CN107698738B - Preparation method of oxidation modified CB/CFDSF/AG-80 epoxy resin composite material - Google Patents

Abstract

The invention relates to a method for preparing oxidation modified CB/CFDSF/AG-80 epoxy resin composite material, which mainly comprises a first step of modifying Carbon Black (CB) by concentrated nitric acid, a second step of carrying out surface cleaning and surface modification treatment on carbon fiber double-layer spacer fabric (CFDSF) and a third step of pouring and thermosetting CFDSF by prepared modified CB/AG-80 epoxy resin system solution, wherein the preparation steps and specific process parameters thereof are adopted to prepare the concentrated nitric acid modified CB/CFDSF/AG-80 epoxy resin composite material which has good conductivity and thermodynamic property and small conductive material consumption, and the modified carbon black of the composite material is uniformly distributed in a matrix, has good conductivity stability, and can be widely applied to electronics, electrostatic protection and electrostatic protection, Electromagnetic shielding, microwave absorption, etc.

Description

Preparation method of oxidatively modified CB/CFDSF/AG-80 epoxy resin composites

technical field

The invention relates to the field of composite materials, in particular to an oxidatively modified CB/CFDSF (carbon fiber double-layer spacer fabric)/AG-80 epoxy resin composite material and a preparation method thereof.

Background technique

With the rapid development of the electronic technology industry, the demand for functional composite materials with good electrical conductivity is also increasing. Since the conductive composite material has the characteristics of light weight, no rust, good dimensional stability, and adjustable electrical conductivity in a wide range, it is also easy to be processed into various complex shapes and easy to be industrialized in large quantities. , electromagnetic shielding, microwave absorption and other fields are widely used. At present, the common conductive composite materials usually use polymers as the matrix, and add conductive materials such as carbon materials and metal fillers at the same time, and composite them by physical or chemical methods to obtain a multiphase composite with both certain electrical conductivity and good mechanical properties. Material.

Carbon-based materials mainly include carbon black (CB for short), graphite, carbon fiber (CF for short), carbon nanotubes (CNTs for short), etc., which are important components of conductive fillers in conductive composite materials. Because carbon-based material-filled polymer composites are easy to mold, not limited by molding size, and resistant to corrosion, they can be used in some specific environments, so they have been paid more and more attention in more and more fields.

CB is currently the most widely used and the largest amount of conductive fillers. It is not only low in price, but also has good electrical conductivity and low density. Therefore, conductive composite materials with CB particles as conductive fillers have excellent electrical conductivity and are widely used in various fields. At the same time, because of the high surface energy of CB particles and the active groups scattered on their surfaces, there is a large cohesive force between CBs, so the particles are easy to polymerize with each other, and it is difficult to disperse. Therefore, in general, it is usually necessary to uniformly disperse CB into the matrix in a fine state. Otherwise, the material properties will be degraded. Therefore, ensuring the uniform dispersion of CB in the matrix is the key to the excellent properties of conductive composites.

The modification of CB generally adopts dispersant modification, oxidant modification and graft modification. Dispersant modification, scholars use surfactants to improve the uniformity of CB. It is believed that the use of dispersants helps CB to be uniformly dispersed in solutions such as benzene cyclohexane and n-heptane, which can effectively improve the system. uniformity. CB can be stably dispersed in benzene solvent by using diisooctane sulfonate, and CB can also be uniformly dispersed in a certain system by using ionic surfactant. However, if some polymer solutions are added to the above system, The uniformity of CB will be greatly destroyed, resulting in sedimentation. Therefore, the application prospects of these dispersants in the coatings and ink industries are not large. There are many methods for oxidative modification of CB, which are mainly divided into gas phase method and liquid phase method. Modification methods such as method and plasma method, the gas phase method mainly uses some gases such as oxygen to modify the surface of CB, and then improves the active groups on the surface of its particles. In the reaction, reactive groups such as hydroxyl and carboxyl groups are introduced on the surface of the particles, so as to achieve the purpose of modification. Plasma is a physical oxidation method; graft modification mainly grafts some polymer chains stably on the surface of CB particles, and uses these polymer chains to generate repulsion in water, thereby ensuring the mutual distance between particles to ensure CB particles. uniformity. Some stable polymer chains are grafted on the surface of the CB particles, which is to convert the hydroxyl groups, carboxyl groups and hydrogen bonds on the CB particles into various active functional groups. These functional groups are easily compatible with the same active end group. reaction, thereby firmly binding the CB particles to the matrix.

At present, the research status of carbon black/epoxy resin composites at home and abroad is as follows:

The physical properties of conductive composites with CB as conductive fillers are related to many factors. The difference of CB type, content and matrix will greatly affect the distribution state of CB and the structural state of the matrix, and then affect the electrical conductivity, mechanical properties, thermal properties and so on of the composite material.

Chen Su et al. studied the electrical conductivity of polystyrene/CB composites in the article "Research on the Electrical Conductivity of PS/Carbon Black Composites. Plastic Industry". The experimental analysis shows that the volume resistivity of the polystyrene/CB system will show a nonlinear decrease when the CB content gradually increases, and the volume resistivity of the composite system when the CB content is between 20% and 30%. rate will drop significantly.

In "AC Impedance Analysis and EMI ShieldingEffectiveness of Conductive SBR Composites.Polymer Engineering and Science", Mohan raj G.T. et al. studied the composite materials with styrene-butadiene rubber as the matrix and CB as the conductive filler, and found that the electromagnetic shielding effect of the composite material increased with the CB filling. content and the thickness of the sample increased. When the frequency range is between 7.8GHz and 12.4GHz, if the filling amount of CB reaches 60% at this time, the shielding performance of the composite material can reach up to 67dB.

Das N.C. et al. prepared CB/CF/ethylene-vinyl acetate copolymer composites that take into account cost, mechanical properties and shielding properties in the study of "Electromagnetic Interference Shielding Effectiveness of Ethylene Vinyl Acetate Based Conductive Composites Containing Carbon Fillers. Journal of Applied Polymer Science". When the CB and CF contents are 30% and 20%, respectively, the shielding effectiveness can reach up to 40dB.

Liao Haisheng et al. studied the mechanical properties of the CB/PP composite system in "The Effect of CB Content and Mixing Time on the Properties of CB/PP Composites. Plastics Industry". The results show that with the gradual increase of CB content, the tensile strength curve of CB/PP system will increase first and then decrease, and the maximum tensile strength of the system is 23.71MPa. At the same time, the elongation at break of the CB/PP system showed a decreasing trend with the gradual increase of the CB content.

In the paper "Research on Conductivity and Toughening of Polymer/Carbon Black Composites", Jing Taoyan studied the effect of changes in CB content on the mechanical properties of HDPE/CB composite systems. Its research and analysis show that with the increase of CB content, the impact strength curve of the composite material will show a downward trend. When the CB content is 18%, its impact strength is only 8.5KJ/m ² .

Zhang Qiuju studied the electrical and mechanical properties of fiber reinforced modified epoxy system in the paper "Research on the Electrical and Mechanical Properties of Fiber Reinforced Modified Epoxy System", which involved the preparation of a carbon fiber/epoxy resin composite material. The carbon fiber is woven into a spacer fabric and then added to the AG-80 epoxy resin matrix as a reinforcement to form a composite material. Although the composite material improves its thermodynamic properties, its electrical conductivity and stability are still unsatisfactory.

Chinese patent application (201310413596.3) discloses a modified carbon fiber/epoxy resin composite material and a preparation method thereof. The preparation method includes the steps of first mixing graphene and liquid epoxy resin to obtain a first mixture, and in the first mixture A curing agent capable of cross-linking and curing the liquid epoxy resin is added to obtain a second mixture, and the carbon fiber and the second mixture are used as raw materials to make the liquid epoxy resin cross-linking and curing to form a modification integrated with the carbon fiber by a composite material molding process. The carbon fiber/epoxy resin composite material has simple process and high production efficiency, but its mechanical properties such as strength are insufficient.

It is easy to know from the above literature that the difference in the type and content of CB will greatly affect the properties of the composite matrix, and then have a great impact on the physical properties of the composite system. In order to make the composite material system have good electrical conductivity, the filling amount of CB is generally large, and a large amount of filling of CB will greatly affect the mechanical properties of the system. Therefore, in order to fully ensure the good electrical conductivity and thermodynamic properties of the composite material under the condition of maintaining a low filling amount, the conductive filler needs to be modified or the synergistic effect of multi-component conductive fillers on the composite material needs to be explored. The above-mentioned bottleneck problem in the current development of composite conductive materials has been solved.

SUMMARY OF THE INVENTION

In order to overcome the above technical problems, the present invention studies the method of improving the electrical properties, mechanical properties, thermal properties, etc. of the composite material system by modifying the conductive fillers and mixing the multi-component fillers, thereby providing a good The invention discloses an oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material with electrical conductivity, thermodynamic properties and a small amount of conductive material and a preparation method thereof. For this reason, the present invention provides the following technical solutions:

A preparation method of oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material, characterized in that the preparation method specifically comprises the following steps:

(1) The carbon black (CB) is modified with concentrated nitric acid, and 4-12 g of carbon black and 50-100 ml of concentrated nitric acid with a concentration of 65-70 wt% are poured into a beaker respectively, heated to 100-110 ° C and fully Stir for 2 to 3 hours, then dilute with distilled water and filter with suction. Carefully scrape the CB after suction filtration, put it into a beaker and pour a large amount of distilled water to continue diluting. After standing for an appropriate time, take the supernatant and pour it out and continue pumping. Filter, repeat the above operation several times, until the pH value of the supernatant is about 7, then place the filtered CB in an oven to dry, and grind it for 0.5 to 1 h after drying to obtain oxidatively modified carbon black O-CB;

(2) The carbon fiber double-layer spacer fabric (CFDSF) is treated, and the pre-woven and cut carbon fiber double-layer spacer fabric is subjected to surface cleaning and surface modification treatment. The specific process is: at room temperature, the cut carbon fiber double-layer spacer The layer spacer fabric is soaked in ultrasonic cleaning solution for 1-2h, washed for 30-50min, then taken out and dried at 95-110℃. The silane coupling agent KH550 solution whose mass percentage of ethanol is 1.5 to 3 wt % is placed at room temperature for 24 h to 36 h, so that the ethanol is completely volatilized, and is sealed for use;

(3) Prepare the modified CB/AG-80 epoxy resin system solution for pouring and thermal curing of CFDSF, mix AG-80 epoxy resin, hexahydrophthalic anhydride curing agent, 2,4,6-diamino The methyl phenol accelerator, acetone and anhydrous ethanol diluent are respectively placed in an oven at 38 to 45 ° C and preheated for 1 to 2 hours. Weigh 1.8 to 9.0 g of epoxy resin that accounts for 3 to 15 wt% of the epoxy resin and grind it to a sufficient extent. The modified carbon black treated in the step (1) is placed in an appropriate amount of acetone solution for ultrasonic treatment for 0.5 to 1 h, poured into epoxy resin according to the proportion, and stirred at 35 to 45 ° C for 3 to 5 hours, and stirred evenly , pour the curing agent, accelerator, and diluent in sequence, fully stir again, ultrasonically treat for 1-2 hours, and vacuumize for 1.5-2.5 hours, thereby obtaining the modified CB/AG-80 epoxy resin system solution; Subsequently, the carbon fiber double-layer spacer fabric treated in the step (2) is placed in the mold, an appropriate amount of methyl silicone oil is applied, and the above modified CB/AG-80 epoxy resin system solution is poured, and the entire mold is evacuated for 1 to 2 hours. , stand for 36-48h, then heat-cured under certain temperature and time conditions, and finally, treated at 180-190℃ for 1.5-3h and then cooled to obtain oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material .

Preferably, the concentration of the concentrated nitric acid in the step (1) is 68 wt %, and the heating and stirring are heated to 100° C. and fully stirred for 2.5 hours.

Preferably, the ultrasonic cleaning solution in the step (2) is a mixed solution of 10-30wt% absolute ethanol solution and 20-40wt% acetone solution by volume 1:1-1:1.5.

Preferably, in the step (3), the ratio of the AG-80 epoxy resin, the curing agent and the diluent is 45-50wt%:40-45wt%:5-15wt%, and the diluent contains no water. The volume ratio of ethanol and acetone is 1:1 to 1:1.5.

Preferably, it is characterized in that the thermal curing in the step (3) is performed according to the curing process of pure CB/CFDSF/AG-80 epoxy resin composite material at 80°C/1h→120°C/4h→160°C/4h Heat cured.

Preferably, in the step (2), the upper and lower layers of the carbon fiber double-layer spacer fabric are plain weave fabrics.

Preferably, the modified carbon black in the step (3) accounts for 12-15 wt % of the epoxy resin.

Beneficial technical effect obtained by the present invention:

1. The present invention uses concentrated nitric acid to modify carbon black, and selects and adopts carbon fiber double-layer spacer fabric as a matrix through its specific modification process and parameter design, so that modified carbon black and AG-80 epoxy resin are first in a certain state. The modified CB/AG-80 epoxy resin system solution is formed by mixing under the same process and parameter conditions, and finally the oxidized modified CB/AG-80 epoxy resin system solution is poured into the mold in which the carbon fiber double-layer spacer fabric is placed in advance. The oxidant-modified CB/CFDSF/AG-80 epoxy resin composite material, which has both good electrical conductivity and thermodynamic properties and less consumption of conductive materials, is prepared by a thermal curing process. The modified CB process of the present invention is adopted and the The carbon fiber double-layer spacer fabric is used as the matrix, and its carbon black can be evenly distributed in the matrix, thus ensuring the stability of its electrical conductivity;

2. The present invention adopts an ultrasonic cleaning process when cleaning the carbon fiber double-layer spacer fabric, and the cleaning solution adopts a mixed solution of 10-30wt% absolute ethanol solution and 20-40wt% acetone solution by volume 1:1-1:1.5 , which can quickly remove the oil stains, impurities, etc. adhered to the carbon fiber surface during the weaving or touching process, so as to be more conducive to its surface modification treatment;

3. the present invention is by performing linear regression analysis to the initial temperature, peak top temperature and peak valley temperature of pure CB/CFDSF/AG-80 system in the process of determining thermal curing, and obtains according to the linear regression analysis of different temperatures: The curing process of the system is determined as: 80℃/1h→120℃/4h→160℃/4h, and finally treated at 180～190℃ for 1.5～3h, which can improve the thermal curing efficiency without affecting the composite material characteristics.

Description of drawings

Fig. 1 is the preparation schematic diagram of O-CB/CFDSF/AG-80 composite material of the present invention;

Fig. 2a is the scanning electron microscope image of the river area of the impact section of the O-CB/CFDSF/AG-80 composite material of the present invention;

Fig. 2b is a scanning electron microscope image of the dimple area of the impact section of the O-CB/CFDSF/AG-80 composite material of the present invention;

Figure 3a is a dynamic analysis diagram of the storage modulus E' of the O-CB/CFDSF/AG-80 composite material of the present invention;

Figure 3b is a dynamic analysis diagram of the loss modulus E" of the O-CB/CFDSF/AG-80 composite material of the present invention;

Fig. 4a is the thermogravimetric TG curve diagram of O-CB/CFDSF/AG-80 composite material of the present invention;

Figure 4b is a DTG curve diagram of the O-CB/CFDSF/AG-80 composite material of the present invention;

Figure 5 shows the effect of the modified CB content of the present invention on the electrical properties of the modified CB/CFDSF/AG-80 composite.

Detailed ways

The technical solutions of the present invention are described in detail below through specific embodiments, which are only specific embodiments or preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention.

Example 1

For the modification treatment of carbon black (CB), the inventors of the present application have studied the modification treatment with a silane coupling agent and the modification treatment with an oxidizing agent. Preparation method of oxygen resin composite material;

A preparation method for preparing oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material, mainly comprising the following steps:

1. The carbon black (CB) is modified with concentrated nitric acid

The carbon black (CB) was modified with concentrated nitric acid. First, 4 g of carbon black and 50 ml of concentrated nitric acid with a concentration of 65 wt% were poured into a beaker, heated to 100 °C, fully stirred for 2 hours, and then diluted with distilled water and filtered with suction. , carefully scrape the CB after suction filtration, put it into a beaker and pour a large amount of distilled water to continue to dilute it. After standing for an appropriate time, take the supernatant and pour it out, continue to suction filtration, and repeat the above operations several times until the supernatant is The pH value is about 7, and then the filtered CB is placed in an oven to dry, and after drying, it is ground for 0.5h to obtain oxidatively modified carbon black O-CB;

2. Treatment of carbon fiber double spacer fabric (CFDSF)

The biggest feature of the woven spacer fabric is that a certain distance can be formed between two parallel plane fabrics. The present invention adopts a woven double-layer spacer fabric. As shown in Figure 1, the upper layer 1 and the lower layer 2 of the fabric are connected by binding yarns. 3 is connected, and the modified CB/AG-80 epoxy resin system solution is cast and cured into the spacer fabric to obtain the composite material of the present invention; in the present invention, since the specification of the mold 4 is 14cm×14.5cm, all CFDSF is required to be The size of fabric cutting is 14cm×14.5cm;

The pre-woven and cut carbon fiber double-layer spacer fabric is subjected to surface cleaning and surface modification treatment, that is, at room temperature, the cut carbon fiber double-layer spacer fabric is placed in an ultrasonic cleaning solution, soaked for 1 hour, washed for 30 minutes, and then taken out Dry at 95°C. After drying, coat a certain amount of water-soluble silane coupling agent KH550 solution containing 1.5wt% of absolute ethanol on the double-layer spacer fabric, and leave it at room temperature for 24h to evaporate the ethanol. Complete, sealed for use;

3. Prepare modified CB/AG-80 epoxy resin system solution for pouring and thermal curing of CFDSF

Preheat AG-80 epoxy resin, hexahydrophthalic anhydride curing agent, 2,4,6-diaminomethylphenol accelerator, acetone and absolute ethanol diluent, respectively, in a 38°C oven For 1 hour, weigh 1.8 g of modified carbon black that accounts for 3wt% of epoxy resin and fully grind the modified carbon black treated in step 1, put it in an appropriate amount of acetone solution and ultrasonically treat it for 0.5 hours, and pour it into epoxy resin according to the proportion. In the resin, stir at 35°C for 5 hours, stir evenly, pour the curing agent, accelerator and diluent in order, stir well again, ultrasonically treat for 1 hour, and vacuumize for 1.5 hours, thereby obtaining the modified CB/AG- 80 epoxy resin system solution; then place the carbon fiber double-layer spacer fabric treated in step 2 in the mold 4, apply an appropriate amount of methyl silicone oil, and pour the above modified CB/AG-80 epoxy resin system solution. The mold 4 was evacuated for 1 hour, left standing for 36 hours, and then thermally cured under a certain temperature and time condition. Finally, it was treated at 180 °C for 1.5 hours and then cooled to obtain an oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material.

Example 2

Modification treatment of carbon black (CB) The inventors of the present application have studied the modification treatment with a silane coupling agent and the modification treatment with an oxidant, and the present invention protects the use of oxidatively modified CB/CFDSF/AG-80 epoxy resin Preparation method of resin composite material;

A preparation method for preparing oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material, mainly comprising the following steps:

1. The carbon black (CB) is modified with concentrated nitric acid

The carbon black (CB) was modified with concentrated nitric acid, 8g of carbon black and 75ml of concentrated nitric acid with a concentration of 68wt% were poured into a beaker, heated to 100°C, fully stirred for 2.5h, then diluted with distilled water and filtered with suction , carefully scrape the CB after suction filtration, put it into a beaker and pour a large amount of distilled water to continue to dilute it. After standing for an appropriate time, take the supernatant and pour it out, continue to suction filtration, and repeat the above operations several times until the supernatant is The pH value is about 7, and then the filtered CB is placed in an oven for drying, and after drying, it is ground for 1 h to obtain oxidatively modified carbon black O-CB;

2. Treat carbon fiber double-layer spacer fabric (CFDSF);

The biggest feature of the woven spacer fabric is that a certain distance can be formed between two parallel plane fabrics. The present invention adopts a woven double-layer spacer fabric. As shown in Figure 1, the upper layer 1 and the lower layer 2 of the fabric are connected by binding yarns. 3 is connected, and the modified CB/AG-80 epoxy resin system solution is cast and cured into the spacer fabric to obtain the composite material of the present invention; in the present invention, since the specification of the mold 4 is 14cm×14.5cm, all CFDSF is required to be The size of fabric cutting is 14cm×14.5cm;

The pre-woven and cut carbon fiber double-layer spacer fabric is subjected to surface cleaning and surface modification treatment, that is, at room temperature, the cut carbon fiber double-layer spacer fabric is placed in an ultrasonic cleaning solution, soaked for 1.5h, and washed for 40min. The ultrasonic cleaning solution is a mixture of 10wt% absolute ethanol solution and 20wt% acetone solution by volume 1:1, then taken out and dried at 105°C. After drying, a certain amount of water-soluble containing The silane coupling agent KH550 solution whose mass percentage of absolute ethanol is 2wt% is placed at room temperature for 30h, so that the ethanol is completely volatilized, and it is sealed for use;

3. Prepare modified CB/AG-80 epoxy resin system solution for pouring and thermal curing of CFDSF

Preheat AG-80 epoxy resin, hexahydrophthalic anhydride curing agent, 2,4,6-diaminomethylphenol accelerator, acetone and absolute ethanol diluent, respectively, in an oven at 42°C After 1.5 hours, weigh 5.4 g of modified carbon black that accounts for 9wt% of epoxy resin and fully grind it after the treatment in step 1, put it in an appropriate amount of acetone solution and ultrasonically treat it for 1 hour, and pour it into epoxy resin according to the proportion. , stir at 40°C for 4h, stir evenly, pour the curing agent, accelerator and diluent in sequence, the ratio of the AG-80 epoxy resin, curing agent and diluent is 45wt%:40wt%:15wt %, the volume ratio of absolute ethanol and acetone in the diluent is 1:1, fully stirred again, ultrasonically treated for 1.5h, and vacuumed for 2h, thereby obtaining the modified CB/AG-80 epoxy resin system solution; Subsequently, the carbon fiber double-layer spacer fabric treated in the step 2 was placed in the mold 4, an appropriate amount of methyl silicone oil was applied, and the above-mentioned modified CB/AG-80 epoxy resin system solution was poured, and the entire mold 4 was evacuated for 1.5 hours. Let stand for 42h, then heat curing according to the curing process of pure CB/CFDSF/AG-80 epoxy resin composite material at 80℃/1h→120℃/4h→160℃/4h, and finally, treat at 185℃ for 2h After cooling, the oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material was obtained.

Example 3

Modification treatment of carbon black (CB) The inventors of the present application have studied the modification treatment with a silane coupling agent and the modification treatment with an oxidant, and the present invention protects the use of oxidatively modified CB/CFDSF/AG-80 epoxy resin Preparation method of resin composite material;

A preparation method for preparing oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material, mainly comprising the following steps:

1. The carbon black (CB) is modified with concentrated nitric acid

The carbon black (CB) was modified with concentrated nitric acid. 12 g of carbon black and 100 ml of concentrated nitric acid with a concentration of 70 wt% were poured into a beaker, heated to 110 ° C and fully stirred for 3 hours, and then diluted with distilled water and suction filtered. Carefully scrape off the CB after suction filtration, put it into a beaker and pour a large amount of distilled water to continue to dilute it. After standing for an appropriate time, take the supernatant and pour it out. Continue suction filtration and repeat the above operation several times until the supernatant is PH. The value is about 7, and then the filtered CB is placed in an oven to dry, and after drying, it is ground for 1 h to obtain oxidatively modified carbon black O-CB;

2. Treat carbon fiber double-layer spacer fabric (CFDSF);

The biggest feature of the woven spacer fabric is that a certain distance can be formed between two parallel plane fabrics. The present invention adopts a woven double-layer spacer fabric. As shown in Figure 1, the upper layer 1 and the lower layer 2 of the fabric are connected by binding yarns. 3 is connected, and the modified CB/AG-80 epoxy resin system solution is cast and cured into the spacer fabric to obtain the composite material of the present invention; in the present invention, since the specification of the mold 4 is 14cm×14.5cm, all CFDSF is required to be The size of fabric cutting is 14cm×14.5cm;

The pre-woven and cut carbon fiber double-layer spacer fabric is subjected to surface cleaning and surface modification treatment, that is, at room temperature, the cut carbon fiber double-layer spacer fabric is placed in an ultrasonic cleaning solution, soaked for 2 hours, and washed for 50 minutes. The cleaning solution is a mixture of 30wt% anhydrous ethanol solution and 40wt% acetone solution by volume 1:1.5, then take it out and dry it at 110°C. After drying, coat a certain amount of water-soluble containing no The silane coupling agent KH550 solution whose mass percentage of water ethanol is 3wt% is placed at room temperature for 36h, so that the ethanol is completely volatilized, and it is sealed for use;

3. Prepare modified CB/AG-80 epoxy resin system solution for pouring and thermal curing of CFDSF

Preheat AG-80 epoxy resin, hexahydrophthalic anhydride curing agent, 2,4,6-diaminomethylphenol accelerator, acetone and absolute ethanol diluent, respectively, in an oven at 45°C For 2 hours, weigh 9g of modified carbon black that accounts for 15wt% of the epoxy resin and fully grind the modified carbon black treated in the step 1, put it in an appropriate amount of acetone solution and ultrasonically treat it for 1h, and pour it into the epoxy resin according to the proportion. , stir at 45 ℃ for 3h, stir evenly, pour the curing agent, accelerator and diluent in order, the ratio of the AG-80 epoxy resin, curing agent and diluent is 50wt%:45wt%:5wt% , the volume ratio of absolute ethanol and acetone in the diluent is 1:1.5, fully stirred again, ultrasonically treated for 2h, and vacuumed for 2.5h, thereby obtaining the modified CB/AG-80 epoxy resin system solution; Place the carbon fiber double-layer spacer fabric treated in step 2 in the mold 4, apply an appropriate amount of methyl silicone oil, pour the above modified CB/AG-80 epoxy resin system solution, and vacuum the entire mold 4 for 2 hours, and let it stand. 48h, then heat-cured according to the curing process of pure CB/CFDSF/AG-80 epoxy resin composite material at 80℃/1h→120℃/4h→160℃/4h, and finally, treated at 190℃ for 3h and then cooled Oxidatively modified CB/CFDSF/AG-80 epoxy resin composites were obtained.

The carbon fiber double-layer spacer fabric used in step 2 in the above embodiment 1-3 is that the upper and lower layers are both plain weave fabrics. Of course, the fabric structure of the carbon fiber double-layer spacer fabric can also be twill, satin or other fabrics. Structured double-layer fabric.

The thermodynamic properties and electrical conductivity properties of the oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material prepared by the present invention are tested and studied below.

1. Research on impact section of oxidatively modified CB/CFDSF/AG-80 composites

Figures 2a and 2b are the SEM images of the river area and the dimple area on the impact section of the O-CB/CFDSF/AG-80 system when the O-CB content is 15%; The river region of the CFDSF/AG-80 system also has many white pullouts that prevent further crack propagation. It can be seen from Figure 2b that the impact section of the system is in the shape of fish scales, and there are many dimples, showing good toughening characteristics.

2. Dynamic mechanical properties of oxidatively modified CB/CFDSF/AG-80 modified CB/CFDSF/AG-80 composites

Dynamic mechanical analysis is a test method for testing the mechanical properties of polymers. The dynamic storage modulus E' and loss modulus E" of the composite material can be obtained through dynamic mechanical analysis. E' and E" can be used to characterize the stiffness of the material and the viscous component of the material, respectively. The mechanical internal friction of the material is generally tanδ It is expressed as the ratio of E" to E'.

Figures 3a and 3b are the E' dynamic analysis diagram and the E" dynamic analysis diagram of the O-CB/CFDSF/AG-80 composite, respectively. It can be seen from the figure that with the increase of temperature, E' and E" will rise first and then fall. And the E' of the O-CB/CFDSF/AG-80 system did not change much from room temperature to 100 °C. By comparing the two figures, it can be seen that when the O-CB content is 3%, the O-CB/CFDSF/AG-80 The storage modulus E' of the system is smaller, and its loss modulus E" is larger, indicating that the system has better toughness at this time. When the O-CB content is 15%, its loss modulus E" is the largest, indicating that its toughness is the most Well, the toughening effect of O-CB is obvious.

3. Thermodynamic test and analysis of oxidatively modified CB/CFDSF/AG-80 composites

The thermal properties of composite materials mainly refer to the corresponding response to ambient temperature during use, thereby showing different thermal properties, which is one of the important properties of composite materials. By analyzing the initial and maximum thermal decomposition temperature of the system, the composite material can be obtained. Stability of thermal properties. As shown in Figures 4a and 4b, which represent the thermal weight loss TG curve and DTG curve of the O-CB/CFDSF/AG-80 composite system with different contents of O-CB, respectively. On the whole, when the content of O-CB gradually increases, the initial thermal decomposition temperature of the O-CB/CFDSF/AG-80 system will gradually increase, and its maximum thermal decomposition temperature will fluctuate slightly. When the content is 15%, the initial and maximum thermal decomposition temperatures of the system are 258.75°C and 389.79°C, respectively. At this time, the heat resistance is the best, and the overall heat resistance of the composite material is good. Because inorganic substances are relatively heat-resistant, the thermal properties of the O-CB system will be improved after adding O-CB.

4. Test and analysis of electrical properties of oxidatively modified CB/CFDSF/AG-80 composites

Figure 5 shows the volume resistivity of the oxidized modified CB composite system O-CB/CFDSF/AG-80. It can be seen from the figure that the volume resistivity of epoxy resin matrix composites filled with CB has been decreasing. When the content of modified CB is small, its volume resistivity does not change significantly. With the increase of CB content, when it reaches a certain content range, its volume resistivity will decrease by a relatively large margin, forming a steep When the content of modified CB exceeds this range, the volume resistivity curve of the system gradually becomes flat. At the same time, it is found that when the CB content is small, its volume resistivity is the largest, which is about 39.7Ω·cm. This is because when the conductive electrode is on the side, it will directly contact the carbon fiber cloth. At this time, the main conductive network is composed of CF, while CB The formed conductive network will also play a synergistic role, so the change of CB content will also affect the volume resistivity of the composite material. Studies have shown that as the content of conductive filler increases to a certain critical content, the conductivity of the system will increase. At this time, this critical content is called the percolation threshold. When the CB content reaches the percolation threshold, the distance between most CBs is small enough, and electrons can transition between adjacent CBs to form interconnected CBs. Conductive network, resulting in a relatively large change in volume resistivity.

The above are the embodiments of the technical solutions of the present invention and the test results of the experiments. For those skilled in the art, changes, modifications, substitutions, integrations and processes can be made to these embodiments without departing from the principle and spirit of the present invention. The parameter changes all fall within the protection scope of the present invention.

Claims (7)

1. a preparation method of oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material, is characterized in that, this preparation method specifically comprises the following steps: (1) The carbon black (CB) is modified with concentrated nitric acid, and 4-12 g of carbon black and 50-100 ml of concentrated nitric acid with a concentration of 65-70 wt% are poured into a beaker respectively, heated to 100-110 ° C and fully Stir for 2 to 3 hours, then dilute with distilled water and filter with suction. Carefully scrape the CB after suction filtration, put it into a beaker and pour a large amount of distilled water to continue diluting. After standing for an appropriate time, take the supernatant and pour it out and continue pumping. Filter, repeat the above operation several times, until the pH value of the supernatant is about 7, then place the filtered CB in an oven to dry, and grind it for 0.5 to 1 h after drying to obtain oxidatively modified carbon black O-CB; (2) The carbon fiber double-layer spacer fabric (CFDSF) is treated, and the pre-woven and cut carbon fiber double-layer spacer fabric is subjected to surface cleaning and surface modification treatment. The specific process is: at room temperature, the cut carbon fiber double-layer spacer The layer spacer fabric is soaked in ultrasonic cleaning solution for 1-2h, washed for 30-50min, then taken out and dried at 95-110℃. The mass percentage of ethanol is 1.5-3wt% of silane coupling agent KH550 solution, placed at room temperature for 24h-36h, so that the ethanol is completely volatilized and sealed for use; the ultrasonic cleaning solution is 10-30wt% anhydrous ethanol solution and 20- 40wt% acetone solution by volume 1:1～1:1.5 mixed solution; (3) Prepare the modified CB/AG-80 epoxy resin system solution for pouring and thermal curing of CFDSF, mix AG-80 epoxy resin, hexahydrophthalic anhydride curing agent, 2,4,6-diamino The methyl phenol accelerator, acetone and anhydrous ethanol diluent are respectively placed in an oven at 38 to 45 ° C and preheated for 1 to 2 hours. The modified carbon black treated in the step (1) is placed in an appropriate amount of acetone solution for ultrasonic treatment for 0.5 to 1 h, poured into epoxy resin according to the proportion, and stirred at 35 to 45 ° C for 3 to 5 hours, and stirred evenly , pour the curing agent, accelerator, and diluent in sequence, fully stir again, ultrasonically treat for 1-2 hours, and vacuumize for 1.5-2.5 hours, thereby obtaining the modified CB/AG-80 epoxy resin system solution; Subsequently, the carbon fiber double-layer spacer fabric treated in the step (2) is placed in the mold, an appropriate amount of methyl silicone oil is applied, and the above modified CB/AG-80 epoxy resin system solution is poured, and the entire mold is evacuated for 1 to 2 hours. , stand for 36-48h, then heat-cured under certain temperature and time conditions, and finally, treated at 180-190℃ for 1.5-3h and then cooled to obtain oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material ; The impact section of the oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material has a white pullout in the river area that can prevent crack propagation, and the impact section under the scanning electron microscope is in the shape of fish scales. 2. the preparation method of oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material according to claim 1, is characterized in that, the concentration of described concentrated nitric acid in described step (1) is 68wt%, so The heating and stirring described above are heated to 100°C and fully stirred for 2.5h. 3. the preparation method of oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material according to claim 1 and 2, is characterized in that, in described step (3), described AG-80 epoxy resin The ratio of curing agent and diluent is 45-50wt%:40-45wt%:5-15wt%, and the volume ratio of absolute ethanol and acetone in the diluent is 1:1-1:1.5. 4. the preparation method of oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material according to claim 1 and 2, is characterized in that, the thermal curing in described step (3) is according to pure CB/CFDSF The curing process of /AG-80 epoxy resin composite material is thermally cured at 80℃/1h→120℃/4h→160℃/4h. 5. the preparation method of oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material according to claim 1 and 2, is characterized in that, in described step (2), described carbon fiber double-layer spacer fabric is The upper and lower layers are plain weave fabrics. 6. the preparation method of oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material according to claim 1 and 2, is characterized in that, described modified carbon black in described step (3) occupies ring 12 to 15 wt% of the oxygen resin. 7. the preparation method of oxidatively modified CB/CFDSF/AG-80 epoxy resin composite material according to claim 1 and 2, is characterized in that, in described step (2), described carbon fiber double-layer spacer fabric adopts Twill, satin weave structure.

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