Disclosure of Invention
In view of the above, the invention provides an adjustable polymer-based porous electromagnetic shielding material, and a preparation method and application thereof, the preparation method disclosed by the invention is simple to operate, raw materials are easy to obtain, and the shielding material prepared by the method provided by the invention has the characteristics of light weight, high elasticity and adjustable pore diameter, can realize shielding of electromagnetic waves in different frequency bands, and is expected to play an important role in the fields of flexible electronics and stealth materials.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of an adjustable polymer-based porous electromagnetic shielding material specifically comprises the following steps:
(1) adding the expanded graphite into the mixed solvent, uniformly stirring, and then adding FeSO4Solution and FeCl3Uniformly stirring the solution to obtain a mixed solution;
(2) heating the mixed solution for reaction, then dropwise adding alkali liquor to adjust the mixed solution to be alkaline, and washing and drying the mixed solution to obtain EG/Fe3O4A composite material;
(3) to the above EG/Fe3O4The composite material is sequentially added with deionized water, triethanolamine, a foam stabilizer and polyether polyol and uniformly mixed, then stannous octoate is added for uniform dispersion, the mixture is added with toluene diisocyanate and stirred, then poured into a mold for applying pressure, and finally the mold is dried to obtain the polymer-based porous electromagnetic shielding material.
The beneficial effects of the preferred technical scheme are as follows: the preparation method disclosed by the invention firstly prepares Fe3O4The nano particles are loaded on expandable graphite to obtain EG/Fe3O4Composite material, EG/Fe3O4The composite material is filled into the polymer-based porous material to obtain the adjustable polymer-based porous electromagnetic shielding material. By adjusting the raw material proportion and the preparation process, the porous material with the average cell diameter of 50-500 mu m is obtained respectivelyDifferent frequency bands of the electromagnetic wave show good electromagnetic shielding effect; the diameter of the porous polymer cell is regulated to realize the shielding of electromagnetic waves in a specific frequency band.
Preferably, the mixed solvent in the step (1) is prepared from water and absolute ethyl alcohol according to the ratio of 7: 2 in a volume ratio;
FeSO4solution and FeCl3The concentration of the solution is 0.5mol/L respectively;
the expanded graphite, the mixed solvent, and the FeSO4Solution and the FeCl3The mixing mass ratio of the solution is 1: (20-35): 10: 10;
the rotating speed of the stirring is 200-300 r/min; the time is 20-40 min.
The beneficial effects of the preferred technical scheme are as follows: the invention adopts an in-situ polymerization method to polymerize Fe3O4The nano particles are loaded on the expanded graphite, so that the expanded graphite with good conductivity and the magnetic Fe3O4The nano particles are combined to obtain the composite material, so that the electromagnetic shielding performance of the filler is further improved.
Preferably, in the step (2), the temperature is raised to 45-60 ℃, the reaction time is 2-4 h, the alkali liquor is ammonia water, and the pH value is 11 after adjustment;
the washing times are 3-5 times;
the drying temperature is 60-80 ℃.
Preferably, the foam stabilizer in the step (3) is one or any combination of a silicone stabilizer and a silicone polyether copolymer stabilizer;
the EG/Fe3O4The mass ratio of the composite material, the deionized water, the triethanolamine, the foam stabilizer, the polyether polyol, the stannous octoate and the toluene diisocyanate is (5-20): (6-15): 0.5: (2-4): 100: 0.5: (60-80).
The beneficial effects of the preferred technical scheme are as follows: the invention uses EG/Fe3O4The composite filler is filled in the polyurethane porous material, so that the polyurethane porous material is endowed with good electric conductivity and magnetism, and the electromagnetic screen of the porous material is enhancedAnd (4) shielding performance.
Preferably, in the step (3), the drying temperature is 80-90 ℃, and the drying time is 10-20 min.
Preferably, the rotating speed of the stirring in the step (3) is 2000 r/min; the applied pressure is 10-100N;
the beneficial effects of the preferred technical scheme are as follows: according to the invention, isocyanate and water are fully reacted by high-speed stirring to generate carbon dioxide gas to obtain the porous material, and the average pore size of the porous material is regulated and controlled by applying different pressures in the chemical foaming process, so that the porous material plays an important role in absorption and reflection attenuation of electromagnetic waves in different frequency bands.
The invention also provides an adjustable polymer-based porous electromagnetic shielding material, which is prepared by adopting the method.
The beneficial effects of the preferred technical scheme are as follows: the invention passes magnetic Fe3O4In-situ growth of nano particles on the surface of conductive expanded graphite to obtain EG/Fe3O4Compounding the filler and introducing the filler into the polymer to obtain the polymer-based conductive electromagnetic shielding material. Wherein the large surface area and loose void structure of the expanded graphite are utilized as Fe3O4The in-situ growth of the nano particles creates conditions, and the nano particles have stronger interaction, thereby providing a good foundation for the preparation of the conductive polymer; the expanded graphite has good conductivity, and is beneficial to the dielectric loss of electromagnetic waves; fe3O4The nano particles have excellent magnetism and can promote the magnetic loss of electromagnetic waves; the combination of the conductive expanded graphite and the magnetic Fe3O4 nano particles improves the impedance matching characteristic, so that more electromagnetic waves enter the material to be lost, and the electromagnetic shielding performance of the material is improved; fe3O4The particles are supported on the expanded graphite to form an interface contact resistance on the surface thereof, thereby forming a capacitor-like structure to promote absorption loss of electromagnetic waves, and having a positive effect on electromagnetic shielding.
The invention further provides an application of the adjustable polymer-based porous electromagnetic shielding material in flexible electronic or stealth materials.
Compared with the prior art, the invention discloses and provides the adjustable polymer-based porous electromagnetic shielding material and the preparation method and application thereof.
(1) The invention utilizes the large surface area and the loose void structure of the expanded graphite as Fe3O4The in-situ growth of the nano particles creates conditions, and the nano particles have stronger interaction, thereby providing a good foundation for the preparation of the conductive polymer;
(2) in addition, the expanded graphite has good conductivity, which is beneficial to the dielectric loss of electromagnetic waves; fe3O4The nanoparticles have excellent magnetic properties, promote magnetic loss of electromagnetic waves, and are Fe3O4The nano particles have simple preparation process and low cost, and are ideal fillers for preparing electromagnetic shielding materials;
(3) conductive expanded graphite and magnetic Fe3O4The combination of the nano particles improves the impedance matching characteristic, so that more electromagnetic waves enter the material to be lost, and the electromagnetic shielding performance of the material is improved; fe3O4The particles are supported on the expanded graphite to form an interface contact resistance on the surface thereof, thereby forming a capacitor-like structure to promote absorption loss of electromagnetic waves, and having a positive effect on electromagnetic shielding.
(4) The invention realizes the high-efficiency shielding of electromagnetic waves in different frequency bands by regulating and controlling the diameter of the foam polymer foam pores;
(5) the polyurethane foam as a three-dimensional network structure provides an effective place for multiple reflection and absorption of electromagnetic waves;
(6) according to the invention, by regulating and controlling the diameter of the polyurethane foam hole, electromagnetic waves are lost when being transmitted to the shielding material, so that the electromagnetic waves are prevented from directly penetrating through the shielding material, and the electromagnetic shielding effect is achieved. The polyurethane foam with the larger diameter of the foam hole has a good shielding effect on the electromagnetic waves in the low frequency band, the polyurethane foam with the smaller diameter of the foam hole has a good shielding effect on the electromagnetic waves in the high frequency band, and the shielding effectiveness of the electromagnetic wave range of 500 MHz-12 GHz, which is larger than 20dB, is realized by adjusting the diameter of the foam hole of the polyurethane foam.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention discloses a preparation method of an adjustable polymer-based porous electromagnetic shielding material, which specifically comprises the following steps:
(1) adding the expanded graphite into the mixed solvent, uniformly stirring, and then adding FeSO4Solution and FeCl3Uniformly stirring the solution to obtain a mixed solution;
wherein the mixed solvent is prepared from water and absolute ethyl alcohol according to the weight ratio of 7: 2 by volume ratio; FeSO4Solution and FeCl3The concentration of the solution is 0.5 mol/L;
expanded graphite, mixed solvent and FeSO4Solution and FeCl3The mass ratio of the solution is 1: (20-35): 10: 10;
the stirring speed is 200-300 r/min; the time is 20-40 min;
(2) heating the mixed solution to 45-60 ℃, reacting for 2-4 h, then dropwise adding ammonia water to adjust the pH value to 11 alkalinity, washing for 3-5 times, and drying at 60-80 ℃ to obtain EG/Fe3O4A composite material;
(3) to the above EG/Fe3O4Sequentially adding deionized water, triethanolamine, a foam stabilizer and polyether polyol into the composite material, uniformly mixing, then adding stannous octoate for uniform dispersion, adding toluene diisocyanate, stirring, pouring into a mold, and applyingPressurizing, finally placing the mold in a vacuum oven, and drying at 80-90 ℃ for 10-20 min to obtain the polymer-based porous electromagnetic shielding material;
the foam stabilizer is one or any combination of a silicone stabilizer and a silicone polyether copolymer stabilizer;
wherein, EG/Fe3O4The mass ratio of the composite material, deionized water, triethanolamine, a foam stabilizer, polyether polyol, stannous octoate and toluene diisocyanate is (5-20): (6-15): 0.5: (2-4): 100: 0.5: (60-80); the stirring speed is 2000 r/min; the applied pressure is 10-100N.
Example 1
The embodiment 1 of the invention discloses a preparation method of an adjustable polymer-based porous electromagnetic shielding material, which specifically comprises the following steps:
(1) 2g of expanded graphite was added to 30mL of a mixed solvent composed of water and absolute ethanol in a ratio of 7: 2, and then 10mL of FeSO with a concentration of 0.5mol/L is added thereto4Solution and 10mL FeCl with concentration of 0.5mol/L3Solution, guaranteed Fe3+With Fe2+In a molar ratio of 1: 1, uniformly stirring, heating to 50 ℃, reacting for 3 hours, then dropwise adding ammonia water until the pH value is 11, washing and drying to obtain EG/Fe3O4A composite material;
(2) to 10g of EG/Fe3O46g of deionized water, 0.4g of triethanolamine, 3g of foam stabilizer and 50g of polyether polyol are sequentially added into the composite material and uniformly mixed, then 0.4g of stannous octoate is added for uniform dispersion, then 30g of toluene diisocyanate is added, the mixture is stirred at the rotating speed of 2000r/min and poured into a mold to apply the pressure of 10N, and then the mixture is placed into a vacuum oven to be dried for 10min at the temperature of 85 ℃ to obtain the polymer-based porous electromagnetic shielding material.
Example 2
The embodiment 2 of the invention discloses a preparation method of an adjustable polymer-based porous electromagnetic shielding material, which specifically comprises the following steps:
(1) 2g of expanded graphite was added to 30mL of a mixed solvent composed of water and absolute ethanol in a ratio of 7: 2 of the bodyMixing the mixture by volume ratio, and adding 10mL of FeSO with the concentration of 0.5mol/L4Solution and 10mL FeCl with concentration of 0.5mol/L3Solution, guaranteed Fe3+With Fe2+In a molar ratio of 1: 1, uniformly stirring, heating to 50 ℃, reacting for 3 hours, then dropwise adding ammonia water until the pH value is 11, washing and drying to obtain EG/Fe3O4A composite material;
(2) to 10g of EG/Fe3O44g of deionized water, 0.4g of triethanolamine, 3g of foam stabilizer and 50g of polyether polyol are sequentially added into the composite material and uniformly mixed, then 0.4g of stannous octoate is added for uniform dispersion, then 30g of toluene diisocyanate is added, the mixture is stirred at the rotating speed of 2000r/min and poured into a mold to apply the pressure of 10N, and then the mixture is placed into a vacuum oven to be dried for 10min at the temperature of 85 ℃ to obtain the polymer-based porous electromagnetic shielding material.
Example 3
The embodiment 3 of the invention discloses a preparation method of an adjustable polymer-based porous electromagnetic shielding material, which specifically comprises the following steps:
(1) 2g of expanded graphite was added to 30mL of a mixed solvent composed of water and absolute ethanol in a ratio of 7: 2, and then 10mL of FeSO with a concentration of 0.5mol/L is added thereto4Solution and 10mL FeCl with concentration of 0.5mol/L3Solution, guaranteed Fe3+With Fe2+In a molar ratio of 1: 1, uniformly stirring, heating to 50 ℃, reacting for 3 hours, then dropwise adding ammonia water until the pH value is 11, washing and drying to obtain EG/Fe3O4A composite material;
(2) to 10g of EG/Fe3O43g of deionized water, 0.4g of triethanolamine, 3g of foam stabilizer and 50g of polyether polyol are sequentially added into the composite material and uniformly mixed, then 0.4g of stannous octoate is added for uniform dispersion, then 30g of toluene diisocyanate is added, the mixture is stirred at the rotating speed of 2000r/min and poured into a mold to apply the pressure of 10N, and then the mixture is placed into a vacuum oven to be dried for 10min at the temperature of 85 ℃ to obtain the polymer-based porous electromagnetic shielding material.
Example 4
The embodiment 4 of the invention discloses a preparation method of an adjustable polymer-based porous electromagnetic shielding material, which specifically comprises the following steps:
(1) 2g of expanded graphite was added to 30mL of a mixed solvent composed of water and absolute ethanol in a ratio of 7: 2, and then 10mL of FeSO with a concentration of 0.5mol/L is added thereto4Solution and 10mL FeCl with concentration of 0.5mol/L3Solution, guaranteed Fe3+With Fe2+In a molar ratio of 1: 1, uniformly stirring, heating to 50 ℃, reacting for 3 hours, then dropwise adding ammonia water until the pH value is 11, washing and drying to obtain EG/Fe3O4A composite material;
(2) to 10g of EG/Fe3O42g of deionized water, 0.4g of triethanolamine, 3g of foam stabilizer and 50g of polyether polyol are sequentially added into the composite material and uniformly mixed, then 0.4g of stannous octoate is added for uniform dispersion, then 30g of toluene diisocyanate is added, the mixture is stirred at the rotating speed of 2000r/min and poured into a mold to apply the pressure of 10N, and then the mixture is placed into a vacuum oven to be dried for 10min at the temperature of 85 ℃ to obtain the polymer-based porous electromagnetic shielding material.
Example 5
The embodiment 5 of the invention discloses a preparation method of an adjustable polymer-based porous electromagnetic shielding material, which specifically comprises the following steps:
(1) 2g of expanded graphite was added to 30mL of a mixed solvent composed of water and absolute ethanol in a ratio of 7: 2, and then 10mL of FeSO with a concentration of 0.5mol/L is added thereto4Solution and 10mL FeCl with concentration of 0.5mol/L3Solution, guaranteed Fe3+With Fe2+In a molar ratio of 1: 1, uniformly stirring, heating to 50 ℃, reacting for 3 hours, then dropwise adding ammonia water until the pH value is 11, washing and drying to obtain EG/Fe3O4A composite material;
(2) to 10g of EG/Fe3O4Sequentially adding 2g of deionized water, 0.4g of triethanolamine, 3g of foam stabilizer and 50g of polyether polyol into the composite material, uniformly mixing, adding 0.4g of stannous octoate, uniformly dispersing, adding 30g of toluene diisocyanate, stirring at the rotating speed of 2000r/min, pouring into a mold, applying the pressure of 20N, and then placing the mold into a vacuum oven at the temperature of 85 DEG CAnd drying the piece for 10min to obtain the polymer-based porous electromagnetic shielding material.
Example 6
The embodiment 6 of the invention discloses a preparation method of an adjustable polymer-based porous electromagnetic shielding material, which specifically comprises the following steps:
(1) 2g of expanded graphite was added to 30mL of a mixed solvent composed of water and absolute ethanol in a ratio of 7: 2, and then 10mL of FeSO with a concentration of 0.5mol/L is added thereto4Solution and 10mL FeCl with concentration of 0.5mol/L3Solution, guaranteed Fe3+With Fe2+In a molar ratio of 1: 1, uniformly stirring, heating to 50 ℃, reacting for 3 hours, then dropwise adding ammonia water until the pH value is 11, washing and drying to obtain EG/Fe3O4A composite material;
(2) to 10g of EG/Fe3O42g of deionized water, 0.4g of triethanolamine, 3g of foam stabilizer and 50g of polyether polyol are sequentially added into the composite material and uniformly mixed, then 0.4g of stannous octoate is added for uniform dispersion, then 30g of toluene diisocyanate is added, the mixture is stirred at the rotating speed of 2000r/min and poured into a mold to apply the pressure of 50N, and then the mixture is placed into a vacuum oven to be dried for 10min at the temperature of 85 ℃ to obtain the polymer-based porous electromagnetic shielding material.
Comparative example 1
The invention discloses a preparation method of a polymer-based porous electromagnetic shielding material, which comprises the following steps:
(1) sequentially adding 6g of deionized water, 0.4g of triethanolamine, 3g of foam stabilizer and 50g of polyether polyol into a beaker, and uniformly mixing;
(2) and adding 0.4g of stannous octoate into the obtained mixed solution, uniformly dispersing, then adding 30g of toluene diisocyanate, stirring at the rotating speed of 2000r/min, pouring into a mould, applying the pressure of 10N, and then placing the mould into a vacuum oven to dry for 10min at the temperature of 85 ℃ to obtain the polymer-based porous electromagnetic shielding material.
Effect verification
1. The average cell diameter of the polymer-based porous electromagnetic shielding composite prepared in examples 1 to 6 was counted and calculated, as shown in table 1.
2. Preparing EG/Fe in the step (1) of the embodiment 1-6 by adopting Zeiss scanning electron microscope SIGMA3003O4The composite material was characterized and the SEM image is shown in FIG. 1.
3. The polymer-based porous electromagnetic shielding composite materials prepared in examples 1-6 were characterized by a zeiss scanning electron microscope SIGMA300, and the obtained SEM image is shown in fig. 2.
4. The electromagnetic shielding performance of the polymer-based porous composite materials obtained in examples 1 to 6 and comparative example 1 was tested by using a vector network analyzer CEYEAR3672A-S, and the obtained results are shown in table 1.
TABLE 1 average cell diameter and Shielding effectiveness of the cellular materials obtained in the examples
As can be seen from Table 1, the polymer-based porous electromagnetic shielding composite material prepared in example 1 has an excellent shielding effect on electromagnetic waves of 500MHz to 1GHz, and the electromagnetic shielding effectiveness reaches 35 dB; the polymer-based porous electromagnetic shielding composite material prepared in the embodiment 2 has a good shielding effect on electromagnetic waves of 1 GHz-3 GHz, and the average electromagnetic shielding effectiveness is 31 dB; the polymer-based porous electromagnetic shielding composite material prepared in the embodiment 3 has a good shielding effect on electromagnetic waves of 3 GHz-6 GHz, and the average electromagnetic shielding effectiveness is 28 dB; the polymer-based porous electromagnetic shielding composite material prepared in the embodiment 4 has a good shielding effect on electromagnetic waves of 6 GHz-8 GHz, and the average electromagnetic shielding effectiveness is 26 dB; the polymer-based porous electromagnetic shielding composite material prepared in the embodiment 5 has a good shielding effect on electromagnetic waves of 8 GHz-10 GHz, and the average electromagnetic shielding effectiveness is 24 dB; the polymer-based porous electromagnetic shielding composite material prepared in example 6 has a good shielding effect on electromagnetic waves of 10 GHz-12 GHz, and the average electromagnetic shielding effectiveness is 21 dB.
In the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed in the embodiment corresponds to the method disclosed in the embodiment, so that the description is simple, and the relevant points can be referred to the description of the method part.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.