CN107698739A - The preparation method of the silane coupler modified epoxy resin composite materials of CNTs/CFDSF/AG 80 - Google Patents

Abstract

The present invention relates to a kind of preparation method of silane coupling agent modified CNTs/CFDSF/AG-80 epoxy resin composite material, and this method mainly comprises adopting the mixed acid solution of concentrated nitric acid and concentrated sulfuric acid to carry out acidification to carbon nanotube (CNTs) The first step, the second step of modifying the O-CNTs obtained after the acidification treatment by a silane coupling agent, the third step of surface cleaning and surface modification of the carbon fiber double-layer spacer fabric (CFDSF) and the preparation of Modified CNTs/AG-80 epoxy resin system solution is the fourth step of pouring and thermosetting CFDSF. Through the above-mentioned preparation steps of the present invention and its specific process parameters, it has both good electrical conductivity and thermodynamic properties. A silane coupling agent modified CNTs/CFDSF/AG‑80 epoxy resin composite material with a small amount of conductive material. The modified carbon nanotubes are evenly distributed in the matrix. The composite material has good conductive stability and can be widely used In electronics, electrostatic protection, electromagnetic shielding, microwave absorption and other fields.

Description

Preparation of CNTs/CFDSF/AG-80 Epoxy Resin Composite Modified by Silane Coupling Agent method

technical field

The invention relates to the field of composite materials, in particular to a silane coupling agent modified CNTs/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 conductivity in a wide range, it is also easy to process into various complex shapes and easy to mass industrial production, so it is used in electrostatic protection. , electromagnetic shielding, microwave absorption and other fields are widely used. At present, the common conductive composite materials usually use polymer as the matrix, and at the same time add conductive substances such as carbon-based materials and metal fillers, and compound them by physical or chemical methods to obtain a multi-phase composite with certain electrical conductivity and good mechanical properties. Material.

Carbon-based materials mainly include carbon black (carbon black for short CB), graphite, carbon fiber (carbon fiber for short CF), carbon nanotubes (carbon nanotubes for short CNTs), etc., which are important components of conductive fillers in conductive composite materials. Because polymer composites filled with carbon-based materials are easy to shape, not limited by the size of the shape, and resistant to corrosion, they can be used in certain specific environments, so they are being valued in more and more fields.

As a one-dimensional nanomaterial, carbon nanotubes are light in weight and perfectly connected in a hexagonal structure. They are called "ultimate" fibers and have many abnormal mechanical, electrical and chemical properties. CNTs can be divided into There are two types of non-helical type and helical type. According to the difference in the number of layers composed of graphite sheets, CNTs are divided into two types: single-walled carbon nanotubes and multi-walled carbon nanotubes. The mechanical properties of CNTs are excellent, its strength is about a hundred times that of steel, and its density is only one-sixth that of steel, and the shear strength between CNTs layers is about 500MPa, which is much higher than most CF reinforced composite materials; Regarding electrical conductivity, CNTs can not only have the excellent electrical conductivity of metal materials, but also fully demonstrate the electrical characteristics of semiconductors, and exhibit superconducting properties at lower temperatures, and the critical superconducting current of CNTs is relatively large; about thermal Performance, the thermal performance of CNTs is not only related to the graphite sheets that make it up, but also related to its unique structure and size. CNTs and graphite have the same composition, and they are excellent heat conductors. The speed can reach 1000m/s.

Although CNTs have specific mechanical, electrical and chemical properties, and have great application value, there are still many key technologies to be overcome in order to truly realize the maximum value of CNTs. The first thing to bear the brunt is the dispersion characteristics of CNTs. Therefore, it is necessary to modify CNTs. At present, the modification methods of CNTs mainly include physical modification and chemical modification. The physical modification method is mainly to change the surface active groups of CNTs through physical effects such as adsorption, coating and coating, so as to improve their binding with the matrix. The typical ones are polymer encapsulation and surfactant modification. method, the C atoms of CNTs are hybridized by SP ² to form highly delocalized π electrons, which can be combined with different polymers that also contain π electrons through π-π non-covalent bonds to obtain some specific functions CNTs; the chemical modification method mainly uses grafting, oxidation and other means to directly introduce small molecular compounds or active functional groups (such as -COOH, OH and -NH ₂ ) on the side wall of CNTs to improve its activity, thereby increasing its Dispersibility and compatibility in solutions and polymers.

At present, the research status of carbon nanotube/epoxy resin composite materials at home and abroad is as follows:

In "Influence of different carbon nanotubes on the mechanical properties of epoxy matrix composites-A comparative study. Composites Science and Technology", Florian et al. explored the effect of the content of CNTs on the electrical conductivity and heat transfer properties of epoxy-based composites. Experimental analysis shows that when the system reaches the percolation threshold, the required content of CNTs is far less than that of CB, and the electrical conductivity of the composite will increase with the increase of CNTs content.

Via Michael D. et al. studied the addition of CNTs, CB and GNP to the polycarbonate matrix in "Electrical conductivity modeling of carbonblack/polycarbonate, carbon nanotube/polycarbonate, and exfoliated Graphitenanoplatelet/polycarbonate composites. Journal of Applied Polymer Science". Different types of conductive fillers were studied, and the conductive properties of the corresponding composite materials were deeply explored. The research found that the threshold value of CNTs is 1.2vol%, and the research results show that the conductivity of the composite material is the best when adding CNTs to PC.

Wei Xiaoxin studied the effect of the content of modified CNTs on the mechanical properties of epoxy-based composites in the paper "Study on the Mechanical Properties of Surface-Modified Carbon Nanotubes/Epoxy Resin Composite Materials". The results show that the dispersibility of modified CNTs is better than that of unmodified CNTs. At the same time, with the gradual increase of CNTs content, the mechanical properties of CNTs/epoxy resin composites increase first and then decrease, and the maximum tensile strength It is 67.3MPa, which fully shows that the modified CNTs can improve the performance of the matrix material.

Zeng Qin explored the effect of the content of CNTs on the thermal properties of epoxy resin in the paper "Preparation and Properties of Carbon Nanotube/Epoxy Resin Composite Materials". The research results show that with the increase of CNTs content, the curing reaction of the composite material can be effectively promoted, and its thermal properties can also be effectively improved, indicating that CNTs have good heat resistance.

Zhang Qiuju studied the electrical and mechanical properties of fiber-reinforced modified epoxy systems in the paper "Research on Electrical and Mechanical Properties of Fiber-Reinforced Modified Epoxy Systems", which involved the preparation of a carbon fiber/epoxy resin composite material. The carbon fiber is woven into a spacer fabric and added as a reinforcement to the AG-80 epoxy resin matrix to form a composite material. Although the composite material has improved its thermodynamic properties, its electrical conductivity and stability are still not satisfied.

Chinese patent application (201010221872.2) discloses a preparation method of multi-walled carbon nanotubes (MWNTs) hybrid CF/EP laminate composite material, the preparation method of the composite material includes ultrasonic treatment of MWNTs dispersant to obtain uniformly dispersed MWNTs Dispersion liquid, and then spray the MWNTs dispersion liquid evenly on the carbon fiber fabric with a sprayer, and then heat-press it with epoxy resin after drying. This application enters MWNTs in the CF/EP composite material to improve the surface properties of the carbon fiber fabric The mechanical properties of the composite material are improved, but the electrical conductivity of the material is insufficient.

From the above studies, it can be seen that the content of CNTs and the modification method are different, and the influence on the performance of the composite material system will also be very different. Although the addition of CNTs can effectively improve the electrical conductivity of the composite material system, as the content of CNTs increases to a certain range, its mechanical properties will show a downward trend instead, and the overall mechanical properties are not excellent, so it is necessary to conduct conductive fillers. Modification treatment may need to explore the synergistic effect of multi-component conductive fillers on composite materials, which has solved the above-mentioned bottleneck problem in the current development of composite conductive materials.

Contents 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. A silane coupling agent-modified CNTs/CFDSF/AG-80 epoxy resin composite material with conductive properties and thermodynamic properties and a small amount of conductive material is used, and a preparation method thereof. For this reason the present invention provides following technical scheme:

A kind of preparation method of silane coupling agent modified CNTs/CFDSF/AG-80 epoxy resin composite material, it is characterized in that, this preparation method specifically comprises the following steps:

(1) Acidify CNTs with a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid, place 2 to 5 g of CNTs in a mixed acid solution of 250 to 500 ml of concentrated nitric acid and concentrated sulfuric acid, wherein the volume ratio of concentrated nitric acid to concentrated sulfuric acid is 3: 1～4:1, after ultrasonic treatment at room temperature for 3～4 hours, add distilled water to the mixed solution for dilution, filter with filter membrane, continue to add appropriate amount of distilled water to dilute after filtration, let it stand, take the supernatant and pour it out, filter with suction, repeat The above operations were performed several times until the pH value of the supernatant was about 7, and the filter membrane was filtered to remove CNTs, placed in an oven to dry, and then ground for 0.5 to 1 hour to obtain acidified carbon nanotube O-CNTs;

(2) Preparation of silane coupling agent-modified CNTs, weigh a certain amount of fully ground O-CNTs obtained in step (1), add appropriate amount of KH550 and DCC, ultrasonically treat for 2 to 3 hours to mix evenly, and stir for 4 ～6h to make it fully react, wash the mixed solution obtained by the reaction with an appropriate amount of absolute ethanol to remove unreacted KH550 and DCC, filter, dry, and grind for 0.5～1h to obtain silane coupling agent-modified carbon nanotubes Si-CNTs;

(3) Treat the carbon fiber double-layer spacer fabric (CFDSF), and perform surface cleaning and surface modification treatment on the pre-woven and cut carbon fiber double-layer spacer fabric. The specific process is: at room temperature, the cut carbon fiber double-layer The interlayer spacer fabric is soaked in ultrasonic cleaning solution for 1 to 2 hours, washed for 30 to 50 minutes, then taken out and dried at 95 to 110°C. After drying, a certain amount of water-soluble water-containing anhydrous The mass percentage of ethanol is 1.5-3wt% silane coupling agent KH550 solution, placed at room temperature for 24h-36h, so that the ethanol is completely volatilized, and sealed for use;

(4) Prepare the modified CNTs/AG-80 epoxy resin system solution to pour and heat-cure CFDSF. AG-80 epoxy resin, hexahydrophthalic anhydride curing agent, 2,4,6-diamino The methyl phenol accelerator, acetone and absolute ethanol diluent are respectively placed in an oven at 38-45°C for 1-2 hours, and 0.3-2.7g of epoxy resin 0.5-4.5wt% is weighed and fully ground After the modified carbon nanotube Si-CNTs processed by the step (2), place it in an appropriate amount of acetone solution and ultrasonically treat it for 0.5 to 1 hour, then pour it into the epoxy resin according to the proportion, and stir it at 35 to 45 ° C for 4 ~6h later, after ultrasonic treatment for 2~3h, vacuumize at 80~90°C for 2~3h, then pour in the curing agent, accelerator and diluent in sequence, and fully stir the mixed solution at 40~50°C for 0.5~1h , evacuated at 65-75°C for 0.5-1h to obtain a modified CNTs/AG-80 epoxy resin system solution; then place the carbon fiber double-layer spacer fabric treated in step (3) in the mold, and coat an appropriate amount of methyl Silicone oil, after pouring the above-mentioned modified CNTs/AG-80 epoxy resin system solution, vacuumize the whole mold for 1-2 hours, let it stand for 36-48 hours, then heat-cure at a certain temperature and time, and obtain a silane coupling agent after cooling Modified CNTs/CFDSF/AG-80 epoxy resin composites.

Preferably, in the step (2), weigh 1 to 3 g of the fully ground O-CNTs obtained in the step (1), and add an appropriate amount of 500 to 1000 ml of KH550 with a mass fraction of 3wt% to 5wt% and 0.2 to 0.3 g of DCC, ultrasonically treated for 2 to 3 hours to make it evenly mixed, and stirred for 4 to 6 hours to make it fully react.

Preferably, the ultrasonic cleaning solution in the step (3) is a mixed solution of 10-30 wt% absolute ethanol solution and 20-40 wt% acetone solution in a volume ratio of 1:1-1:1.5.

Preferably, in the step (4), the ratio of the AG-80 epoxy resin, curing agent, and diluent is 45-50wt%: 40-45wt%: 5-15wt%, and there is no water in the diluent The volume ratio of ethanol and acetone is 1:1～1:1.5.

Preferably, the thermal curing in step (4) is carried out according to the curing process of pure CNTs/CFDSF/AG-80 composite material 80°C/0.5h→110°C/0.5h→120°C/4h→150°C/4h heat cure.

Preferably, in the step (3), the carbon fiber double-layer spacer fabric is a plain weave fabric for the upper and lower layers.

Preferably, the modified carbon nanotubes in the step (4) account for 2.5-4.5 wt% of the epoxy resin.

Beneficial technical effect that the present invention obtains:

1. The present invention adopts silane coupling agent to modify carbon nanotubes. Through its specific modification process and parameter design and selection of carbon fiber double-layer spacer fabric as the matrix, the modified carbon nanotubes are first combined with the AG-80 ring Oxygen resin is mixed under certain process and parameter conditions to form a modified CNTs/AG-80 epoxy resin system solution, and finally the modified CNTs/AG-80 epoxy resin system solution is poured into a pre-placed carbon fiber double-layer spacer fabric The silane coupling agent modified CNTs/CFDSF/AG-80 epoxy resin composite material with good electrical conductivity and thermodynamic properties and less consumption of conductive materials has been prepared by thermal curing process in the mold of the present invention. Modified CNTs technology and carbon fiber double-layer spacer fabric as the matrix, the carbon nanotubes can be evenly distributed in the matrix, thus ensuring the stability of its conductivity;

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

3. The present invention is by doing linear regression analysis to the initial temperature, peak top temperature and peak valley temperature of pure CNTs/CFDSF/AG-80 system in the process of determining thermal curing, and obtains according to the linear regression analysis of different temperatures: final The curing process of this system is determined as: 80℃/0.5h→110℃/0.5h→120℃/4h→150℃/4h for thermal curing, which will not affect the properties of the composite material while improving the thermal curing efficiency.

Description of drawings

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

Figure 2a is a scanning electron micrograph of the dimple area of the impact section of the Si-CNTs/CFDSF/AG-80 composite material of the present invention;

Figure 2b is a scanning electron microscope image of the river area of the impact section of the Si-CNTs/CFDSF/AG-80 composite material of the present invention;

Fig. 3 a is the dynamic analysis diagram of storage modulus E ' of Si-CNTs/CFDSF/AG-80 composite material of the present invention;

Fig. 3 b is the dynamic analysis figure of Si-CNTs/CFDSF/AG-80 composite loss modulus E of the present invention ";

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

Fig. 4b is the DTG curve diagram of Si-CNTs/CFDSF/AG-80 composite material of the present invention;

Fig. 5 shows the influence of the modified CNTs content of the present invention on the electrical properties of the modified CNTs/CFDSF/AG-80 composite material.

detailed description

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

Example 1

For the modification of carbon nanotubes (CNTs), the inventors of the present application have studied the use of silane coupling agents for modification and only acidification for modification. The present invention protects the use of silane coupling agents to modify CNTs/CFDSF /AG-80 preparation method of epoxy resin composite material;

A preparation method for preparing silane coupling agent modified CNTs/CFDSF/AG-80 epoxy resin composite material, mainly comprising the following steps:

1. Modification of carbon nanotubes (CNTs) with silane coupling agent

1.1) The carbon nanotubes (CNTs) are modified with a silane coupling agent, and first acidified:

The CNTs were acidified with a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid, and 2g of CNTs was placed in 250ml of a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid, wherein the volume ratio of concentrated nitric acid to concentrated sulfuric acid was 3:1. After ultrasonic treatment at room temperature for 3 hours Add distilled water to the mixed solution to dilute, filter with filter membrane, continue to add appropriate amount of distilled water to dilute after filtering, let it stand, take the supernatant, pour it out, filter with suction, repeat the above operation several times, until the pH value of the supernatant is 7 Left and right, filter the CNTs out of the filter membrane, place them in an oven to dry, and then grind them for 0.5 hours to obtain acidified carbon nanotube O-CNTs;

1.2) Preparation of silane coupling agent modified CNTs

Weigh a certain amount of fully ground O-CNTs obtained in step 1.1), add an appropriate amount of KH550 and DCC, ultrasonically treat for 2 hours to mix evenly, stir for 4 hours to fully react, and mix the resulting mixed solution with an appropriate amount of anhydrous Washing with ethanol to remove unreacted KH550 and DCC, filter, dry, and grind for 0.5h to obtain carbon nanotube Si-CNTs modified by silane coupling agent;

2. Treatment of Carbon Fiber Double Spacer Fabric (CFDSF)

The biggest feature of the woven spacer fabric is that it can form a certain distance between two parallel plane fabrics. The present invention adopts a woven double-layer spacer fabric, and the upper layer 1 and the lower layer 2 of the fabric are passed through the binding yarn 3 connection, casting and solidifying the modified CNTs/AG-80 epoxy resin system solution into the spacer fabric to obtain the composite material of the present invention; in the present invention, since the mold 1 is adopted with a specification of 14cm×14.5cm, all CFDSF 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 soaked in ultrasonic cleaning solution for 1 hour, washed for 30 minutes, and then taken out Dry at 95°C. After drying, apply a certain amount of silane coupling agent KH550 solution containing absolute ethanol with a mass percentage of 1.5 wt% dissolved in water on the double-layer spacer fabric, and place it at room temperature for 24 hours to allow the ethanol to volatilize complete, sealed for use;

3. Prepare the modified CNTs/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 38°C For 1 hour, weigh 0.3g of Si-CNTs that accounted for 0.5wt% of epoxy resin and grind them sufficiently after treatment and modification in step 1.2), put them in an appropriate amount of acetone solution and ultrasonically treat them for 0.5h, then pour them into the ring according to the proportion In oxygen resin, after stirring at 35°C for 6h, ultrasonic treatment for 2h, vacuuming at 80°C for 2h, then pouring the curing agent, accelerator and diluent in sequence, fully stirring the mixed solution at 40°C for 0.5h, 65 Vacuum at ℃ for 0.5h to obtain a modified CNTs/AG-80 epoxy resin system solution; then place the carbon fiber double-layer spacer fabric treated in step 2 in the mold, apply an appropriate amount of methyl silicone oil, and pour the above-mentioned modified CNTs After /AG-80 epoxy resin system solution, vacuum the whole mold for 1h, let it stand for 36h, then heat-cure under certain temperature and time conditions, and obtain silane coupling agent modified CNTs/CFDSF/AG-80 epoxy after cooling Resin composites.

Example 2

For the modification of carbon nanotubes (CNTs), the inventors of the present application have studied the use of silane coupling agents for modification and only acidification for modification. The present invention protects the use of silane coupling agents to modify CNTs/CFDSF /AG-80 preparation method of epoxy resin composite material;

A preparation method for preparing silane coupling agent modified CNTs/CFDSF/AG-80 epoxy resin composite material, mainly comprising the following steps:

1. Modification of carbon nanotubes (CNTs) with silane coupling agent

1.1) The carbon nanotubes (CNTs) are modified with a silane coupling agent, and first acidified:

The CNTs were acidified with a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid, and 3.5g of CNTs were placed in 375ml of a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid, wherein the volume ratio of concentrated nitric acid to concentrated sulfuric acid was 3:1, and ultrasonic treatment at room temperature was performed for 3.5 After h, add distilled water to the mixed solution for dilution, filter with filter membrane, continue to add appropriate amount of distilled water to dilute after filtration, let it stand, take the supernatant and pour it out, filter with suction, repeat the above operation several times, until the pH value of the supernatant is about 7, filter the CNTs out of the filter membrane, place it in an oven to dry, and grind for 1 hour to obtain acidified carbon nanotube O-CNTs;

1.2) Preparation of silane coupling agent modified CNTs

Weigh 1g of the fully ground O-CNTs obtained in step 1.1), add 500ml of KH550 with a mass fraction of 3wt% and 0.2g of dicyclohexylcarbodiimide (DCC), sonicate for 3h to mix evenly, and stir for 5h Make it fully react, wash the mixed solution obtained by the reaction with an appropriate amount of absolute ethanol, so as to remove unreacted KH550 and DCC, filter, dry, and grind for 1 hour, thereby obtaining carbon nanotube Si-CNTs modified by a silane coupling agent;

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

The biggest feature of the woven spacer fabric is that it can form a certain distance between two parallel plane fabrics. The present invention adopts a woven double-layer spacer fabric, and the upper layer 1 and the lower layer 2 of the fabric are passed through the binding yarn 3 connection, casting and solidifying the modified CNTs/AG-80 epoxy resin system solution into the spacer fabric to obtain the composite material of the present invention; in the present invention, since the mold 1 is adopted with a specification of 14cm×14.5cm, all CFDSF 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 soaked in an ultrasonic cleaning solution for 1.5 hours and then washed for 40 minutes. The ultrasonic cleaning solution is a 1:1 mixed solution of 10wt% absolute ethanol solution and 20wt% acetone solution by volume, then take it out and dry it at 105°C, and coat a certain amount of water-soluble The mass percent of absolute ethanol is 2wt% silane coupling agent KH550 solution, placed at room temperature for 30h, so that the ethanol is completely volatilized, and sealed for use;

3. Prepare the modified CNTs/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 1.5 hours, weigh 1.5g accounted for 2.5wt% of epoxy resin and grind fully the modified carbon nanotubes treated by the step 1.2), put it in an appropriate amount of acetone solution and ultrasonically treat it for 1h, then pour it into In the epoxy resin, after stirring at 40°C for 5h, ultrasonic treatment for 2.5h, vacuuming at 85°C for 2.5h, then sequentially pour the curing agent, accelerator, diluent, the AG-80 epoxy resin, curing The ratio of solvent and diluent is 45wt%: 40wt%: 15wt%. The volume ratio of absolute ethanol and acetone in the diluent is 1:1, then the mixed solution is fully stirred at 45°C for 1h, and then vacuumized at 70°C for 1h , to obtain the modified CNTs/AG-80 epoxy resin system solution; then place the carbon fiber double-layer spacer fabric after the step 2 treatment in the mold, coat an appropriate amount of methyl silicone oil, and cast the above-mentioned modified CNTs/AG-80 ring Vacuum the entire mold for 1.5h after the oxygen resin system solution, let it stand for 42h, and then follow the curing process of pure CNTs/CFDSF/AG-80 composite material 80℃/0.5h→110℃/0.5h→120℃/4h→150 ℃/4h for thermal curing, and the silane coupling agent modified CNTs/CFDSF/AG-80 epoxy resin composite material was obtained after cooling.

Example 3

For the modification of carbon nanotubes (CNTs), the inventors of the present application have studied the use of silane coupling agents for modification and only acidification for modification. The present invention protects the use of silane coupling agents to modify CNTs/CFDSF /AG-80 preparation method of epoxy resin composite material;

A preparation method for preparing silane coupling agent modified CNTs/CFDSF/AG-80 epoxy resin composite material, mainly comprising the following steps:

1. Modification of carbon nanotubes (CNTs) with silane coupling agent

1.1) The carbon nanotubes (CNTs) are modified with a silane coupling agent, and first acidified:

The CNTs were acidified with a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid, and 5 g of CNTs were placed in 500 ml of a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid, wherein the volume ratio of concentrated nitric acid to concentrated sulfuric acid was 4:1. After ultrasonic treatment at room temperature for 4 hours Add distilled water to the mixed solution to dilute, filter with filter membrane, continue to add appropriate amount of distilled water to dilute after filtering, let it stand, take the supernatant, pour it out, filter with suction, repeat the above operation several times, until the pH value of the supernatant is 7 Left and right, filter the CNTs out of the filter membrane, put them in an oven to dry, and then grind them for 1 hour to obtain acidified carbon nanotube O-CNTs;

1.2) Preparation of silane coupling agent modified CNTs

Weigh 2g of the fully ground O-CNTs obtained in step 1.1), add 750ml of KH550 with a mass fraction of 4wt% and 0.25g of dicyclohexylcarbodiimide (DCC), sonicate for 2.5h to mix evenly, and stir 6h to make it fully react, wash the mixed solution obtained by the reaction with an appropriate amount of absolute ethanol to remove unreacted KH550 and DCC, filter, dry, and grind for 1h to obtain carbon nanotube Si-CNTs modified by silane coupling agent ;

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

The biggest feature of the woven spacer fabric is that it can form a certain distance between two parallel plane fabrics. The present invention adopts a woven double-layer spacer fabric, and the upper layer 1 and the lower layer 2 of the fabric are passed through the binding yarn 3 connection, casting and solidifying the modified CNTs/AG-80 epoxy resin system solution into the spacer fabric to obtain the composite material of the present invention; in the present invention, since the mold 1 is adopted with a specification of 14cm×14.5cm, all CFDSF 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 soaked in an ultrasonic cleaning solution for 1.5 hours and then washed for 40 minutes. The ultrasonic cleaning solution is a 1:1 mixed solution of 10wt% absolute ethanol solution and 20wt% acetone solution by volume, then take it out and dry it at 105°C, and coat a certain amount of water-soluble The mass percent of absolute ethanol is 2wt% silane coupling agent KH550 solution, placed at room temperature for 30h, so that the ethanol is completely volatilized, and sealed for use;

3. Prepare the modified CNTs/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 2.7g of modified carbon nanotubes that account for 4.5wt% of epoxy resin and grind them sufficiently after the treatment in step 1.2), place them in an appropriate amount of acetone solution for ultrasonic treatment for 1 hour, and then pour In the epoxy resin, after stirring at 45°C for 4h, ultrasonic treatment for 3h and vacuuming at 90°C for 3h, then pour the curing agent, accelerator, diluent, the AG-80 epoxy resin, curing agent, The ratio of the diluent is 50wt%: 45wt%: 5wt%, the volume ratio of absolute ethanol and acetone in the diluent is 1:1.5, then the mixed solution is fully stirred at 50°C for 1h, and vacuumized at 75°C for 1h to obtain Modified CNTs/AG-80 epoxy resin system solution; then place the carbon fiber double-layer spacer fabric after the step 2 treatment in the mold, coat an appropriate amount of methyl silicone oil, and pour the above-mentioned modified CNTs/AG-80 epoxy resin After the system solution, vacuumize the whole mold for 2h, let it stand for 48h, and then follow the curing process of pure CNTs/CFDSF/AG-80 composite material 80℃/0.5h→110℃/0.5h→120℃/4h→150℃/4h Carry out thermal curing, and obtain the silane coupling agent modified CNTs/CFDSF/AG-80 epoxy resin composite material after cooling.

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

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

1. Study on impact section of CNTs/CFDSF/AG-80 composite modified by silane coupling agent

Figures 2a and 2b are the scanning electron micrographs of Si-CNTs/CFDSF/AG-80 composite impact section dimple area and impact section river area when the Si-CNTs content is 2.5%, respectively; from Figure 2a we can see that Si- The dimple area of the CNTs/CFDSF/AG-80 system is concave-convex like fish scales, and the number of dimples per unit area is more. From Figure 2b, it can be seen that the river pattern of the cross-section of the composite material of this system is relatively fine and dense, and the long diameter is relatively large, and white protrusions that can prevent crack propagation can be seen, all of which illustrate the enhancement of Si-CNTs to the composite material system. Toughness.

2. Study on the dynamic mechanical properties of CNTs/CFDSF/AG-80 modified CNTs/CFDSF/AG-80 composites modified by silane coupling agent

Dynamic mechanical analysis is a test method for testing the mechanical properties of polymers. Through dynamic mechanical analysis, the dynamic storage modulus E' and loss modulus E" of the composite material can be obtained. 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 expressed by tanδ To express, that is, the ratio of E" to E'.

Figure 3a and 3b are the dynamic analysis diagrams of the storage modulus E' and the loss modulus E" of the Si-CNTs/CFDSF/AG-80 composite material system respectively. It can be seen from the figure that with the gradual increase of temperature, Si -The storage modulus E' of the CNTs/CFDSF/AG-80 system will gradually decrease, and the decrease is not obvious from room temperature to 100 °C, while the loss modulus E" will first increase and then decrease. When the Si-CNTs content is 4.5%, the storage modulus E' of the Si-CNTs/CFDSF/AG-80 system is small, indicating that its rigidity is small, and its loss modulus E" is large, indicating that its toughness is good ; and when the content of Si-CNTs is 2.5%, its loss modulus E" is the largest, indicating that the toughness of the system is better, which shows that the silane coupling agent modified CNTs has a certain toughening effect on epoxy resin.

3. Thermodynamic analysis of CNTs/CFDSF/AG-80 composite modified by silane coupling agent

The thermal properties of composite materials mainly refer to the corresponding response to the ambient temperature during use, thus showing different thermal properties, which is one of the important properties of composite materials. The composite materials are obtained by analyzing the initial and maximum thermal decomposition temperatures of the system. Stability of thermal properties. As shown in Figures 4a and 4b, they are the thermogravimetric TG curve and DTG curve of the Si-CNTs/CFDSF/AG-80 system, respectively. In general, with the increase of Si-CNTs content, the initial and maximum thermal decomposition temperatures of the Si-CNTs/CFDSF/AG-80 system have a tendency to gradually increase, and the overall heat resistance effect is good. Since inorganic substances are relatively heat-resistant, their heat resistance will be improved after adding Si-CNTs.

4. Test and analysis of electrical properties of silane coupling agent modified CNTs/CFDSF/AG-80 composites

Figure 5 shows the volume resistivity of the silane coupling agent modified CNTs composite material Si-CNTs/CFDSF/AG-80 system. It can be seen from the curve in the figure that when the content of modified CNTs increases continuously, the volume of the CNTs is filled. The volume resistivity of the epoxy resin-based system will continue to decrease. When the CNTs content is relatively small, the volume resistivity is high. At this time, because the CNTs are dispersed, the CNTs cannot form a connection, and it is difficult for the electrons to be in the adjacent area. The interparticle movement has a weaker synergistic effect on the CF conductive network. With the further increase of modified CNTs content, a sudden change will appear in the resistivity-CNTs content curve of the composite material, and the volume resistivity will drop significantly at this time, indicating that the CNTs content has reached the percolation threshold. At this time, the distance between most of the CNTs is small enough or they are already in contact with each other, thus forming a conductive network of CNTs, and the synergistic effect on the conductive network of CF is strengthened, so that the volume resistivity of the composite material changes abruptly. With the further increase of the modified CNTs content, the change of the resistivity of the composite tends to be flat after the percolation threshold is exceeded, indicating that the conductive path has been formed, and the modified CNTs have been in contact or electrons can move freely to form a conductive network. , it is difficult to have a large change in the resistivity at this time.

The above are the embodiments of the technical solution of the present invention and the test results. For those skilled in the art, these embodiments can be changed, modified, replaced, integrated and processed without departing from the principle and spirit of the present invention. All parameter changes fall within the protection scope of the present invention.

Claims (7)

1. a kind of preparation method of silane coupler modified CNTs/CFDSF/AG-80 epoxy resin composite materials, its feature exist In the preparation method specifically includes following steps：

(1) CNTs is acidified using the mixed acid solution of concentrated nitric acid and the concentrated sulfuric acid, 2~5g CNTs is placed in 250~500ml Concentrated nitric acid and the concentrated sulfuric acid mixed acid solution in, wherein the volume ratio of concentrated nitric acid and the concentrated sulfuric acid be 3:1~4:1, room temperature ultrasound at Distilled water is added in mixed solution to be diluted, filtered with filter membrane, it is dilute that appropriate distilled water is continuously added after filtering after 3~4h of reason Release, stand, take supernatant liquor to outwell, filter, repeat operation above for several times, until supernatant liquor pH value is 7 or so, by filter membrane mistake CNTs is filtered out, 0.5~1h, the CNT O-CNTs being acidified are ground after placing oven drying；

(2) silane coupler modified CNTs preparation, the sufficient O-CNTs of grinding that a certain amount of step (1) obtains is weighed, is added Enter appropriate KH550 and DCC, being ultrasonically treated makes it well mixed for 2~3 hours, and 4~6h of stirring makes it fully react, and will react The appropriate washes of absolute alcohol of the mixed solution arrived, to remove unreacted KH550 and DCC, filtering, dry, grinding 0.5~ 1h, so as to obtain silane coupler modified CNT Si-CNTs；

(3) carbon fiber double-layer partition fabric (CFDSF) is handled, the carbon fiber double-layer partition that will in advance weave, cut Fabric carries out surface clean and surface modification treatment, concrete technology are：At room temperature, the carbon fiber double-layer partition cut is knitted Thing, which is placed in ultrasonic cleaning solution, to carry out washing 30~50min after 1~2h of immersion, then takes out and is done under the conditions of 95~110 DEG C It is dry, coated after drying on double-layer partition fabric a certain amount of mass percent containing absolute ethyl alcohol for being dissolved in water for 1.5~ 3wt% Silane coupling agent KH550 solution, 24h~36h is placed at room temperature, so that ethanol volatilization is complete, seal up for safekeeping stand-by；

(4) prepare modified CNTs/AG-80 epoxy-resin systems solution to pour CFDSF and heat cure, by AG-80 epoxies Resin, hexahydrophthalic anhydride curing agent, 2,4,6- bis aminomethyl phenol accelerator, acetone and absolute ethyl alcohol diluent, It is respectively placed in 38~45 DEG C of baking oven and preheats 1~2 hour, weighs 0.3~2.7g and account for 0.5~4.5wt% of epoxy resin and grind The modified carbon nano-tube Si-CNTs sufficiently after the step (2) processing is ground, places it in ultrasonic wave in proper amount of acetone solution After handling 0.5~1h, pour into epoxy resin by proportioning, after 35~45 DEG C are stirred 4~6h, be ultrasonically treated after 2~3h 80 ~90 DEG C vacuumize 2~3h, after then pouring into the curing agent, accelerator, diluent successively, by mixed solution at 40~50 DEG C 0.5~1h is sufficiently stirred, 65~75 DEG C vacuumize 0.5~1h, obtain being modified CNTs/AG-80 epoxy-resin systems solution；Then The carbon fiber double-layer partition fabric after the step (3) processing is placed in a mold, is coated appropriate methyl-silicone oil, is poured above-mentioned change Property CNTs/AG-80 epoxy-resin systems solution after whole mould vacuumized into 1~2h, 36~48h is stood, then in a constant temperature Heat cure is carried out under degree time conditions, silane coupler modified CNTs/CFDSF/AG-80 epoxy resin composite wood is obtained through cooling Material.

2. the preparation of silane coupler modified CNTs/CFDSF/AG-80 epoxy resin composite materials according to claim 1 Method, it is characterised in that the sufficient O-CNTs of grinding that 1~3g obtains through the step (1) is weighed in the step (2), is added Enter KH550 and 0.2~0.3g that appropriate 500~1000ml mass fractions are 3wt%~5wt% DCC, it is small to be ultrasonically treated 2~3 When make it well mixed, 4~6h of stirring makes it fully react.

3. the preparation of silane coupler modified CNTs/CFDSF/AG-80 epoxy resin composite materials according to claim 1 Method, it is characterised in that ultrasonic cleaning solution described in the step (3) be 10~30wt% ethanol solutions and 20~ 40wt% acetone solns press volume 1:1~1:1.5 mixed liquor.

4. the silane coupler modified CNTs/CFDSF/AG-80 epoxy resin composite wood according to claim any one of 1-3 The preparation method of material, it is characterised in that in the step (4), the AG-80 epoxy resin, curing agent, the ratio of diluent are 45~50wt%：40~45wt%:5~15wt%, the volume ratio of absolute ethyl alcohol and acetone is 1 in the diluent:1~1: 1.5。

5. according to any one of the claim 1-3 silane coupler modified CNTs/CFDSF/AG-80 epoxy resin composite materials Preparation method, it is characterised in that the heat cure in the step (4) is according to pure CNTs/CFDSF/AG-80 composites 80 DEG C/0.5h → 110 DEG C of curing process/0.5h → 120 DEG C/4h → 150 DEG C/4h carries out heat cure.

6. the silane coupler modified CNTs/CFDSF/AG-80 epoxy resin composite wood according to claim any one of 1-3 The preparation method of material, it is characterised in that be that the carbon fiber double-layer partition fabric is that upper and lower surface layer is flat in the step (3) Line tissue fabric.

7. the silane coupler modified CNTs/CFDSF/AG-80 epoxy resin composite wood according to claim any one of 1-3 The preparation method of material, it is characterised in that the modified carbon nano-tube in the step (4) account for epoxy resin 2.5~ 4.5wt%.