A high-strength insulating composite material and preparation method thereof

Abstract

The present invention belongs to the technical field of insulating material preparation, and specifically relates to a high-strength insulating composite material and its preparation method. The method comprises: 1) extracting and cleaning raw materials and solvents, adding acid solution for acidification and desizing, filtering and cleaning, adding a coupling agent for reaction, and then filtering, cleaning, and drying to obtain a filler; 2) taking an alkaline earth metal oxide and a dispersant, mixing them evenly, adding a coupling agent for heating reaction, adding a filler and mixing them evenly, and obtaining a modified filler through reflux, cooling, cleaning, and drying; 3) mixing the modified filler with a thermoplastic material, an organic metal salt, an acyclic carboxylic acid, and an antioxidant, and kneading at high temperature to obtain a high-strength insulating composite material. The composite material prepared by the present invention can effectively prevent current leakage, has high safety and insulation, and at the same time has good high-temperature stability and chemical corrosion resistance. It can maintain good arc resistance and strength in a high temperature and high humidity environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of insulating material preparation, and in particular relates to a high-strength insulating composite material and a preparation method thereof. Background Art

[0002] Compared to metal components, plastic components are lightweight and easy to handle and install, offering advantages particularly in applications requiring reduced structural loads or increased portability. They are also rust-resistant and water-resistant, providing excellent electrical insulation properties and are widely used in the manufacture of electronic equipment such as computers, mobile phones, and circuit boards. Insulating plastics are primarily used in the power industry for insulation and support structures of electrical equipment, such as insulators, transformer and motor casings, and connectors. They provide stable performance in high-voltage, high-temperature, and humid environments, ensuring the stable operation of power transmission lines. Using insulating plastics to manufacture components such as automobile exteriors, train cars, and trackbeds can reduce the weight of vehicles and improve operational efficiency. They can also be used to manufacture components such as automotive ABS anti-lock braking systems, seals, gaskets, and bearings, achieving lightweighting and improving fuel efficiency.

[0003] Insulating plastic components have diverse uses in modern industry, but their low strength, poor rigidity, and susceptibility to aging prevent them from completely replacing metal components. When exposed to high temperatures, high humidity, ultraviolet light, chemical corrosion, and other conditions for a long time, insulating plastic components are prone to aging and cracking, significantly reducing their mechanical strength and, along with it, electrical insulation. Prolonged operation in high-temperature environments can even lead to the loss of structural integrity. Plastic components that are too thin or have poor dielectric properties can experience electrical breakdown under the influence of an electric field, leading to short circuits. If the material is not flame-retardant, this can cause fires.

[0004] To enhance the strength of plastic components, glass fiber is typically added to the plastic material. However, if the glass fiber content is too low, the strength and rigidity of the plastic component will not meet the requirements of metal accessories. If the glass fiber content is too high, it can easily cause surface blemishes, color mixing, and floating fibers on the workpiece surface, and can easily lead to mold release difficulties, whitening, and deformation during the injection molding process. Therefore, there is an urgent need to develop a preparation method that can both enhance the strength of plastic components and ensure component surface quality. Summary of the Invention

[0005] In order to solve a series of problems commonly found in existing insulating plastic parts, such as insufficient strength, easy occurrence of floating fibers, and high processing difficulty, the present invention proposes a high-strength insulating composite material and a preparation method of the high-strength insulating composite material.

[0006] The objects of the present invention are:

[0007] 1. Improve the arc resistance and insulation properties of materials;

[0008] 2. Improve the high temperature stability of materials;

[0009] 3. Improve the mechanical properties of materials.

[0010] To achieve the above objectives, the present invention adopts the following technical solutions.

[0011] A method for preparing a high-strength insulating composite material.

[0012] The method comprises:

[0013] 1) extracting and washing the raw materials and solvent, adding acid solution for desizing, filtering and washing, adding coupling agent for reaction, and then filtering, washing, and drying to obtain the filler;

[0014] 2) mixing alkaline earth metal oxide and dispersant evenly, adding coupling agent and heating to react, adding filler and mixing evenly, refluxing, cooling, washing, and drying to obtain modified filler;

[0015] 3) The modified filler is uniformly mixed with a thermoplastic material, an organic metal salt, an acyclic carboxylic acid, and an antioxidant, and kneaded at high temperature to obtain a high-strength insulating composite material.

[0016] As a preference,

[0017] The raw material in step 1) is aramid fiber with a diameter of 6 to 7 μm and a length of 2 to 3 mm; the solvent in step 1) is acetone in an amount of 5 to 15 mL / g of raw material;

[0018] The extraction time in step 1) is 46 to 50 hours.

[0019] As a preference,

[0020] Step 1) The acid solution is concentrated nitric acid with a concentration of 6-7 mol / L and an amount of 2-4 mL / g of raw material;

[0021] In step 1), the acid desizing is carried out at a constant temperature of 70 to 80° C. for 2.5 to 3 hours.

[0022] As a preference,

[0023] Step 1) The coupling agent is an ethanol solution of KH550 with a concentration of 3-4 wt% and an amount of 0.1-0.2 mL / g raw material;

[0024] In step 1), the coupling agent is added and then refluxed at 58-60° C. in a protective atmosphere for 3-3.5 hours.

[0025] As a preference,

[0026] Step 2) the alkaline earth metal oxide is magnesium oxide, the particle size of which is 0.8 to 1.2 μm, and the amount thereof is 0.5 to 1 g / g of raw material;

[0027] Step 2) the dispersant is N,N-dimethylformamide, and the amount thereof is 10-15 mL / g alkaline earth metal oxide;

[0028] Step 2) The coupling agent is an ethanol solution of KH550 with a concentration of 3-4 wt% and an amount of 0.1-0.2 mL / g alkaline earth metal oxide.

[0029] As a preference,

[0030] Step 2) the heating reaction is carried out at 80-90° C. for 6-6.5 hours;

[0031] In step 2), the reflux is carried out at a constant temperature of 155-160° C. for 2-2.5 hours.

[0032] As a preference,

[0033] In step 3), the thermoplastic material is polyetheretherketone, and its usage is 20-22g / g modified filler; in step 3), the organic metal salt is a mixture of lead stearate and calcium stearate, and its usage is 0.03-0.04g / g modified filler, and the lead stearate and calcium stearate are mixed in a mass ratio of 1: (0.5-0.7);

[0034] In step 3), the acyclic carboxylic acid is stearic acid, and its usage is 0.01-0.02 g / g of modified filler; in step 3), the antioxidant is antioxidant 1010, and its usage is 0.01-0.02 mL / g of modified filler.

[0035] As a preference,

[0036] Step 3) The high-temperature mixing is controlled at a temperature of 355-360° C. and a mixing time of 3-8 minutes. After mixing, the high-strength insulating composite material is obtained.

[0037] As a preference,

[0038] In step 3), after the high-temperature mixing, the mixture can be granulated to form a masterbatch, or directly extruded, injection molded, or blow molded to form a product.

[0039] A high-strength insulating composite material.

[0040] The technical solution of the present invention uses aramid fiber as raw material to prepare a modified filler to enhance the high-temperature stability of composite materials. Short-cut aramid fibers of an initial specific length can overlap with each other to form a heat conduction path. Because the initial length of the fibers is long, it will be difficult to disperse during filling, and local agglomeration is likely to occur. That is, fibers that are too long will cause uneven extrusion, which in turn can significantly affect the high-temperature stability of the composite material. Fibers with a short initial length can be evenly dispersed, but fibers that are too short will affect their overlapping effect, and the effect of improving the high-temperature stability of the composite material is small. In addition, fibers with a lower filling amount are dispersed in thermoplastic materials, and the overlapping effect is poor. The fibers and thermoplastic materials do not form a complete heat conduction path, and the effect of improving the high-temperature stability of the composite material is also small. As the filling amount increases, the fibers are evenly distributed in the material to form a continuous phase. At the same time, the tensile strength of the material gradually increases, and the increase is smaller and smaller. In order to ensure the effect of fiber overlapping and improving the high-temperature stability of the material, the present invention limits the length of the short-cut fibers and the relative amount of the modified filler.

[0041] In addition to selecting aramid fibers of appropriate length, the fibers also need to be pretreated. Unacidified aramid fibers have a smooth surface. After nitric acid treatment, the surface roughness of the fibers increases, with noticeable corrosion grooves. To bind the MgO particles, the present invention treats the aramid fibers with a coupling agent, introducing a large number of active groups such as amino and carboxyl groups onto their surfaces. Furthermore, the present invention utilizes an aminosilane coupling agent, KH550, at a concentration of 3-4 wt%, filling the grooves to create more and richer active groups. Aramid fibers that have not been treated with a coupling agent bind to thermoplastic materials through relatively weak physical interactions, resulting in a low fiber reinforcement effect. However, after being compounded with MgO particles through a coupling agent, the new chemical bonds formed by the ring-opening reaction within the system allow the material to absorb a large amount of energy when subjected to stress. This is because the weak physical bonds and chemical crosslinking enhance the tensile properties of the material. However, after only coupling treatment of the aramid fibers, the actual binding stability of the MgO particles and the aramid fibers is still relatively limited. KH550 has a self-condensation reaction activity. Therefore, the present invention uses KH550 to treat MgO in a modified manner, and then links MgO and aramid fibers through self-condensation, which can significantly optimize the linking effect between the two. In addition, the aramid fibers can also reduce the loss of their own active groups. The introduced groups interact with the thermoplastic material, improving the compatibility between the two and reducing the volume resistivity of the material.

[0042] Based on the above conclusions, it can be seen that it is difficult to control the insulation properties of a composite material solely by the relative content of aramid fiber. To enhance the insulation properties of the composite material while also taking into account the material's high-temperature stability, insulation properties, and mechanical strength, the present invention modifies the aramid fiber. Furthermore, to ensure that the MgO particles are attached to the aramid fiber surface, thereby obtaining a composite material with high chemical bonding strength, the present invention first disperses the MgO in N,N-dimethylformamide, adds a coupling agent, then heat treats it, and then mixes the filler. During this process, the grafting rate of the MgO particles is affected by the concentration of the silane coupling agent. As the mass fraction of the silane coupling agent increases, the excess coupling agent undergoes hydrolysis and condensation, resulting in a competitive reaction with the KH550-treated MgO. As the competitive reaction increases, the grafting rate of the MgO significantly decreases. A low MgO grafting rate not only affects the material's insulation properties but also its high-temperature stability. Under harsh, high-temperature environments, the composite material's insulation properties are prone to failure. Similarly, a low KH550 mass fraction can lead to reduced grafting rate and grafting stability, necessitating relatively strict control of the KH550 silane coupling agent dosage. Heat treatment temperature also has a certain impact on the MgO grafting rate. As the temperature increases, the intermolecular collision rate increases, enhancing the activity of the MgO particles and ultimately increasing the grafting rate of the MgO particles. However, excessively high temperatures lead to excessive molecular motion. The self-condensation of hydroxyl groups on the particle surface and the silanols produced by the hydrolysis of the coupling agent compete with the grafting reaction, potentially causing problems such as curling of the aramid fiber or agglomeration of the MgO, significantly reducing the grafting rate of MgO onto the aramid fiber.

[0043] In addition, the present invention should avoid the phenomenon of unstable MgO particles detaching due to excessive mixing time, so as to ensure that the grafting rate of MgO particles reaches the expected level, and the MgO particles are randomly grafted and coated on the fiber surface, which aggravates the roughness of the fiber. The high grafting rate of MgO increases the nucleation points of the thermoplastic material, thereby enhancing the crystallinity of the composite material. At the same time, MgO particles fill the gaps between fibers and fibers, and between fibers and thermoplastic materials, avoiding heat loss due to interface pores, and cooperating with a complete thermal conductive network to enhance the high-temperature stability of the material. More importantly, MgO particles are present in large quantities on the surface of the aramid fiber, so that a thermally conductive insulating area is formed at the interface between the aramid fiber and the thermoplastic material. Aramid fibers and MgO particles synergistically improve the high-temperature stability and insulation of the material. The composite material of the present invention has a high volume resistivity, showing the properties of an insulating material.

[0044] Subsequently, at high temperatures, the epoxy groups on the surface of the MgO particles bonded with the amino groups on the surface of the aramid fibers to form a modified filler. Characterization revealed that the epoxy groups introduced during the grafting process and the ring-opening reaction between the amino groups and the epoxy groups replaced hydrogen atoms, forming more -NH- bonds. This indicates that the filler and MgO particles are chemically bonded, and the modified filler has an increased surface CO bond content.

[0045] On the other hand, the present invention adopts polyetheretherketone as the base material. During the melting process, the polyetheretherketone wraps the modified filler and constructs a good thermal conductive path with the aramid fiber. Furthermore, the present invention adds additives to improve the performance of polyetheretherketone. Lead stearate is mainly used to enhance the thermal stability and electrical insulation of the material, prevent the decomposition of thermoplastic materials during high-temperature processing, provide a certain lubricity, and help improve the fluidity and processability of the material. The carboxyl group in the molecular structure of lead stearate can capture free radicals that easily trigger chain reactions and cause rapid aging of the material, help to interrupt the generation and linking of free radicals, synergize antioxidants, and extend the service life of the material. As an additive, calcium stearate can enhance the hardness and strength of the composite material, thereby improving its impact resistance. Calcium stearate has a high melting point, which enhances the high-temperature stability of the material to a certain extent, and makes the material have good flame retardancy. It is suitable for the preparation of insulating materials used for a long time outdoors or in high-temperature environments. The present invention also adds stearic acid, which allows the aforementioned materials to be better dispersed within the thermoplastic matrix, reducing porosity to prevent current leakage, thereby improving the composite's volume resistivity and electrical insulation properties. It also enhances chemical bonding, reduces stress concentration at interfaces, and improves the composite's overall mechanical and electrical insulation properties. Furthermore, since moisture is a significant factor in degrading electrical insulation properties, stearic acid modification can reduce the composite's surface hydrophilicity, improve its water resistance, and extend its service life.

[0046] The beneficial effects of the present invention are as follows:

[0047] (1) The composite material prepared by the present invention can effectively prevent current leakage and has high safety and insulation properties;

[0048] (2) The composite material prepared by the present invention has good high-temperature stability and chemical corrosion resistance, and can maintain good arc resistance in high-temperature and high-humidity environments;

[0049] (3) The composite material prepared by the present invention has high strength and maintains high toughness under continuous high temperature conditions. DETAILED DESCRIPTION

[0050] The present invention is further described in detail below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only a portion of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0051] Unless otherwise specified, the raw materials used in the examples of the present invention are all commercially available or available to those skilled in the art; unless otherwise specified, the methods used in the examples of the present invention are all methods known to those skilled in the art.

[0052] Example 1

[0053] A method for preparing a high-strength insulating composite material, the method comprising:

[0054] 1) 100 g of aramid fiber with a diameter of 7 μm and a length of 2 mm was extracted with 500 mL of acetone for 48 h. The aramid fiber extracted with acetone was separated by filtration and ultrasonically rinsed with deionized water. 200 mL of 6 mol / L concentrated nitric acid was added and kept constant at 80° C. for 2.5 h. The acid-treated aramid fiber was separated by filtration and ultrasonically rinsed with anhydrous ethanol. 10 mL of a 3 wt% KH550-ethanol solution was added and reacted at 60° C. in a N2 atmosphere and refluxed for 3 h. The coupled aramid fiber was separated by filtration and rinsed with deionized water. The filler was dried at 50° C.;

[0055] 2) 50 g of 1 μm magnesium oxide and 500 mL of N,N-dimethylformamide were mixed uniformly, 5 mL of a 3 wt% KH550-ethanol solution was added, and the mixture was incubated at 90°C for 6 hours. The filler was added and mixed uniformly, and the mixture was refluxed at 160°C for 2 hours. After cooling to room temperature, the mixture was filtered, and the filter residue was ultrasonically washed with anhydrous ethanol. The mixture was then dried at 50°C to obtain a modified filler.

[0056] 3) Add 20 g of polyetheretherketone, 0.02 g of lead stearate, 0.01 g of calcium stearate, 0.01 g of stearic acid, and 0.01 mL of antioxidant 1010 per gram of modified filler, mix evenly, mix at 355° C. for 5 minutes, and then extrude to obtain a high-strength insulating composite material.

[0057] The composite material prepared in this example, which has no distortion and no surface defects, was subjected to performance testing. The specific testing method is as follows.

[0058] 1. Impact resistance:

[0059] According to GB / T 1043.1-200, a ZBC1000 cantilever beam impact tester is used to determine the impact resistance of composite materials. At 25°C (if the material performance data indicates that its impact resistance decreases at low temperatures, the test should be conducted at the lowest temperature in the specified temperature range), a 1kg, intact punch is dropped vertically from a height of 0.2m. The instrument value is recorded and the impact strength is calculated.

[0060] 2. Toughness test:

[0061] The single-sided notched beam method is used. At 25°C, the three-point or four-point bending method is used to measure the critical load when the single-sided prefabricated notch specimen breaks on a mechanical properties testing machine. The tensile strength of the tested sample is calculated based on the prefabricated notch depth, sample size, and the span between the two support points of the sample.

[0062] 3. Anti-bending performance:

[0063] According to GB / T 9341-2008, the flexural strength of composite materials was determined by using a WDW-2 electronic universal testing machine and a three-point bending method with a span of 69 mm.

[0064] 4. Flame retardant properties:

[0065] The limiting oxygen concentration (LOI) was determined by adjusting the oxygen concentration using an oxygen index meter. LOI represents the minimum oxygen concentration required to allow a flame to burn in a mixture of oxygen and nitrogen. Composite materials with an LOI index exceeding 40 were marked as "○", and those with an LOI index exceeding 40 were marked as "×".

[0066] 5. High temperature stability:

[0067] In the range of 30-110°C, in a N2 atmosphere, the composite material was heated using a STA6000 thermogravimetric analyzer at a heating rate of 20°C / min and kept warm for 10 minutes each time. If no defects such as cracking, bubbles, peeling, wrinkles, or deformation appeared during the heating and holding process, the temperature was continued to be raised until the composite material had no obvious defects after being heated to 110°C, and it was recorded as "○". Otherwise, it was recorded as "×".

[0068] 6. Insulation performance:

[0069] According to GB / T 1410–2006, the volume resistivity of the composite materials was measured using the four-terminal method ST2722-SD with ST2255 high resistance meter to characterize the volume resistivity.

[0070] 7. Arc resistance performance:

[0071] According to the GB / T 29311-2020 standard, an AC high voltage and low current are used. The high voltage generates an arc between two electrodes, and the time it takes for a conductive layer to form on the surface of the composite material is measured.

[0072] 8. Anti-puncture performance:

[0073] Under the action of the electric field, the maximum electric field intensity that the composite material can withstand is calculated based on the breakdown voltage and the thickness of the composite material.

[0074] The results are as follows.

[0075] <![CDATA[Impact resistance (kJ / m 2 )]]> Tensile strength (MPa) Flexural strength (MPa) Flame retardant properties 21.9 98.2 139.5 ○ High temperature stability Volume resistivity (Ω·cm) Arc resistance performance(s) Anti-puncture performance (kV / mm) ○ 1.8×1016 119 54.8

[0076] Based on the results in the table above, it can be seen that this material has good mechanical properties. When the material was heated to 110°C and kept at this temperature for 2 hours, it was found that the material still had high toughness. At room temperature, the material cannot be ignited. When polyetheretherketone burns, it easily forms a high carbon layer that wraps the aramid fiber. The LOI index meets the standard, showing a certain degree of flame retardancy. Combined with the high-temperature stability experiment, it is shown that this material has good high-temperature resistance. This material has good insulation properties and can effectively prevent current leakage, ensuring the stable operation of electronic products. This material has a certain degree of water resistance. Compared with commercially available materials, it can maintain good arc resistance in high temperature and high humidity environments.

[0077] Example 2

[0078] A method for preparing a high-strength insulating composite material, the method comprising:

[0079] 1) aramid fiber with a diameter of 7 μm and a length of 2.4 mm was taken, 100 g of the aramid fiber was extracted with 500 mL of acetone for 48 h, the aramid fiber extracted with acetone was separated by filtration, ultrasonically rinsed with deionized water, and then 200 mL of concentrated nitric acid with a concentration of 6 mol / L was added. The mixture was kept constant at 80° C. for 2.5 h, the acid-treated aramid fiber was separated by filtration, ultrasonically rinsed with anhydrous ethanol, and then 10 mL of a 3 wt% KH550-ethanol solution was added. The mixture was reacted and refluxed at 60° C. in a N2 atmosphere for 3 h, and the coupled aramid fiber was separated by filtration, rinsed with deionized water, and dried at 50° C. to obtain a filler.

[0080] 2) 50 g of 1 μm magnesium oxide and 500 mL of N,N-dimethylformamide were mixed uniformly, 5 mL of a 3 wt% KH550-ethanol solution was added, and the mixture was incubated at 90°C for 6 hours. The filler was added and mixed uniformly, and the mixture was refluxed at 160°C for 2 hours. After cooling to room temperature, the mixture was filtered, and the filter residue was ultrasonically washed with anhydrous ethanol. The mixture was then dried at 50°C to obtain a modified filler.

[0081] 3) Add 20 g of polyetheretherketone, 0.02 g of lead stearate, 0.01 g of calcium stearate, 0.01 g of stearic acid, and 0.01 mL of antioxidant 1010 per gram of modified filler, mix evenly, mix at 355° C. for 5 minutes, and then extrude to obtain a high-strength insulating composite material.

[0082] The composite material prepared in this example, which had no distortion in the components and no surface defects, was subjected to the same performance tests as in Example 1, and the results were as follows.

[0083] <![CDATA[Impact resistance (kJ / m 2 )]]> Tensile strength (MPa) Flexural strength (MPa) Flame retardant properties 22.3 98.6 139.8 ○ High temperature stability Volume resistivity (Ω·cm) Arc resistance performance(s) Anti-puncture performance (kV / mm) ○ <![CDATA[1.9×10 16 ]]> 124 55.3

[0084] Based on the results in the table above, this example produced aramid fibers with a longer initial length. These fibers were evenly dispersed and overlapped to form a thermal conductivity path. This material exhibited excellent high-temperature stability, maintaining good performance at 130°C compared to Example 1.

[0085] Example 3

[0086] A method for preparing a high-strength insulating composite material, the method comprising:

[0087] 1) aramid fiber with a diameter of 7 μm and a length of 3 mm was taken, 100 g of the aramid fiber was extracted with 500 mL of acetone for 48 h, the aramid fiber extracted with acetone was separated by filtration, ultrasonically rinsed with deionized water, and then 200 mL of concentrated nitric acid with a concentration of 6 mol / L was added. The mixture was kept constant at 80° C. for 2.5 h, the acid-treated aramid fiber was separated by filtration, ultrasonically rinsed with anhydrous ethanol, and then 10 mL of a 3 wt% KH550-ethanol solution was added. The mixture was reacted and refluxed at 60° C. in a N2 atmosphere for 3 h, and the coupled aramid fiber was separated by filtration, rinsed with deionized water, and dried at 50° C. to obtain a filler.

[0088] 2) 50 g of 1 μm magnesium oxide and 500 mL of N,N-dimethylformamide were mixed uniformly, 5 mL of a 3 wt% KH550-ethanol solution was added, and the mixture was incubated at 90°C for 6 hours. The filler was added and mixed uniformly, and the mixture was refluxed at 160°C for 2 hours. After cooling to room temperature, the mixture was filtered, and the filter residue was ultrasonically washed with anhydrous ethanol. The mixture was then dried at 50°C to obtain a modified filler.

[0089] 3) Add 20 g of polyetheretherketone, 0.02 g of lead stearate, 0.01 g of calcium stearate, 0.01 g of stearic acid, and 0.01 mL of antioxidant 1010 per gram of modified filler, mix evenly, mix at 355° C. for 5 minutes, and then extrude to obtain a high-strength insulating composite material.

[0090] The composite material prepared in this example, which had no distortion in the components and no surface defects, was subjected to the same performance tests as in Example 1, and the results were as follows.

[0091]

[0092]

[0093] After testing, it was found that the fibers with longer initial length caused uneven high-temperature extrusion, affecting the high-temperature stability of the composite material. At 110°C, the qualified rate of products with no surface defects such as wrinkles, bubbles, and peeling dropped to 96%.

[0094] Comparative Example 1

[0095] A method for preparing a high-strength insulating composite material, the method comprising:

[0096] 1) aramid fiber with a diameter of 7 μm and a length of 2.4 mm was taken, 100 g of the aramid fiber was extracted with 500 mL of acetone for 48 h, the aramid fiber extracted with acetone was separated by filtration, ultrasonically rinsed with deionized water, and then 200 mL of concentrated nitric acid with a concentration of 6 mol / L was added. The mixture was kept constant at 80° C. for 2.5 h, the acid-treated aramid fiber was separated by filtration, ultrasonically rinsed with anhydrous ethanol, and then 10 mL of a 3 wt% KH550-ethanol solution was added. The mixture was reacted and refluxed at 60° C. in a N2 atmosphere for 3 h, and the coupled aramid fiber was separated by filtration, rinsed with deionized water, and dried at 50° C. to obtain a filler.

[0097] 2) 50 g of 1 μm magnesium oxide and 500 mL of N,N-dimethylformamide were mixed uniformly, 5 mL of a 3 wt% KH550-ethanol solution was added, and the mixture was incubated at 90°C for 6 hours. The filler was added and mixed uniformly, and the mixture was refluxed at 160°C for 2 hours. After cooling to room temperature, the mixture was filtered, and the filter residue was ultrasonically washed with anhydrous ethanol. The mixture was then dried at 50°C to obtain a modified filler.

[0098] 3) Add 24 g of polyetheretherketone, 0.02 g of lead stearate, 0.01 g of calcium stearate, 0.01 g of stearic acid, and 0.01 mL of antioxidant 1010 per gram of modified filler, mix well, mix at 355° C. for 5 minutes, and then extrude to obtain a high-strength insulating composite material.

[0099] The composite material prepared in this example, which had no distortion in the components and no surface defects, was subjected to the same performance tests as in Example 1, and the results were as follows.

[0100] <![CDATA[Impact resistance (kJ / m 2 )]]> Tensile strength (MPa) Flexural strength (MPa) Flame retardant properties 19.8 87.1 138.8 ○ High temperature stability Volume resistivity (Ω·cm) Arc resistance performance(s) Anti-puncture performance (kV / mm) × <![CDATA[1.9×10 16 ]]> 115 54.5

[0101] The results in the table above indicate that the relatively low content of the modified filler in this example clearly indicates poor fiber overlap. The fibers and thermoplastic material fail to form a complete thermal conductivity pathway, resulting in minimal improvement in the composite's high-temperature stability, failing to meet the "high-temperature stability within 110°C" requirement of the present invention. Furthermore, the fibers fail to form a continuous phase, significantly impacting toughness. Compared to Example 2, the composite exhibits inferior impact and tensile properties.

[0102] The above preparation was performed except that step 3) "adding 24 g of polyetheretherketone per gram of modified filler" was changed to "adding 16 g of polyetheretherketone per gram of modified filler". The performance test of the prepared composite material was performed in the same manner as in Example 1, and the results are as follows.

[0103] <![CDATA[Impact resistance (kJ / m 2 )]]> Tensile strength (MPa) Flexural strength (MPa) Flame retardant properties 18.7 84.2 138.5 ○ High temperature stability Volume resistivity (Ω·cm) Arc resistance performance(s) Anti-puncture performance (kV / mm) ○ <![CDATA[6.3×10 15 ]]> 110 51.7

[0104] According to the results in the table above, excessive fiber addition leads to uneven fiber distribution, resulting in agglomeration and stress concentration. The reinforcement effect is far less than the performance degradation caused by agglomeration, which significantly affects the composite's flexural strength. At the same time, the composite's brittleness increases, and pores appear on its surface, resulting in a decrease in the material's impact resistance. However, this has a relatively small impact on the material's high-temperature stability and flame retardancy. Furthermore, excessive aramid fiber leads to a significant decrease in the composite's electrical properties, with even greater decreases in its volume resistivity and puncture resistance.

[0105] Comparative Example 2

[0106] A method for preparing a high-strength insulating composite material, the method comprising:

[0107] 1) 100 g of aramid fiber with a diameter of 7 μm and a length of 2.4 mm was extracted with 500 mL of acetone for 48 hours. The aramid fiber extracted with acetone was separated by filtration and ultrasonically washed with deionized water. 200 mL of 6 mol / L concentrated nitric acid was added and the mixture was incubated at 80° C. for 2.5 hours. The mixture was filtered, washed, and dried to obtain a filler.

[0108] 2) 50 g of 1 μm magnesium oxide and 500 mL of N,N-dimethylformamide were mixed uniformly, 5 mL of a 3 wt% KH550-ethanol solution was added, and the mixture was incubated at 90°C for 6 hours. The filler was added and mixed uniformly, and the mixture was refluxed at 160°C for 2 hours. After cooling to room temperature, the mixture was filtered, and the filter residue was ultrasonically washed with anhydrous ethanol. The mixture was then dried at 50°C to obtain a modified filler.

[0109] 3) Add 20 g of polyetheretherketone, 0.02 g of lead stearate, 0.01 g of calcium stearate, 0.01 g of stearic acid, and 0.01 mL of antioxidant 1010 per gram of modified filler, mix evenly, mix at 355° C. for 5 minutes, and then extrude to obtain a high-strength insulating composite material.

[0110] The composite material prepared in this example, which had no distortion in the components and no surface defects, was subjected to the same performance tests as in Example 1, and the results were as follows.

[0111]

[0112]

[0113] The results in the table above show that aramid fibers untreated with a coupling agent bond to thermoplastics through relatively weak physical interactions, resulting in minimal fiber reinforcement. When composited with MgO particles, the system forms a weak physical bond with the reinforcing material. Experimental results indicate that this material exhibits poor tensile properties. Furthermore, due to the large interfacial gap within the system, the composite material exhibits poor high-temperature stability. This poor compatibility between aramid fibers and thermoplastics reduces the material's volume resistivity.

[0114] Comparative Example 3

[0115] A method for preparing a high-strength insulating composite material, the method comprising:

[0116] 1) aramid fiber with a diameter of 7 μm and a length of 2.4 mm was taken, 100 g of the aramid fiber was extracted with 500 mL of acetone for 48 h, the aramid fiber extracted with acetone was separated by filtration, ultrasonically rinsed with deionized water, and then 200 mL of concentrated nitric acid with a concentration of 6 mol / L was added. The mixture was kept constant at 80° C. for 2.5 h, the acid-treated aramid fiber was separated by filtration, ultrasonically rinsed with anhydrous ethanol, and then 10 mL of a 3 wt% KH550-ethanol solution was added. The mixture was reacted and refluxed at 60° C. in a N2 atmosphere for 3 h, and the coupled aramid fiber was separated by filtration, rinsed with deionized water, and dried at 50° C. to obtain a filler.

[0117] 2) 50 g of 1 μm magnesium oxide and 500 mL of N,N-dimethylformamide were mixed uniformly, 5 mL of a 5 wt% KH550-ethanol solution was added, and the mixture was incubated at 90°C for 6 hours. The filler was added and mixed uniformly, and the mixture was refluxed at 160°C for 2 hours. After cooling to room temperature, the mixture was filtered, and the filter residue was ultrasonically washed with anhydrous ethanol. The mixture was then dried at 50°C to obtain a modified filler.

[0118] 3) Add 20 g of polyetheretherketone, 0.02 g of lead stearate, 0.01 g of calcium stearate, 0.01 g of stearic acid, and 0.01 mL of antioxidant 1010 per gram of modified filler, mix evenly, mix at 355° C. for 5 minutes, and then extrude to obtain a high-strength insulating composite material.

[0119] The composite material prepared in this example, which had no distortion in the components and no surface defects, was subjected to the same performance tests as in Example 1, and the results were as follows.

[0120] <![CDATA[Impact resistance (kJ / m 2 )]]> Tensile strength (MPa) Flexural strength (MPa) Flame retardant properties 18.4 85.8 137.9 × High temperature stability Volume resistivity (Ω·cm) Arc resistance performance(s) Anti-puncture performance (kV / mm) × <![CDATA[1.5×10 16 ]]> 113 52.4

[0121] To ensure that MgO particles are attached to the aramid fiber surface, resulting in a composite material with high chemical bond strength, the present invention disperses MgO in N,N-dimethylformamide, adds a coupling agent, and then performs a heat treatment. During the heat treatment, the grafting rate of the MgO particles is affected by the concentration of the silane coupling agent. In this example, increasing the mass fraction of the silane coupling agent causes hydrolysis and condensation of the coupling agent, significantly enhancing the competitive reaction and leading to a significant decrease in the MgO grafting rate. A low MgO grafting rate not only affects the insulation performance of the material but also its high-temperature stability. Under harsh high-temperature conditions, the composite material is prone to insulation failure.

[0122] Comparative Example 4

[0123] A method for preparing a high-strength insulating composite material, the method comprising:

[0124] 1) aramid fiber with a diameter of 7 μm and a length of 2.4 mm was taken, 100 g of the aramid fiber was extracted with 500 mL of acetone for 48 h, the aramid fiber extracted with acetone was separated by filtration, ultrasonically rinsed with deionized water, and then 200 mL of concentrated nitric acid with a concentration of 6 mol / L was added. The mixture was kept constant at 80° C. for 2.5 h, the acid-treated aramid fiber was separated by filtration, ultrasonically rinsed with anhydrous ethanol, and then 10 mL of a 3 wt% KH550-ethanol solution was added. The mixture was reacted and refluxed at 60° C. in a N2 atmosphere for 3 h, and the coupled aramid fiber was separated by filtration, rinsed with deionized water, and dried at 50° C. to obtain a filler.

[0125] 2) 50 g of 1 μm magnesium oxide and 500 mL of N,N-dimethylformamide were mixed uniformly, 5 mL of a 3 wt% KH550-ethanol solution was added, and the mixture was incubated at 90°C for 6 hours. The filler was added and mixed uniformly, and the mixture was refluxed at 170°C for 2 hours. After cooling to room temperature, the mixture was filtered, and the filter residue was ultrasonically washed with anhydrous ethanol. The mixture was then dried at 50°C to obtain a modified filler.

[0126] 3) Add 20 g of polyetheretherketone, 0.02 g of lead stearate, 0.01 g of calcium stearate, 0.01 g of stearic acid, and 0.01 mL of antioxidant 1010 per gram of modified filler, mix evenly, mix at 355° C. for 5 minutes, and then extrude to obtain a high-strength insulating composite material.

[0127] The composite material prepared in this example, which had no distortion in the components and no surface defects, was subjected to the same performance tests as in Example 1, and the results were as follows.

[0128] <![CDATA[Impact resistance (kJ / m 2 )]]> Tensile strength (MPa) Flexural strength (MPa) Flame retardant properties 18.2 85.1 137.5 × High temperature stability Volume resistivity (Ω·cm) Arc resistance performance(s) Anti-puncture performance (kV / mm) × <![CDATA[1.6×10 16 ]]> 114 52.6

[0129] According to the results in the above table, excessively high temperatures cause excessively violent molecular collisions, and the self-condensation reaction of the hydroxyl groups on the particle surface and the self-condensation reaction between the silanols produced by the hydrolysis of the coupling agent compete with the grafting reaction, resulting in a significant decrease in the MgO grafting rate. The low MgO grafting rate not only leads to a decrease in the nucleation points of the thermoplastic material and reduces the crystallinity of the composite material, but also fails to completely fill the gaps between fibers and fibers, and between fibers and thermoplastic materials. The interfacial pores generate heat loss, resulting in a decrease in the high-temperature stability of the composite material. At the same time, the volume resistivity of the composite material prepared by distributing aramid fibers in polyetheretherketone is reduced, which affects its insulation effect.

[0130] Comparative Example 5

[0131] A method for preparing a high-strength insulating composite material, the method comprising:

[0132] 1) aramid fiber with a diameter of 7 μm and a length of 2.4 mm was taken, 100 g of the aramid fiber was extracted with 500 mL of acetone for 48 h, the aramid fiber extracted with acetone was separated by filtration, ultrasonically rinsed with deionized water, and then 200 mL of concentrated nitric acid with a concentration of 6 mol / L was added. The mixture was kept constant at 80° C. for 2.5 h, the acid-treated aramid fiber was separated by filtration, ultrasonically rinsed with anhydrous ethanol, and then 10 mL of a 3 wt% KH550-ethanol solution was added. The mixture was reacted and refluxed at 60° C. in a N2 atmosphere for 3 h, and the coupled aramid fiber was separated by filtration, rinsed with deionized water, and dried at 50° C. to obtain a filler.

[0133] 2) 50 g of 1 μm magnesium oxide and 500 mL of N,N-dimethylformamide were mixed uniformly, 5 mL of a 3 wt% KH550-ethanol solution was added, and the mixture was incubated at 90°C for 6 hours. The filler was added and mixed uniformly, and the mixture was refluxed at 160°C for 2 hours. After cooling to room temperature, the mixture was filtered, and the filter residue was ultrasonically washed with anhydrous ethanol. The mixture was then dried at 50°C to obtain a modified filler.

[0134] 3) Add 20 g of polyetheretherketone, 0.01 g of stearic acid, and 0.01 mL of antioxidant 1010 per gram of modified filler, mix well, mix at 355° C. for 5 minutes, and then extrude to obtain a high-strength insulating composite material.

[0135] The composite material prepared in this example, which had no distortion in the components and no surface defects, was subjected to the same performance tests as in Example 1, and the results were as follows.

[0136] <![CDATA[Impact resistance (kJ / m 2 )]]> Tensile strength (MPa) Flexural strength (MPa) Flame retardant properties 21.8 96.3 138.9 ○ High temperature stability Volume resistivity (Ω·cm) Arc resistance performance(s) Anti-puncture performance (kV / mm) × <![CDATA[1.5×10 16 ]]> 108 53.2

[0137] Lead stearate is primarily used to enhance the material's thermal stability and electrical insulation, while also providing a certain degree of lubricity, which helps improve the material's fluidity and workability. Calcium stearate, on the other hand, enhances the composite's hardness and strength, thereby improving its impact resistance. The results in the table above show a significant decrease in the composite's mechanical and electrical properties. This reduction in thermal stability significantly shortens the material's service life in outdoor or high-temperature environments. This demonstrates the essential role of the organic metal salt additive.

[0138] Comparative Example 6

[0139] A method for preparing a high-strength insulating composite material, the method comprising:

[0140] 1) aramid fiber with a diameter of 7 μm and a length of 2.4 mm was taken, 100 g of the aramid fiber was extracted with 500 mL of acetone for 48 h, the aramid fiber extracted with acetone was separated by filtration, ultrasonically rinsed with deionized water, and then 200 mL of concentrated nitric acid with a concentration of 6 mol / L was added. The mixture was kept constant at 80° C. for 2.5 h, the acid-treated aramid fiber was separated by filtration, ultrasonically rinsed with anhydrous ethanol, and then 10 mL of a 3 wt% KH550-ethanol solution was added. The mixture was reacted and refluxed at 60° C. in a N2 atmosphere for 3 h, and the coupled aramid fiber was separated by filtration, rinsed with deionized water, and dried at 50° C. to obtain a filler.

[0141] 2) 50 g of 1 μm magnesium oxide and 500 mL of N,N-dimethylformamide were mixed uniformly, 5 mL of a 3 wt% KH550-ethanol solution was added, and the mixture was incubated at 90°C for 6 hours. The filler was added and mixed uniformly, and the mixture was refluxed at 160°C for 2 hours. After cooling to room temperature, the mixture was filtered, and the filter residue was ultrasonically washed with anhydrous ethanol. The mixture was then dried at 50°C to obtain a modified filler.

[0142] 3) Add 20 g of polyetheretherketone, 0.02 g of lead stearate, 0.01 g of calcium stearate, and 0.01 mL of antioxidant 1010 per gram of modified filler, mix well, mix at 355° C. for 5 minutes, and then extrude to obtain a high-strength insulating composite material.

[0143] The composite material prepared in this example, which had no distortion in the components and no surface defects, was subjected to the same performance tests as in Example 1, and the results were as follows.

[0144] <![CDATA[Impact resistance (kJ / m 2 )]]> Tensile strength (MPa) Flexural strength (MPa) Flame retardant properties 21.8 98.1 139.0 ○ High temperature stability Volume resistivity (Ω·cm) Arc resistance performance(s) Anti-puncture performance (kV / mm) ○ <![CDATA[1.3×10 16 ]]> 106 52.9

[0145] According to the results in the above table, pores appeared inside the material, resulting in a lower volume resistivity and poorer electrical insulation performance. Although it still maintained good high-temperature stability, its water resistance was relatively poor, which had an adverse effect on the application of the material in high-temperature and high-humidity environments.

[0146] Comparative Example 7

[0147] A method for preparing a high-strength insulating composite material, the method comprising:

[0148] 1) Taking wood fiber with a diameter of 7 μm and a length of 2.4 mm, taking 100 g of the wood fiber, extracting with 500 mL of acetone for 48 hours, filtering and separating the aramid fiber treated with acetone, ultrasonically rinsing with deionized water, adding 200 mL of concentrated nitric acid with a concentration of 6 mol / L, and maintaining the temperature at 80° C. for 2.5 hours, filtering and separating the acid-treated aramid fiber, ultrasonically rinsing with anhydrous ethanol, adding 10 mL of a 3 wt% KH550-ethanol solution, reacting at 60° C. in a N2 atmosphere and refluxing for 3 hours, and then filtering and separating the coupled aramid fiber, washing with deionized water, and drying at 50° C. to obtain a filler;

[0149] 2) 50 g of 1 μm magnesium oxide and 500 mL of N,N-dimethylformamide were mixed uniformly, 5 mL of a 3 wt% KH550-ethanol solution was added, and the mixture was incubated at 90°C for 6 hours. The filler was added and mixed uniformly, and the mixture was refluxed at 160°C for 2 hours. After cooling to room temperature, the mixture was filtered, and the filter residue was ultrasonically washed with anhydrous ethanol. The mixture was then dried at 50°C to obtain a modified filler.

[0150] 3) Add 20 g of polyetheretherketone, 0.02 g of lead stearate, 0.01 g of calcium stearate, 0.01 g of stearic acid, and 0.01 mL of antioxidant 1010 per gram of modified filler, mix evenly, mix at 355° C. for 5 minutes, and then extrude to obtain a high-strength insulating composite material.

[0151] The composite material prepared in this example, which had no distortion in the components and no surface defects, was subjected to the same performance tests as in Example 1, and the results were as follows.

[0152]

[0153]

[0154] The results in the table above show that the wood fibers, due to the large number of hydrophilic free hydroxyl groups exposed on their surfaces, have high hygroscopicity. This allows them to easily absorb HO from the air, forming conductive substances, which results in a decrease in the volume resistivity of the composite material. Furthermore, the interfacial compatibility between the wood fibers and PEEK is poor. PEEK incompletely encapsulates the wood fibers, which contain a large number of active hydroxyl groups, exposing numerous water absorption sites and significantly reducing electrical properties.

Claims

1. A method for preparing a high-strength insulating composite material, characterized in that: The method comprises: 1) Extract and clean the raw materials and solvent, add acid solution for desizing, filter and clean, add coupling agent for reaction, and then filter, clean and dry to obtain the filler; 2) Alkaline earth metal oxide and dispersant are mixed evenly, coupling agent is added and heated to react, filler is added and mixed evenly, and modified filler is obtained by reflux, cooling, washing and drying; 3) uniformly mixing the modified filler with the thermoplastic material, the organic metal salt, the acyclic carboxylic acid, and the antioxidant, and kneading at high temperature to obtain a high-strength insulating composite material; Step 1) The raw material is aramid fiber; Step 1) The acid solution is concentrated nitric acid with a concentration of 6-7 mol / L and an amount of 2-4 mL / g of raw material; Step 1) The coupling agent is an ethanol solution of KH550 with a concentration of 3-4 wt% and an amount of 0.1-0.2 mL / g raw material; Step 2) the alkaline earth metal oxide is magnesium oxide, the particle size of which is 0.8 to 1.2 μm, and the amount thereof is 0.5 to 1 g / g of raw material; Step 2) the coupling agent is an ethanol solution of KH550 with a concentration of 3-4 wt% and an amount of 0.1-0.2 mL / g alkaline earth metal oxide; Step 2) the reflux is carried out at a constant temperature of 155-160° C. for 2-2.5 hours; Step 3) the thermoplastic material is polyetheretherketone, and the amount thereof is 20-22 g / g modified filler; Step 3) the organic metal salt is a mixture of lead stearate and calcium stearate, with an amount of 0.03-0.04 g / g of modified filler, and the lead stearate and calcium stearate are mixed in a mass ratio of 1:(0.5-0.7); Step 3) the acyclic carboxylic acid is stearic acid, and the amount thereof is 0.01 to 0.02 g / g of the modified filler; Step 3) The antioxidant is antioxidant 1010, and its dosage is 0.01-0.02 mL / g modified filler.

2. The method for preparing a high-strength insulating composite material according to claim 1, characterized in that: Step 1) The aramid fiber has a diameter of 6 to 7 μm and a length of 2 to 3 mm; Step 1) The solvent is acetone, and the amount used is 5-15 mL / g raw material; The extraction time in step 1) is 46 to 50 hours.

3. The method for preparing a high-strength insulating composite material according to claim 1 or 2, characterized in that: In step 1), the acid desizing is carried out at a constant temperature of 70 to 80° C. for 2.5 to 3 hours.

4. The method for preparing a high-strength insulating composite material according to claim 1, characterized in that: In step 1), the coupling agent is added and then refluxed at 58-60° C. in a protective atmosphere for 3-3.5 h.

5. The method for preparing a high-strength insulating composite material according to claim 1, characterized in that: Step 2) The dispersant is N,N-dimethylformamide, and the amount used is 10-15 mL / g alkaline earth metal oxide.

6. The method for preparing a high-strength insulating composite material according to claim 1 or 5, characterized in that: In step 2), the heating reaction is carried out at a constant temperature of 80-90°C for 6-6.5 hours.

7. The method for preparing a high-strength insulating composite material according to claim 1, characterized in that: In step 3), the high-temperature mixing is controlled at a temperature of 355-360° C. and a mixing time of 3-8 minutes. After mixing, the high-strength insulating composite material is obtained.

8. The method for preparing a high-strength insulating composite material according to claim 7, characterized in that: Step 3) After the high-temperature mixing, the mixture can be granulated to form a masterbatch, or directly extruded, injection-molded, or blow-molded to form a product.

9. A high-strength insulating composite material produced by the method according to any one of claims 1 to 8.

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