CN101875758A - Polyester/nano-expanded graphite/carbon fiber high-strength conductive composite material and preparation method thereof - Google Patents

Abstract

The invention discloses a polyester/nano expanded graphite/carbon fiber high-strength conducting composite material and a preparation method thereof. The composite material is prepared from the following components in parts by mass: 100 parts of main substrate polyester, 1-8 parts of expanded graphite of which the expansion ratio is more than 100 times, and 1-30 parts of reinforcer carbon fiber. The main substrate polyester is polyethylene terephthalate or polybutylene terephthalate. The reinforcer carbon fiber is added to a polyester/nano expanded graphite compound system to prepare the high-strength high-conductivity composite material. Although the content of the carbon fiber and the expanded graphite is small, the bulk conductivity of the system can reach 10-2S/m, the mechanical properties of the system are excellent, the tensile strength can reach 66.48 MPa, the bending strength reaches 153.81 MPa, and the impact strength is 19.23 KJ/m<2>.

Description

Polyester/nano-expanded graphite/carbon fiber high-strength conductive composite material and preparation method thereof

technical field

The invention relates to a polyester/nano-expanded graphite/carbon fiber high-strength conductive composite material and its preparation method and related performance research. On the basis of the existing polyester/graphite nano-conductive composite material preparation method, carbon fiber is added through A polyester/nano-expanded graphite/carbon fiber high-strength conductive composite material with good electrical conductivity and excellent mechanical properties was prepared by a simple melt-blending intercalation method.

Background technique

Polyethylene terephthalate (PET) is the most common saturated polyester and is widely used in the manufacture of fibers, films, bottles, engineering plastics and many other fields. PBT has heat resistance, weather resistance, chemical resistance, low water absorption, good gloss, and is widely used in electronic appliances, auto parts, machinery, household goods, etc. In recent years, polymer-based conductive composites have been widely promoted and applied due to their advantages such as low density, excellent electrical conductivity, and good chemical corrosion resistance. However, according to current reports, the conductive composite materials with polymer as the matrix mostly use carbon black, metal powder, metal oxide, etc. as conductive fillers, and adopt the preparation process of intercalation polymerization or solution intercalation. Materials often require more conductive fillers to achieve the desired conductive effect, and the content of conductive fillers is generally in the range of 15-25%. The increase of filler content and the weak interfacial adhesion with the matrix lead to poor processability and mechanical properties of such polymer-based conductive composites, thus limiting their applications.

In our previous research results, we reported that polyester/graphite nano-conductive composites were prepared by melting intercalation method. The polyester-based graphite nano-composites prepared by this method can obtain relatively low conductive filler content. High volume conductivity, its percolation threshold is 4-5%. Compared with other polymer-based conductive composite materials, the content of inorganic conductive fillers has been greatly reduced, thereby reducing production costs. However, the mechanical properties of the polyester/graphite nano-conductive composite material prepared by this method are lower than those of the pure polyamide matrix with the addition of graphite, which also limits its industrial application.

Contents of the invention

The purpose of the present invention is to invent a polyester/nano-expanded graphite/carbon fiber high-strength conductive composite material that has good antistatic performance, shielding performance within a certain range, excellent electrical conductivity, good processability, and excellent mechanical properties, and can meet industrial applications. and its preparation method.

The technical method that the object of the present invention realizes is, described composite material is made up of polyester, the expanded graphite that expansion ratio is more than 100 times and reinforcing body carbon fiber, and the mass parts of each component is: polyester 100 parts, expansion ratio 100 1-8 parts of expanded graphite and 1-30 parts of reinforced carbon fiber; the polyester is polyethylene terephthalate or polybutylene terephthalate.

The reinforcing carbon fibers are carbon fibers of various grades and different aspect ratios.

The expanded graphite is nano-expanded graphite (nano-graphite sheet).

The optimum mass ratio of polyester and nano-expanded graphite is 100:8.

Experimental results show that the invention has lower percolation threshold, higher electrical conductivity and excellent mechanical properties. As a reinforcing material, carbon fiber itself has good electrical conductivity. Therefore, with the addition of carbon fiber, a good conductive network is realized with expanded graphite inside the composite material, giving the main matrix excellent electrical conductivity. At the same time, carbon fiber also has a reinforcing effect. Compared with pure polyester matrix, the tensile strength, bending strength and impact strength of polyester/nano-expanded graphite/carbon fiber composite materials have been greatly improved. Compared with other polymer-based conductive composite materials It is also much higher than that. Therefore, the polyester/nano-expanded graphite/carbon fiber high-strength conductive composite material has broad industrialization prospects and is expected to be widely used in antistatic materials, electromagnetic shielding materials, microwave absorption and other fields.

The preparation method of above-mentioned polyester/nano-expanded graphite/carbon fiber high-strength conductive composite material comprises the following steps:

1) Add natural flake graphite to the mixture of concentrated sulfuric acid and concentrated nitric acid and soak for 24±3 hours, then wash and dry the natural flake graphite, and then heat and expand it in a muffle furnace at a temperature of 900-1100°C , to obtain expanded graphite with an expansion multiple of more than 100 times; then disperse the expanded graphite in 70% ethanol aqueous solution and place it for 24 ± 1 hour, and then ultrasonically obtain nano-graphite sheets (nano-expanded graphite) for 4 ± 0.2 hours;

2) Mix 1-8 parts of nano-graphite flakes (nano-expanded graphite) with 100 parts of main matrix polyester and add them together with 1-30 parts of reinforcing carbon fiber to provide shear force and simultaneously heat the polymer to Melting and blending in equipment above the melting point to obtain conductive composite materials; the polyester is polyethylene terephthalate or polybutylene terephthalate.

The particle size of the natural flake graphite is 100 μm˜500 μm.

The reinforcing carbon fibers are carbon fibers with different aspect ratios.

The present invention utilizes the excellent electrical conductivity of carbon fiber and the advantages that it can be used as a polymer reinforcing filler. On the basis of the research results obtained, a polyester/nano-expanded graphite/carbon fiber high-strength conductive material is prepared by adding carbon fiber and adopting a melt blending method. composite material. The specific method is to place a certain proportion of nano-expanded graphite and the main matrix polyester in a high-speed mixer and stir them well to make them evenly mixed; In a screw extruder, etc.), the temperature is raised to above the melting point of the matrix for kneading to obtain a conductive composite material. The preparation method is simple and easy, and the cost is low.

Detailed ways

1. Preparation of expanded graphite:

Add natural flake graphite (particle size 100μm~500μm) into a mixture of concentrated sulfuric acid and concentrated nitric acid with a mass ratio of 4:1 and soak for 24 hours, then wash and dry, and then put it in a muffler with a temperature of 900~1100℃ Heat and expand in the furnace to obtain expanded graphite with an expansion factor of more than 100 times for use.

2. Preparation of nano-graphite sheets:

The expanded graphite was dispersed in 70% ethanol aqueous solution and left for 24 hours, and then ultrasonicated for 4 hours to obtain nano-graphite sheets (nano-expanded graphite), which were ready for use.

3. Blending of composite materials

Put a certain ratio of nano-expanded graphite and the main matrix in a high-speed mixer, and stir for 10 minutes to make the filler nano-expanded graphite evenly dispersed in the matrix.

The following main matrix polyester takes PET as an example, with specific examples:

Nano-expanded graphite (nano-graphite flakes) accounted for 8 parts by mass of the total system and 100 parts of the main matrix PET were fully stirred and mixed evenly on a high-speed mixer, and then transferred to the internal mixer with 2 to 30 parts of reinforced carbon fiber materials (Hacke torque rheometer or twin-screw extruder) at 270 ° C for 8 minutes, and discharged to obtain a high-strength conductive composite material. The electrical conductivity data and mechanical property data of the composite materials are shown in Table 1.

Table I

When nano-expanded graphite accounts for 1 part (or 2 parts, or 3 parts, or 4 parts, or 5 parts, or 6 parts, or 7 parts) of the total system mass fraction, it is fully stirred and mixed with 100 parts of the main matrix PET on a high-speed mixer Finally, transfer it and 2 to 30 parts of reinforced carbon fiber materials to an internal mixer (Hacker torque rheometer or twin-screw extruder) and knead at 270°C for 8 minutes, and discharge the material to obtain high Strength Conductive Composite. The electrical conductivity data and mechanical properties data of the composite materials are similar to those in Table 1. The optimum mass ratio of main matrix polyester to nano-expanded graphite is 100:8.

The main matrix polyester is polybutylene terephthalate, and its technological process, material mass ratio, electrical conductivity data and mechanical property data of the prepared composite material are different from the main matrix polyester of polyethylene terephthalate. Glycol ester (PET) is similar.

Claims (5)

1. Polyester/nano-expanded graphite/carbon fiber high-strength conductive composite material is characterized in that said composite material is made up of main matrix polyester, expanded graphite and reinforcement carbon fiber with an expansion multiple of more than 100 times, and the mass parts of each component are : 100 parts of main matrix polyester, 1 to 8 parts of expanded graphite with an expansion ratio of more than 100 times, and 1 to 30 parts of reinforced carbon fiber; the main matrix polyester is polyethylene terephthalate or polyethylene terephthalate Butylene glycol dicarboxylate. 2. The polyester/nano-expanded graphite/carbon fiber high-strength conductive composite material according to claim 1, wherein the reinforcing body carbon fibers are carbon fibers of various grades and different aspect ratios. 3. a preparation method of polyester/nano-expanded graphite/carbon fiber high-strength conductive composite material as claimed in claim 1, is characterized in that comprising the following steps: 1) Add natural flake graphite to the mixture of concentrated sulfuric acid and concentrated nitric acid and soak for 24±3 hours, then wash and dry the natural flake graphite, and then heat and expand it in a muffle furnace at a temperature of 900-1100°C , to obtain expanded graphite with an expansion factor of more than 100 times; then disperse the expanded graphite in 70% ethanol aqueous solution for 24 ± 1 hour, and ultrasonically obtain nanographite sheets for 4 ± 0.2 hours; 2) Mix 1-8 parts of nano-graphite flakes with 100 parts of main matrix polyester and add them together with 1-30 parts of reinforcing carbon fiber into the equipment that can provide shear force and heat the polymer above the melting point at the same time The conductive composite material is obtained by melting and blending; the main matrix polyester is polyethylene terephthalate or polybutylene terephthalate. 4. The preparation method of the polyester/nano-expanded graphite/carbon fiber high-strength conductive composite material according to claim 4, characterized in that the particle size of the natural flake graphite is 100 μm˜500 μm. 5. according to the preparation method of the described polyester/nano-expanded graphite/carbon fiber high-strength conductive composite material of claim 4, it is characterized in that described reinforcing body carbon fiber is the carbon fiber of different length-to-diameter ratios.