CN113527836A - Electromagnetic shielding composite material and preparation method thereof - Google Patents
Electromagnetic shielding composite material and preparation method thereof Download PDFInfo
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Abstract
The invention provides an electromagnetic shielding composite material, and belongs to the technical field of shielding materials. An electromagnetic shielding composite material is prepared from the following raw materials in parts by weight: 35-52 parts of high imino methylated melamine resin, 10-20 parts of hydroxy acrylic resin, 15-23 parts of graphene oxide, 8-14 parts of carbon fiber, 3-9 parts of azodicarbonamide, 0-5 parts of filler and 2-7 parts of adhesive. According to the invention, the graphene oxide and the carbon fiber are introduced into the compound resin to prepare the electromagnetic shielding composite material, so that the electromagnetic wave can be effectively attenuated, the electromagnetic shielding purpose is achieved, and the maximum electromagnetic shielding efficiency of the composite material can reach about 35 dB.
Description
Technical Field
The invention belongs to the technical field of shielding materials, and particularly relates to an electromagnetic shielding composite material and a preparation method thereof.
Background
In recent years, with the rapid development of economy in China, the demand of various industries on electric power also shows a great increase situation, the scale and the pattern of a power grid are changed greatly, and besides transformer substations with voltage levels of 500kV and above, which are built in areas far away from residential areas of people, a plurality of transformer substations with voltage levels of 110kV, 220kV and 500kV are built in some urban and rural areas. The transformer substation with lower voltage level is gradually closely connected with our life, and the influence of electromagnetic radiation brought by the transformer substation on the production, life and living environment of enterprises and masses in cities is gradually shown. The electromagnetic pollution of the transformer substation is mainly caused by the comprehensive electromagnetic influence generated by components such as a main transformer, a high-voltage circuit breaker, an isolating switch, a voltage (current) transformer, a high-voltage reactor, a high-voltage capacitor, a bus, a high-voltage arrester and the like in the operation process. Therefore, it is necessary to adopt reasonable shielding measures to reduce the electromagnetic pollution of the substation.
In the prior art, patent document CN101812214A discloses an electromagnetic shielding material and a method for preparing the same. An electromagnetic shielding material is prepared from the following raw materials in parts by weight: 30-35 parts of ABS plastic, 20-25 parts of conductive carbon black, 20-23 parts of ABS plasticizer, 16-20 parts of magnetic powder and 3-5 parts of carbon fiber. The magnetic powder is one or the mixture of iron nickel powder and nickel zinc powder. The electromagnetic shielding material is prepared by mixing ABS plastic and ABS plasticizer, heating, pretreating, adding conductive carbon black, uniformly mixing magnetic powder and carbon fiber by a high-speed mixer, extruding in a double-screw extruder, and granulating; the electromagnetic wave radiation-proof coating has a good electromagnetic wave radiation-proof effect, and can be applied to the fields of electric power, wireless communication, household appliances and military affairs. The published patent document CN103031058A provides an electromagnetic shielding coating of room temperature vulcanized silicone rubber and a preparation method thereof, the coating comprises a base rubber, a reinforcing filler, a conductive filler, a cross-linking agent, a catalyst and a diluent, the matrix resin is hydroxyl-terminated polysiloxane, and the conductive filler is silicon dioxide with nickel or silver plated on the surface. The preparation method of the coating is that hydroxyl-terminated polysiloxane, silicon dioxide with nickel plated on the surface, reinforcing filler, cross-linking agent and catalyst are mixed and diluted to obtain the coating. The coating is particularly suitable for outdoor electromagnetic shielding in the power industry. The electromagnetic shielding material can realize electromagnetic shielding effect to a certain degree, and meanwhile, the raw material composition, the electromagnetic shielding effect and the like still have room for improvement along with the generation of new materials.
Disclosure of Invention
The invention aims to solve the technical problem of providing an electromagnetic shielding composite material aiming at the defects of the prior art so as to simultaneously improve the deformation resistance and the electromagnetic shielding performance of the composite material.
An electromagnetic shielding composite material is prepared from the following raw materials in parts by weight: 35-52 parts of high imino methylated melamine resin, 10-20 parts of hydroxy acrylic resin, 15-23 parts of graphene oxide, 8-14 parts of carbon fiber, 3-9 parts of azodicarbonamide, 0-5 parts of filler and 2-7 parts of adhesive.
Preferably, the viscosity of the high imino hypermethylated melamine resin is 2000-4800 mpa & s, the content of hydroxymethyl is less than or equal to 9%, and the content of free formaldehyde is less than or equal to 1%.
Preferably, the filler is one or more of nano active calcium carbonate, nano magnesium oxide powder and nano diatomite.
Preferably, the binder is a combination of polyethylene glycol and beta-cyclodextrin.
Preferably, the preparation method of the electromagnetic shielding composite material comprises the following steps:
firstly, weighing the raw materials in parts by weight, and fully and uniformly mixing high imino hypermethylated melamine resin, hydroxy acrylic resin and azodicarbonamide to obtain a first mixture;
then, adding graphene oxide, carbon fibers and a filler into the first mixture, and fully mixing again to obtain a second mixture;
and adding an adhesive into the second mixture, uniformly stirring, putting the obtained mixture into a mold, putting the mold on a vulcanizing instrument for preheating, foaming at a certain temperature and pressure, cooling the mold to room temperature after foaming is finished, and demolding to obtain the polyurethane foam.
Preferably, the preheating temperature is 75-90 ℃ and the time is 10-15 minutes.
Preferably, the certain temperature and pressure are: the temperature is 190 ℃ and 210 ℃, and the time is 1-2 hours.
With the acceleration of urbanization, various distribution facilities and transformer substations are closer to our lives, and residents located around the distribution facilities and transformer substations are also puzzled by the problems. As is well known in the art, the choice of the matrix is critical in addition to the metallic or non-metallic substance having an electromagnetic shielding effect. The variety of the matrixes is wide, the performance difference is large, and generally, researchers can screen suitable matrixes according to the application environment and the requirement of the material. Different base materials can endow the composite material with different thermal stability, mechanical property, corrosion resistance and processability. Therefore, the selection of a suitable resin as a matrix is crucial for the development of composite materials. Moreover, many existing researches show that a single matrix often has some performance short plates, so that the functions of the prepared material are limited, and scientific compounding of the matrix is also the key for obtaining better performance of the composite material.
Firstly, the high imino high methylated melamine resin not only retains a certain amount of unreacted active hydrogen atoms, but also leaves a certain amount of hydroxymethyl groups; when reacting with hydroxy acrylic resin, it has faster curing property due to higher content of imino group. In addition, the high imino high methylated melamine resin is compounded with the hydroxyl acrylic resin, and the obtained composite material also has good elastic deformation resistance and aging resistance, and can adapt to the outdoor environment with multiple changes.
Secondly, the graphene oxide and the carbon fiber are introduced into the compound resin to prepare the electromagnetic shielding composite material, so that the electromagnetic wave can be effectively attenuated, the electromagnetic shielding purpose is achieved, and the maximum electromagnetic shielding efficiency of the composite material can reach about 35 dB.
Thirdly, according to the characteristics of the raw materials, the proper foaming material azodicarbonamide is selected, the proper amount of foaming material is used, the size and the distribution of the foam holes of the obtained composite material are uniform, the phenomena of obvious foam hole structure collapse and foam hole combination are avoided, and a certain structural basis is provided for the improvement of the electromagnetic shielding efficiency. The research shows that when the content of azodicarbonamide in the foaming material is higher, obvious phenomena of collapse of a cellular structure and combination of cells can be observed, and the mechanical property of the composite material can be seriously influenced. The filler in the invention adopts one or more than two of nano active calcium carbonate, nano magnesium oxide powder and nano diatomite to improve the hardness of the material and assist in improving the electromagnetic shielding performance of the composite material. The adhesive of the invention adopts the combination of polyethylene glycol and beta-cyclodextrin, and the weight ratio of the polyethylene glycol to the beta-cyclodextrin is 1: (1-2) so that the internal combination performance of different materials is better and the flexibility performance is more remarkable.
Detailed Description
In order to better understand the present invention, the following examples are further provided to clearly illustrate the contents of the present invention, but the contents of the present invention are not limited to the following examples. In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details.
In the following examples of the present invention, hydroxy acrylic resin, graphene oxide, carbon fiber, azodicarbonamide, nano activated calcium carbonate, nano magnesium oxide powder, nano diatomaceous earth, polyethylene glycol, and β -cyclodextrin are all commercially available. The high-imino high-methylated melamine resin is self-made according to the publication CN106432658A, the viscosity of the high-imino high-methylated melamine resin is 2000-4800 mpa & s, the content of hydroxymethyl is less than or equal to 9%, and the content of free formaldehyde is less than or equal to 1%.
Example 1
An electromagnetic shielding composite material is prepared from the following raw materials in parts by weight: 35 parts of high imino high methylated melamine resin, 10 parts of hydroxy acrylic resin, 15 parts of graphene oxide, 8 parts of carbon fiber, 3 parts of azodicarbonamide and 2 parts of adhesive.
In this embodiment, the binder is a combination of polyethylene glycol and β -cyclodextrin in a weight ratio of 1: 1.
the preparation method of the electromagnetic shielding composite material comprises the following steps:
firstly, weighing the raw materials in parts by weight, and fully and uniformly mixing high imino hypermethylated melamine resin, hydroxy acrylic resin and azodicarbonamide to obtain a first mixture;
then, adding graphene oxide, carbon fibers and a filler into the first mixture, and fully mixing again to obtain a second mixture;
and adding an adhesive into the second mixture, uniformly stirring, putting the obtained mixture into a mold, putting the mold on a vulcanizing instrument for preheating, foaming at a certain temperature and pressure, cooling the mold to room temperature after foaming is finished, and demolding to obtain the polyurethane foam.
Wherein the preheating temperature is 75 ℃ and the preheating time is 15 minutes.
The certain temperature and pressure are: the temperature was 190 ℃ and the time was 1.5 hours.
Example 2
An electromagnetic shielding composite material is prepared from the following raw materials in parts by weight: 38 parts of high imino hypermethylated melamine resin, 12 parts of hydroxy acrylic resin, 16 parts of graphene oxide, 9 parts of carbon fiber, 5 parts of azodicarbonamide, 1 part of filler and 2 parts of adhesive.
In this example, the filler is nano-active calcium carbonate. The adhesive is a combination of polyethylene glycol and beta-cyclodextrin, and the weight ratio of the polyethylene glycol to the beta-cyclodextrin is 1: 2.
the preparation method of the electromagnetic shielding composite material comprises the following steps:
firstly, weighing the raw materials in parts by weight, and fully and uniformly mixing high imino hypermethylated melamine resin, hydroxy acrylic resin and azodicarbonamide to obtain a first mixture;
then, adding graphene oxide, carbon fibers and a filler into the first mixture, and fully mixing again to obtain a second mixture;
and adding an adhesive into the second mixture, uniformly stirring, putting the obtained mixture into a mold, putting the mold on a vulcanizing instrument for preheating, foaming at a certain temperature and pressure, cooling the mold to room temperature after foaming is finished, and demolding to obtain the polyurethane foam.
The preheating temperature is 80 ℃ and the preheating time is 12 minutes.
The certain temperature and pressure are: the temperature was 195 ℃ and the time was 1.8 hours.
Example 3
An electromagnetic shielding composite material is prepared from the following raw materials in parts by weight: 40 parts of high imino high methylated melamine resin, 15 parts of hydroxy acrylic resin, 20 parts of graphene oxide, 12 parts of carbon fiber, 6 parts of azodicarbonamide, 3 parts of filler and 3 parts of adhesive.
In this embodiment, the filler is a nano-magnesia powder. The adhesive is a combination of polyethylene glycol and beta-cyclodextrin, and the weight ratio of the polyethylene glycol to the beta-cyclodextrin is 1: 1.2.
the preparation method of the electromagnetic shielding composite material comprises the following steps:
firstly, weighing the raw materials in parts by weight, and fully and uniformly mixing high imino hypermethylated melamine resin, hydroxy acrylic resin and azodicarbonamide to obtain a first mixture;
then, adding graphene oxide, carbon fibers and a filler into the first mixture, and fully mixing again to obtain a second mixture;
and adding an adhesive into the second mixture, uniformly stirring, putting the obtained mixture into a mold, putting the mold on a vulcanizing instrument for preheating, foaming at a certain temperature and pressure, cooling the mold to room temperature after foaming is finished, and demolding to obtain the polyurethane foam.
The preheating temperature is 85 ℃ and the preheating time is 10 minutes.
The certain temperature and pressure are: the temperature was 200 ℃ for 1.2 hours.
Example 4
An electromagnetic shielding composite material is prepared from the following raw materials in parts by weight: 45 parts of high imino methylated melamine resin, 18 parts of hydroxy acrylic resin, 20 parts of graphene oxide, 10 parts of carbon fiber, 8 parts of azodicarbonamide, 4 parts of filler and 5 parts of adhesive.
In this embodiment, the filler is nano diatomaceous earth. The adhesive is a combination of polyethylene glycol and beta-cyclodextrin, and the weight ratio of the polyethylene glycol to the beta-cyclodextrin is 1: 1.5.
the preparation method of the electromagnetic shielding composite material comprises the following steps:
firstly, weighing the raw materials in parts by weight, and fully and uniformly mixing high imino hypermethylated melamine resin, hydroxy acrylic resin and azodicarbonamide to obtain a first mixture;
then, adding graphene oxide, carbon fibers and a filler into the first mixture, and fully mixing again to obtain a second mixture;
and adding an adhesive into the second mixture, uniformly stirring, putting the obtained mixture into a mold, putting the mold on a vulcanizing instrument for preheating, foaming at a certain temperature and pressure, cooling the mold to room temperature after foaming is finished, and demolding to obtain the polyurethane foam.
The preheating temperature is 90 ℃ and the preheating time is 10 minutes.
The certain temperature and pressure are: the temperature was 210 ℃ for 1 hour.
Example 5
An electromagnetic shielding composite material is prepared from the following raw materials in parts by weight: 52 parts of high imino hypermethylated melamine resin, 20 parts of hydroxy acrylic resin, 23 parts of graphene oxide, 14 parts of carbon fiber, 9 parts of azodicarbonamide, 5 parts of filler and 7 parts of adhesive.
In this embodiment, the filler is two combinations of nano activated calcium carbonate and nano diatomite, and the weight ratio of the two combinations is 1: 1. the adhesive is a combination of polyethylene glycol and beta-cyclodextrin, and the weight ratio of the polyethylene glycol to the beta-cyclodextrin is 1: 1.8.
the preparation method of the electromagnetic shielding composite material comprises the following steps:
firstly, weighing the raw materials in parts by weight, and fully and uniformly mixing high imino hypermethylated melamine resin, hydroxy acrylic resin and azodicarbonamide to obtain a first mixture;
then, adding graphene oxide, carbon fibers and a filler into the first mixture, and fully mixing again to obtain a second mixture;
and adding an adhesive into the second mixture, uniformly stirring, putting the obtained mixture into a mold, putting the mold on a vulcanizing instrument for preheating, foaming at a certain temperature and pressure, cooling the mold to room temperature after foaming is finished, and demolding to obtain the polyurethane foam.
The preheating temperature is 85 ℃ and the preheating time is 12 minutes.
The certain temperature and pressure are: the temperature was 205 ℃ and the time was 1.2 hours.
Comparative example 1: comparative example 1 differs from example 1 in that: the hydroxyacrylic resin was omitted. The preparation method is shown in example 1.
Comparative example 2: an electromagnetic shielding composite material is prepared from the following raw materials in parts by weight: 15 parts of high imino methylated melamine resin, 35 parts of hydroxy acrylic resin, 16 parts of graphene oxide, 9 parts of carbon fiber, 5 parts of azodicarbonamide, 1 part of filler and 2 parts of adhesive. The preparation method is shown in example 2.
Comparative example 3: this comparative example differs from example 2 in that: dinitrosopentamethylenetetramine is used for replacing azodicarbonamide, and the rest raw materials and the content thereof are unchanged. The preparation method is shown in example 2.
Comparative example 4: this comparative example differs from example 2 in that: the adhesive is polyvinyl butyral and alpha-cyclodextrin in the same weight, and the rest material and its content are unchanged. The preparation method is shown in example 2.
And (3) performance characterization: (1) mechanical properties: the bending strength of the composite material is tested by using a universal mechanical testing machine under the condition of room temperature according to the national standard GB/T9341-2008, the testing speed of the testing machine is set to be 10mm/min, the length of a sample is 100mm, and the span of the sample is 64 mm. Each set of 3 test specimens was averaged and the results are shown in table 1.
(2) Electromagnetic shielding effectiveness: under the room temperature condition (the temperature is 25 ℃, and the relative humidity is 60%), a sample is made into a wafer with the diameter of 12.00cm and the thickness of 1.00mm, an electromagnetic shielding tester and a vector network analyzer are used for measuring the electromagnetic shielding effectiveness SE of the composite material under the frequency of 30-1200 MHz, and key frequency point data are recorded, and the results are shown in tables 2-1 and 2-2.
(3) And (3) testing results:
TABLE 1 mechanical Property test results
As can be seen from the data in the table above, the composite material of the invention has the bending strength of 87.7-95.4 MPa, the bending modulus of 8.6-9.4 GPa and better elastic deformation resistance. The comparative examples 1 and 2 change the compounding and the proportion of the matrix resin, have different degrees of influence on the elastic deformation capacity of the composite material, and show that the compounding combination of the matrix of the invention obtains better synergistic effect. Further, the selection of the foaming material and the binder should be made in consideration of the properties of the matrix resin, and the selection is made only by the action of a single raw material, and it is not always possible to obtain a composite material having a desired effect and excellent performance.
Table 2-1 key frequency point test results for examples 1-4
Tables 2-2 key frequency point test results for comparative examples 1-4
The results in tables 2-1 and 2-2 show that the electromagnetic shielding effectiveness of the composite material can reach about 35dB, and the composite material has a remarkable electromagnetic shielding effect. Meanwhile, comparative examples 1 to 4 show that the selection and the collocation of the matrix, the foam material and the adhesive are reasonable, which is beneficial to improving the electromagnetic shielding performance of the composite material, and also show that even if the electromagnetic shielding reinforcing material is the same in type, the electromagnetic shielding effect of the composite material can still be influenced when some raw materials forming a system are changed, which shows that the final display structure of the composite material can influence the exertion of the electromagnetic shielding effect of the composite material, and the reasonable foam structure is beneficial to improving the electromagnetic shielding effect.
Finally, the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting, and other modifications or equivalent substitutions made by the technical solutions of the present invention by those of ordinary skill in the art should be covered within the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solutions of the present invention.
Claims (7)
1. An electromagnetic shielding composite, comprising: the feed is prepared from the following raw materials in parts by weight: 35-52 parts of high imino methylated melamine resin, 10-20 parts of hydroxy acrylic resin, 15-23 parts of graphene oxide, 8-14 parts of carbon fiber, 3-9 parts of azodicarbonamide, 0-5 parts of filler and 2-7 parts of adhesive.
2. The electromagnetically shielding composite as claimed in claim 1, wherein: the viscosity of the high-imino high-methylated melamine resin is 2000-4800 mpa & s, the content of hydroxymethyl is less than or equal to 9%, and the content of free formaldehyde is less than or equal to 1%.
3. The electromagnetically shielding composite as claimed in claim 1, wherein: the filler is one or more than two of nano active calcium carbonate, nano magnesium oxide powder and nano diatomite.
4. The electromagnetically shielding composite as claimed in claim 1, wherein: the binder is a combination of polyethylene glycol and beta-cyclodextrin.
5. The electromagnetically shielding composite as claimed in any one of claims 1 to 4, wherein: the preparation method of the electromagnetic shielding composite material comprises the following steps:
firstly, weighing the raw materials in parts by weight, and fully and uniformly mixing high imino hypermethylated melamine resin, hydroxy acrylic resin and azodicarbonamide to obtain a first mixture;
then, adding graphene oxide, carbon fibers and a filler into the first mixture, and fully mixing again to obtain a second mixture;
and adding an adhesive into the second mixture, uniformly stirring, putting the obtained mixture into a mold, putting the mold on a vulcanizing instrument for preheating, foaming at a certain temperature and pressure, cooling the mold to room temperature after foaming is finished, and demolding to obtain the polyurethane foam.
6. The electromagnetically shielding composite as claimed in claim 5, wherein: the preheating temperature is 75-90 ℃, and the preheating time is 10-15 minutes.
7. The electromagnetically shielding composite as claimed in claim 5, wherein: the certain temperature and pressure are: the temperature is 190 ℃ and 210 ℃, and the time is 1-2 hours.
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