CN115819921A - Preparation method and application of interface modified aramid fiber/epoxy resin composite material - Google Patents
Preparation method and application of interface modified aramid fiber/epoxy resin composite material Download PDFInfo
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- CN115819921A CN115819921A CN202211418820.3A CN202211418820A CN115819921A CN 115819921 A CN115819921 A CN 115819921A CN 202211418820 A CN202211418820 A CN 202211418820A CN 115819921 A CN115819921 A CN 115819921A
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Images
Abstract
The invention discloses a preparation method for improving the performance of an aramid fiber/epoxy resin composite material. According to the method, active groups are introduced to the surface of the aramid fiber through plasma surface treatment, and then the number of the active groups is further increased by combining with the surface treatment of a silane coupling agent, so that more binding sites are provided, and the interface binding capacity of the aramid fiber woven cloth as a fiber reinforced material and the epoxy resin as a matrix material is favorably realized. The invention also introduces hollow Al of particle reinforced material 2 O 3 Microspheres which are homogeneously mixed with the matrix material to maintain the matrix materialThe structural stability of the material is improved, the mechanical property of the material is improved, and the shock absorption effect and the insulating property are enhanced. The method disclosed by the invention is based on the actual production process of the aramid fiber-resin composite material, is improved from the aspect of improving the interface characteristic of the composite material, has the advantages of simple implementation, convenience in operation and strong industrial applicability, and can be applied to gas-insulated metal-enclosed switchgear.
Description
Technical Field
The invention relates to an epoxy resin composite material, in particular to an aramid fiber reinforced epoxy resin composite material modified through a plasma interface and application thereof in extra-high voltage power transmission and transformation equipment.
Background
The extra-high voltage is the voltage grade of over 1000 kV of direct current +/-800 kV and alternating current, and research data shows that the transmission capacity of +/-800 kV direct current engineering is 2-3 times of that of +/-500 kV direct current engineering, and the economic transmission distance is improved to 2-2.5 times. Therefore, the research and application of the extra-high voltage power transmission and transformation project have wide economic benefits.
As the voltage increases, higher demands are placed on the insulation, safety and reliability of the equipment. Among them, gas insulated metal enclosed switchgear (GIS) has been widely used in the extra-high voltage field due to its compact structure, high reliability, high safety, and high environmental adaptability.
The insulating pull rod is an important component in an extra-high voltage GIS breaker, and is mainly applied to connecting a grounding part and transmitting the grounding part to a high-potential part to play a role in making and breaking electrical connection. The insulating pull rod is thin and long in structure, so that impact voltage of tensile and compressive loads to a certain degree needs to be borne in the electrical operation, and the switching-on and switching-off times in the operation are more, so that the structural design and the quality of the insulating pull rod are extremely strict. The design of the insulating pull rod particularly pays attention to the electrical insulating property and the mechanical property: breakdown or flashover along the surface cannot occur, and the insulation performance cannot be reduced under the long-term action of mechanical force and heat; and meanwhile, the high standard requirement of fatigue performance is also met for manufacturing materials. According to the requirements and characteristics of the insulated pull rod product, the key point of development is mainly to solve the technologies of voltage resistance, mechanical tensile strength, interface shear strength and the like.
At present, almost all insulation pull rods for GIS circuit breakers are made of fiber-reinforced epoxy materials, and glass fibers, polyester fibers and the like are commonly used. The manufacturing processes used in the early stages of development were mainly die pressing, hand pasting, spraying and winding, and drawing. However, the products produced by the above manufacturing process have some defects, have more air gaps, have poor high-voltage tolerance, and are easy to cause insulation breakdown due to free discharge. With the technical progress and the maturity of the manufacturing process, a process route of vacuum pressure impregnation is formed in China, and the effect of practical application is greatly improved.
Amide groups and benzene rings in the molecular structure of the Aramid Fiber (AF) have a conjugate effect, the internal rotation energy in the molecular structure is higher, and the molecular chain of the aramid fiber is a planar rigid straight chain, so that the orientation degree and the crystallinity of the aramid fiber are higher, and the molecular arrangement is more compact due to the linear structure. Therefore, the aramid fiber has extremely high tensile strength, has the advantages of good insulating property, good heat resistance, high wear resistance and low conductivity, and has wide prospect in the preparation of extra-high voltage GIS circuit breakers. But its disadvantages are also apparent: the surface of the aramid fiber is smooth and inert, and the aramid fiber and the epoxy resin matrix have no meshing point of a physical layer, so that the wettability of the aramid fiber and the epoxy resin is poor, the interfacial adhesion is poor when the composite material is formed, and the comprehensive performance, especially the insulating property and the mechanical property, of the aramid fiber/epoxy composite material are reduced.
Therefore, how to improve the bonding performance of the aramid fiber and the epoxy resin becomes the key for preparing the extra-high voltage GIS circuit breaker with excellent performance. The surface modification method can effectively reduce the orientation degree of the molecular structure on the surface of the aramid fiber, increase the active groups on the surface, further improve the roughness of the surface of the aramid fiber material, enhance the interface performance of the composite material and achieve the purpose of improving the overall performance of the composite material.
Currently, surface modification methods for materials mainly include physical modification and chemical modification. The chemical method mainly comprises chemical etching, chemical surface grafting and the like. The prior research shows that the properties of surface roughness, interfacial shear strength (IFSS) and the like after chemical treatment are obviously improved. Chemical treatment may corrode the aramid and reduce its mechanical properties; furthermore, chemical treatment requires large amounts of water and chemicals and is not environmentally friendly. The physical methods include coating the surface of the aramid fiber material, plasma modification, irradiation of the aramid fiber with high energy radiation, ultrasonic impregnation, and the like.
In recent years, plasma treatment has been greatly developed as a physical method for surface modification, and not only does the plasma treatment cause physical and changes of the polymer surface, but also maximally maintains the original bulk quality of the aramid fiber. Furthermore, it is a dry process and therefore environmentally friendly. However, the process parameters such as the plasma treatment time, the discharge power and the like, and the modified aramid fiber and epoxy resin compounding process have important influences on the mechanical property and the electrical property of the composite material. On the other hand, it has been reported that the surface treatment of aramid fibers with a silane coupling agent increases the number of active functional groups on the surface.
Disclosure of Invention
Aiming at the problems of the aramid fiber in the application of the extra-high voltage GIS circuit breaker, the invention improves the combination mode of the aramid fiber reinforced material and the epoxy resin matrix material by adjusting the plasma treatment process parameters and combining the silane coupling agent modification process, realizes the successful preparation of the resin matrix material reinforced by the fiber and the particles together, and the obtained composite material has excellent mechanical property and electrical property and is expected to promote the application prospect of the aramid fiber in the extra-high voltage GIS circuit breaker.
The first aspect of the invention provides a preparation method of an interface modified aramid fiber/epoxy resin composite material, which comprises the following detailed operations:
cleaning and drying the aramid fiber woven cloth, fixing the aramid fiber woven cloth on a substrate, and performing plasma modification treatment on the surface of the aramid fiber woven cloth in an air environment by using a plasma brush as a high-voltage electrode;
soaking the aramid fiber woven cloth subjected to plasma modification treatment at 30-50 ℃ for 4-6h by using KH550 or KH570, and naturally drying for later use;
uniformly mixing the epoxy resin, the curing agent, the accelerator and the particle reinforcing material to obtain a blending system serving as a matrix material for later use;
coating a layer of matrix material on an inner die, then laying a layer of aramid fiber woven cloth subjected to plasma modification treatment, and then sequentially repeating the steps of coating the matrix material and laying a layer of aramid fiber woven cloth subjected to plasma modification treatment for a plurality of times to obtain a sandwich structure;
and combining the outer mold and the inner mold, applying pressure to carry out hot-pressing curing, demolding, heating again to carry out post-curing, and obtaining the interface modified aramid fiber/epoxy resin composite laminated structure.
According to the scheme, the Kevlar aramid fiber woven cloth is preferably selected as the aramid fiber woven cloth, the thickness is usually 0.3-0.5mm, and the requirements of moderate thickness and standard performance of a sandwich structure obtained after multilayer stacking are met.
The substrate may be a glass substrate, and is required to have a flat surface and no foreign matter. The glass substrate may be previously cleaned with alcohol and then dried by blowing.
According to the scheme, the mass ratio of the epoxy resin, the curing agent, the accelerator and the particle reinforcing material in the matrix material is 100 (65-80): 1-6: 0.3-8), wherein the epoxy resin is DGEBA, the curing agent is an anhydride curing agent, the accelerator is methyldiethanolamine or aminophenol, and the particle reinforcing material is hollow Al with the particle size of 30-70 mu m 2 O 3 The wall thickness of the microspheres is 10-25 μm.
The invention selects and adds proper amount of hollow Al 2 O 3 The microspheres are used as particle reinforcing materials and improve the strength of the resin-based material together with aramid fiber woven cloth. The hollow structure of the particle reinforced material is beneficial to improving the insulating property of the composite material, and the formed cavity structure can realize the lightening of the material and improve the effect of reducing vibration. Through screening, hollow spheres with the particle size of 30-70 mu m (the wall thickness is about 10-25 mu m) are selected, the reinforcing effect on the composite material is optimal, the particles are uniformly dispersed in the matrix to form uniformly distributed cavities, and the insulating property is improved.
According to the scheme, the parameters of the plasma modification treatment are as follows: the high-voltage output voltage is 3-7kV, the frequency is 50 +/-1 kHz, the discharge power is 80W, the moving speed of the plasma brush is 1mm/s, and the processing time is 600-900s.
According to the scheme, the die used by the invention is preferably made of stainless steel, and comprises an inner die and an outer die. The mould can be designed into different shapes according to requirements, for example, when the insulating pull rod is prepared, the inner mould can be a mandrel, and the shape is formed through the outer mould. The inner mold and the outer mold are cleaned with alcohol before use, and thermosetting epoxy resin high-temperature resistant release agent is uniformly sprayed on the surfaces of the inner mold and the outer mold.
According to the scheme, the mass ratio of the aramid fiber woven cloth to the matrix material is 1. That is, in the present invention, the amount of the resin used as the matrix material in the composite material exceeds 60%, and the amount of the aramid fiber woven fabric used is relatively significantly smaller than that of the matrix material, and the aramid fiber woven fabric is substantially used as a reinforcing material.
According to the scheme, in the sandwich structure, the preferable base material is 2-5 layers, and the number of the aramid fiber woven fabric layers is 1 less than that of the base material layers. The base material and the aramid fiber woven cloth are overlapped in a staggered mode, the first layer is the base material, and the number of layers of the aramid fiber woven cloth is 1 less than that of the base material, so that the last layer is also the base material. After the base material is paved each time, the aramid fiber woven cloth is laminated again after the base material is completely soaked.
According to the scheme, if the number of layers of the aramid fiber woven cloth in the sandwich structure is more than 1, the aramid fiber woven cloth is required to keep consistent directions (namely warp directions are required to be kept consistent), so that the directionality of mechanical and electrical properties of the composite material is improved.
According to the scheme, the hot-pressing curing is preferably carried out under the conditions that 1-2MPa of pressure is applied at 120-165 ℃ and the pressure is kept for 2 hours, so that the curing of the resin is realized; and then post-curing is carried out, the curing is carried out for 12-16h under the condition of 140-160 ℃, the stability of the whole structure of the material is further improved through high-temperature treatment, the heat treatment effect on the aramid fiber and the particle reinforced material is realized, the interfaces of different components are fused, and the mechanical property of the material is obviously improved.
In a second aspect of the invention, the application of the interface modified aramid fiber/epoxy resin composite material in gas insulated metal enclosed switchgear is provided. The sandwich structure is obtained by selecting a proper mould and taking the mandrel as an inner mould for winding, and the insulating pull rod with good mechanical property and insulativity can be obtained by curing and demoulding.
The technical scheme of the invention provides a preparation method for improving the performance of an aramid fiber/epoxy resin composite material. According to the method, active groups are introduced to the surface of the aramid fiber through plasma surface treatment, and the number of the active groups is further increased by combining with the surface treatment of a silane coupling agent, so that more binding sites are provided, the interface binding capability of the fiber reinforced material aramid fiber woven cloth and the matrix material epoxy resin is favorably realized, and the properties of the aramid fiber/epoxy resin composite material, such as breakdown strength, are improved. The mass of the matrix material is at least 3 times of that of the aramid fiber woven cloth, and the matrix material is required to be fully soaked in the aramid fiber woven cloth in the laminating process.
On the other hand, the invention also introduces a particle reinforced material, and finally determines the hollow Al with the particle size of 30-70 mu m and the wall thickness of 10-25 mu m through multiple orthogonal experiment comparison screening 2 O 3 The microsphere has optimal effect, is uniformly mixed with the matrix material, maintains the structural stability of the matrix material, improves the mechanical property of the matrix material, and enhances the shock absorption effect and the insulation property.
In conclusion, the method disclosed by the invention is based on the actual production process of the aramid fiber-resin composite material, is improved from the aspect of improving the interface characteristics of the composite material, has the advantages of simplicity in implementation, convenience in operation and stronger industrial applicability, and can be applied to gas insulated metal enclosed switchgear.
Drawings
FIG. 1 is a process flow diagram of the preparation of an interfacial modified aramid fiber/epoxy resin composite of example 1;
fig. 2 is an SEM image of the interface-modified aramid fiber/epoxy resin composite obtained in example 1;
fig. 3 is an SEM image of the interface-modified aramid fiber/epoxy resin composite obtained in example 2;
fig. 4 is an SEM image of the interface-modified aramid fiber/epoxy resin composite obtained in comparative example 1;
fig. 5 is an SEM image of the interface-modified aramid fiber/epoxy resin composite obtained in comparative example 2;
FIG. 6 is an SEM image of aramid fibers stripped off from the composite material of example 1;
FIG. 7 is an SEM image of aramid fibers stripped from the composite material in example 2;
fig. 8 is an SEM image of aramid fibers peeled off from the composite material in comparative example 1;
fig. 9 is an SEM image of aramid fibers peeled off from the composite material in comparative example 2;
fig. 10 is a graph showing the results of the shear strength at the drawing interface of the monofilament of the interface-modified aramid fiber/epoxy resin composite materials obtained in example 3 and comparative examples 3 to 6.
Detailed Description
In order to better explain the present invention, the invention is explained and illustrated by the following detailed description.
Example 1
As shown in figure 1, the preparation method of the interface modified aramid fiber/epoxy resin composite material is applied to the insulating pull rod in the field of extra-high voltage power transmission and transformation. The method comprises the following specific steps:
firstly, kevlar aramid fiber woven cloth with the thickness of 0.3mm is alternately washed for 12 hours by using acetone and deionized water, and then the Kevlar aramid fiber woven cloth is placed in a vacuum drying box to be dried by hot air at the temperature of 110 ℃ and is fixed on the surface of a clean and flat glass substrate. Wherein the size of the Kevlar aramid fiber woven cloth is equal to that of the glass substrate. The plasma brush is used as a high-voltage electrode to carry out plasma modification treatment on the surface of the aramid fiber woven cloth in an air environment, and the treatment conditions are as follows: the high-voltage output voltage is 7kV, the frequency is 50kHz, the discharge power is 80W, the moving speed of the plasma brush is 1mm/s, and the processing time is 600s.
And secondly, soaking the Kevlar aramid fiber woven cloth subjected to the plasma modification treatment in KH550 at 50 ℃ for 4 hours, and naturally drying for later use.
Further, 100 parts by mass of DGEBA, 70 parts by mass of MTHPA curing agent, 6 parts by mass of methyldiethanolamine, and 4 parts by mass of hollow Al 2 O 3 The microspheres are uniformly mixed to obtain a blending system which is used as a matrix material for standby. Hollow Al 2 O 3 The D50 particle size of the microspheres was 65 μm with an average wall thickness of 16 μm.
Then preparing materials according to 1 part by mass of Kevlar woven cloth and 3 parts by mass of base materials, taking an insulating pull rod mandrel as an inner mold, cleaning with alcohol, coating a layer of thermosetting epoxy resin high-temperature-resistant release agent, coating a layer of base materials (preferably, after the Kevlar woven cloth is soaked, the woven cloth does not contact with the mandrel), tightly winding a layer of treated Kevlar woven cloth, then coating a layer of base materials, ensuring that the Kevlar woven cloth is completely soaked by the base materials, tightly winding a layer of treated Kevlar woven cloth, repeating the operation, coating three layers of base materials, and winding two layers of Kevlar woven cloth to obtain a cylindrical sandwich structure (the mandrel is not removed), wherein the warp directions of the two layers of Kevlar woven cloth are kept consistent (the weaving trend of the Kevlar woven cloth is consistent).
And finally, sheathing and tightly wrapping an outer die on the outer surface of the sandwich structure, applying 2MPa pressure to perform hot-pressing curing at 165 ℃ for 2h, demolding after the hot-pressing curing is completed, heating to 140 ℃ again to cure for 12h, and obtaining the insulating pull rod made of the interface modified aramid fiber/epoxy resin composite material.
Example 2
A preparation method of an interface modified aramid fiber/epoxy resin composite material comprises the following specific steps:
firstly, kevlar aramid fiber woven cloth with the thickness of 0.5mm is alternately cleaned for 8 hours by using acetone and deionized water, then the Kevlar aramid fiber woven cloth is placed in a vacuum drying box to be dried by hot air at 120 ℃, and is fixed on the surface of a glass substrate, wherein the glass substrate is cleaned by using alcohol in advance and then is dried by blowing. The size of the Kevlar aramid fiber woven cloth is slightly smaller than that of the glass substrate.
The plasma brush is used as a high-voltage electrode to carry out plasma modification treatment on the surface of the aramid fiber woven cloth in an air environment, and the treatment conditions are as follows: the high-voltage output voltage is 7kV, the frequency is 50kHz, the discharge power is 80W, the moving speed of the plasma brush is 1mm/s, the processing time is 900s, and the plasma brush is reserved.
And secondly, soaking the Kevlar aramid fiber woven cloth subjected to the plasma modification treatment for 6 hours at the temperature of 30 ℃, and naturally drying for later use.
In addition, 100 parts by mass of DGEBA, 80 parts by mass of MTHPA curing agent, 1 part by mass of aminophenol and 1 part by mass of hollow Al 2 O 3 The microspheres are uniformly mixed to obtain a blending system which is used as a matrix material for standby. Hollow Al 2 O 3 The D50 particle size of the microspheres was 30 μm with an average wall thickness of 10 μm.
Then preparing materials according to 1 part by mass of Kevlar aramid fiber woven cloth and 5 parts by mass of base materials, cleaning the surface of a stainless steel inner die by using alcohol, coating a layer of thermosetting epoxy resin high-temperature-resistant release agent, drying at 70 ℃ for 15min, coating a layer of base materials (after the Kevlar aramid fiber woven cloth is soaked, the woven cloth does not contact with the inner die), then paving a layer of treated Kevlar aramid fiber woven cloth, then coating a layer of base materials, ensuring that the Kevlar aramid fiber woven cloth is completely soaked by the base materials, then paving a layer of treated Kevlar aramid fiber woven cloth, repeating the above operation, coating 5 layers of base materials altogether, and paving 4 layers of Kevlar aramid fiber woven cloth to obtain a flat sandwich structure, wherein the warp directions of the 4 layers of Kevlar aramid fiber woven cloth are kept consistent (the weaving trend of the woven cloth is consistent).
And finally, assembling the outer die, applying 1MPa of pressure to perform hot-pressing curing at 120 ℃ for 2h, demolding after the completion, heating to 160 ℃ again to cure for 16h, and obtaining the interface modified aramid fiber/epoxy resin composite material.
Comparative example 1
The preparation method of the interface modified aramid fiber/epoxy resin composite material is different from that of the embodiment 2 in that plasma treatment is not carried out.
Comparative example 2
The difference between the method and the example 2 is that the treatment time of plasma is 300s.
The Kevlar aramid fiber woven fabrics after plasma treatment in the embodiments 1, 2, 1 and 2 are respectively characterized by XPS, and it can be found that after the Kevlar aramid fiber woven fabrics are subjected to plasma treatment for 5min, the chemical components of the surface of the aramid fiber are not changed greatly, the element peak is not changed, the functional groups of the aramid fiber are still in a dominant position, and only the number of C = O on the surface of the aramid fiber is obviously improved. Under the same plasma power, after the plasma treatment time is prolonged to 10min, the aramid fiber surface has-O-C = O bonds, which indicates that the aramid fiber is successfully modified by the plasma. The number of-O-C = O bonds on the surface of the aramid fiber continues to increase at a plasma treatment time of 15 min.
From this, it can be determined that the number and the occupied proportion of C = O increase in the case of a short processing time, and at this time the — O-C = O bond may have started to appear, but the number is particularly small. When the treatment time is long, many bonds of-O-C = O are generated, but when the treatment time is continued to be long, carbonization of the surface of the aramid fiber is accompanied. Suitable plasma treatment times are 600-900s.
Fig. 2 to 5 are SEM images of the composite materials obtained in example 1, example 2, comparative example 1 and comparative example 2, respectively.
As can be seen from a comparison of fig. 2-5, the etching effect of the plasma-treated aramid is strongly dependent on the treatment time, and the surface roughness of the aramid increases with increasing treatment time: the surface of the fiber treated for 15min is uneven, the surface of the aramid fiber untreated is clean and smooth, and the surface of the aramid fiber treated by plasma for 5min is slightly rough and slightly scratched and raised.
From the surface morphology, the roughness and damage of the fiber surface become more severe as the plasma treatment time is prolonged, and the aramid fiber tends to peel off during the "fibrillation" process. The fibrillation process can greatly improve the roughness of the aramid fiber, and further improve the adhesion of the aramid fiber and the epoxy resin.
Further, fig. 6 to 9 are SEM images of the composite materials obtained in example 1, example 2, comparative example 1, and comparative example 2, in which the aramid fibers were peeled off.
Compared with fig. 6-9, the aramid fiber of the peeling surface of the composite material formed by the aramid fiber and the epoxy resin which are not treated by the plasma still presents a smooth interface, and the adhesion degree of the aramid fiber and the epoxy resin is weaker. However, when the treatment time was increased to 5min, the aramid fiber surface exhibited a lesser degree of fiber damage of the interstitial surface. When the treatment time was increased to 10 and 15min, the bond and fiber damage reached the highest strength. The result shows that the surface roughness of the aramid fiber can be improved by the fibrillation modification of the aramid fiber by the plasma, so that the interface bonding strength of the aramid fiber woven cloth and the epoxy resin matrix is further enhanced.
In comparison with the above SEM images, there is a better treatment time for the plasma treatment of the aramid fiber. Comprehensively, 15min of plasma treatment time is successful in aramid fiber surface modification treatment.
Example 3
A preparation method of an interface modified aramid fiber/epoxy resin composite material comprises the following specific steps:
firstly, kevlar aramid fiber woven cloth with the thickness of 0.3mm is alternately cleaned for 6 hours by using acetone and deionized water, then the Kevlar aramid fiber woven cloth is placed in a vacuum drying oven for drying by hot air at 100 ℃, and is fixed on the surface of a glass substrate, wherein the glass substrate is cleaned by using alcohol in advance and then is dried by blowing. The size of the Kevlar aramid fiber woven cloth is equal to that of the glass substrate, and four corners are fixed by heat-resistant glue.
The plasma brush is used as a high-voltage electrode to carry out plasma modification treatment on the surface of the aramid fiber woven cloth in an air environment, and the treatment conditions are as follows: the high-voltage output voltage is 3kV, the frequency is 50kHz, the discharge power is 80W, the moving speed of the plasma brush is 1mm/s, the processing time is 900s, and the plasma brush is reserved.
Secondly, soaking the Kevlar aramid fiber woven cloth subjected to the plasma modification treatment for 5 hours at the temperature of 30 ℃, and naturally drying for later use.
Further, 100 parts by mass of DGEBA, 65 parts by mass of MTHPA curing agent, 3 parts by mass of aminophenol, and 8 parts by mass of hollow Al 2 O 3 The microspheres are uniformly mixed to obtain a blending system which is used as a matrix material for standby. Hollow Al 2 O 3 The D50 particle size of the microspheres was 50 μm, with an average wall thickness of 20 μm.
Then preparing materials according to 1 part by mass of Kevlar aramid fiber woven cloth and 4 parts by mass of base materials, cleaning the surface of a stainless steel inner die by using alcohol, coating a layer of thermosetting epoxy resin high-temperature-resistant release agent, drying at 70 ℃ for 10min, coating a layer of base materials (after the Kevlar aramid fiber woven cloth is soaked, the woven cloth does not contact with the inner die), then paving a layer of treated Kevlar aramid fiber woven cloth, then coating a layer of base materials, ensuring that the Kevlar aramid fiber woven cloth is completely soaked by the base materials, then paving a layer of treated Kevlar aramid fiber woven cloth, repeating the operation, coating 4 layers of base materials altogether, and paving 3 layers of Kevlar aramid fiber woven cloth to obtain a flat sandwich structure, wherein the warp directions of the 3 layers of Kevlar aramid fiber woven cloth are kept consistent.
And finally, assembling the outer die, applying 2MPa of pressure to perform hot-pressing curing at 140 ℃ for 2h, demolding after the hot-pressing curing is completed, heating to 150 ℃ again, and curing for 16h to obtain the interface modified aramid fiber/epoxy resin composite material.
Comparative example 3
The difference between the method and the embodiment 3 is that hollow Al is not added into the matrix material 2 O 3 And (3) microspheres.
Comparative example 4
The difference between the method and the embodiment 3 is that Kevlar aramid fiber woven cloth does not undergo KH550 soaking treatment.
Comparative example 5
The difference between the method and the embodiment 3 is that the Kevlar aramid fiber woven cloth is not subjected to plasma treatment.
Comparative example 6
The difference between the method and the embodiment 3 is that Kevlar aramid fiber woven cloth does not undergo KH550 soaking treatment, and hollow Al is not added into a matrix material 2 O 3 And (3) microspheres.
The mechanical properties of the interface modified aramid fiber/epoxy resin composite materials obtained in example 3 and comparative examples 3 to 6 were tested by a monofilament strength tester.
Recording the force F at the moment of debonding of the epoxy resin droplets, measuring the diameter d of the aramid fibers and the embedding length L of the epoxy droplets by a microscope, wherein the number of samples to be tested is 10 times, and averaging. The formula for calculating the interfacial shear strength is as follows:
in the formula tau IFSS The interfacial shear strength is the interfacial shear strength of aramid fiber monofilament-epoxy resin microdroplet, pa; f is the instant force of debonding of the epoxy microdroplets, N; d is the diameter of the fiber, m; l is the length of the fibers embedded in the resin, m. The obtained results are shown in FIG. 10.
As can be seen from figure 10, the shear strength of the monofilament drawing interface of the obtained aramid fiber is obviously superior to that of other comparative examples, and the strength of the aramid fiber is 25.4% higher than that of the fiber which is only subjected to plasma treatment.
Further, the applicant also explored hollow Al 2 O 3 The influence of the particle size of the microspheres. It was found that when the particle size exceeds 100 μm, the overall performance of the material is adversely affected, and it is presumed that the particle size is large, the effect of particle reinforcement is hardly exerted, and the large particle size affects the impregnation of the resin and the aramid fiber. While hollow Al of between 30 and 70 μm is selected 2 O 3 The microsphere has a good promoting effect, and the strength is improved by 12.1% as can be seen from example 3 and comparative example 3.
Claims (10)
1. The preparation method of the interface modified aramid fiber/epoxy resin composite material is characterized by comprising the following steps of:
cleaning and drying the aramid fiber woven cloth, fixing the aramid fiber woven cloth on a substrate, and performing plasma modification treatment on the surface of the aramid fiber woven cloth in an air environment by using a plasma brush as a high-voltage electrode;
soaking the aramid fiber woven cloth subjected to plasma modification treatment at 30-50 ℃ for 4-6h by using KH550 or KH570, and naturally drying for later use;
uniformly mixing the epoxy resin, the curing agent, the accelerator and the particle reinforcing material to obtain a blending system serving as a matrix material for later use;
coating a layer of the matrix material on an inner die, then laying a layer of the aramid fiber woven cloth subjected to plasma modification treatment, and then sequentially repeating the steps of coating the matrix material and laying a layer of the aramid fiber woven cloth subjected to plasma modification treatment for a plurality of times to obtain a sandwich structure;
and combining the outer mold and the inner mold, applying pressure to perform hot-pressing curing, demolding, heating again to perform post-curing, and obtaining the interface modified aramid fiber/epoxy resin composite laminated structure.
2. The preparation method of the interface modified aramid fiber/epoxy resin composite material as claimed in claim 1, wherein the aramid fiber woven cloth is Kevlar aramid fiber woven cloth, the thickness of the Kevlar aramid fiber woven cloth is 0.3-0.5mm, and the substrate is a glass substrate.
3. The method for preparing the interfacial modified aramid fiber/epoxy resin composite material according to claim 1, wherein the mass ratio of the epoxy resin, the curing agent, the accelerator and the particulate reinforcing material in the matrix material is 100 (65-80) to (1-6) to (0.3-8), wherein the epoxy resin is DGEBA, the curing agent is an anhydride curing agent, the accelerator is methyldiethanolamine or aminophenol, and the particulate reinforcing material is hollow Al with the particle size of 30-70 μm 2 O 3 And (3) microspheres.
4. The preparation method of the interface modified aramid fiber/epoxy resin composite material as claimed in claim 1, wherein the parameters of the plasma modification treatment are as follows: the high-voltage output voltage is 3-7kV, the frequency is 50 +/-1 kHz, the discharge power is 80W, the moving speed of the plasma brush is 1mm/s, and the processing time is 600-900s.
5. The preparation method of the interface modified aramid fiber/epoxy resin composite material as claimed in claim 1, wherein the inner mold and the outer mold are made of stainless steel, and are cleaned with alcohol before use, and thermosetting epoxy resin high-temperature-resistant release agent is uniformly sprayed on the surfaces of the inner mold and the outer mold.
6. The preparation method of the interface modified aramid fiber/epoxy resin composite material as claimed in claim 1, wherein the mass ratio of the aramid fiber woven cloth to the matrix material is 1.
7. The preparation method of the interface modified aramid fiber/epoxy resin composite material as claimed in claim 1, wherein in the sandwich structure, the base material has 2-5 layers, and the number of the aramid fiber woven fabric layers is 1 less than that of the base material layers.
8. The method for preparing the interface modified aramid fiber/epoxy resin composite material as claimed in any one of claims 1 or 7, wherein warp directions of the plurality of layers of the aramid fiber woven cloth in the sandwich structure are kept consistent.
9. The preparation method of the interface modified aramid fiber/epoxy resin composite material as claimed in claim 1, wherein the hot press curing is performed under the condition of applying 1-2MPa pressure at 120-165 ℃ and maintaining for 2h, and the post curing is performed under the condition of curing at 140-160 ℃ for 12-16h.
10. Use of the interface modified aramid fiber/epoxy resin composite material obtained by the preparation method according to any one of claims 1 to 9 in gas insulated metal enclosed switchgear.
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