A basalt fiber reinforced thermoplastic composite material with electromagnetic wave shielding function and its preparation method

Abstract

The present invention discloses a basalt fiber reinforced thermoplastic composite material with electromagnetic wave shielding function and its preparation method. The composite material is prepared by melt blending basalt short fibers after surface modification and thermoplastic plastics in a certain proportion. The preparation method of the surface-modified basalt short fibers is as follows: The basalt fibers, surface lipophilized modified Fe3O4 nanoparticles, carbon nanotubes or graphene nanosheets, and dopamine that have undergone surface cleaning treatment are dispersed in a buffer solution for polymerization reaction, and a polydopamine / Fe3O4 nanoparticle composite coating layer is formed on the surface of the basalt fibers, and at the same time, carbon nanotubes or graphene nanosheets are adhered to its surface. The composite material of the present invention not only obtains more excellent mechanical strength, but also has electromagnetic wave shielding function at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of plastic modification and composite material preparation, and particularly relates to a basalt fiber-reinforced thermoplastic composite material with electromagnetic wave shielding function and a preparation method thereof. Background Art

[0002] Fiber-reinforced thermoplastic engineering plastics are a common means of plastic modification and have been widely used in the technical field of high-performance composite material preparation. The composite material products prepared are also widely used in various fields such as automobiles, electronic and electrical appliances, office equipment, and industrial machinery. Traditional inorganic fibers such as glass fibers and carbon fiber-reinforced organic polymer materials have excellent tensile properties, bending properties, and high rigidity, but their toughness often suffers certain losses due to the introduction of rigid fibers. With the deepening of the concept of sustainable development, the research and development of energy conservation and emission reduction technologies have received extensive attention, and the development of automotive lightweight technologies has also received extensive attention. This field urgently needs a large number of high-performance lightweight composite materials to be applied therein. In addition, the rapid development of high-performance unmanned aerial vehicles also urgently requires composite materials with high performance, lightweight, and electromagnetic wave shielding function. It is precisely in this application background that the need for lightweight polymer fiber-reinforced thermoplastic engineering plastic composite materials is continuously increasing. Among them, the application of high-performance synthetic fibers represented by basalt fibers in the field of engineering plastic reinforcement and modification has received attention. Basalt fibers have high strength (between glass fibers and carbon fibers), and their density is only about 2.8 g / cm 3 or so, with obvious lightweight advantages and obvious cost price advantages. Therefore, applying it to the reinforcement and modification of engineering plastics can not only effectively improve the tensile strength and modulus of the material, but also make the density of the reinforced plastic significantly lower than that of the composite material reinforced by traditional inorganic glass fibers, and the price is much lower than that of the carbon fiber-reinforced composite material.

[0003] Traditional fiber-reinforced thermoplastics are usually prepared by directly melting and blending short-cut fibers through a twin-screw extruder, or by melting long fibers after pultrusion. Since basalt inorganic fibers are smooth, difficult to be compatible with organic polymer materials, and have a large interfacial tension, it is not only difficult to be evenly dispersed in the plastic matrix, but also extremely easy to be pulled out when the material breaks, resulting in poor reinforcement effect. In view of the fact that the performance of fiber-reinforced plastic composite materials largely depends on the interfacial bonding situation between each component. The interface of the composite material is the intermediate bridge between the reinforcing phase and the matrix phase, and also the transmitter of energy and information. Good interfacial bonding can effectively transmit the load and thus improve the mechanical properties of the composite material. Therefore, making full use of the superiority of good interfacial effects, increasing the surface roughness and specific surface area of basalt fibers, and enhancing their interfacial bonding performance with the matrix material can greatly improve the mechanical properties and mechanical performance of the composite material.

[0004] If a composite material is to obtain a wide-band electromagnetic wave shielding function, it is also necessary to add conductive fillers and magnetic fillers to it, and achieve synchronous shielding efficiency of electromagnetic waves in the high-frequency band and low-frequency band through electric field and magnetic field shielding. However, adding foreign inorganic fillers will cause a decline in the mechanical properties of the composite material, resulting in deterioration of the comprehensive properties of the material. For example, by adding carbon nanotubes or graphene nanosheets to the composite material, the high-frequency band electromagnetic wave shielding efficiency of the composite material can be obtained by using their electric field shielding effect; and by adding paramagnetic inorganic particles of iron oxide (Fe3O4) to the composite material, the electromagnetic wave shielding efficiency of the composite material in the low-frequency band can be achieved through the magnetic eddy current loss of the electromagnetic wave, and finally the prepared composite material can obtain an electromagnetic wave shielding function in the wide-frequency region. However, the addition of these inorganic conductive and magnetic additives will cause a decline in the mechanical properties of the composite material. However, nanostructured carbon materials such as carbon nanotubes and graphene nanosheets are also important candidate materials for the surface modification of basalt fibers, because they have many unique physical and chemical properties. Since the C═C covalent bond in these two kinds of nanocarbon materials is considered to be the most stable chemical bond in nature, the surface roughness of the basalt fiber is significantly increased after surface modification by carbon nanotubes and graphene nanosheets, so the enhancement effect on thermoplastic composites can be significantly improved. Therefore, if the above inorganic additives can be organically combined with basalt fibers through interface modification, not only can the composite material obtain electromagnetic shielding function, but also the enhancement effect of basalt fibers can be significantly improved, so as to obtain a composite material with excellent comprehensive properties. Summary of the Invention

[0005] The problem to be solved by the present invention is to change the surface inertness of basalt fibers and the deterioration problem of the mechanical properties of thermoplastic composites caused by electromagnetic shielding functional additives. By using surface-adhered nanocarbon materials, the surface roughness, surface energy, hydrophilicity and specific surface area of basalt fibers can be effectively improved, and at the same time, the interfacial bonding performance between the fibers and the matrix resin can be improved, which is beneficial to its application in the enhancement and modification of thermoplastic plastics. In addition, Fe3O4 inorganic particles are embedded in the surface bonding layer of basalt fibers to organically combine the electromagnetic shielding functional filler with basalt fibers. The surface-modified basalt fibers prepared by the present invention are compounded with thermoplastic plastics to prepare thermoplastic composites, which not only significantly improve the mechanical properties of the composites compared with traditional reinforcing materials, but also obtain excellent wide-band electromagnetic shielding functions. Thus, a composite material with excellent electromagnetic wave shielding function is obtained.

[0006] The present invention is realized through the following technical solutions:

[0007] (1) Cut the basalt fibers into short fibers of 2-3 mm, and wash them with clean water;

[0008] (2) Use an acetone solution containing sodium dodecylbenzenesulfonate to perform surface lipophilic modification on those with a diameter of about 50 nm;

[0009] (2) Disperse the surface-cleaned basalt fibers, surface-lipophilically modified Fe3O4 nanoparticles, carbon nanotubes or graphene nanosheets, and dopamine in a buffer solution for polymerization reaction. The reaction temperature is room temperature, the reaction time is 6 h. After the reaction, a polydopamine / Fe3O4 nanoparticle composite coating layer is formed on the surface of the basalt fibers, and at the same time, carbon nanotubes or graphene nanosheets are adhered to its surface;

[0010] (3) Mix a certain amount of chopped basalt fibers with surface-adhered carbon nanotubes or graphene nanosheets and having a polydopamine / Fe3O4 nanoparticle composite coating layer with a thermoplastic plastic by melt blending to obtain a reinforced thermoplastic composite.

[0011] The thermoplastic plastic resin is any one of polypropylene, polyethylene, ABS resin, HIPS resin general plastics, and engineering plastics including nylon 6, nylon 66, polycarbonate, and PBT resin.

[0012] The diameter of the Fe3O4 nanoparticles is about 50 nm.

[0013] The method for surface lipophilic modification of the Fe3O4 nanoparticles is as follows: Using sodium dodecylbenzenesulfonate as an anionic surfactant, dissolve it in an acetone solvent to form a solution with a mass percentage concentration of 5 wt.%. Disperse every 100 g of Fe3O4 nanoparticles in 200 g of the acetone solution containing sodium dodecylbenzenesulfonate, and mechanically stir at room temperature for 3 hours. Then, filter and dry in a vacuum oven at 80 °C for 12 hours.

[0014] The buffer solution is prepared from a tris(hydroxymethyl)aminomethane solution with a concentration of 1.2 mg / mL and a hydrochloric acid solution with a concentration of 1 mol / L, and is weakly alkaline with a pH value of 8.5.

[0015] The carbon nanotubes are multi-walled carbon nanotubes, the graphene nanosheets are ultra-thin graphene with 10 - 30 layers, and the addition amount in the reaction solution is 1.0 - 2.0 parts by mass per 100 parts of the chopped basalt fibers; the surface-lipophilically modified Fe3O4 nanoparticles, the addition amount in the reaction solution is 2.0 - 3.0 parts by mass per 100 parts of the chopped basalt fibers; the addition amount concentration of dopamine in the reaction solution is 10.0 - 15.0 parts by mass per 100 parts of the chopped basalt fibers.

[0016] The mass percentage content of the basalt short fibers with carbon nanotubes or graphene nanosheets adhered to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer in the thermoplastic is 25 to 30 wt.%.

[0017] In the composite material, 0.3 parts of antioxidant are required to be added per 100 parts by mass of the thermoplastic. The antioxidant is a mixture of antioxidant 1010 and antioxidant 168, and their mass ratio is 1:1.

[0018] By the above method, basalt short fibers with carbon nanotubes or graphene nanosheets adhered to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer are obtained, which improves the surface roughness, reduces the surface energy, increases the hydrophilicity and specific surface area of the basalt fibers, and at the same time improves the interfacial bonding performance between the fibers and the matrix resin, thus being beneficial to its application in the enhancement and modification of thermoplastics. At the same time, by adding magnetic Fe3O4 nanoparticles to the polydopamine layer on the surface of the basalt fibers, the thermoplastic composite material prepared by using the basalt fibers can, through the combined action of the carbon nanotubes or graphene nanosheet conductive materials adhered to the surface and the magnetic Fe3O4 nanoparticles, endow the prepared thermoplastic composite material with a wide-band electromagnetic wave shielding effect.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. The basalt short fibers with carbon nanotubes or graphene nanosheets adhered to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer used in the present invention are used as reinforcing fibers to reinforce thermoplastics. Compared with traditional basalt short fibers, the surface roughness of the basalt fibers is significantly improved, the specific surface area of the modified basalt fibers is greatly increased, and at the same time, the interfacial bonding performance between the fibers and the matrix thermoplastics is effectively improved, thereby obtaining a better reinforcing effect than traditional basalt short fibers.

[0021] 2. The thermoplastic composite material reinforced by traditional basalt short fibers only improves the strength and modulus of the material and does not introduce other functions to the composite material. However, the composite material of the present invention, due to using basalt short fibers with carbon nanotubes or graphene nanosheets adhered to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer as reinforcing fibers, not only significantly improves the strength and modulus of the material, but also through the high-frequency electric field shielding effect generated by the carbon nanotubes or graphene nanosheets adhered to the surface and the low-frequency electric field shielding effect generated by the Fe3O4 magnetic nanoparticles in the polydopamine / Fe3O4 nanoparticle composite coating layer, so that the prepared composite material obtains a wide-band electromagnetic wave shielding function.

[0022] 3. By perfectly integrating conductive fillers and magnetic nanoparticles with basalt short fibers instead of directly adding them as functional fillers to thermoplastics, the present invention avoids the deterioration of the mechanical properties of the composite material caused by direct addition, thereby obtaining better comprehensive mechanical properties than traditional basalt fiber-reinforced electromagnetic wave shielding functional composite materials. Detailed implementation manners

[0023] The present invention will be further described below in conjunction with embodiments. The preferred embodiments do not describe all details in detail, nor do they limit the invention to the specific implementation manners described. Unless otherwise specified, the methods in the embodiments are all conventional experimental methods, and the experimental materials used can be easily obtained from commercial companies.

[0024] Embodiment 1:

[0025] A basalt fiber-reinforced thermoplastic composite material with electromagnetic wave shielding function, the mass percentage of its raw material composition is: 30.0 wt.% of basalt fibers with carbon nanotubes attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer, 70 wt.% of nylon 6 resin, and 0.3 parts of antioxidant equivalent to 100 parts by mass of nylon 6 resin are added to the composite material. The antioxidant is a mixture of antioxidant 1010 and antioxidant 168, and their mass ratio is 1:1.

[0026] The preparation steps of the basalt short fibers with carbon nanotubes attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer are as follows:

[0027] (1) Cut the basalt fiber filaments into short fibers of 2 mm, then wash 1.0 kg of basalt short fibers in an ultrasonic environment in water for 2 hours, and then put the washed basalt short fibers into a blast drying oven for drying.

[0028] (2) Disperse 20 g of Fe3O4 nanoparticles in an acetone solution of 40 g of sodium dodecylbenzenesulfonate, mechanically stir at room temperature for 3 hours, obtain Fe3O4 nanoparticles with lipophilic modification on the surface after filtration, and dry them in a vacuum oven at 80 °C for 12 hours.

[0029] (3) Weigh 1.0 kg of clean basalt chopped fibers, 120.0 g of dopamine powder, 20.0 g of multi-walled carbon nanotubes, and 20.0 g of surface lipophilic modified Fe3O4 nanoparticles. Disperse them in 2.0 L of a tris(hydroxymethyl)aminomethane buffer solution with a concentration of 1.2 g / L and stir evenly. Then, carry out a copolymerization reaction at room temperature for 6 h. After the reaction is completed, wash the obtained chopped fibers 3 times with deionized water. Put the washed basalt chopped fibers with carbon nanotubes attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer into a blast drying oven for drying, and then seal and store them in a self-sealing bag.

[0030] (4) Weigh various raw materials according to the mass percentage of the above composite material, and carry out melt blending and granulation with a twin-screw extrusion granulation unit. The feeding method is as follows: Nylon 6 resin and antioxidant are fed from the main feeding port of the twin-screw extrusion granulation unit through a loss-in-weight metering scale, and basalt chopped fibers with carbon nanotubes attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer are fed from the side feeding port. The temperature of the twin-screw extruder is set to be 185 - 245 °C from the main feeding port to the die head, and the screw speed is 300 rpm.

[0031] Example 2:

[0032] A basalt fiber-reinforced thermoplastic composite material with electromagnetic wave shielding function, the mass percentage of its raw material composition is: 25.0 wt.% of basalt fibers with graphene nanosheets attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer, 75 wt.% of nylon 6 resin, and an antioxidant equivalent to 0.3 parts by mass of 100 parts by mass of nylon 6 resin is added to the composite material. The antioxidant is a mixture of antioxidant 1010 and antioxidant 168, and their mass ratio is 1:1.

[0033] The preparation steps of basalt chopped fibers with graphene nanosheets attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer are as follows:

[0034] (1) Cut basalt fiber filaments into 2.5-mm chopped fibers. Then, wash 1.0 kg of basalt chopped fibers in an ultrasonic environment in clean water for 2 hours, and then put the washed basalt chopped fibers into a blast drying oven for drying.

[0035] (2) Disperse 25 g of Fe3O4 nanoparticles in an acetone solution of 50 g of sodium dodecylbenzenesulfonate, mechanically stir at room temperature for 3 hours, obtain surface lipophilic modified Fe3O4 nanoparticles after filtration, and dry them in a vacuum oven at 80 °C for 12 hours.

[0036] (3) Weigh 1.0 kg of clean basalt chopped fibers, 150.0 g of dopamine powder, 15.0 g of graphene nanosheets, and 25.0 g of surface lipophilic modified Fe3O4 nanoparticles. Disperse them in 2.0 L of a tris(hydroxymethyl)aminomethane buffer solution with a concentration of 1.2 g / L and stir evenly. Then, carry out a copolymerization reaction at room temperature for 6 h. After the reaction is completed, wash the obtained chopped fibers 3 times with deionized water. Put the washed basalt chopped fibers with graphene nanosheets attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer into a forced-air drying oven for drying, and then seal and store them in a self-sealing bag.

[0037] (4) Weigh various raw materials according to the mass percentages of the above composite materials and carry out melt blending and granulation using a twin-screw extrusion granulation unit. The feeding method is as follows: Nylon 6 resin and antioxidant are fed from the main feeding port of the twin-screw extrusion granulation unit through a loss-in-weight metering scale, and basalt chopped fibers with graphene nanosheets attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer are fed from the side feeding port. The temperature of the twin-screw extruder is set to be 185 - 245 °C from the main feeding port to the head, and the screw speed is 300 rpm.

[0038] Example 3:

[0039] A basalt fiber-reinforced thermoplastic composite material with electromagnetic wave shielding function, the mass percentages of its raw material composition are: 30.0 wt.% of basalt fibers with carbon nanotubes attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer, 70 wt.% of polycarbonate resin, and an antioxidant equivalent to 0.3 parts by mass of 100 parts by mass of polycarbonate resin is added to the composite material. The antioxidant is a mixture of antioxidant 1010 and antioxidant 168, and their mass ratio is 1:1.

[0040] The preparation steps of basalt chopped fibers with carbon nanotubes attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer are as follows:

[0041] (1) Cut basalt fiber filaments into 2-mm chopped fibers. Then, wash 1.0 kg of basalt chopped fibers in an ultrasonic environment in water for 2 hours, and then put the washed basalt chopped fibers into a forced-air drying oven for drying.

[0042] (2) Disperse 30 g of Fe3O4 nanoparticles in an acetone solution of 60 g of sodium dodecylbenzenesulfonate and mechanically stir at room temperature for 3 hours. After filtration, obtain surface lipophilic modified Fe3O4 nanoparticles and dry them in a vacuum oven at 80 °C for 12 hours.

[0043] (3) Weigh 1.0 kg of clean basalt chopped fibers, 100.0 g of dopamine powder, 10.0 g of multi-walled carbon nanotubes, and 30.0 g of surface lipophilic modified Fe3O4 nanoparticles. Disperse them in 2.0 L of a tris(hydroxymethyl)aminomethane buffer solution with a concentration of 1.2 g / L and stir evenly. Then, carry out a copolymerization reaction at room temperature for 6 h. After the reaction is completed, wash the obtained chopped fibers 3 times with deionized water. Put the washed basalt chopped fibers with carbon nanotubes attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer into a blast drying oven for drying, and then seal and store them in a self-sealing bag.

[0044] (4) Weigh various raw materials according to the mass percentage of the above composite material, and carry out melt blending and granulation with a twin-screw extrusion granulation unit. The feeding method is as follows: Polycarbonate resin and antioxidant are fed from the main feeding port of the twin-screw extrusion granulation unit through a loss-in-weight metering scale, and basalt chopped fibers with carbon nanotubes attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer are fed from the side feeding port. The temperature of the twin-screw extruder is set to be 205 - 240 °C from the main feeding port to the head, and the screw speed is 300 rpm.

[0045] Example 4:

[0046] A basalt fiber-reinforced thermoplastic composite material with electromagnetic wave shielding function, the mass percentage of its raw material composition is: 30.0 wt.% of basalt fibers with carbon nanotubes attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer, 70 wt.% of polybutylene terephthalate (PBT) resin, and an antioxidant equivalent to 0.3 parts by mass of 100 parts by mass of polycarbonate resin is added to the composite material. The antioxidant is a mixture of antioxidant 1010 and antioxidant 168, and their mass ratio is 1:1.

[0047] The preparation steps of basalt chopped fibers with carbon nanotubes attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer are as follows:

[0048] (1) Cut the basalt fiber filaments into 3-mm chopped fibers. Then, wash 1.0 kg of basalt chopped fibers in an ultrasonic environment in clean water for 2 hours, and then put the washed basalt chopped fibers into a blast drying oven for drying.

[0049] (2) Disperse 25 g of Fe3O4 nanoparticles in 50 g of an acetone solution of sodium dodecylbenzenesulfonate, and mechanically stir at room temperature for 3 hours. After filtration, obtain surface lipophilic modified Fe3O4 nanoparticles, and dry them in a vacuum oven at 80 °C for 12 hours.

[0050] (3) Weigh 1.0 kg of clean basalt chopped fibers, 150.0 g of dopamine powder, 20.0 g of multi-walled carbon nanotubes, and 25.0 g of surface lipophilic modified Fe3O4 nanoparticles. Disperse them in 2.0 L of a tris(hydroxymethyl)aminomethane buffer solution with a concentration of 1.2 g / L and stir evenly. Then, carry out a copolymerization reaction at room temperature for 6 h. After the reaction is completed, wash the obtained chopped fibers 3 times with deionized water. Put the washed basalt chopped fibers with carbon nanotubes attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer into a blast drying oven for drying, and then seal and store them in a self-sealing bag.

[0051] (4) Weigh various raw materials according to the mass percentage of the above composite material, and carry out melt blending and granulation with a twin-screw extrusion granulation unit. The feeding method is as follows: PBT resin and antioxidant are fed into the main feeding port of the twin-screw extrusion granulation unit through a loss-in-weight metering scale. Basalt chopped fibers with carbon nanotubes attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer are fed into the side feeding port. The temperature of the twin-screw extruder is set to be 255 - 280 °C from the main feeding port to the die head, and the screw speed is 300 rpm.

[0052] Example 5:

[0053] A basalt fiber-reinforced thermoplastic composite material with electromagnetic wave shielding function, the mass percentage of its raw material composition is: 30.0 wt.% of basalt fibers with carbon nanotubes attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer, 70 wt.% of ABS resin, and an antioxidant equivalent to 0.3 parts by mass of 100 parts by mass of polycarbonate resin is added to the composite material. The antioxidant is a mixture of antioxidant 1010 and antioxidant 168, and their mass ratio is 1:1.

[0054] The preparation steps of basalt chopped fibers with carbon nanotubes attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer are as follows:

[0055] (1) Cut the basalt fiber filaments into 2.5 mm chopped fibers. Then, wash 1.0 kg of basalt chopped fibers in an ultrasonic environment in water for 2 hours, and then put the washed basalt chopped fibers into a blast drying oven for drying.

[0056] (2) Disperse 20 g of Fe3O4 nanoparticles in an acetone solution of 40 g of sodium dodecylbenzenesulfonate, and mechanically stir at room temperature for 3 hours. After filtration, obtain surface lipophilic modified Fe3O4 nanoparticles, and dry them in a vacuum oven at 80 °C for 12 hours.

[0057] (3) Weigh 1.0 kg of clean basalt chopped fibers, 130.0 g of dopamine powder, 20.0 g of multi-walled carbon nanotubes, and 20.0 g of surface lipophilic modified Fe3O4 nanoparticles. Disperse them in 2.0 L of a tris(hydroxymethyl)aminomethane buffer solution with a concentration of 1.2 g / L and stir evenly. Then, carry out a copolymerization reaction at room temperature for 6 h. After the reaction is completed, wash the obtained chopped fibers 3 times with deionized water. Put the washed basalt chopped fibers with carbon nanotubes attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer into a forced-air drying oven for drying, and then seal and store them in a self-sealing bag.

[0058] (4) Weigh various raw materials according to the mass percentage of the above composite material, and carry out melt blending and granulation with a twin-screw extrusion granulation unit. The feeding method is as follows: ABS resin and antioxidant are fed into the main feeding port of the twin-screw extrusion granulation unit through a loss-in-weight metering scale, and basalt chopped fibers with carbon nanotubes attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer are fed into the side feeding port. The temperature of the twin-screw extruder is set to be 165 - 240 °C from the main feeding port to the die head, and the screw speed is 300 rpm.

[0059] Example 6:

[0060] A basalt fiber-reinforced thermoplastic composite material with electromagnetic wave shielding function, the mass percentage of its raw material composition is: 30.0 wt.% of basalt fibers with graphene nanosheets attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer, 70 wt.% of polypropylene resin, and an antioxidant equivalent to 0.3 parts by mass of 100 parts by mass of nylon 6 resin is added to the composite material. The antioxidant is a mixture of antioxidant 1010 and antioxidant 168, and their mass ratio is 1:1.

[0061] The preparation steps of basalt chopped fibers with graphene nanosheets attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer are as follows:

[0062] (1) Cut the basalt fiber filaments into 2.5-mm chopped fibers, then wash 1.0 kg of basalt chopped fibers in an ultrasonic environment in clean water for 2 hours, and then put the washed basalt chopped fibers into a forced-air drying oven for drying;

[0063] (2) Disperse 30 g of Fe3O4 nanoparticles in 50 g of an acetone solution of sodium dodecylbenzenesulfonate, mechanically stir at room temperature for 3 hours, obtain surface lipophilic modified Fe3O4 nanoparticles after filtration, and dry them in a vacuum oven at 80 °C for 12 hours.

[0064] (3) Weigh 1.0 kg of clean basalt chopped fibers, 150.0 g of dopamine powder, 20.0 g of graphene nanosheets, and 30.0 g of surface lipophilic modified Fe3O4 nanoparticles. Disperse them in 2.0 L of a tris(hydroxymethyl)aminomethane buffer solution with a concentration of 1.2 g / L and stir evenly. Then, carry out a copolymerization reaction at room temperature for 6 h. After the reaction is completed, wash the obtained chopped fibers 3 times with deionized water. Put the washed basalt chopped fibers with graphene nanosheets attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer into a forced-air drying oven for drying, and then seal and store them in a self-sealing bag.

[0065] (4) Weigh various raw materials according to the mass percentages of the above composite materials and carry out melt blending and granulation using a twin-screw extrusion granulation unit. The feeding method is as follows: polypropylene resin and antioxidant are fed from the main feeding port of the twin-screw extrusion granulation unit through a loss-in-weight metering scale, and basalt chopped fibers with graphene nanosheets attached to the surface and containing a polydopamine / Fe3O4 nanoparticle composite coating layer are fed from the side feeding port. The temperature of the twin-screw extruder is set to be 165 - 245 °C from the main feeding port to the die head, and the screw speed is 300 rpm.

[0066] To verify the implementation effect of the present invention in preparing basalt fiber-reinforced thermoplastic composites with electromagnetic wave shielding function, the basalt fiber-reinforced thermoplastic composites prepared in the above examples of the present invention are used to prepare test specimens by injection molding for various performance tests, and basalt fiber-reinforced thermoplastic composites with the same formulation and the same mass percentage of the same thermoplastic resin matrix without any surface modification are used as a control example. The test standards adopted for tensile property testing are: GB / T1040 - 2008, the test standards adopted for flexural property testing are: GB / T 9341 - 2008, and the test standards adopted for electromagnetic shielding effectiveness testing are: GB / T 30142 - 2013. All performance test results are shown in Table 1. It can be found that the basalt fiber-reinforced thermoplastic composites prepared in the examples of the present invention have more excellent mechanical strength than the basalt fiber-reinforced thermoplastic composites prepared by traditional technologies, and have a relatively high industrial-grade electromagnetic wave shielding effectiveness, while the basalt fiber-reinforced thermoplastic composites prepared by traditional technologies have no electromagnetic wave shielding function at all.

[0067] The above are only the preferred examples of the preparation of the present invention, and do not impose any form of limitation on the present invention. Although the present invention is disclosed as above with preferred examples, it is not intended to limit the present invention. Those skilled in the art can still make some changes or modifications to the above-disclosed technical content within the scope of the technical solution of the present invention to obtain equivalent embodiments of equivalent changes. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are all within the scope of the technical solution of the present invention.

[0068] Table 1 Performance comparison between the basalt fiber-reinforced thermoplastic composites with electromagnetic wave shielding function prepared in Examples 1-6 and the basalt fiber-reinforced thermoplastic composites without any surface modification with the same formulation and the same mass percentage of the same thermoplastic resin matrix

[0069]

Claims

1. A basalt fiber reinforced thermoplastic composite material with electromagnetic wave shielding function, characterized in that: The thermoplastic composite material is prepared by melt blending 25.0 - 30.0 wt.% of surface-modified basalt short fibers and 70.0 - 75.0 wt.% of thermoplastic resin. An antioxidant is added during processing, and the addition amount of the antioxidant is equivalent to adding 0.3 parts by mass of antioxidant to 100 parts by mass of thermoplastic resin. The preparation method of the surface-modified basalt short fibers is as follows: (1) Cut the basalt fibers into short fibers with a length of 2 - 3 mm and wash them with clean water. (2) Perform surface lipophilization modification on Fe3O4 nanoparticles with a diameter of 50 nm using an acetone solution containing sodium dodecylbenzenesulfonate. (3) Disperse the surface-cleaned basalt short fibers, surface-lipophilized modified Fe3O4 nanoparticles, carbon nanotubes or graphene nanosheets, and dopamine in a buffer solution for a polymerization reaction. The reaction temperature is room temperature, and the reaction time is 6 h. After the reaction, a polydopamine / Fe3O4 nanoparticle composite coating layer is formed on the surface of the basalt short fibers, and carbon nanotubes or graphene nanosheets are adhered to the surface simultaneously.

2. The basalt fiber reinforced thermoplastic composite material with electromagnetic wave shielding function according to claim 1, characterized in that: The thermoplastic resin is any one of general plastics such as polypropylene, polyethylene, ABS resin, and HIPS resin, and engineering plastics including nylon 6, nylon 66, polycarbonate, and PBT resin.

3. The basalt fiber reinforced thermoplastic composite material with electromagnetic wave shielding function according to claim 1, characterized in that: The specific operation of step (2) is as follows: Using sodium dodecylbenzenesulfonate as an anionic surfactant, dissolve it in an acetone solvent to form a solution with a mass percentage concentration of 5 wt.%. Disperse 100 g of Fe3O4 nanoparticles in 200 g of the acetone solution containing sodium dodecylbenzenesulfonate, and mechanically stir at room temperature for 3 hours. Then, filter and dry in a vacuum oven at 80°C for 12 hours.

4. The basalt fiber reinforced thermoplastic composite material with electromagnetic wave shielding function according to claim 1, characterized in that: The carbon nanotubes are multi-walled carbon nanotubes, and the graphene nanosheets are ultra-thin graphene with 10 - 30 layers. The addition amount in the reaction solution is 1.0 - 2.0 parts by mass relative to every 100 parts by mass of basalt short fibers; the addition amount of the surface-lipophilized modified Fe3O4 nanoparticles in the reaction solution is 2.0 - 3.0 parts by mass relative to every 100 parts by mass of basalt short fibers; the addition amount of dopamine in the reaction solution is 10.0 - 15.0 parts by mass relative to every 100 parts by mass of basalt short fibers.

5. The basalt fiber reinforced thermoplastic composite material with electromagnetic wave shielding function according to claim 1, characterized in that: The buffer solution is prepared from a tris(hydroxymethyl)aminomethane solution with a concentration of 1.2 mg / mL and a hydrochloric acid solution with a concentration of 1 mol / L, and is weakly alkaline with a pH value of 8.

5.

6. A preparation method of the basalt fiber reinforced thermoplastic composite material with electromagnetic wave shielding function according to any one of claims 1-5, characterized in that: It includes the following steps: Weigh various raw materials according to the mass percentage of the composite material, and perform melt blending and granulation using a twin-screw extrusion granulation unit; The feeding method is as follows: The thermoplastic resin and the antioxidant are fed into the main feeding port of the twin-screw extrusion granulation unit through a loss-in-weight metering scale, and the basalt short fibers adhered with carbon nanotubes or graphene nanosheets and containing a polydopamine / Fe3O4 nanoparticle composite coating layer are fed into the side feeding port. The temperature of the twin-screw extruder is set according to the thermoplastic resin used from the main feeding port to the head, and the screw speed is 300 rpm.

7. The preparation method according to claim 6, characterized in that: The antioxidant is a mixture of antioxidant 1010 and antioxidant 168, and their mass ratio is 1:1.

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