polyethylene wax.

4. The application according to claim 1, characterized in that, The heat stabilizer is selected from one or more of calcium stearate, zinc stearate, or methyltin mercaptan.

5. The application according to claim 1, characterized in that, The trolley cable sheath material comprises the following components by weight: 100 parts PVC, 35 parts aconitate, 0.6 parts UV absorbent additive, 7 parts flame retardant, 1 part lubricant, and 3 parts heat stabilizer.

6. The application according to claim 1, characterized in that, The preparation method of the tram cable sheath material includes the following steps: 1) Mixing absorbent UV-resistant additives, flame retardants, lubricants, and heat stabilizers into a stirrer, setting the rotation speed to 450~550 rpm, and stirring time to 5~15 min to obtain an additive mixture; 2) Mixing PVC, aconitate, and the additive mixture obtained in step 1) into a twin-screw extruder, adjusting the temperature of each zone of the twin screw to 120℃, 130℃, 150℃, 170℃, 170℃, and 160℃, the rotation speed to 50~70 rpm, and the extrusion mass flow rate to 30~40 kg / h. After melt blending, it is extruded onto the outside of the cable core; 3) Passing the coated cable core through a thermoplastic box to form a protective layer, and finally cooling and solidifying to obtain a tram cable containing the tram cable sheath.

7. The application according to claim 6, characterized in that, The preparation method includes the following steps: 1) Mixing absorbent UV-resistant additives, flame retardants, lubricants, and heat stabilizers into a stirrer, setting the rotation speed to 500 rpm and the stirring time to 10 min, to obtain an additive mixture; 2) Mixing PVC, aconitate, and the additive mixture obtained in step 1) into a twin-screw extruder, adjusting the temperature of each zone of the twin screw to 120℃, 130℃, 150℃, 170℃, 170℃, and 160℃, the rotation speed to 60 rpm, and the extrusion mass flow rate to 35 kg / h, and then extruding it onto the outside of the cable core after melt blending; 3) Passing the coated cable core through a thermoplastic box to form a protective layer, and finally cooling and solidifying to obtain a tram cable containing the tram cable sheath.

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