High-strength insulating composite material and preparation method thereof

Abstract

The invention belongs to the technical field of insulating material preparation, and particularly relates to a high-strength insulating composite material and a preparation method thereof. The method comprises the following steps: 1) taking raw materials and a solvent for extraction and cleaning, adding an acid liquor for acidification and desizing, adding a coupling agent for reaction after filtering and cleaning, and then filtering, cleaning and drying to obtain a filler; (2) uniformly mixing alkaline earth metal oxide and a dispersing agent, adding a coupling agent, carrying out heating reaction, adding a filler, uniformly mixing, refluxing, cooling, cleaning and drying to obtain a modified filler; and 3) uniformly mixing the modified filler with a thermoplastic material, organic metal salt, acyclic carboxylic acid and an antioxidant, and performing high-temperature mixing to obtain the high-strength insulating composite material. The prepared composite material can effectively prevent current leakage, has high safety and insulativity, meanwhile, is good in high-temperature stability and chemical corrosion resistance, and can keep good arc resistance and strength in a high-temperature and high-humidity environment.

Description

Technical Field

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

[0002] Compared with metal components, plastic components are lightweight and easy to carry and install, especially in applications that require reducing structural loads or improving portability. They are not easy to rust and have good water resistance. They can provide good electrical insulation performance and are widely used in the manufacture of electronic equipment such as computers, mobile phones, and circuit boards. Insulating plastics are mainly used in the power industry for the insulation and support structures of power equipment, such as insulators, transformer and motor housings, connectors, etc. They provide stable performance in high-voltage, high-temperature, and humid environments to ensure the stable operation of transmission lines. Using insulating plastics to manufacture components such as automobile housings, train carriages, and track beds can reduce the weight of vehicles and improve operating efficiency; manufacturing automotive ABS anti-lock braking devices, seals, gaskets, bearings and other parts can achieve lightweighting and improve fuel efficiency.

[0003] Insulating plastic components have a variety of uses in modern industry. However, they are low in strength, poor in rigidity, and prone to aging, and cannot completely replace metal components. When insulating plastic components are exposed to high temperature, high humidity, ultraviolet rays, chemical corrosion, and other environments for a long time, they are prone to aging and cracking, resulting in a significant reduction in their mechanical strength, accompanied by a reduction in electrical insulation. After working for a long time in a high temperature environment, insulating plastic components may not even be able to maintain structural integrity. Under the action of an electric field, plastic components that are too thin or have poor dielectric properties will experience electrical breakdown, resulting in a short circuit. If the material is not flame retardant, it may cause a fire.

[0004] In order to enhance the strength of plastic components, glass fiber is generally added to the plastic material. However, if the glass fiber content is too low, the strength and rigidity of the plastic components cannot meet the requirements of metal accessories. If the glass fiber content is too high, it is easy to cause floating, mixed colors and floating fibers on the surface of the workpiece, and it is easy to cause difficult demolding, white top and deformation in the injection molding process. Therefore, it is urgent to develop a preparation method that can both enhance the strength of plastic components and ensure the surface quality of components. Summary of the invention

[0005] In order to solve a series of problems commonly existing 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 material and solvent, adding acid solution for desizing, filtering and washing, adding coupling agent for reaction, filtering, washing and drying to obtain the filler;

[0014] 2) taking alkaline earth metal oxide and dispersant and mixing them 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 the thermoplastic material, the organic metal salt, the acyclic carboxylic acid and the antioxidant, and a high-strength insulating composite material is obtained through high-temperature kneading.

[0016] As a preference,

[0017] The raw material of step 1) is aramid fiber, the diameter of which is 6-7 μm and the length of which is 2-3 mm; the solvent of step 1) is acetone, and the amount used is 5-15 mL / g raw material;

[0018] The extraction time of 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 raw material;

[0021] The acid desizing in step 1) 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] The reaction of adding coupling agent in step 1) is to add coupling agent and reflux for 3 to 3.5 hours in protective atmosphere at 58 to 60°C.

[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 of 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] Step 3) the thermoplastic material is polyetheretherketone, and its dosage is 20-22 g / g modified filler; Step 3) the organic metal salt is a mixture of lead stearate and calcium stearate, and its dosage is 0.03-0.04 g / g modified filler, and the lead stearate and calcium stearate are mixed according to 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 modified filler; in step 3), the antioxidant is antioxidant 1010, and its usage is 0.01-0.02 mL / g 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 min. After mixing, the high-strength insulating composite material is obtained.

[0037] As a preference,

[0038] Step 3) After the high temperature kneading, the mixture can be granulated into a material masterbatch, or directly extruded, injection molded, or blow molded into 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 the composite material. Short-cut aramid fibers of an initial specific length can overlap each other to construct a heat conduction path. Because the initial length of the fiber is long, it will cause it to be difficult to disperse during filling, and local agglomeration is likely to occur, that is, the overly long fiber causes uneven extrusion, which is likely to 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 effect of overlapping each other is poor. The fibers and the thermoplastic material do not form a complete heat conduction path, and the effect of improving the high temperature stability of the composite material is also small. With the increase of the filling amount, the fibers are evenly distributed in the material to form a continuous phase, and the tensile strength of the material gradually increases, and the increase is getting smaller and smaller. In order to ensure the effect of fiber overlap to improve 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] On the basis of selecting aramid fibers of appropriate length, the aramid fibers also need to be pretreated. The surface of unacidified aramid fibers is smooth. After being acidified with nitric acid, the surface roughness of the aramid fibers increases, and there are obvious corrosion grooves. In order to combine MgO particles, the present invention treats the aramid fibers with a coupling agent, and a large number of active groups such as amino groups and carboxyl groups are introduced onto the surface. Furthermore, the present invention uses an aminosilane coupling agent KH550 with a concentration of 3 to 4 wt%, and the grooves are filled to form more and richer active groups. Aramid fibers that have not been treated with coupling agents are combined with thermoplastic materials by relatively weak physical effects, and the fiber reinforcement effect is small. After the coupling agent is compounded with MgO particles, the new chemical bonds formed by the ring-opening reaction in the system make the material absorb a large amount of energy when it is stressed, that is, the physical weak bond and chemical cross-linking enhance the tensile properties of the material. However, after only coupling treatment of aramid fibers, the actual bonding stability of MgO particles and aramid fibers is still relatively limited, and KH550 has the reaction activity of self-condensation. Therefore, the present invention treats MgO with KH550 in a modified manner, and then links MgO and aramid fibers by self-condensation, which can significantly optimize the linking effect of the two. In addition, aramid fibers can also reduce the loss of their own active groups, and the groups introduced by them interact with thermoplastic materials, improve the compatibility of the two, and reduce the volume resistivity of the material.

[0042] According to the above conclusions, it can be known that it is difficult to regulate the insulation of the composite material only by the relative content of aramid fiber. In order to enhance the insulation of the composite material and take into account the high temperature stability, insulation and mechanical strength of the material, the present invention is based on the modification of aramid fiber. At the same time, in order to ensure that the MgO particles are connected to the surface of the aramid fiber to obtain a composite material with high chemical bonding strength, the present invention first disperses MgO in N, N-dimethylformamide, adds a coupling agent, performs heat treatment, and then mixes the filler. In this process, the grafting rate of 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, and produces a competitive reaction with the MgO treated with KH550. With the enhancement of the competitive reaction, the grafting rate of MgO will be significantly reduced. Low MgO grafting rate not only affects the insulation performance of the material, but also affects the high-temperature stability of the material. In harsh high-temperature environments, the insulation performance of composite materials is prone to failure. If the mass fraction of KH550 is too low, there will also be problems such as reduced grafting rate and grafting stability. Therefore, it is necessary to strictly control the amount of KH550 silane coupling agent. At the same time, the heat treatment temperature has a certain effect on the grafting rate of MgO. With the increase of temperature, the intermolecular collision rate increases, the activity of MgO particles increases, and finally the analysis shows that the grafting rate of MgO particles increases. However, when the temperature is too high, the molecular movement is too violent, and the self-condensation reaction of the hydroxyl group on the particle surface and the self-condensation reaction of the silanol produced by the hydrolysis of the coupling agent compete with the grafting reaction, which may cause problems such as curling of aramid fibers or agglomeration of MgO, resulting in a significant reduction in the grafting rate of MgO and aramid fibers.

[0043] In addition, the present invention should avoid the phenomenon of unstable MgO particles detaching due to too long mixing time, so as to ensure that the grafting rate of MgO particles reaches the expected level, and MgO particles are randomly grafted and coated on the fiber surface, and the fiber roughness is aggravated. The high grafting rate of MgO increases the nucleation points of thermoplastic materials, 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 aramid fibers, so that a thermally conductive insulating area is formed at the interface between aramid fibers and thermoplastic materials. 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 and exhibits the properties of an insulating material.

[0044] Subsequently, at high temperature, the epoxy groups on the surface of the MgO particles combined with the amino groups on the surface of the aramid fibers to form a modified filler. Characterization revealed that due to the introduction of epoxy groups during the grafting process, the amino groups and epoxy groups underwent a ring-opening reaction, replacing H atoms and forming more -NH- bonds, indicating that the filler and MgO particles were bonded by chemical bonds, and the CO bond content on the surface of the modified filler increased.

[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 heat conduction 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 thermoplastic material from decomposing 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 interrupt the generation and linking of free radicals, cooperate with 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, enhances the high-temperature stability of the material to a certain extent, and makes the material have good flame retardancy, which 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 enables the above-mentioned material to be better dispersed in the thermoplastic matrix, reduces pores to prevent current leakage, helps to improve the volume resistivity and electrical insulation performance of the composite material, and at the same time enhances chemical bonding, reduces stress concentration at the interface, and improves the overall mechanical properties and electrical insulation performance of the composite material. In addition, moisture is an important factor that causes the electrical insulation performance to decline. Stearic acid modification can reduce the hydrophilicity of the composite surface, improve its water resistance, and extend the service life of the material.

[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 a high temperature and high humidity environment;

[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 in conjunction with specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work 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) Take aramid fiber with a diameter of 7 μm and a length of 2 mm, take 100 g of aramid fiber, extract with 500 mL of acetone for 48 hours, filter and separate the aramid fiber treated with acetone, ultrasonically rinse with deionized water, add 200 mL of concentrated nitric acid with a concentration of 6 mol / L, keep constant temperature at 80° C. for 2.5 hours, filter and separate the acid-treated aramid fiber, ultrasonically rinse with anhydrous ethanol, add 10 mL of KH550-ethanol solution with a mass fraction of 3 wt%, react and reflux for 3 hours in a N2 atmosphere at 60° C., then filter and separate the coupling-treated aramid fiber, rinse with deionized water, and dry at 50° C. to obtain a filler;

[0055] 2) 50 g of magnesium oxide with a particle size of 1 μm and 500 mL of N,N-dimethylformamide were mixed evenly, 5 mL of KH550-ethanol solution with a mass fraction of 3 wt% was added, and the mixture was kept constant at 90° C. for 6 h, and the filler was added and mixed evenly, and the mixture was kept constant at 160° C. for 2 h. After cooling to room temperature, the mixture was filtered and the filter residue was ultrasonically washed with anhydrous ethanol, and 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 well, knead at 355° C. for 5 min, and then extrude to obtain a high-strength insulating composite material.

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

[0058] 1. Impact resistance:

[0059] According to GB / T 1043.1-200 standard, the impact resistance of composite materials is determined by using a ZBC1000 cantilever beam impact tester. At 25°C (if the material performance data shows that its impact resistance decreases in a low temperature environment, the experiment should be carried out at the lowest temperature in the specified temperature range), a punch with a mass of 1kg and a complete appearance is dropped vertically from a height of 0.2m, the instrument values ​​are recorded, and the impact strength is calculated.

[0060] 2. Toughness test:

[0061] The single-sided notch 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 supporting points of the sample.

[0062] 3. Anti-bending performance:

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

[0064] 4. Flame retardant properties:

[0065] The limiting oxygen concentration (LOI) is 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 are marked as "○", otherwise they are marked as "×".

[0066] 5. High temperature stability:

[0067] In the range of 30-110°C, in N2 atmosphere, the composite material is heated using a STA6000 thermogravimetric analyzer at a heating rate of 20°C / min and kept warm for 10 min each time. If no cracking, bubbling, peeling, wrinkling, deformation or other defects occur during the heating and keeping warm process, the temperature is continued to be raised until the composite material has no obvious defects after the temperature is raised to 110°C, and it is recorded as "○", otherwise it is recorded as "×".

[0068] 6. Insulation performance:

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

[0070] 7. Arc resistance performance:

[0071] According to GB / T 29311-2020 standard, AC high voltage and low current are used to generate an arc between two electrodes, and the time it takes for a conductive layer to be formed 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 strength 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) Bending 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] According to the results in the above table, it can be seen that the material in this example has good mechanical properties. The material is heated to 110°C and kept at a constant temperature for 2 hours, and the material is still measured to have high toughness. At room temperature, the material cannot be ignited. When polyetheretherketone burns, it is easy to form a high carbon layer, wrapping the aramid fiber, and the LOI index meets the standard, showing a certain flame retardancy. Combined with the high temperature stability experiment, it shows that the material in this example has good high temperature resistance. The material in this example has good insulation, which can effectively prevent current leakage and ensure the stable operation of electronic products. The material in this example has a certain 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) Take aramid fiber with a diameter of 7 μm and a length of 2.4 mm, take 100 g of aramid fiber, extract with 500 mL of acetone for 48 hours, filter and separate the aramid fiber treated with acetone, ultrasonically rinse with deionized water, add 200 mL of concentrated nitric acid with a concentration of 6 mol / L, keep constant temperature at 80° C. for 2.5 hours, filter and separate the aramid fiber treated with acid, ultrasonically rinse with anhydrous ethanol, add 10 mL of KH550-ethanol solution with a mass fraction of 3 wt%, react and reflux for 3 hours in a N2 atmosphere at 60° C., and then filter and separate the aramid fiber treated with coupling, rinse with deionized water, and dry at 50° C. to obtain a filler;

[0080] 2) 50 g of magnesium oxide with a particle size of 1 μm and 500 mL of N,N-dimethylformamide were mixed evenly, 5 mL of KH550-ethanol solution with a mass fraction of 3 wt% was added, and the mixture was kept constant at 90° C. for 6 h, and the filler was added and mixed evenly, and the mixture was kept constant at 160° C. for 2 h. After cooling to room temperature, the mixture was filtered and the filter residue was ultrasonically washed with anhydrous ethanol, and 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 well, knead at 355° C. for 5 min, and then extrude to obtain a high-strength insulating composite material.

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

[0083] <![CDATA[Impact resistance (kJ / m 2 )]]> Tensile strength(MPa) Bending 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] According to the results in the above table, this example prepared aramid fibers with a longer initial length, and the fibers of this length can be evenly dispersed and overlapped to form a heat conduction path. The material in this example has good high temperature stability. Compared with Example 1, the material in this example can maintain good performance in an environment of 130°C.

[0085] Example 3

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

[0087] 1) Take aramid fiber with a diameter of 7 μm and a length of 3 mm, take 100 g of aramid fiber, extract with 500 mL of acetone for 48 hours, filter and separate the aramid fiber treated with acetone, ultrasonically rinse with deionized water, add 200 mL of concentrated nitric acid with a concentration of 6 mol / L, keep constant temperature at 80°C for 2.5 hours, filter and separate the acid-treated aramid fiber, ultrasonically rinse with anhydrous ethanol, add 10 mL of KH550-ethanol solution with a mass fraction of 3 wt%, react and reflux for 3 hours in a N2 atmosphere at 60°C, filter and separate the coupled aramid fiber, rinse with deionized water, and dry at 50°C to obtain a filler;

[0088] 2) 50 g of magnesium oxide with a particle size of 1 μm and 500 mL of N,N-dimethylformamide were mixed evenly, 5 mL of KH550-ethanol solution with a mass fraction of 3 wt% was added, and the mixture was kept constant at 90° C. for 6 h, and the filler was added and mixed evenly, and the mixture was kept constant at 160° C. for 2 h. After cooling to room temperature, the mixture was filtered and the filter residue was ultrasonically washed with anhydrous ethanol, and 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 well, knead at 355° C. for 5 min, and then extrude to obtain a high-strength insulating composite material.

[0090] The composite material prepared in this example, which has no distortion in the components and no surface defects, was subjected to the same performance test as in Example 1, and the results are 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) Take aramid fiber with a diameter of 7 μm and a length of 2.4 mm, take 100 g of aramid fiber, extract with 500 mL of acetone for 48 hours, filter and separate the aramid fiber treated with acetone, ultrasonically rinse with deionized water, add 200 mL of concentrated nitric acid with a concentration of 6 mol / L, keep constant temperature at 80° C. for 2.5 hours, filter and separate the aramid fiber treated with acid, ultrasonically rinse with anhydrous ethanol, add 10 mL of KH550-ethanol solution with a mass fraction of 3 wt%, react and reflux for 3 hours in a N2 atmosphere at 60° C., and then filter and separate the aramid fiber treated with coupling, rinse with deionized water, and dry at 50° C. to obtain a filler;

[0097] 2) 50 g of magnesium oxide with a particle size of 1 μm and 500 mL of N,N-dimethylformamide were mixed evenly, 5 mL of KH550-ethanol solution with a mass fraction of 3 wt% was added, and the mixture was kept constant at 90° C. for 6 h, and the filler was added and mixed evenly, and the mixture was kept constant at 160° C. for 2 h. After cooling to room temperature, the mixture was filtered and the filter residue was ultrasonically washed with anhydrous ethanol, and 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 min, and then extrude to obtain a high-strength insulating composite material.

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

[0100] <![CDATA[Impact resistance (kJ / m 2 )]]> Tensile strength(MPa) Bending 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] According to the results in the above table, the relative content of the modified filler in this example is low, and it is obvious that the overlap effect between the fibers is poor, the fibers and the thermoplastic material do not form a complete heat conduction path, and the effect of improving the high-temperature stability of the composite material is also very small, which does not meet the requirement of "high-temperature stability within 110°C" of the present invention. At the same time, the fibers failed to form a continuous phase, which had a more obvious impact on toughness. Compared with Example 2, the composite material has poor impact resistance and tensile resistance.

[0102] The above preparation was performed by changing step 3) "adding 24 g of polyetheretherketone per gram of modified filler" 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) Bending 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 above table, excessive fiber was added, but the fiber distribution was uneven, and agglomeration occurred, resulting in stress concentration. The reinforcement effect was far lower than the performance degradation caused by agglomeration, which significantly affected the bending strength of the composite material. At the same time, the brittleness of the composite material increased, and pores appeared on its surface, resulting in a decrease in the impact resistance of the material. However, this has a relatively small effect on the high temperature stability and flame retardant properties of the material. In addition, excessive aramid fiber also led to a significant decrease in the electrical properties of the composite material, with a greater decrease in its volume resistivity and anti-puncture performance.

[0105] Comparative Example 2

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

[0107] 1) Take aramid fiber with a diameter of 7 μm and a length of 2.4 mm, take 100 g of aramid fiber, extract with 500 mL of acetone for 48 hours, filter and separate the aramid fiber extracted with acetone, ultrasonically wash with deionized water, add 200 mL of concentrated nitric acid with a concentration of 6 mol / L, keep constant temperature at 80° C. for 2.5 hours, filter, wash and dry to obtain a filler;

[0108] 2) 50 g of magnesium oxide with a particle size of 1 μm and 500 mL of N,N-dimethylformamide were mixed evenly, 5 mL of KH550-ethanol solution with a mass fraction of 3 wt% was added, and the mixture was kept constant at 90° C. for 6 h, and the filler was added and mixed evenly, and the mixture was kept constant at 160° C. for 2 h. After cooling to room temperature, the mixture was filtered and the filter residue was ultrasonically washed with anhydrous ethanol, and 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 well, knead at 355° C. for 5 min, and then extrude to obtain a high-strength insulating composite material.

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

[0111]

[0112]

[0113] According to the results in the above table, the aramid fiber without coupling agent treatment is combined with the thermoplastic material by relatively weak physical action, and the fiber reinforcement effect is small. After compounding with MgO particles, the system combines the reinforcing material with physical weak bonds. After experiments, it is found that the tensile strength of this material is poor. At the same time, due to the large interface gap in the system, the high-temperature stability of the composite material is poor. The compatibility of aramid fiber and thermoplastic material deteriorates, which reduces the volume resistivity of the material.

[0114] Comparative Example 3

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

[0116] 1) Take aramid fiber with a diameter of 7 μm and a length of 2.4 mm, take 100 g of aramid fiber, extract with 500 mL of acetone for 48 hours, filter and separate the aramid fiber treated with acetone, ultrasonically rinse with deionized water, add 200 mL of concentrated nitric acid with a concentration of 6 mol / L, keep constant temperature at 80° C. for 2.5 hours, filter and separate the aramid fiber treated with acid, ultrasonically rinse with anhydrous ethanol, add 10 mL of KH550-ethanol solution with a mass fraction of 3 wt%, react and reflux for 3 hours in a N2 atmosphere at 60° C., and then filter and separate the aramid fiber treated with coupling, rinse with deionized water, and dry at 50° C. to obtain a filler;

[0117] 2) 50 g of magnesium oxide with a particle size of 1 μm and 500 mL of N,N-dimethylformamide were mixed evenly, 5 mL of KH550-ethanol solution with a mass fraction of 5 wt% was added, and the mixture was kept constant at 90° C. for 6 h, and the filler was added and mixed evenly, and the mixture was kept constant at 160° C. for 2 h. After cooling to room temperature, the mixture was filtered and the filter residue was ultrasonically washed with anhydrous ethanol, and 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 well, knead at 355° C. for 5 min, and then extrude to obtain a high-strength insulating composite material.

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

[0120] <![CDATA[Impact resistance (kJ / m 2 )]]> Tensile strength(MPa) Bending 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] In order to ensure that MgO particles are attached to the surface of aramid fibers to obtain a composite material with high chemical bonding strength, the present invention disperses MgO in N,N-dimethylformamide, adds a coupling agent and then performs heat treatment. During the heat treatment, the grafting rate of MgO particles is affected by the concentration of the silane coupling agent. In this example, the mass fraction of the silane coupling agent is increased, the coupling agent undergoes hydrolysis and condensation, and the competitive reaction is significantly enhanced, resulting in a significant decrease in the grafting rate of MgO. A low MgO grafting rate not only affects the insulation performance of the material, but also affects the high-temperature stability of the material. In a high-temperature harsh environment, the insulation performance of the composite material is easily lost.

[0122] Comparative Example 4

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

[0124] 1) Take aramid fiber with a diameter of 7 μm and a length of 2.4 mm, take 100 g of aramid fiber, extract with 500 mL of acetone for 48 hours, filter and separate the aramid fiber treated with acetone, ultrasonically rinse with deionized water, add 200 mL of concentrated nitric acid with a concentration of 6 mol / L, keep constant temperature at 80° C. for 2.5 hours, filter and separate the aramid fiber treated with acid, ultrasonically rinse with anhydrous ethanol, add 10 mL of KH550-ethanol solution with a mass fraction of 3 wt%, react and reflux for 3 hours in a N2 atmosphere at 60° C., and then filter and separate the aramid fiber treated with coupling, rinse with deionized water, and dry at 50° C. to obtain a filler;

[0125] 2) 50 g of magnesium oxide with a particle size of 1 μm and 500 mL of N,N-dimethylformamide were mixed evenly, 5 mL of KH550-ethanol solution with a mass fraction of 3 wt% was added, and the mixture was kept constant at 90° C. for 6 h, and the filler was added and mixed evenly, and the mixture was kept constant at 170° C. for 2 h. After cooling to room temperature, the mixture was filtered and the filter residue was ultrasonically washed with anhydrous ethanol, and 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 well, knead at 355° C. for 5 min, and then extrude to obtain a high-strength insulating composite material.

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

[0128] <![CDATA[Impact resistance (kJ / m 2 )]]> Tensile strength(MPa) Bending 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 molecular collisions to be too violent, and the self-condensation reaction of the hydroxyl groups on the particle surface and the self-condensation reaction of the silanols produced by the hydrolysis of the coupling agent compete with the grafting reaction, resulting in a significant decrease in the grafting rate of MgO. 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 the fibers and the fibers and the thermoplastic material. 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 will affect its insulation effect.

[0130] Comparative Example 5

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

[0132] 1) Take aramid fiber with a diameter of 7 μm and a length of 2.4 mm, take 100 g of aramid fiber, extract with 500 mL of acetone for 48 hours, filter and separate the aramid fiber treated with acetone, ultrasonically rinse with deionized water, add 200 mL of concentrated nitric acid with a concentration of 6 mol / L, keep constant temperature at 80° C. for 2.5 hours, filter and separate the aramid fiber treated with acid, ultrasonically rinse with anhydrous ethanol, add 10 mL of KH550-ethanol solution with a mass fraction of 3 wt%, react and reflux for 3 hours in a N2 atmosphere at 60° C., and then filter and separate the aramid fiber treated with coupling, rinse with deionized water, and dry at 50° C. to obtain a filler;

[0133] 2) 50 g of magnesium oxide with a particle size of 1 μm and 500 mL of N,N-dimethylformamide were mixed evenly, 5 mL of KH550-ethanol solution with a mass fraction of 3 wt% was added, and the mixture was kept constant at 90° C. for 6 h, and the filler was added and mixed evenly, and the mixture was kept constant at 160° C. for 2 h. After cooling to room temperature, the mixture was filtered and the filter residue was ultrasonically washed with anhydrous ethanol, and 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 and mix well. Mix at 355° C. for 5 min and then extrude to obtain a high-strength insulating composite material.

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

[0136] <![CDATA[Impact resistance (kJ / m 2 )]]> Tensile strength(MPa) Bending 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 mainly used to enhance the thermal stability and electrical insulation of materials, while providing a certain lubricity, which is beneficial to improving the fluidity and processability of materials. Calcium stearate can enhance the hardness and strength of composite materials, thereby improving their impact resistance. According to the results in the above table, the mechanical and electrical properties of composite materials have been significantly reduced, and the reduced thermal stability has led to a significant shortening of the service life of the material in outdoor or high temperature environments. This shows the necessary role of organic metal salt additives.

[0138] Comparative Example 6

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

[0140] 1) Take aramid fiber with a diameter of 7 μm and a length of 2.4 mm, take 100 g of aramid fiber, extract with 500 mL of acetone for 48 hours, filter and separate the aramid fiber treated with acetone, ultrasonically rinse with deionized water, add 200 mL of concentrated nitric acid with a concentration of 6 mol / L, keep constant temperature at 80° C. for 2.5 hours, filter and separate the aramid fiber treated with acid, ultrasonically rinse with anhydrous ethanol, add 10 mL of KH550-ethanol solution with a mass fraction of 3 wt%, react and reflux for 3 hours in a N2 atmosphere at 60° C., and then filter and separate the aramid fiber treated with coupling, rinse with deionized water, and dry at 50° C. to obtain a filler;

[0141] 2) 50 g of magnesium oxide with a particle size of 1 μm and 500 mL of N,N-dimethylformamide were mixed evenly, 5 mL of KH550-ethanol solution with a mass fraction of 3 wt% was added, and the mixture was kept constant at 90° C. for 6 h, and the filler was added and mixed evenly, and the mixture was kept constant at 160° C. for 2 h. After cooling to room temperature, the mixture was filtered and the filter residue was ultrasonically washed with anhydrous ethanol, and 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 and mix well. After kneading at 355° C. for 5 minutes, extrude and mold to obtain a high-strength insulating composite material.

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

[0144] <![CDATA[Impact resistance (kJ / m 2 )]]> Tensile strength(MPa) Bending 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, causing the volume resistivity to decrease and the electrical insulation performance to deteriorate. Although it still maintains good high-temperature stability, the water resistance is relatively poor, which has 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) Take wood fiber with a diameter of 7 μm and a length of 2.4 mm, take 100 g of wood fiber, extract with 500 mL of acetone for 48 hours, filter and separate the aramid fiber treated with acetone, ultrasonically soak with deionized water, add 200 mL of concentrated nitric acid with a concentration of 6 mol / L, keep constant temperature at 80°C for 2.5 hours, filter and separate the acid-treated aramid fiber, ultrasonically soak with anhydrous ethanol, add 10 mL of KH550-ethanol solution with a mass fraction of 3 wt%, react and reflux for 3 hours in a N2 atmosphere at 60°C, filter and separate the coupled aramid fiber, wash with deionized water, and dry at 50°C to obtain a filler;

[0149] 2) 50 g of magnesium oxide with a particle size of 1 μm and 500 mL of N,N-dimethylformamide were mixed evenly, 5 mL of KH550-ethanol solution with a mass fraction of 3 wt% was added, and the mixture was kept constant at 90° C. for 6 h, and the filler was added and mixed evenly, and the mixture was kept constant at 160° C. for 2 h. After cooling to room temperature, the mixture was filtered and the filter residue was ultrasonically washed with anhydrous ethanol, and 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 well, knead at 355° C. for 5 min, and then extrude to obtain a high-strength insulating composite material.

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

[0152]

[0153]

[0154] According to the results in the above table, due to the large number of hydrophilic free hydroxyl groups exposed on the surface of wood fiber, wood fiber has a high hygroscopic capacity, which makes it easy for wood fiber to absorb ·HO in the air to form conductive substances, thereby causing the volume resistivity of the composite material to decrease. At the same time, the interface compatibility between wood fiber and polyetheretherketone is poor, and polyetheretherketone does not completely wrap wood fiber containing a large number of active hydroxyl groups, exposing more water absorption sites, resulting in a significant decrease in electrical properties.

Claims

1. A method for preparing a high-strength insulating composite material, characterized in that: The method comprises: 1) extracting and washing the raw material and solvent, adding acid solution for desizing, filtering and washing, adding coupling agent for reaction, filtering, washing and drying to obtain the filler; 2) taking alkaline earth metal oxide and dispersant and mixing them evenly, adding coupling agent and heating to react, adding filler and mixing evenly, refluxing, cooling, washing and drying to obtain modified filler; 3) The modified filler is uniformly mixed with the thermoplastic material, the organic metal salt, the acyclic carboxylic acid and the antioxidant, and a high-strength insulating composite material is obtained through high-temperature kneading.

2. The method for preparing a high-strength insulating composite material according to claim 1, characterized in that: Step 1) The raw material is aramid fiber, the diameter of which is 6-7 μm and the length is 2-3 mm; Step 1) The solvent is acetone, and the amount thereof is 5 to 15 mL / g of raw material; The extraction time of 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: 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 raw material; The acid desizing in step 1) 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: 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; The reaction of adding coupling agent in step 1) is to add coupling agent and reflux for 3 to 3.5 hours in protective atmosphere at 58 to 60°C.

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

6. The method for preparing a high-strength insulating composite material according to claim 1 or 5, characterized in that: Step 2) The heating reaction is carried out at 80-90°C for 6-6.5 hours; In step 2), the reflux is carried out at a constant temperature of 155-160° C. for 2-2.5 hours.

7. The method for preparing a high-strength insulating composite material according to claim 1, characterized in that: Step 3) the thermoplastic material is polyetheretherketone, and its dosage is 20-22 g / g modified filler; Step 3) the organic metal salt is a mixture of lead stearate and calcium stearate, and its dosage is 0.03-0.04 g / g modified filler, and the lead stearate and calcium stearate are mixed according to a mass ratio of 1: (0.5-0.7); In step 3), the acyclic carboxylic acid is stearic acid, and its usage is 0.01-0.02 g / g modified filler; in step 3), the antioxidant is antioxidant 1010, and its usage is 0.01-0.02 mL / g modified filler.

8. A high-strength insulating composite material according to claim 1 or 7, characterized in that: Step 3) The high-temperature mixing is controlled at a temperature of 355-360° C. and a mixing time of 3-8 min. After mixing, the high-strength insulating composite material is obtained.

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

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

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