Polyamide material with electromagnetic shielding function

Abstract

The invention discloses a polyamide material with an electromagnetic shielding function, and relates to the technical field of polymer composite materials. The invention discloses a polyamide material with an electromagnetic shielding function. The conductive composite material is prepared from the following raw materials in parts by weight: 40 to 60 parts of modified polyamide resin, 20 to 35 parts of modified conductive filler, 5 to 10 parts of maleic anhydride grafted polyamide, 0.5 to 2 parts of antioxidant, 1 to 3 parts of stearic acid, 3 to 8 parts of ethylene-vinyl acetate, 5 to 10 parts of triphenyl phosphate, 10 to 20 parts of aluminum nitride, 0.5 to 1 part of dodecyl dimethyl benzyl ammonium chloride and 1 to 3 parts of silane coupling agent KH-550 hydrolysate. And 30-60 parts of a 20% silane coupling agent KH-560 ethanol solution. The polyamide material has efficient electromagnetic shielding performance and excellent mechanical strength, high shielding effectiveness under low filler content is achieved through modification design, the melt index adapts to a low-pressure injection molding process, the damp-heat aging performance is stable, the problems of contradiction between shielding and processability, mechanical deterioration and the like of a traditional material are solved, and the polyamide material is suitable for electronic module packaging.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer composite materials, in particular to a polyamide material with electromagnetic shielding function. BACKGROUND

[0002] At present, electronic control modules are developing towards miniaturization and high integration, and the internal components are facing increasingly serious high-frequency signal interference problems. Traditional metal shielding covers are gradually replaced by high polymer shielding materials due to their heavy weight, complex processing and short circuit risk. However, the existing high polymer shielding materials have many technical bottlenecks: first, in order to achieve a shielding effectiveness of SE≥30dB, more than 30wt% of high-conductivity fillers (such as carbon fibers) need to be filled, which makes the material melt index <15g / 10min, making it difficult to meet the requirements of low-pressure injection molding process (pressure <5MPa), and the processing adaptability is poor; second, high filler content can cause stress concentration, making the impact strength of the material <6kJ / m 2 , which is prone to cracking in a vibrating environment, and the mechanical properties are greatly deteriorated; third, the shielding performance of the material decays by more than 25% after hygrothermal aging (85℃ / 85%RH), and the long-term stability is insufficient. In addition, in the field of high-frequency such as 5G communication and millimeter wave radar, the traditional polyamide material has a high dielectric constant (>3.5) due to its polar molecular structure, and the dielectric performance decays significantly under high temperature and humidity, and adding fillers can cause brittleness and other new problems. Under this background, there is an urgent need for a polyamide-based electromagnetic shielding material with high shielding efficiency, excellent mechanical properties, good processability and environmental resistance. SUMMARY

[0003] In view of the deficiencies of the prior art, the present application provides a polyamide material with electromagnetic shielding function, which solves the problem of contradiction between shielding and processability of traditional materials and mechanical deterioration.

[0004] To achieve the above purpose, the present application is implemented by the following technical scheme: A polyamide material with electromagnetic shielding function comprises the following raw materials by weight: 40-60 parts of modified polyamide resin, 20-35 parts of modified conductive filler, 5-10 parts of maleic anhydride grafted polyamide, 0.5-2 parts of antioxidant, 1-3 parts of stearic acid, 3-8 parts of ethylene-vinyl acetate, 5-10 parts of triphenyl phosphate, 10-20 parts of aluminum nitride, 0.5-1 part of dodecyl dimethyl benzyl ammonium chloride, 1-3 parts of silane coupling agent KH-550 hydrolysate, and 30-60 parts of 20% silane coupling agent KH-560 ethanol solution.

[0005] Further, the grafting rate of the maleic anhydride grafted polyamide is 1.5-2.0%; the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0006] Further, the preparation method of the silane coupling agent KH-550 hydrolysate is as follows: the silane coupling agent KH-550 is mixed with an ethanol-water solution with a volume ratio of 19:1, 0.1M acetic acid is used to adjust the pH to 4.5, and hydrolysis is carried out at 25°C and 300rpm for 30min; wherein the dosage ratio of the silane coupling agent KH-550 and the ethanol-water solution is 1.5g:15mL.

[0007] Further, the modified polyamide resin is prepared according to the following specific preparation steps: A1, PA66 pellets with a particle size of 3mm are placed in a drying box and dried at 100°C and-0.095MPa for 8h; perfluorophenoxy acrylate is poured into a round-bottom flask, and the oil bath temperature is 80°C, the vacuum degree is 5mmHg, and the fraction is collected by reduced pressure distillation to obtain purified fluorine-containing monomer; the fluorine-containing monomer is dissolved in acetone and injected into the melt zone of the twin-screw extruder at a flow rate of 2mL / min, and the pump pressure is controlled at 0.4MPa; the silane coupling agent KH-550 hydrolysate is injected into the devolatilization zone through the lateral port, the injection speed is 1.5mL / min, and the vacuum devolatilization section is maintained at a vacuum degree of-0.08MPa to remove ethanol; A2, the first modified PA66 is crushed to a particle size of 1mm and dissolved in hexafluoroisopropanol, and placed in a three-necked flask and heated to 70°C in an oil bath with stirring at 400rpm until the solution is completely transparent; deionized water, sodium dodecylbenzenesulfonate, and maleic anhydride grafted styrene-ethylene-butylene-styrene block copolymer are sequentially added to another three-necked flask, oxygen is removed by bubbling nitrogen for 30min at a gas flow rate of 500mL / min, the system is heated to 70°C with stirring at 800rpm, and the PA66 / hexafluoroisopropanol solution is added at a rate of 5mL / min; after the addition is completed, potassium persulfate is added and reacted for 2h; after the reaction is completed, methanol is slowly added to the system, and stirred at 300rpm until white flocculent precipitate appears; the mixture is transferred to a centrifuge tube and centrifuged at 10000rpm for 10min in a refrigerated centrifuge at 4°C; the precipitate is washed with methanol for 3 times, and the washed product is placed in a vacuum drying oven and dried at 60°C and a vacuum degree of-0.09MPa until the weight is constant; A3, the second modified product, TGDDM epoxy resin, and benzyltriethylammonium chloride are added to a high-speed mixer, set to 40°C and a rotation speed of 800rpm, mixed for 5min, and then added to a twin-screw extruder for dynamic crosslinking at a shear rate of 500s-1 and-0.09MPa; immediately after reaching the end point of dynamic crosslinking, water cooling and granulation are carried out.

[0008] Further, the PA66 particle end amino content in A1 is 80±5 mmol / kg; the L / D of the twin-screw extruder is ≥40:1, equipped with side liquid injection and vacuum devolatilization, the feeding zone of the twin-screw extruder is 220℃, the melting zone is 255℃, the reaction zone is 250℃, the devolatilization section is 245℃, and the head section is 240℃; the PA66 particle, fluorine-containing monomer, acetone, and silane coupling agent KH-550 hydrolysate are used in a ratio of 100g:6g:30mL:15mL; the siloxane layer thickness of the A1 product is 1.2±0.2nm.

[0009] Further, the first modified PA66 and hexafluoroisopropanol in A2 are used in a ratio of 25g:100mL, deionized water, sodium dodecylbenzenesulfonate, maleic anhydride grafted styrene-ethylene-butylene-styrene block copolymer, PA66 / hexafluoroisopropanol solution, and potassium persulfate are used in a ratio of 200mL:4g:20g:100mL:0.5g; the maleic anhydride grafting rate of the maleic anhydride grafted styrene-ethylene-butylene-styrene block copolymer is 1.2%; the shell layer thickness of the A2 product detected by TEM is 20±5nm; and the core-shell particle size D50 is 80±5nm.

[0010] Further, the second modified product, TGDDM epoxy resin, and benzyltriethylammonium chloride in A3 are used in a ratio of 100g:1.8g:0.1g; the epoxy equivalent weight of the TGDDM epoxy resin is 190-210g / eq; the end point of dynamic crosslinking is determined when the melt viscosity reaches 1.5 times the initial value, the online NIR detection of epoxy group conversion rate is ≥90%, and the melt pressure fluctuation is ≤±5%.

[0011] Further, the modified conductive filler is prepared according to the following specific steps: B1, cut the carbon fibers with a diameter of 7μm into 5cm long segments, put them into a round-bottom flask, add concentrated nitric acid to immerse the fibers and heat to 120℃, reflux and oxidize for 2h, stir every 30min during the reaction, after the reaction, wash to neutral, filter and dry at 120℃ for 4h; put the fibers in a quartz tube reactor, vacuum to 20mbar, introduce Ar / H2 and heat to 900℃, then introduce CH4, react for 20min, stop introducing CH4 after the reaction, continue to introduce Ar / H2 and cool to room temperature; B2, the modified fiber is ultrasonically dispersed in a 0.4M Zn(NO3)2 solution, the pH of the solution is adjusted to 9 with 25% concentrated ammonia water, and then the solution is transferred to an autoclave for reaction at 120℃ for 3h. After the reaction, the fiber is naturally cooled to room temperature, taken out, and washed with deionized water for 3 times. The product ZnO nanorod is vacuum dried at 60℃ for 12h. The fiber is immersed in a 0.05M AgNO3 solution, 0.1M glucose is added as a reducing agent, and the mixture is reacted at 60℃ in a water bath at 200rpm for 20min. After the reaction, the fiber is washed with deionized water for 5 times and then with ethanol for 2 times; B3, the filler is placed in the reaction cavity of an atomic layer deposition device, heated to 200℃, pulsed with trimethylaluminum precursor for 0.1s, purged with N2 for 30s, pulsed with water for 0.1s, purged with N2 for 30s, and the cycle is repeated for 10 times. The sample holder is rotated by 180° at the 6th time to avoid the shadow effect. After completion, the modified conductive filler is obtained by immersing in a silane coupling agent KH-550 ethanol solution and refluxing at 70℃ for 4h.

[0012] Further, in the B1, the Ar flow rate is 500sccm, the H2 flow rate is 50sccm, and the CH4 flow rate is 100sccm. In the B2, the amount ratio of the modified fiber, glucose, Zn(NO3)2·6H2O, and AgNO3 is 10g:0.9g:120g:17g, and the length-diameter ratio of the ZnO nanorod is 22-28:1. In the B3, the N2 flow rate is 200sccm, the silane coupling agent KH-550 ethanol solution contains 5g of silane coupling agent KH-550 and 95mL of ethanol, and the surface amino group density of the modified conductive filler is 0.8-1.2mmol / g.

[0013] A preparation method of a polyamide material with electromagnetic shielding function, specifically comprising the following steps: S1, aluminum nitride is placed in a 20% silane coupling agent KH-560 ethanol solution, ultrasonically treated at 60℃ for 1h, filtered after treatment, and vacuum dried at 120℃ for 8h. Dodecyl dimethyl benzyl ammonium chloride and stearic acid are melted at 80℃, and blended at 200rpm for 10min; S2, the dried modified polyamide resin is put into a double-shaft mixer and pre-mixed at 600rpm for 2min. The modified conductive filler and maleic anhydride grafted polyamide are pre-mixed in a high-speed mixer at 1000rpm for 5min, the silane coupling agent KH-550 hydrolysate is added, 20L / min of nitrogen gas is introduced for protection, and the mixture is put into a double-shaft mixer and mixed at 800rpm for 5min; S3, the antioxidant and stearic acid are premixed at 400 rpm for 3 min, the premix is added to the mixer, mixed at 1000 rpm for 3 min while controlling the temperature at 50-60 DEG C, then ethylene-vinyl acetate and triphenyl phosphate are co-melted at 110 DEG C for 10 min at 150 rpm, cooled through three-stage cooling jacket pipes of 110 DEG C, 85 DEG C and 55 DEG C, injected into the mixer at 20 mL / min, mixed at 1200 rpm for 4 min, the pretreated aluminum nitride and dodecyl dimethyl benzyl ammonium chloride-stearic acid complex are mixed, melted and stirred at 80 DEG C for 5 min, the coated filler is put into the mixer, mixed at 400 rpm for 3 min, the cooling system is started before the end, the water temperature is set at 15 DEG C, and the mixing temperature is controlled at 40 DEG C; S4, the double screw extruder is controlled by temperature in stages, the mixture is added to the extruder through a quantitative feeder, the extrudate is cooled and shaped through 20-25 DEG C circulating water, cut into 3*2 mm pellets through a pelletizer, the pelletizing speed is synchronized with the extrusion rate, the pellets are dried at 100 DEG C under a vacuum condition of -0.095 MPa for 6 h, the water content is reduced to below 0.05%, and the dried pellets are sealed and packaged with aluminum foil bags to prevent moisture absorption from affecting the dielectric properties.

[0014] Further, the pretreated aluminum nitride in S3 is mixed with the dodecyl dimethyl benzyl ammonium chloride-stearic acid complex at a ratio of 10:1.

[0015] The application provides a polyamide material with electromagnetic shielding function, and has the following beneficial effects: 1. By surface modification design of the conductive filler and interface functionalization treatment of the polyamide resin, the use amount of the conductive filler is significantly reduced under the premise of forming a continuous conductive network of the filler and the resin matrix. This design enables the material to achieve excellent electromagnetic shielding effect when the amount of filler is appropriate, avoids the problem of rapid increase of melt viscosity caused by traditional high filler content, and fundamentally solves the contradiction between shielding efficiency and material processing fluidity.

[0016] 2. The polyamide resin is modified by grafting a fluorine-containing monomer, and the molecular chain flexibility and interface bonding strength of the material are effectively improved through the synergistic effect of the core-shell structure design and the dynamic crosslinking process. The modified polyamide material not only has excellent impact resistance and can resist external vibration and stress, but also maintains appropriate melt flowability, which can perfectly adapt to the processing requirements of low-pressure injection molding process, and solves the technical bottleneck of material brittleness and poor processability under high filler system.

[0017] 3、Through the surface coating treatment of the aluminum nitride filler with silane coupling agent and the matching of the high-efficiency antioxidant system, a multiple protection mechanism is constructed. This treatment effectively inhibits the interfacial corrosion and oxidative degradation of the material in the humid heat environment, so that the material can still maintain stable shielding performance and mechanical properties in harsh environmental conditions, greatly prolonging the service life of the electronic module after packaging and meeting the long-term reliability requirements under complex working conditions.

[0018] 4、By reducing the molecular polarity through fluorine modification of the polyamide resin and introducing a filler with low dielectric constant for synergistic modification, the material realizes efficient electromagnetic shielding while significantly optimizing the dielectric properties of the material. This design enables the material to maintain low signal loss and stable transmission performance in high-frequency signal transmission scenarios, solving the problem of high dielectric constant of traditional shielding materials that cannot adapt to 5G communication and other high-frequency fields, and realizing diversified application expansion of functions. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0020] Embodiment 1, a polyamide material with electromagnetic shielding function is prepared, and the specific preparation steps are as follows: S1, 10 parts of aluminum nitride are placed in 30 parts of 20% silane coupling agent KH-560 ethanol solution, ultrasonic treatment at 60℃ for 1h, after treatment, filter, vacuum drying at 120℃ for 8h; take 0.5 parts of dodecyl dimethyl benzyl ammonium chloride and 0.5 parts of stearic acid, melt at 80℃, blend at 200rpm for 10min; S2, 40 parts of dried modified polyamide resin are put into a double shaft mixer, pre-mixed at 600rpm for 2min; 20 parts of modified conductive filler and 5 parts of maleic anhydride grafted polyamide are pre-mixed in a high-speed stirrer at 1000rpm for 5min, 1 part of silane coupling agent KH-550 hydrolyzate is added, and 20L / min of nitrogen gas is introduced at the same time, the mixture is put into a double shaft mixer, mixed at 800rpm for 5min; S3, 0.5 parts of antioxidant and 0.5 parts of stearic acid were premixed at 400 rpm for 3 min, the premix was added to the mixer, mixed at 1000 rpm for 3 min while controlling the temperature at 50-60°C, then 3 parts of ethylene-vinyl acetate and 5 parts of triphenyl phosphate were co-melted at 110°C for 10 min at 150 rpm, cooled through three-stage cooling jackets at 110°C→85°C→55°C, injected into the mixer at 20 mL / min, mixed at 1200 rpm for 4 min, 10 parts of pretreated aluminum nitride and 1 part of dodecyl dimethyl benzyl ammonium chloride-stearic acid complex were mixed, melted and stirred at 80°C for 5 min, the coated filler was put into the mixer, mixed at 400 rpm for 3 min, the cooling system was started before the end, the water temperature was set at 15°C, and the mixing temperature was controlled at 40°C; S4, the twin-screw extruder was controlled by temperature in stages, the mixture was fed into the extruder through a quantitative feeder, the extrudate was cooled and shaped through 20°C circulating water, cut into 3x2 mm pellets through a pelletizer at a speed synchronized with the extrusion rate, the pellets were dried at 100°C under a vacuum of -0.095 MPa for 6 h, the water content was reduced to below 0.05%, and the dried pellets were sealed with aluminum foil bags to prevent moisture absorption from affecting the dielectric properties.

[0021] Example 2, a polyamide material with electromagnetic shielding function was prepared, and the specific preparation steps were as follows: S1, 20 parts of aluminum nitride were placed in 60 parts of 20% silane coupling agent KH-560 ethanol solution, ultrasonic treated at 60°C for 1 h, filtered after treatment, and vacuum dried at 120°C for 8 h; 1 part of dodecyl dimethyl benzyl ammonium chloride and 1 part of stearic acid were melted at 80°C, and blended at 200 rpm for 10 min; S2, 60 parts of dried modified polyamide resin were put into a double-shaft mixer, and premixed at 600 rpm for 2 min; 35 parts of modified conductive filler and 10 parts of maleic anhydride grafted polyamide were premixed in a high-speed mixer at 1000 rpm for 5 min, 3 parts of silane coupling agent KH-550 hydrolyzate were added, and 20 L / min of nitrogen was introduced synchronously, the mixture was put into a double-shaft mixer, and mixed at 800 rpm for 5 min; S3, take 2 parts of antioxidant and 2 parts of stearic acid in 400 rpm pre-mixed 3 min, the premix is added to the mixer, mixed at 1000 rpm for 3 min, while the temperature is controlled at 50-60℃, then 8 parts of ethylene-vinyl acetate and 10 parts of triphenyl phosphate are co-melted at 110℃ for 10 min at 150 rpm, cooled by 110℃→85℃→55℃ three-stage cooling jacket, injected into the mixer at 20 mL / min, mixed at 1200 rpm for 4 min, 20 parts of pretreated aluminum nitride and 2 parts of dodecyl dimethyl benzyl ammonium chloride-stearic acid complex are mixed, melted and stirred at 80℃ for 5 min, the coated filler is put into the mixer, mixed at 400 rpm for 3 min, the cooling system is started before the end, the water temperature is set to 15℃, and the mixing temperature is controlled at 50℃; S4, the double screw extruder is controlled by temperature, the mixture is fed into the extruder by a quantitative feeder, the extrudate is cooled and shaped by circulating water at 25℃, cut into 3x2mm pellets by a pelletizer, the cutting speed is synchronized with the extrusion rate, the pellets are dried at 100℃ under a vacuum of-0.095MPa for 6h, the water content is reduced to below 0.05%, and the dried pellets are sealed with aluminum foil bags to prevent moisture absorption from affecting the dielectric properties.

[0022] Example 3, preparation of polyamide material with electromagnetic shielding function, the specific preparation steps are as follows: S1, 15 parts of aluminum nitride are placed in 45 parts of 20% silane coupling agent KH-560 ethanol solution, ultrasonic treated at 60℃ for 1h, filtered after treatment, and dried at 120℃ under vacuum for 8h; take 0.75 parts of dodecyl dimethyl benzyl ammonium chloride and 0.75 parts of stearic acid, melt at 80℃, and blend at 200 rpm for 10 min; S2, 50 parts of dried modified polyamide resin is put into a double shaft mixer, pre-mixed at 600 rpm for 2 min; 25 parts of modified conductive filler and 7 parts of maleic anhydride grafted polyamide are pre-mixed in a high-speed mixer at 1000 rpm for 5 min, 2 parts of silane coupling agent KH-550 hydrolyzate is added, and 20L / min of nitrogen gas is introduced synchronously, the mixture is put into a double shaft mixer, mixed at 800 rpm for 5 min; S3, take 1 part antioxidant and 1 part stearic acid in 400 rpm pre-mixing 3 min, the premix is added to the mixer, mixed at 1000 rpm for 3 min, while the temperature is controlled at 50-60℃, then 5 parts of ethylene-vinyl acetate and 7 parts of triphenyl phosphate are co-melted at 110℃ for 10 min at 150 rpm, cooled by 110℃→85℃→55℃ three-stage cooling jacket, injected into the mixer at 20 mL / min, mixed at 1200 rpm for 4 min, mixed 15 parts of pretreated aluminum nitride with 1.5 parts of dodecyl dimethyl benzyl ammonium chloride-stearic acid complex, melt and stir at 80℃ for 5 min, put the coated filler into the mixer, mix at 400 rpm for 3 min, turn on the cooling system before the end, set the water temperature to 15℃, control the mixing temperature at 47℃; S4, the twin-screw extruder is controlled by temperature, the mixture is fed into the extruder by a quantitative feeder, the extrudate is cooled and shaped by 22℃ circulating water, cut into 3×2mm pellets by a pelletizer, the cutting speed is synchronized with the extrusion rate, the pellets are dried at 100℃ under-0.095MPa vacuum for 6h, the water content is reduced to below 0.05%, then sealed with aluminum foil bag after drying to prevent moisture absorption affecting the dielectric properties.

[0023] Example 4, preparation of modified polyamide resin, the specific preparation steps are as follows: A1, put 100g of PA66 pellets with a particle size of 3mm into a drying box, dry at 100℃ under-0.095MPa for 8h; pour the perfluorophenoxy acrylate into a round-bottom flask, collect the distillate by vacuum distillation at 80℃ oil bath temperature and 5mmHg vacuum degree, get the purified fluorine-containing monomer; dissolve 6g of fluorine-containing monomer in 30mL of acetone, set the feeding zone of the twin-screw extruder to 220℃, the melting zone to 255℃, the reaction zone to 250℃, the devolatilization section to 245℃, and the die section to 240℃, inject into the melting zone of the twin-screw extruder at a flow rate of 2mL / min, and control the pump pressure at 0.4MPa; inject 15mL of silane coupling agent KH-550 hydrolysate through the lateral port into the devolatilization zone at a speed of 1.5mL / min, maintain the vacuum degree at-0.08MPa in the vacuum devolatilization section to remove ethanol; A2, 25 g of the first modified PA66 was crushed to a particle size of 1 mm and dissolved in 100 mL of hexafluoroisopropanol, and placed in an oil bath of a three-necked flask heated to 70°C, stirred at 400 rpm until the solution was completely transparent; 200 mL of deionized water, 4 g of sodium dodecyl benzene sulfonate, and 20 g of maleic anhydride grafted styrene-ethylene-butylene-styrene block copolymer were sequentially added to another three-necked flask, oxygen was removed by bubbling nitrogen for 30 min, the gas flow was 500 mL / min, the system was heated to 70°C and stirred at 800 rpm, 100 mL of PA66 / hexafluoroisopropanol solution was added at a speed of 5 mL / min, after the addition was completed, 0.5 g of potassium persulfate was added and reacted for 2 h; after the reaction was completed, methanol was slowly added to the system, stirred at 300 rpm until white flocculent precipitate appeared, the mixture was transferred to a centrifuge tube, centrifuged at 10000 rpm for 10 min in a refrigerated centrifuge at 4°C, the precipitate was washed with methanol for 3 times, and the washed product was placed in a vacuum drying oven, dried at 60°C and a vacuum degree of -0.09 MPa until the weight was constant; A3, 100 g of the second modified product was added to a high-speed mixer with 1.8 g of TGDDM epoxy resin and 0.1 g of benzyl triethyl ammonium chloride, set to 40°C and 800 rpm, mixed for 5 min, then put into a twin-screw extruder, dynamically cross-linked at a shear rate of 500 s -1 , -0.09 MPa, and immediately water-cooled and pelletized after reaching the end point of dynamic cross-linking.

[0024] Example 5, preparation of modified conductive filler, the specific preparation steps are as follows: B1, carbon fibers with a diameter of 7 μm were cut into 5 cm long segments and placed in a round-bottom flask, concentrated nitric acid was added to immerse the fibers and heated to 120°C, refluxed and oxidized for 2 h, stirring was performed every 30 min during the reaction, after the reaction was completed, water was washed until neutral, and then filtered and dried at 120°C for 4 h; the fibers were placed in a quartz tube reactor, vacuumed to 20 mbar, 500 sccm of Ar and 50 sccm of H2 were introduced and heated to 900°C, then 100 sccm of CH4 was introduced, reacted for 20 min, after the reaction was completed, the introduction of CH4 was stopped and the introduction of Ar / H2 was continued to cool to room temperature; B2, 10 g of modified fibers were ultrasonically dispersed in 120 g of 0.4 M Zn(NO3)2 solution, the pH of the solution was adjusted to 9 with 25% concentrated ammonia water, then transferred to an autoclave and reacted at 120°C for 3 h, after the reaction was completed, naturally cooled to room temperature, the fibers were taken out and washed with deionized water for 3 times, the product ZnO nanorods were vacuum dried at 60°C for 12 h; the above fibers were immersed in 17 g of 0.05 M AgNO3 solution, 0.9 g of 0.1 M glucose was added as a reducing agent, reacted at 60°C water bath for 20 min at 200 rpm, after the reaction was completed, the fibers were washed with deionized water for 5 times and then with ethanol for 2 times; B3, the filler was placed in the reaction cavity of the atomic layer deposition equipment, and was heated to 200°C, pulse trimethylaluminum precursor 0.1s, 200sccm N2purging 30s, pulse water 0.1s, 200sccm N2purging 30s, cycle 10 times, the 6th time rotating the sample holder 180° to avoid shadow effect, after completion, immerse in 100mL silane coupling agent KH-550 ethanol solution, 70°C reflux 4h, to obtain modified conductive filler.

[0025] Comparative Example 1, preparation of polyamide material with electromagnetic shielding function, the specific preparation steps are as follows: The remaining steps are unchanged, only the modified polyamide resin of Example 3 is replaced with polyamide resin without any treatment, to prepare polyamide material with electromagnetic shielding function.

[0026] Comparative Example 2, preparation of polyamide material with electromagnetic shielding function, the specific preparation steps are as follows: The remaining steps are unchanged, only the modified conductive filler of Example 3 is replaced with carbon fiber without any treatment, to prepare polyamide material with electromagnetic shielding function.

[0027] Performance test

[0028] At a frequency of 1GHz, the electromagnetic shielding effectiveness of Examples 1-3 is 32-35dB, the impact strength is 16-18kJ / m 2 , the melt flow rate is between 25-30g / 10min, the shielding attenuation after 1000h of damp heat aging at 85°C / 85%RH is 7%-9%, the dielectric constant at 1GHz is 2.7-2.9, and the dielectric loss is 0.007-0.009; while the electromagnetic shielding effectiveness of the unmodified polyamide resin of Comparative Example 1 and the unmodified carbon fiber of Comparative Example 2 is 26-28dB, the impact strength is 7-8kJ / m 2 , the melt flow rate is 16-18g / 10min, the shielding attenuation after damp heat aging is 20%-22%, the dielectric constant is 3.2-3.3, and the dielectric loss is 0.015-0.016. This shows that the modified polyamide material is superior to the unmodified material in electromagnetic shielding, mechanical properties, processing flowability, damp heat aging resistance and dielectric properties.

[0029] The above is only an example and description of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, as long as they do not deviate from the invention or exceed the scope defined by the present claims, which shall belong to the protection scope of the present application.

Claims

1. A polyamide material with electromagnetic shielding function, characterized in that: It contains the following raw materials in parts by weight: 40-60 parts modified polyamide resin, 20-35 parts modified conductive filler, 5-10 parts maleic anhydride grafted polyamide, 0.5-2 parts antioxidant, 1-3 parts stearic acid, 3-8 parts ethylene-vinyl acetate, 5-10 parts triphenyl phosphate, 10-20 parts aluminum nitride, 0.5-1 part dodecyl dimethyl benzyl ammonium chloride, 1-3 parts silane coupling agent KH-550 hydrolysate, and 30-60 parts 20% silane coupling agent KH-560 ethanol solution.

2. The polyamide material with electromagnetic shielding function according to claim 1, characterized in that: The grafting rate of the maleic anhydride-grafted polyamide is 1.5-2.0%; the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:

1.

3. The polyamide material with electromagnetic shielding function according to claim 1, characterized in that: The preparation method of the hydrolysate of the silane coupling agent KH-550 is as follows: silane coupling agent KH-550 is mixed with an ethanol-water solution at a volume ratio of 19:1, the pH is adjusted to 4.5 with 0.1M acetic acid, and the mixture is hydrolyzed at 25°C and 300 rpm for 30 min; wherein the volume ratio of silane coupling agent KH-550 to ethanol-water solution is 1.5 g: 15 mL.

4. The polyamide material with electromagnetic shielding function according to claim 1, characterized in that: The modified polyamide resin is prepared using the following specific steps: A1. PA66 granules with a particle size of 3 mm were placed in a drying oven and dried at 100℃ and -0.095 MPa for 8 hours. Perfluorophenoxy acrylate was poured into a round-bottom flask and collected by vacuum distillation at 80℃ and 5 mmHg in an oil bath to obtain purified fluorinated monomer. The fluorinated monomer was dissolved in acetone and injected into the melting zone of a twin-screw extruder at a flow rate of 2 mL / min, with the pump pressure controlled at 0.4 MPa. The hydrolysate of silane coupling agent KH-550 was injected into the devolatilization zone through a side port at a rate of 1.5 mL / min. The vacuum devolatilization section maintained a vacuum of -0.08 MPa to remove ethanol. A2. The first-modified PA66 was pulverized to a particle size of 1 mm, dissolved in hexafluoroisopropanol, and heated to 70°C in an oil bath in a three-necked flask. The mixture was stirred at 400 rpm until the solution was completely transparent. Deionized water, sodium dodecylbenzenesulfonate, and maleic anhydride-grafted styrene-ethylene-butene-styrene block copolymer were added sequentially to another three-necked flask. Nitrogen gas was bubbled through the flask for 30 min to remove oxygen at a flow rate of 500 mL / min. The system was heated to 70°C and stirred at 800 rpm. The PA66 / hexafluoroisopropanol solution was added dropwise at a rate of 5 mL / min. After the addition was complete, potassium persulfate was added and the reaction was carried out for 2 h. After the reaction was completed, methanol was slowly added to the system and stirred at 300 rpm until a white flocculent precipitate appeared. The mixture was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 10 min at 4°C in a refrigerated centrifuge. The precipitate was washed three times with methanol. The washed product was placed in a vacuum drying oven and dried at 60°C and a vacuum of -0.09 MPa to constant weight. A3. Add the second modified product, TGDDM epoxy resin, and benzyltriethylammonium chloride to a high-speed mixer, set to 40°C and 800 rpm, mix for 5 minutes, then feed into a twin-screw extruder with a shear rate of 500 s. -1 Dynamic cross-linking at -0.09MPa, followed by immediate water cooling and pelletizing upon reaching the endpoint of dynamic cross-linking.

5. A polyamide material with electromagnetic shielding function according to claim 4, characterized in that: The A1 product contains 80±5 mmol / kg of PA66 granules with terminal amino groups; the twin-screw extruder has an L / D ratio of ≥40:1, is equipped with side liquid injection and vacuum devolatilization, and has a feeding zone temperature of 220°C, a melting zone temperature of 255°C, a reaction zone temperature of 250°C, a devolatilization zone temperature of 245°C, and a die head temperature of 240°C; the ratio of PA66 granules, fluorinated monomer, acetone, and silane coupling agent KH-550 hydrolysate is 100g:6g:30mL:15mL; the A1 product has a siloxane layer thickness of 1.2±0.2nm; In A2, the ratio of the first modified PA66 to hexafluoroisopropanol is 25g:100mL, and the ratio of deionized water, sodium dodecylbenzenesulfonate, maleic anhydride-grafted styrene-ethylene-butene-styrene block copolymer, PA66 / hexafluoroisopropanol solution, and potassium persulfate is 200mL:4g:20g:100mL:0.5g. The maleic anhydride grafting rate of the maleic anhydride-grafted styrene-ethylene-butene-styrene block copolymer is 1.2%. The shell thickness of the A2 product, as detected by TEM, is 20±5nm, and the core-shell particle size D50 is 80±5nm. The ratio of the second modified product, TGDDM epoxy resin, and benzyltriethylammonium chloride in A3 is 100g:1.8g:0.1g; the epoxy equivalent of TGDDM epoxy resin is 190-210g / eq; the endpoint of dynamic crosslinking is determined as follows: when the melt viscosity reaches 1.5 times the initial value and the online NIR detection of epoxy group conversion rate is ≥90%, and the melt pressure fluctuation is ≤±5%, it is considered as the endpoint of dynamic crosslinking.

6. A polyamide material with electromagnetic shielding function according to claim 1, characterized in that: The modified conductive filler is prepared using the following specific steps: B1. Cut 7μm diameter carbon fibers into 5cm long segments, place them in a round-bottom flask, add concentrated nitric acid to immerse the fibers and heat to 120℃, reflux for oxidization for 2h, stirring once every 30min during the process. After the reaction is complete, wash with water until neutral, filter and dry at 120℃ for 4h; place the fibers in a quartz tube reactor, evacuate to 20mbar, introduce Ar / H2 and heat to 900℃, then introduce CH4, react for 20min, stop introducing CH4 after the reaction is complete, continue to introduce Ar / H2 and cool to room temperature; B2. The modified fibers were ultrasonically dispersed in a 0.4M Zn(NO3)2 solution. The pH of the solution was adjusted to 9 with 25% concentrated ammonia. The solution was then transferred to an autoclave and reacted at 120℃ for 3 hours. After the reaction, the solution was allowed to cool naturally to room temperature. The fibers were then removed and washed three times with deionized water. The ZnO nanorods were vacuum dried at 60℃ for 12 hours. The fibers were then immersed in a 0.05M AgNO3 solution with 0.1M glucose added as a reducing agent. The solution was reacted in a 60℃ water bath at 200 rpm for 20 minutes. After the reaction, the fibers were washed five times with deionized water and then twice with ethanol. B3. Place the packing material in the reaction chamber of the atomic layer deposition equipment, heat to 200℃, pulse trimethylaluminum precursor for 0.1s, purge with N2 for 30s, pulse water for 0.1s, purge with N2 for 30s, cycle 10 times, rotate the sample holder 180° on the 6th time to avoid shadowing effect, after completion, immerse in silane coupling agent KH-550 ethanol solution, reflux at 70℃ for 4h to obtain modified conductive packing material.

7. A polyamide material with electromagnetic shielding function according to claim 6, characterized in that: In B1, the flow rate of Ar is 500 sccm, the flow rate of H2 is 50 sccm, and the flow rate of CH4 is 100 sccm; in B2, the ratio of modified fiber, glucose, Zn(NO3)2·6H2O, and AgNO3 is 10g:0.9g:120g:17g, and the aspect ratio of ZnO nanorods is 22-28:1; in B3, the flow rate of N2 is 200 sccm, the silane coupling agent KH-550 ethanol solution contains 5g of silane coupling agent KH-550 and 95mL of ethanol, and the amino density on the surface of the modified conductive filler is 0.8-1.2mmol / g.

8. A method for preparing a polyamide material with electromagnetic shielding function, characterized in that: Specifically, it includes the following steps: S1. Place aluminum nitride in an ethanol solution of 20% silane coupling agent KH-560, sonicate at 60℃ for 1h, filter after treatment, and vacuum dry at 120℃ for 8h; take dodecyl dimethyl benzyl ammonium chloride and stearic acid, melt at 80℃, and mix at 200rpm for 10min. S2. Add the dried modified polyamide resin to a biaxial mixer and premix at 600 rpm for 2 min. Premix the modified conductive filler and maleic anhydride grafted polyamide in a high-speed mixer at 1000 rpm for 5 min. Add the silane coupling agent KH-550 hydrolysate and simultaneously purge with 20 L / min nitrogen for protection. Add the mixture to the biaxial mixer and mix at 800 rpm for 5 min. S3. Take antioxidant and stearic acid and premix at 400 rpm for 3 min. Add the premix to the mixer and mix at 1000 rpm for 3 min, while controlling the temperature at 50-60℃. Then, co-melt ethylene-vinyl acetate and triphenyl phosphate at 110℃ and 150 rpm for 10 min. Cool through a three-stage cooling sleeve of 110℃→85℃→55℃. Inject into the mixer at 20 mL / min and mix at 1200 rpm for 4 min. Mix the pretreated aluminum nitride and dodecyl dimethyl benzyl ammonium chloride-stearic acid complex and melt and stir at 80℃ for 5 min. Add the coated filler to the mixer and mix at 400 rpm for 3 min. Before the end, turn on the cooling system and set the water temperature to 15℃ to control the mixing temperature at 40℃. S4. The twin-screw extruder features segmented temperature control. The mixed material is fed into the extruder via a metering feeder. The extrudate is cooled and shaped by circulating water at 20-25℃. It is then cut into 3×2mm pellets by a pelletizer. The pelletizing speed is synchronized with the extrusion rate. The pellets are dried at 100℃ and under a vacuum of -0.095MPa for 6 hours until the moisture content drops below 0.05%. After drying, the pellets are sealed in aluminum foil bags to prevent moisture absorption from affecting the dielectric properties.

9. The method for preparing a polyamide material with electromagnetic shielding function according to claim 8, characterized in that: The pretreated aluminum nitride in S3 is mixed with the dodecyl dimethyl benzyl ammonium chloride-stearic acid complex in a ratio of 10:1.

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