阅读说明：本技术 多尺度碳纤维、增强增韧环氧复合材料及其制备方法 (Multi-scale carbon fiber, reinforced and toughened epoxy composite material and preparation method thereof ) 是由 王新龙 詹亿兴 王雅婷 丁晓庆 王明 王康琪 于 2019-09-29 设计创作，主要内容包括：本发明公开了一种多尺度碳纤维、增强增韧环氧复合材料及其制备方法。所述的多尺度碳纤维由氧化碳纤维和纳米粒子ZIF-8组成,ZIF-8通过化学键键合作用直接接枝在氧化碳纤维表面。所述的增强增韧环氧复合材料由质量比为97.0～99.0：3.0～1.0的环氧树脂和多尺度碳纤维增强体组成,采用浇铸的方法将混合均匀的环氧树脂、多尺度碳纤维和固化剂浇筑于涂覆有脱模剂的模具中制得。本发明的多尺度碳纤维制备过程简单,成本低廉,显著地改善了碳纤维与环氧的界面结合,提高了环氧复合材料的力学性能和热机械性能,起到了增强增韧的作用,冲击强度最高提升135.5％,玻璃化转变温度最高提高了64.2％。(The invention discloses a multi-scale carbon fiber, reinforced and toughened epoxy composite material and a preparation method thereof. The multi-scale carbon fiber consists of oxidized carbon fiber and nano particle ZIF-8, wherein the ZIF-8 is directly grafted on the surface of the oxidized carbon fiber through chemical bond bonding. The reinforced toughened epoxy composite material is prepared from the following components in parts by mass of 97.0-99.0: 3.0-1.0 parts of epoxy resin and multi-scale carbon fiber reinforcement, and pouring the uniformly mixed epoxy resin, multi-scale carbon fiber and curing agent into a mold coated with a release agent by adopting a casting method. The multi-scale carbon fiber provided by the invention is simple in preparation process and low in cost, the interface bonding of the carbon fiber and epoxy is obviously improved, the mechanical property and the thermal mechanical property of the epoxy composite material are improved, the effects of enhancing and toughening are achieved, the impact strength is improved by 135.5% to the maximum, and the glass transition temperature is improved by 64.2% to the maximum.)

1. The multi-scale carbon fiber is characterized by consisting of oxidized carbon fiber and nano particle ZIF-8, wherein the nano particle ZIF-8 is directly grafted on the surface of the oxidized carbon fiber through chemical bond bonding.

2. The multi-scale carbon fiber as claimed in claim 1, wherein the carbon fiber is a chopped carbon fiber, a long carbon fiber or a carbon fiber cloth.

3. The method for preparing multi-scale carbon fiber according to claim 1 or 2, characterized by comprising the following steps:

step 1, soaking carbon fibers in acetone to remove impurities on the surfaces of the carbon fibers, drying the carbon fibers, dispersing the carbon fibers in 65% concentrated nitric acid, etching the surfaces of the carbon fibers under an ultrasonic condition, washing the carbon fibers to be neutral, and drying the carbon fibers to obtain oxidized carbon fibers;

and 2, ultrasonically dispersing the oxidized carbon fiber in methanol, respectively dissolving 2-methylimidazole and zinc nitrate hexahydrate in the methanol, sequentially adding the mixture into a methanol solution of the oxidized carbon fiber, reacting under an ultrasonic condition, centrifuging after the reaction is finished, washing with water, and drying to obtain the multi-scale carbon fiber.

4. The preparation method according to claim 3, wherein in the step 1, the carbon fiber is soaked in acetone for more than 24 hours, the ultrasonic time is 1.5-2 hours, and in the steps 1 and 2, the drying temperature is 70-80 ℃; in the step 2, the molar ratio of the 2-methylimidazole to the zinc nitrate hexahydrate is 3.5: 1; in the step 2, the ultrasonic time is 4-6 h.

5. The reinforcing and toughening epoxy composite material containing the multi-scale carbon fiber of claim 1 or 2, which is characterized by consisting of an epoxy resin, a curing agent and the multi-scale carbon fiber, wherein the mass ratio of the epoxy resin to the multi-scale carbon fiber is 97.0-99.0: 3.0 to 1.0.

6. The reinforced toughened epoxy composite material as claimed in claim 5, wherein said curing agent is selected from tetraethylenepentamine or 2, 4-diaminodiphenylmethane.

7. The reinforced and toughened epoxy composite material as claimed in claim 5, wherein the content of said curing agent is 13-15% by mass of epoxy resin.

8. The reinforced and toughened epoxy composite material as claimed in claim 5, wherein said curing agent is contained in an amount of 14% by mass based on the epoxy resin.

9. The preparation method of the reinforced and toughened epoxy composite material containing the multi-scale carbon fibers as claimed in claim 5, is characterized by comprising the following specific steps:

adding multi-scale carbon fibers into an ethyl acetate solution of epoxy resin according to a proportion, stirring, vacuumizing under the heating of a water bath to remove ethyl acetate and bubbles, then adding a curing agent according to a proportion, stirring, casting in a mold, and curing to obtain the reinforced and toughened epoxy composite material.

10. The preparation method according to claim 9, wherein the stirring time is 5-6 hours; when the curing agent is tetraethylenepentamine, a three-step curing process is adopted, specifically, the curing is carried out for 4 hours at normal temperature, then the heating is carried out for 4 hours at 90 ℃, and finally the post-treatment is carried out for 30 minutes at 150 ℃; the mould is a polytetrafluoroethylene mould coated with a release agent.

Technical Field

The invention belongs to the technical field of epoxy composite materials, and relates to a multi-scale carbon fiber, reinforced and toughened epoxy composite material and a preparation method thereof.

Background

Carbon fiber reinforced epoxy composite materials have been widely used in aerospace and automotive industries in recent years, and have excellent physical and chemical properties including high specific strength, high specific modulus, light weight, high thermal stability, excellent corrosion resistance and the like. However, the full potential of carbon fiber composites has not been fully exploited due to the smooth and inert nature of the Carbon Fiber (CFs) surface, and poor interfacial properties can lead to delamination or delamination between the fibers and the matrix, resulting in catastrophic failure. In order to overcome the above problems, it is necessary to adjust and optimize the microstructure of the interface between the matrix and the reinforcement.

In the surface modification of carbon fibers, the development of multi-scale reinforcement materials by grafting nanomaterials onto the surfaces of CFs under chemical reaction provides an effective solution for the surface modification of carbon fibers. The chemical grafting method can overcome the problem of weak combination of nano-scale materials and CFs in other methods (such as CVD, coating, electrophoretic deposition and the like), not only reduces the damage degree to the fiber strength, but also contributes to environmental protection and energy conservation. Zhao et al (Zhao ZB, et al composite structures,2017,159,761-772) attach Carbon Nanotubes (CNTs) to carbon fibers by electrophoretic deposition, which enhances the layering of composite materials, and found that the interfacial shear strength of composite materials is increased by 10% and the glass transition temperature is increased by only 4%. S. Rahmanian et al (S.Rahmanian, et al materials and Design,2013,43,10-16) adopt a chemical vapor deposition method to uniformly grow dense Carbon Nanotubes (CNTs) on the surface of carbon fibers and prepare a short carbon fiber reinforced polypropylene composite material, and the result shows that the impact strength of the composite material is only improved by about 34%. These fiber treatments, while improving the interfacial properties of the final composite to some extent, have several disadvantages such as cumbersome treatment processes, expensive equipment, high energy consumption and complex catalyst processing.

As a typical 3D nano material, the zeolite imidazolate framework material (ZIF-8) has the advantages of excellent mechanical and thermal properties, stable porosity, high chemical stability, simple preparation process and the like. In addition, it can provide a site for the ring-opening reaction of the epoxy group, promoting the formation of an epoxy network without the need for a catalyst or coupling agent.

Disclosure of Invention

Aiming at the problems of complicated treatment process, expensive equipment and catalyst processing requirement of the conventional carbon fiber surface modification treatment, the invention provides a nano particle modified multi-scale carbon fiber, a reinforcing and toughening epoxy composite material containing the multi-scale carbon fiber and a preparation method thereof. According to the invention, the nano particle ZIF-8 is successfully grafted on the surface of the oxidized carbon fiber in one step through a chemical action for the first time, so that the roughness is increased, the wettability is improved, the mechanical property and the thermal mechanical property of the epoxy composite material are improved, and the effect of promoting the curing of an epoxy system is achieved.

The technical scheme of the invention is as follows:

the multi-scale carbon fiber consists of oxidized carbon fiber and nano particle ZIF-8, wherein the nano particle ZIF-8 is directly grafted on the surface of the oxidized carbon fiber through the chemical bond bonding effect.

The carbon fiber of the present invention is conventionally used in the art, and may be a chopped carbon fiber, a long carbon fiber or a carbon fiber cloth.

The invention provides a preparation method of the multi-scale carbon fiber, which comprises the following specific steps:

step 1, soaking carbon fibers in acetone to remove impurities on the surfaces of the carbon fibers, drying the carbon fibers, dispersing the carbon fibers in 65% concentrated nitric acid, etching the surfaces of the carbon fibers under an ultrasonic condition, washing the carbon fibers to be neutral, and drying the carbon fibers to obtain oxidized carbon fibers;

and 2, ultrasonically dispersing the oxidized carbon fiber in methanol, respectively dissolving 2-methylimidazole and zinc nitrate hexahydrate in the methanol, sequentially adding the mixture into a methanol solution of the oxidized carbon fiber, reacting under an ultrasonic condition, centrifuging after the reaction is finished, washing with water, and drying to obtain the multi-scale carbon fiber.

Preferably, in step 1, the soaking time of the carbon fiber in acetone is more than 24 h.

Preferably, in the step 1, the ultrasonic time is 1.5-2 h.

Preferably, in the steps 1 and 2, the drying temperature is 70-80 ℃.

Preferably, in the step 2, the molar ratio of the 2-methylimidazole to the zinc nitrate hexahydrate is 3.5: 1.

preferably, in the step 2, the ultrasonic time is 4-6 h.

The invention provides a reinforcing and toughening epoxy composite material containing multi-scale carbon fibers, which consists of epoxy resin, a curing agent and the multi-scale carbon fibers, wherein the mass ratio of the epoxy resin to the multi-scale carbon fibers is 97.0-99.0: 3.0 to 1.0.

The curing agent is an amine curing agent which is conventionally used in the field, and can be tetraethylenepentamine and 2, 4-diaminodiphenylmethane, and preferably tetraethylenepentamine. The content of the curing agent is 13 to 15 percent of the mass of the epoxy resin, and is preferably 14 percent.

Further, the invention provides a preparation method of the reinforced and toughened epoxy composite material containing the multi-scale carbon fibers, which comprises the following specific steps:

adding multi-scale carbon fibers into an ethyl acetate solution of epoxy resin according to a proportion, stirring, vacuumizing under the heating of a water bath to remove ethyl acetate and bubbles, then adding a curing agent according to a proportion, stirring, casting in a mold, and curing to obtain the reinforced and toughened epoxy composite material.

Preferably, the stirring time is 5-6 h.

When the curing agent is tetraethylenepentamine, a three-step curing process is adopted, specifically, the curing is carried out for 4 hours at normal temperature, then the heating is carried out for 4 hours at 90 ℃, and finally the post-treatment is carried out for 30 minutes at 150 ℃.

The mold is preferably a polytetrafluoroethylene mold coated with a release agent.

Compared with the prior art, the invention has the following advantages:

(1) according to the preparation method of the multi-scale carbon fiber, 2-methylimidazole and zinc nitrate hexahydrate are sequentially added into a methanol solution for oxidizing the carbon fiber and are grafted to the surface of the carbon fiber through a chemical action, so that the preparation method has the advantages of low cost, simplicity in operation and simplicity and convenience in equipment;

(2) according to the multi-scale carbon fiber, the grafted nano particle ZIF-8 can effectively improve the roughness, polarity and wettability of the surface of the carbon fiber and promote the compatibility of the chopped carbon fiber and a resin matrix;

(3) in the curing process, imidazole groups contained in the nano particles ZIF-8 can provide action sites for ring-opening reaction of epoxy groups, and Zn⁺The epoxy resin composite material contains open sites, and can form coordinate bonds with hydroxyl on epoxy chains, so that a large number of epoxy chains are captured around the epoxy resin composite material, and the formation of an epoxy network cross-linked structure is promoted to reinforce the epoxy composite material;

(4) the nano particle ZIF-8 introduced on the surface of the carbon fiber can improve the wettability of the carbon fiber and resin, enhance mechanical interlocking, increase chemical bonding force, and obviously improve the toughness (impact strength) and mechanical strength of the composite material, and the impact strength is improved by 135.5 percent to the maximum.

(5) The invention greatly improves the thermal mechanical property of the material and the glass transition temperature of the material by 64.2 percent at most while enhancing and toughening the epoxy composite material.

Drawings

FIG. 1 is a graph showing impact strengths of carbon fiber/epoxy resin composite materials and pure epoxy resin materials prepared in examples and comparative examples.

FIG. 2 shows T of carbon fiber/epoxy resin composite material and pure epoxy resin material prepared in each example and comparative example_gFigure (a).

Detailed Description

The present invention will be described in more detail with reference to the following examples and the accompanying drawings.