阅读说明：本技术 改性聚四氟乙烯及其制备方法和改性聚四氟乙烯制件 (Modified polytetrafluoroethylene, preparation method thereof and modified polytetrafluoroethylene product ) 是由 朱巧思 郭建强 李炯利 *** 李岳 梁佳丰 于 2019-09-27 设计创作，主要内容包括：本发明涉及一种改性聚四氟乙烯的制备方法,包括以下步骤：提供聚四氟乙烯微球,并在所述聚四氟乙烯微球颗粒表面修饰氨基得到氨基化聚四氟乙烯微球；提供氧化石墨烯片,并对所述氧化石墨烯片进行酰氯化改性得到酰氯化氧化石墨烯片；将所述氨基化聚四氟乙烯微球与所述酰氯化氧化石墨烯片进行酰胺反应得到聚四氟乙烯微球表面化学键合氧化石墨烯片的改性聚四氟乙烯。本发明进一步涉及一种改性聚四氟乙烯以及一种改性聚四氟乙烯制件。(The invention relates to a preparation method of modified polytetrafluoroethylene, which comprises the following steps: providing polytetrafluoroethylene microspheres, and modifying amino groups on the surfaces of the polytetrafluoroethylene microsphere particles to obtain aminated polytetrafluoroethylene microspheres; providing a graphene oxide sheet, and performing acylchlorination modification on the graphene oxide sheet to obtain an acylchlorinated graphene oxide sheet; and carrying out amide reaction on the aminated polytetrafluoroethylene microsphere and the acylchloridized graphene oxide sheet to obtain the modified polytetrafluoroethylene with the graphene oxide sheet chemically bonded on the surface of the polytetrafluoroethylene microsphere. The invention further relates to a modified polytetrafluoroethylene and a modified polytetrafluoroethylene product.)

1. The preparation method of the modified polytetrafluoroethylene is characterized by comprising the following steps:

carrying out amide reaction on the polytetrafluoroethylene microsphere with the surface modified with amino and the graphene oxide sheet modified by acyl chloride to obtain the modified polytetrafluoroethylene with the graphene oxide sheet chemically bonded on the surface of the polytetrafluoroethylene microsphere.

2. The method for preparing modified polytetrafluoroethylene according to claim 1, wherein said step of modifying amino groups on the surface of said polytetrafluoroethylene microspheres comprises:

the aminated polytetrafluoroethylene microsphere is obtained by modifying a polytetrafluoroethylene microsphere with a surface coated with hydroxyl through an aminosilane coupling agent, and the polytetrafluoroethylene microsphere with the surface coated with the hydroxyl is prepared from a polyhydroxy organic matter with an annular structure and the polytetrafluoroethylene microsphere through a hydrothermal carbonization reaction.

3. The method for preparing modified polytetrafluoroethylene according to claim 2, wherein said polyhydroxylated organic substance having a cyclic structure comprises one or more of glucose, fructose, galactose, sorbose and psicose.

4. The method for producing modified polytetrafluoroethylene according to claim 2, wherein said polyhydroxyorganic substance having a cyclic structure and said polytetrafluoroethylene microspheres are present in a mass ratio of 0.9 to 4.5, and the concentration of polyhydroxyorganic substance is 0.05mol/L to 0.25 mol/L.

5. The method for preparing modified polytetrafluoroethylene according to claim 2, wherein said hydrothermal carbonization is carried out at a temperature of 150 ℃ to 180 ℃ for a reaction time of 10 hours to 15 hours.

6. The method for producing modified polytetrafluoroethylene according to claim 1, wherein said polytetrafluoroethylene microspheres have an average particle diameter of from 2 μm to 10 μm.

7. The method of claim 1, wherein the content of the amino groups on the surface of the polytetrafluoroethylene microspheres with amino groups modified thereon is 0.045 to 0.072 mol/g.

8. The method for producing a modified polytetrafluoroethylene according to claim 1, wherein said graphene oxide sheets have a sheet diameter of 1 to 2 μm.

9. The method for preparing modified polytetrafluoroethylene according to claim 1, wherein said acylchloridized graphene oxide sheets have a surface acyl chloride group content of 0.050 to 0.080 mol/g.

10. The method for preparing modified polytetrafluoroethylene according to claim 1, wherein the mass ratio of said polytetrafluoroethylene microspheres with amino groups modified on the surface to said acylchloridized modified graphene oxide sheets is 20 to 200.

11. The method of claim 1, further comprising spray-drying the modified polytetrafluoroethylene to coat the polytetrafluoroethylene microspheres with the graphene oxide sheets.

12. The method for preparing modified polytetrafluoroethylene according to claim 11, wherein the temperature of the inlet air is 180-200 ℃ and the temperature of the outlet air is 100-110 ℃ in the spray drying.

13. A modified polytetrafluoroethylene obtained by the process for producing a modified polytetrafluoroethylene according to any one of claims 1 to 12.

14. A modified polytetrafluoroethylene article prepared from the modified polytetrafluoroethylene of claim 13 by powder cold pressing and sintering.

Technical Field

The invention relates to the technical field of modified polytetrafluoroethylene materials, in particular to modified polytetrafluoroethylene, a preparation method thereof and a modified polytetrafluoroethylene product.

Background

Polytetrafluoroethylene (PTFE) is widely applied to various fields as a special engineering plastic, has the characteristics of good acid-base resistance, solvent resistance, high-temperature resistance and weather resistance, and most importantly, has a low friction coefficient compared with other materials, and can be used as a good sealing material. But PTFE has poor wear resistance, easy loss and short service life, which greatly restricts the wider application of the PTFE. Therefore, the research on the modified polytetrafluoroethylene composite material has important practical significance. Graphene as a novel two-dimensional nano material has a plurality of excellent properties, and based on the excellent mechanical properties and the basic structural unit of the carbon solid lubricating material, the graphene can bring excellent tribological properties to a composite material, and the wear resistance of the material can be remarkably improved by adding a small amount of graphene into a matrix. However, since graphene is a nanoscale material, and is very easy to agglomerate by using a conventional mixing method when being mixed with polytetrafluoroethylene, uniform and stable dispersion of graphene in polytetrafluoroethylene is difficult to realize, so that the modification effect of graphene on polytetrafluoroethylene is difficult to reach an ideal level.

Disclosure of Invention

Therefore, it is necessary to provide a modified polytetrafluoroethylene, a preparation method thereof and a modified polytetrafluoroethylene product, aiming at the problem that graphene is difficult to be uniformly dispersed in polytetrafluoroethylene.

The invention provides a preparation method of modified polytetrafluoroethylene, which comprises the following steps:

carrying out amide reaction on the polytetrafluoroethylene microsphere with the surface modified with amino and the graphene oxide sheet modified by acyl chloride to obtain the modified polytetrafluoroethylene with the graphene oxide sheet chemically bonded on the surface of the polytetrafluoroethylene microsphere.

In one embodiment, the step of modifying amino groups on the surface of the polytetrafluoroethylene microsphere comprises:

the aminated polytetrafluoroethylene microsphere is obtained by modifying a polytetrafluoroethylene microsphere with a surface coated with hydroxyl through an aminosilane coupling agent, and the polytetrafluoroethylene microsphere with the surface coated with the hydroxyl is prepared from a polyhydroxy organic matter with an annular structure and the polytetrafluoroethylene microsphere through a hydrothermal carbonization reaction.

In one embodiment, the polyhydroxy organic compound having a cyclic structure includes one or more of glucose, fructose, galactose, sorbose, and psicose.

In one embodiment, the mass ratio of the polyhydroxy organic matter with the annular structure to the polytetrafluoroethylene microspheres is 0.9-4.5, and the concentration of the polyhydroxy organic matter is 0.05-0.25 mol/L.

In one embodiment, the temperature of the hydrothermal carbonization reaction is 150 ℃ to 180 ℃, and the reaction time is 10 hours to 15 hours.

In one embodiment, the polytetrafluoroethylene microspheres have an average particle size of from 2 μm to 10 μm.

In one embodiment, the content of the amino groups on the surface of the polytetrafluoroethylene microsphere with the modified amino groups is 0.045mol/g to 0.072 mol/g.

In one embodiment, the graphene oxide sheets have a sheet diameter of 1 μm to 2 μm.

In one embodiment, the content of the acyl chloride groups on the surface of the graphene oxide sheet modified by acyl chloride is 0.050mol/g to 0.080 mol/g.

In one embodiment, the mass ratio of the polytetrafluoroethylene microsphere with the modified amino group on the surface to the acylchlorination-modified graphene oxide sheet is 20 to 200.

In one embodiment, the preparation method of the modified polytetrafluoroethylene further includes spray drying the modified polytetrafluoroethylene, so that the graphene oxide sheets coat the polytetrafluoroethylene microspheres.

In one embodiment, in the spray drying, the air inlet temperature is 180-200 ℃ and the air outlet temperature is 100-110 ℃.

The invention also provides the modified polytetrafluoroethylene prepared by the preparation method of the modified polytetrafluoroethylene.

The invention further provides a modified polytetrafluoroethylene product which is prepared from the modified polytetrafluoroethylene through powder cold pressing and sintering.

Due to the thin-layer structure of graphene, after being peeled off, the single-layer or few-layer graphene has large inter-sheet attraction force and is easy to be stacked again, so that the graphene is difficult to be uniformly dispersed in a polytetrafluoroethylene matrix in a single-layer or few-layer state. According to the modified polytetrafluoroethylene and the preparation method thereof, graphene oxide is used as a precursor to modify acyl chloride groups on a graphene oxide sheet, amino groups are modified on the surface of the polytetrafluoroethylene, and the amino groups and the acyl chloride groups are subjected to amide reaction to combine the polytetrafluoroethylene and the graphene oxide sheet through chemical bonds, so that the modified polytetrafluoroethylene is obtained. Through the action of chemical bonds, the graphene oxide sheets can well coat the polytetrafluoroethylene microspheres, so that the uniform and stable existence of single-layer or few-layer graphene oxide in the polytetrafluoroethylene substrate is realized, and the graphene oxide sheets are not easy to reunite. The preparation method of the modified polytetrafluoroethylene provided by the invention has the advantages that the grafting rate of chemical groups is high, the coating degree of graphene oxide sheets on the surfaces of polytetrafluoroethylene microspheres is high, and the dispersion degree of the graphene oxide sheets in a polytetrafluoroethylene matrix is better.

Drawings

FIG. 1 is a scanning electron micrograph of the polytetrafluoroethylene micropowder of the invention;

FIG. 2 is a scanning electron micrograph of a graphene oxychloride sheet prepared in example 1 of the present invention;

FIG. 3 is a scanning electron micrograph of modified PTFE prepared in example 1 of the present invention.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

The embodiment of the invention provides a preparation method of modified polytetrafluoroethylene, which comprises the following steps:

carrying out amide reaction on the polytetrafluoroethylene microsphere with the surface modified with amino and the graphene oxide sheet modified by acyl chloride to obtain the modified polytetrafluoroethylene with the graphene oxide sheet chemically bonded on the surface of the polytetrafluoroethylene microsphere.

According to the modified polytetrafluoroethylene and the preparation method thereof provided by the embodiment of the invention, amino groups are modified on the surface of polytetrafluoroethylene, acyl chloride groups are modified on graphene oxide sheets, and the polytetrafluoroethylene and the graphene oxide sheets are combined through chemical bonds by utilizing amide reaction of the amino groups and the acyl chloride groups, so that the modified polytetrafluoroethylene is obtained. Through the action of chemical bonds, the graphene oxide sheets can well coat the polytetrafluoroethylene microspheres, so that the uniform and stable existence of single-layer or few-layer graphene oxide in the polytetrafluoroethylene substrate is realized, and the graphene oxide sheets are not easy to reunite. The preparation method of the modified polytetrafluoroethylene provided by the invention has the advantages that the grafting rate of chemical groups is high, the coating degree of graphene oxide sheets on the surfaces of polytetrafluoroethylene microspheres is high, and the dispersion degree of the graphene oxide sheets in a polytetrafluoroethylene matrix is better.

The step of modifying amino groups on the surface of the polytetrafluoroethylene microsphere comprises the following steps:

the aminated polytetrafluoroethylene microsphere is obtained by modifying a polytetrafluoroethylene microsphere with a surface coated with hydroxyl through an aminosilane coupling agent, and the polytetrafluoroethylene microsphere with the surface coated with the hydroxyl is prepared from a polyhydroxy organic matter with an annular structure and the polytetrafluoroethylene microsphere through a hydrothermal carbonization reaction.

In the hydrothermal carbonization reaction process, a polyhydroxy organic matter with an annular structure has a coating characteristic, polytetrafluoroethylene microsphere particles are taken as cores to carry out coating carbonization reaction, and a carbon material coating layer with a plurality of hydroxyl groups is formed on the surface of the polytetrafluoroethylene microsphere to obtain the polytetrafluoroethylene microsphere with the surface coated with the hydroxyl groups.

Preferably, the polyhydroxy organic matter with the annular structure and the polytetrafluoroethylene microspheres are subjected to hydrothermal carbonization reaction in a hydrothermal reaction kettle.

The content of polyhydroxy organic matters with a ring structure and the temperature of the hydrothermal carbonization reaction influence the hydroxyl groups on the surfaces of the polytetrafluoroethylene microspheres.

The mass ratio of the polyhydroxy organic matter with the annular structure to the polytetrafluoroethylene microspheres is 0.9 to 4.5, and can be any ratio within the interval range.

The concentration of the organic polyhydroxy compound may be 0.05mol/L, 0.10mol/L, 0.15mol/L, 0.20mol/L, 0.25mol/L, and the concentration of the organic polyhydroxy compound may be any value within a range from 0.05mol/L to 0.25 mol/L.

The temperature of the hydrothermal carbonization reaction is 150 ℃, 160 ℃, 170 ℃ and 180 ℃, and the temperature of the hydrothermal carbonization reaction can be any value within the range of 150 ℃ to 180 ℃. The hydrothermal carbonization reaction time is 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, and 15 hours, and the hydrothermal carbonization reaction time may be any value within a range from 10 hours to 15 hours.

In one embodiment, the polyhydroxy organic compound having a cyclic structure includes one or more of glucose, fructose, galactose, sorbose, and psicose.

The aminosilane coupling agent may be 3-aminopropyltriethoxysilane or aminopropyltrimethoxysilane. And (3) reacting the aminosilane coupling agent with hydroxyl coated on the surface of the polytetrafluoroethylene microsphere to coat amino groups on the surface of the polytetrafluoroethylene microsphere to obtain the aminated polytetrafluoroethylene microsphere. The content of amino groups on the surfaces of the aminated polytetrafluoroethylene microspheres is 0.045mol/g to 0.072 mol/g.

The acylchlorination-modified graphene oxide sheet can be obtained by performing acylchlorination modification on a graphene oxide sheet.

The graphene oxide sheet may be a commercially available graphene oxide sheet or may be obtained by a conventional preparation method. Preferably, the method can be prepared by pre-oxidizing a scalene toner (325 meshes, purity 99.5%) by concentrated sulfuric acid and concentrated nitric acid by using an improved Hummers method, and oxidizing the scalene toner by using hydrogen peroxide, so that a large amount of carboxyl groups and hydroxyl groups are formed on graphene oxide sheets, the oxygen content of the graphene oxide sheets can be selected to be 32.59% to 36.17%, and the sheet diameter of the graphene oxide sheets can be selected to be 1 μm to 2 μm.

The modification step of the graphene oxide sheet by acylchlorination may be performed using thionyl chloride (SOCl)₂) As a reagent for acyl chlorination reaction, N-Dimethylformamide (DMF) is selected as a solvent, and thionyl chloride reacts with carboxyl and hydroxyl on graphene oxide sheets in the DMF environment to form acyl chloride groups. The content of acyl chloride groups on the surface of the prepared acylchloridized graphene oxide sheet is 0.050mol/g to 0.080 mol/g.

The mass ratio of the polytetrafluoroethylene microsphere with the modified amino group on the surface to the graphene oxide sheet modified by acyl chloride is 20-200. And carrying out amidation reaction on an amino group on the surface of the polytetrafluoroethylene microsphere with the modified amino group and an acyl chloride group on the acylchloridized modified graphene oxide sheet to form an amide bond, and bonding the graphene oxide sheet on the surface of the polytetrafluoroethylene microsphere through the amide bond to obtain the modified polytetrafluoroethylene.

In one embodiment, the step of preparing the modified polytetrafluoroethylene further comprises:

and (3) carrying out spray drying on the modified polytetrafluoroethylene to coat the polytetrafluoroethylene microspheres with the graphene oxide sheets.

The spray drying can adopt airflow type spray drying equipment, the air inlet temperature is set to be 180-200 ℃, the air outlet temperature is set to be 100-110 ℃, the frequency of a fan is set to be 35-50 Hz, and the rotating speed of a peristaltic pump is set to be 50-60R/min. In the step, the polytetrafluoroethylene microspheres in the modified polytetrafluoroethylene have a nucleating effect, the graphene oxide sheets are further close to the surfaces of the polytetrafluoroethylene microspheres under the spray drying condition, the polytetrafluoroethylene microspheres are taken as cores, and the graphene oxide sheets form coatings on the polytetrafluoroethylene microspheres on the outer surfaces of the cores. The structure enables the combination of the polytetrafluoroethylene microspheres and the graphene oxide sheets to be tighter, the friction coefficient of the modified polytetrafluoroethylene part can be further reduced, the wear resistance of the modified polytetrafluoroethylene part is improved, and the mechanical strength of the modified polytetrafluoroethylene part is enhanced.

In some embodiments, the polytetrafluoroethylene microspheres have an average particle size of 10 μm to 30 μm, and preferably, before step S10, the polytetrafluoroethylene microspheres may be left at 23 ℃ to 25 ℃ for 24 to 28 hours,

the invention also provides modified polytetrafluoroethylene obtained by the preparation method of the modified polytetrafluoroethylene.

The invention further provides a modified polytetrafluoroethylene product which is prepared from the modified polytetrafluoroethylene through powder cold pressing and sintering. The pressure of powder cold pressing is 27 MPa-37 MPa, and the sintering temperature is 380-385 ℃.

The oxygen content of the graphene mentioned in the invention is less than 5%, and the graphene is different from the graphene oxide.

The following are specific examples.