Conductive resin grounding body and preparation method thereof

Abstract

The invention relates to the field of conductive resin, in particular to a conductive resin grounding body and a preparation method thereof.The conductive resin grounding body utilizes a polyurethane-organic silicon composite system, meanwhile, adopts a combination of carbon fibers and graphite micro powder as filler, and utilizes a combination of linear filler and granular filler to form a structure capable of giving consideration to both elasticity and softness in the system; therefore, the protection effect of the conductive rubber system on the grounding body main body is improved while the conductive performance is ensured.

Description

Technical Field

[0001] The present application relates to the field of conductive resins, and in particular to a conductive resin grounding body and a preparation method thereof. Background Art

[0002] A conductive grounding device is a device used to safely conduct current in an electrical system or equipment underground. Its core function is to ensure the normal operation of the equipment, prevent the risk of electric shock, and reduce damage caused by lightning strikes or short circuit faults.

[0003] Conductive resin usually needs to be combined with and coated with a conductive metal matrix in a grounding body, which is achieved by adding conductive fillers. In order to improve conductivity, the amount of conductive fillers added to the conductive resin is usually large. In some solutions, it can even be close to 50% or even more of the resin mass. Usually, the conductive filler is graphene, graphite or carbon fiber, which has poor bonding performance with the resin and is prone to breakage, especially when adding carbon fiber. Although carbon fiber has a longer length and can form better conductivity as a whole and provide better strength support internally, during the resin coating, extrusion and bonding process, if the amount of carbon fiber added is too little, it is easy to cause the carbon fiber to break during processing, affecting the overall conductivity to a certain extent. Adding too much will lead to a decrease in the bonding performance between the conductive resin and the internal grounding body, as well as the elasticity and toughness of the conductive resin itself, and it will not provide a good protective effect. Summary of the Invention

[0004] The purpose of this application is to provide a conductive grounding body and a corresponding preparation method, which aims to improve the elasticity, toughness, adhesion and other mechanical properties of a conductive resin by adding a higher content of conductive filler.

[0005] First, the present application relates to a conductive resin grounding body, which includes a conductive resin and a grounding body body coated with the conductive resin. The grounding body body is a conductive material. The conductive resin has a polyamide-silicone mixed resin system. For every 100 parts by mass of the polyamide-silicone mixed resin system, 50 to 70 parts by mass of a conductive filler are added. The conductive filler includes carbon fiber and graphite powder, wherein the average diameter of the graphite powder does not exceed 50% of the average diameter of the carbon fiber, and the mass of the graphite powder accounts for 15 to 40% of the mass of the conductive filler. For every 100 parts by mass of the polyamide-silicone mixed resin system, the polyamide content is 50 to 90 parts by mass; For every 100 parts by mass of the polyamide-silicone mixed resin system, 0.5 to 5 parts of a coupling agent are also included; The conductive resin further comprises any number of a compatibilizer, an impact resistant agent, a toughening agent, an antioxidant, and an anti-aging agent; It also contains fatty alcohol polyoxyethylene ether, and the mass of the fatty alcohol polyoxyethylene ether is 0.05 to 0.1 times the mass of the carbon fiber.

[0006] In the above scheme, a polyamide and silicone hybrid system is first adopted, with the polyamide providing better adhesion, while the silicone system provides better overall strength and wear resistance. Overall, with the assistance of compatibilizers and other additives, the above system can form a uniform and stable mixed rubber system after uniform mixing. The compatibilizer can be an anhydride-modified polyolefin, such as the commonly used maleic anhydride-grafted polyethylene. Silicone rubber has certain elastomeric properties and is relatively stable at high temperatures. It can be extruded and injection molded together with the polyamide system, while also improving the overall mechanical strength.

[0007] On the basis of the above, a combination of carbon fiber and graphite powder is added to the system as the conductive material in the system. The carbon fiber provides better overall conductivity, while the graphite powder provides filling properties, increasing the area of ​​connection between carbon fibers and reducing the impact on adhesion and elasticity, so as to better balance the conductivity and adhesion properties of the system. In order to reduce the agglomeration of carbon fiber and graphite powder in the system and improve their dispersion uniformity, fatty alcohol polyoxyethylene ether is also added. In this system, fatty alcohol polyoxyethylene ether has a small impact on the overall strength, and its small addition will not affect the toughness of the system. At the same time, it can improve the dispersion of carbon fiber and reduce the clustering of carbon fiber during processing.

[0008] In the above scheme, the following additives may be selectively added, such as an impact resistant agent, a compatibilizer, a toughening agent, an antioxidant, an anti-aging agent, etc. Specifically, the coupling agent is a titanate coupling agent NDZ-201; and / or the compatibilizer is an anhydride-modified polyolefin; and / or the impact resistant agent is MBS; and / or the toughening agent is an ethylene-octene copolymer.

[0009] More preferably, the silicone is methyl silicone rubber, and the mass fraction of the polyamide is 75 to 85 parts per 100 parts by mass of the polyamide-silicone mixed resin system. Experiments have shown that the above composition ratio has better elasticity, adhesion and conductivity as a whole.

[0010] Preferably, in the polyamide-silicone hybrid resin system, the polyamide is a combination of PA6T or PA9T and an aliphatic polyamide, wherein the weight of the aliphatic polyamide accounts for 50-75% of the weight of the polyamide. Further preferably, the aliphatic polyamide is PA11, PA12, or PA1212.

[0011] In the above scheme, the components of polyamide are further limited, and a combination of aliphatic polyamide and semi-aromatic polyamide is adopted. After experiments, it was found that the use of aromatic polyamide in this system will reduce the flexibility of the system due to its excessive internal chain rigidity, which will have an adverse effect on the conductive properties of carbon fiber and its overall uniformity. Aliphatic polyamide has a more flexible molecular chain in the system, which can be better mixed with the silicone system and can also better coat the carbon fiber. However, if it relies solely on aliphatic polyamide, the toughness and strength of the system will be reduced to a certain extent. In this scheme, by adding semi-aromatic polyamides such as PA6T or PA9T, the reduction of aromatic rings in its molecular chain is utilized to provide better winding performance and toughness, thereby making the conductive resin itself have better strength.

[0012] Preferably, the conductive resin further comprises polyolefin, and the mass fraction of the polyolefin is 5 to 20 parts per 100 parts by mass of the polyamide-organic silicone mixed resin system.

[0013] In the above solution, by adding a certain amount of polyolefin, the overall extrusion performance, molding performance and elasticity after molding can be improved, while the overall processing temperature is appropriately reduced. Further preferably, the polyolefin has a viscosity not higher than 0.91 g / cm 3 The density range of the polyolefin is such that it can have a smaller molecular chain or more branched structure, making it difficult for the polyolefin itself to form a uniform phase in the system, but better mixed in the overall rubber system to improve the softness and elasticity of the rubber itself.

[0014] Preferably, EVA is further included, and the added mass parts of the EVA are 2.5 to 10 parts for every 100 parts by mass of the polyamide-silicone mixed resin system.

[0015] In the above scheme, by adding a certain amount of EVA, on the one hand, the connection relationship between the coupling agent and the organic phase is improved, and EVA itself provides good elasticity and bonding properties, and has better compatibility, dispersibility and bonding properties with inorganic fillers, and also better bonding properties with the grounding body.

[0016] More preferably, the vinyl acetate content of the EVA is 15-28%, which not only provides good bonding properties, but also has good softness and is not prone to crystallization within the system, thus significantly improving the overall mechanical properties.

[0017] In addition, the present application also relates to a method for preparing a conductive resin grounding body, which is obtained by extruding a conductive resin and then injection molding the conductive resin outside the grounding body.

[0018] In summary, the present application provides a conductive resin grounding body and a preparation method thereof, which utilizes a polyurethane-silicone composite system and adopts a combination of carbon fiber and graphite powder as filler. A combination of linear fillers and granular fillers is used to form a structure in the system that can take into account both elasticity and softness, thereby improving the protective effect of the conductive rubber system on the grounding body while ensuring the conductive performance. DETAILED DESCRIPTION

[0019] The technical solution in this application is further explained through the following specific implementation methods.

[0020] Design an experiment to verify the performance of the conductive grounding body after molding and the performance of the conductive resin prepared in the process.

[0021] Experiment 1: Dumbbell-shaped specimens were injection molded according to ASTM D638 and tested for elastic modulus and tensile strength. The specimen thickness was set to 2 mm, the tensile rate was 5 mm / min, and the strain was cycled from 0 to 50% 10 times. The elastic recovery was calculated.

[0022] Experiment 2: Referring to GB / T 2439-2001, a conductive resin was prepared into a dumbbell-shaped sample, which was brittle-fractured by cooling with liquid nitrogen. Silver paste was then coated on the cross section, and its volume resistivity was then measured using a high resistance / microammeter.

[0023] In Experiment 3, a conductive resin was extruded and injection-molded onto the surface of a copper grounding body. After curing, a T-shaped pattern was formed. The average peel strength was then calculated according to ASTM D1876 at a peel rate of 50 mm / min.

[0024] Example 1: In this example, the proportion and selection of the conductive filler are verified. Specifically, a conductive resin is provided, and a conductive grounding body is prepared using the conductive resin. Specifically, in this example, the specific conductive resin is calculated by weight, and the specific amount of each component is as follows: 100 parts of a polyamide-silicone hybrid resin system, comprising 80 parts polyamide and 20 parts silicone resin. Furthermore, the polyamide is a combination of PA6T and PA12, with 20 parts by weight of PA6T and 60 parts by weight of PA66. The silicone is methyl silicone rubber with a nominal viscosity of 300,000 cps.

[0025] The filler is 60 parts, and the filler is a combination of carbon fiber and graphite powder. The specific parameters and dosage are shown in Table 1. In Table 1, the carbon fibers are all chopped carbon fibers with a length of about 6 mm.

[0026] Table 1 10 parts of polyolefin, LDPE is selected, and its density is 0.904g / cm³.

[0027] 1 part of coupling agent, coupling agent NDZ-201 is selected.

[0028] 5 parts of compatibilizer, maleic anhydride grafted polyethylene is selected.

[0029] 2.5 parts of impact-resistant agent, MBS is selected.

[0030] 2.5 parts of toughening agent, ethylene-octene copolymer is selected.

[0031] 6 parts of fatty alcohol polyoxyethylene ether, specifically AEO-9.

[0032] On the basis of the above, antioxidants, anti-aging agents, colorants, flame retardants, lubricants, release agents, etc. can be added to the system if necessary. The addition of a small amount will not have a significant effect on the performance of the rubber.

[0033] The processing method of the above conductive resin is as follows: The materials except the conductive filler were added to a high-speed mixer and mixed for 4 minutes, and then added to a twin-screw extruder. Carbon fiber and graphite powder were added to the upper hopper of the extruder (about 20% of the extruder position). The extrusion temperature was 220°C and the die temperature was 230°C.

[0034] After the conductive resin is extruded, in addition to preparing samples for testing, it is directly injection molded onto the surface of the grounding body. The grounding body is made of copper.

[0035] The experimental group in Example 1 was tested, and the results are shown in Table 2.

[0036] Table 2 In the above scheme, first it can be seen that the coexistence system of carbon fiber and graphite powder not only provides good electrical conductivity, but also improves overall elasticity, and correspondingly reduces overall Young's modulus, so that it has better feasible deformation. In the filler combination of various particle size specifications, it can be seen that when the addition of graphite powder is too low, the resistivity of the system increases, and the overall elasticity has a certain reduction, and when graphite powder is added too much, the problem of overall resistivity increasing is also arranged. On the whole, electrical conductivity needs to utilize the linking effect of carbon fiber on a large scale and the filling effect of graphite powder in a small area. In addition, the reduction of carbon fiber consumption also causes the bonding performance of the system to have a certain reduction, which may be the anchoring effect of the missing carbon fiber.

[0037] When switching between carbon fibers and graphite powders of different specifications, the particle size of the graphite powder needs to be no greater than half the diameter of the carbon fibers. This allows for better filling and connection effects. Finer graphite powders can reduce the elastic modulus and flexural modulus while also reducing resistivity in the system, resulting in better overall performance while increasing costs. The carbon fibers can be of any commercially available standard specification. In this embodiment, three specifications of carbon fibers, 7 μm, 5 μm, and 10 μm, are used. As long as the average diameter of the graphite powder does not exceed 50% of the average diameter of the carbon fibers, good strength and conductivity can be achieved.

[0038] Example 2. This example selected Examples 1-4, 1-10, 1-18, and 1-29 from Example 1 and tested the effect of the quality of the added inorganic filler on the system performance. The specific results are shown in Table 3. In Table 3, each experimental group increased or decreased the amount of conductive filler in equal proportion to the basic experimental group.

[0039] Table 3 The above experiments show that even if the ratio of carbon fiber and graphite powder remains unchanged, the overall filler usage still needs to be controlled so that the overall conductive filler usage does not exceed 70 parts, which can provide good elasticity, mechanical properties and conductivity. However, when it exceeds 70 parts, different proportions and selections of conductive filler combinations will show a significant decrease in elasticity and elastic recovery rate.

[0040] Example 3: Based on Examples 1-4, this example adjusts the ratio of polyamide to silicone resin and the specific ratio of polyamide, as shown in Table 4.

[0041] Table 4 The experiment was conducted on the experimental groups in Table 4, and the results are shown in Table 5.

[0042] Table 5 Through the above experiments, it is not difficult to see that in this solution, the combination of semi-aliphatic polyamide and aliphatic polyamide is used, the main purpose of which is to take into account the softness and elasticity of the system. Among the types of aliphatic polyamides, whether PA6, PA11, PA1212 or PA12, the rebound performance of the system is reduced and the adhesion is slightly reduced. The use of too much semi-aliphatic polyamide will lead to a slight decrease in the strength and conductivity of the system and a stiffness. If an aromatic polyamide and aliphatic polyamide are combined, the overall adhesion will also be reduced and the hardness of the system will be too high. In addition, the crystallization of the aromatic polyamide will easily lead to a decrease in the continuity of the carbon fiber in the system, and to a certain extent, its conductivity will also be slightly reduced.

[0043] Silicone provides good elasticity and strength in the above system. With the help of a coupling agent, it has better mixing properties with the conductive filler and can be used in the main body of the grounding body. However, when the silane doping level is too high, it will destroy the crystallinity of the polyamide. While it improves elasticity when added in small amounts, too much can also damage the strength and bonding properties of the system.

[0044] Example 4. In the examples, different types of EVA are further added to Examples 1-4. In this example, five types of EVA with different VA contents are selected, and an orthogonal experiment is conducted on their addition amounts. The results are shown in Table 6.

[0045] Table 6 The above experiments show that adding EVA to the system significantly improves both elasticity and adhesion. Overall, the VA content should not exceed 28% for various EVAs. Otherwise, it will easily form a continuous EVA phase in the system, which will lead to a decrease in strength.

[0046] Example 5. In this example, based on Examples 4-8, the amount and type of polyolefin in the system are further adjusted. In this solution, different types of polyolefins are used. The specific types and amounts selected in the orthogonal experiment are shown in Table 7.

[0047] Table 7 Further experiments were conducted on the experimental groups in Table 7, and the results are shown in Table 8.

[0048] Table 8 The above experimental groups show that adding polyolefins to the system helps improve hardness and rebound properties, while also reducing hardness to a certain extent. Furthermore, in the above system, the addition of polyolefins can also improve processing performance. Overall, the addition of polyolefins can moderately reduce processing temperature. The addition of polyolefins should not be too high, otherwise it will significantly reduce tensile strength and elastic recovery. Furthermore, among various polyolefins, those with higher density tend to form neat arrangements in the system, resulting in denser molecular chains, which can significantly damage the system's strength.

[0049] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A conductive resin grounding body, characterized in that: The invention comprises a conductive resin and a grounding body coated with the conductive resin. The grounding body is made of a conductive material. The conductive resin comprises a polyamide-organic silicone mixed resin system. For every 100 parts by mass of the polyamide-organic silicone mixed resin system, 50 to 70 parts by mass of a conductive filler are added. The conductive filler comprises carbon fiber and graphite powder, wherein the average diameter of the graphite powder does not exceed 50% of the average diameter of the carbon fiber, and the mass of the graphite powder accounts for 15 to 40% of the mass of the conductive filler. For every 100 parts by mass of the polyamide-silicone mixed resin system, the polyamide content is 50 to 90 parts by mass; For every 100 parts by mass of the polyamide-silicone mixed resin system, 0.5 to 5 parts of a coupling agent are also included; The conductive resin further comprises any number of a compatibilizer, an impact resistant agent, a toughening agent, an antioxidant, and an anti-aging agent; It also contains fatty alcohol polyoxyethylene ether, and the mass of the fatty alcohol polyoxyethylene ether is 0.05 to 0.1 times the mass of the carbon fiber.

2. A conductive resin grounding body according to claim 1, characterized in that: In the polyamide-organic silicone hybrid resin system, the polyamide is selected from a combination of PA6T or PA9T and aliphatic polyamide, and the mass of the aliphatic polyamide accounts for 50-75% of the mass of the polyamide.

3. A conductive resin grounding body according to claim 2, characterized in that: The aliphatic polyamide is selected from PA11, PA12 or PA1212.

4. The conductive resin grounding body according to claim 1, characterized in that: The conductive resin further comprises polyolefin, and the mass portion of the polyolefin is 5 to 20 parts for every 100 parts by mass of the polyamide-organic silicone mixed resin system.

5. The conductive resin grounding body according to claim 4, characterized in that: The polyolefin has a g / cm 3 density range.

6. The conductive resin grounding body according to claim 1, characterized in that: The organosilicon is methyl silicone rubber, and the mass portion of the polyamide is 75 to 85 parts per 100 parts by mass of the polyamide-organosilicon mixed resin system.

7. The conductive resin grounding body according to claim 1, characterized in that: The coupling agent is titanate coupling agent NDZ-201; and / or, The compatibilizer is an anhydride-modified polyolefin; and / or, The impact-resistant agent is MBS; and / or, The toughening agent is ethylene-octene copolymer.

8. The conductive resin grounding body according to claim 1, characterized in that: The invention also contains EVA, and the added mass parts of the EVA are 2.5 to 10 parts for every 100 parts by mass of the polyamide-organic silicone mixed resin system.

9. The conductive resin grounding body according to claim 8, characterized in that: The vinyl acetate content of the EVA is 15-28%.

10. The method for preparing a conductive resin grounding body according to any one of claims 1 to 9, characterized in that: The conductive resin is extruded and then injection molded outside the grounding body.

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