阅读说明：本技术 聚酰亚胺/二氧化硅复合材料及其制备方法 (polyimide/silicon dioxide composite material and preparation method thereof ) 是由 武德珍 李小兰 田国峰 于 2018-06-07 设计创作，主要内容包括：本发明涉及高分子材料技术领域,公开了一种聚酰亚胺/二氧化硅复合材料的制备方法以及由该方法制备的材料,该方法包括：将聚酰亚胺基体与碱液接触,得到经碱液处理的聚酰亚胺基体；将含有硅源的分散液置于反应器中,将经碱液处理的聚酰亚胺基体置于所述分散液上方,密闭反应器,将分散液的温度升高至反应温度为100-160℃,并保持2-24小时；将得到的聚酰亚胺基体进行热处理。根据本发明的聚酰亚胺/二氧化硅复合材料的制备方法,在聚酰亚胺薄膜和具有大的比表面积的聚酰亚胺纤维、纳米纤维膜等基体材料的表面均能形成均匀生长的二氧化硅层,不仅保持了聚酰亚胺材料本身的力学性能,而且有利于提高聚酰亚胺材料表面的抗原子氧能力。(The invention relates to the technical field of high polymer materials, and discloses a preparation method of a polyimide/silicon dioxide composite material and a material prepared by the method, wherein the method comprises the following steps: contacting the polyimide substrate with alkali liquor to obtain a polyimide substrate treated by the alkali liquor; placing the dispersion liquid containing the silicon source in a reactor, placing the polyimide substrate treated by alkali liquor above the dispersion liquid, sealing the reactor, raising the temperature of the dispersion liquid to 160 ℃ with the reaction temperature of 100 ℃ and keeping the temperature for 2-24 hours; the polyimide substrate obtained is subjected to heat treatment. According to the preparation method of the polyimide/silicon dioxide composite material, the silicon dioxide layer which grows uniformly can be formed on the surfaces of the polyimide film and the substrate materials such as the polyimide fiber, the nanofiber membrane and the like with large specific surface areas, so that the mechanical property of the polyimide material is maintained, and the improvement of the atomic oxygen resisting capability of the surface of the polyimide material is facilitated.)

1. a preparation method of a polyimide/silicon dioxide composite material is characterized by comprising the following steps:

(1) Contacting the polyimide substrate with alkali liquor to obtain a polyimide substrate treated by the alkali liquor;

(2) placing dispersion liquid containing a silicon source in a reactor, placing a polyimide substrate treated by alkali liquor above the dispersion liquid, sealing the reactor, raising the temperature of the dispersion liquid to a reaction temperature of 100-160 ℃, and keeping the temperature for 2-24 hours at the reaction temperature;

(3) And (3) carrying out heat treatment on the polyimide substrate obtained in the step (2).

2. the production method according to claim 1, wherein the polyimide substrate is at least one of a polyimide fiber, a polyimide film, a polyimide nanofiber membrane, and a polyimide felt.

3. The preparation method according to claim 1 or 2, wherein in the step (1), the concentration of the alkali liquor is 0.5-10mol/L, preferably 4-7 mol/L;

Preferably, the alkali liquor is an aqueous solution of sodium hydroxide and/or potassium hydroxide;

Preferably, in step (1), the contacting is carried out at a temperature of 0-60 ℃, preferably at a temperature of 10-50 ℃;

Preferably, in step (1), the duration of said contact is between 1 and 20min, preferably between 2 and 10 min.

4. the production method according to any one of claims 1 to 3, wherein in the step (2), the dispersion is a silica sol and/or a siloxane-containing hydrolysate;

Preferably, the siloxane is at least one of ethyl orthosilicate, methyl orthosilicate, methyltriethoxysilane and methyltrimethoxysilane.

5. The production method according to any one of claims 1 to 4, wherein the siloxane-containing hydrolyzate contains siloxane, alcohol, water, and a catalyst;

The alcohol is preferably at least one of methanol, ethanol, propanol and butanol;

The catalyst is preferably an acid or a base, more preferably an acid, and further preferably at least one of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, formic acid, and acetic acid;

preferably, the dispersion has a siloxane, alcohol and water molar ratio of 1: (1-8): (1-10), preferably 1: (3-5): (4-7);

The catalyst is used in such an amount that the pH of the dispersion is from 0 to 5, preferably from 1 to 4.

6. The production method according to any one of claims 1 to 5, wherein in the step (2), the volume of the dispersion is 0.05 to 0.08 based on the total volume of the reactor.

7. The production method according to any one of claims 1 to 6, wherein in the step (2), the temperature of the dispersion is raised to the reaction temperature at a rate of 1 to 3 ℃/min.

8. The preparation method according to any one of claims 1 to 7, wherein, in step (3), the heat treatment is carried out at a temperature of 200-360 ℃, preferably at a temperature of 280-350 ℃;

preferably, the duration of the heat treatment is 0.5 to 2 h.

9. a polyimide/silica composite prepared by the method of any one of claims 1-8, comprising a polyimide matrix and silica particles attached to the surface of the polyimide matrix.

10. The material of claim 9, wherein the silica particles have a particle size of 50-500 nm.

Technical Field

the invention relates to the technical field of high polymer materials, in particular to a preparation method of a polyimide/silicon dioxide composite material, and the invention also relates to the polyimide/silicon dioxide composite material prepared by the method.

Background

The polyimide material has a unique aromatic heterocyclic rigid structure, and has the characteristics of excellent high-temperature resistance, mechanical property, insulating property, corrosion resistance, irradiation resistance and the like. The high-performance polyimide is widely applied to the field of aerospace, is used as a multilayer thermal insulation blanket in a space vehicle, a flexible substrate of a solar cell array, an insulation protection layer of a circuit system and the like, and is generally oxidized and corroded by atomic oxygen on the surface of a material in a low-space orbit environment to generate obvious denudation and performance degradation, so that the performance and the service life of the material are influenced finally. The research on the steric property of the material mainly focuses on the research and modification of the anti-atomic oxygen property of the organic polymer, and how to treat the surface of the polymer to increase the resistance of the contact steric surface to atomic oxygen is the most important way to solve the problem that the polymer material is not damaged by the steric oxygen at present. The preparation of the silicon dioxide coating is one of the common protection methods, namely, a silicon dioxide protective layer which is not easy to react with atomic oxygen is coated on the surface of a material which is easy to be corroded by the atomic oxygen, so that gas atomic oxygen cannot penetrate through the protective layer to enter the surface of a polymer to react with carbon elements, and the effect of resisting atomic oxygen is realized.

At present, the research on atomic oxygen resistant modification of polyimide mainly adopts a dipping and pulling method to prepare a polyimide film of a silicon dioxide coating, and also adopts an in-situ polymerization method or a blending method to prepare a polyimide/silicon dioxide hybrid material. Due to the fact that the application and popularization time of the polyimide fiber is short, the research on atomic oxygen resistant surface modification is relatively few, due to the special physical appearance characteristics of the fiber that the tow is large and the monofilament diameter is small, the specific surface area is large, the large-area surface area is not flat, and the surface modified coating which is completely covered uniformly is difficult to achieve. Meanwhile, it is difficult to coat silica on the base materials with large specific surface area, such as polyimide nanofiber membranes and felts, and therefore, a method for effectively coating silica on the surface of polyimide materials with different forms to improve the atomic oxygen resistance of the polyimide materials is urgently needed.

Disclosure of Invention

The invention aims to overcome the problem that silica is difficult to coat on a substrate material with large specific surface area in the prior art, and provides a preparation method of a polyimide/silica composite material and a material prepared by the same.

In order to achieve the above object, a first aspect of the present invention provides a method for preparing a polyimide/silica composite, wherein the method comprises the steps of:

(1) Contacting the polyimide substrate with alkali liquor to obtain a polyimide substrate treated by the alkali liquor;

(2) Placing dispersion liquid containing a silicon source in a reactor, placing a polyimide substrate treated by alkali liquor above the dispersion liquid, sealing the reactor, raising the temperature of the dispersion liquid to a reaction temperature of 100-160 ℃, and keeping the temperature for 2-24 hours at the reaction temperature;

(3) and (3) carrying out heat treatment on the polyimide substrate obtained in the step (2).

In a second aspect, the present invention provides a polyimide/silica composite material prepared by the preparation method according to the first aspect of the present invention, the composite material comprising a polyimide matrix and silica particles attached to the surface of the polyimide matrix.

according to the preparation method of the polyimide/silicon dioxide composite material, the silicon dioxide layer which grows uniformly can be formed on the surfaces of the polyimide film and the substrate materials such as the polyimide fiber, the nanofiber membrane and the like with large specific surface areas, so that the mechanical property of the polyimide material is maintained, and the improvement of the atomic oxygen resisting capability of the surface of the polyimide material is facilitated.

Drawings

FIG. 1a is an infrared spectrum of a polyimide fiber as a raw material, which was not subjected to any treatment in example 1, a polyimide fiber after alkali etching, and a polyimide fiber/silica composite A1 obtained;

FIG. 1b is an SEM topography of the untreated polyimide fiber of example 1, at 1000 times magnification;

FIG. 1c is an SEM topography of a polyimide fiber/silica composite A1 obtained in example 1, wherein the magnifications are 3000 times and 10000 times respectively;

FIG. 2a is an infrared spectrum of a polyimide film/silica composite A2 obtained in example 2;

FIG. 2b is an SEM topography of the untreated polyimide film of example 2, at a magnification of 5000;

FIG. 2c is an SEM topography of the polyimide film/silica composite A2 obtained in example 2, wherein the magnifications are 3000 times and 20000 times respectively;

FIG. 2d is an Atomic Force Microscope (AFM) topography of the polyimide film/silica composite A2 obtained in example 2 and the untreated virgin polyimide film;

FIG. 3 is an SEM topography of the polyimide fiber/silica composite A4 obtained in example 4, at 1000 times magnification;

FIG. 4 is an SEM topography of the polyimide fiber/silica composite A5 obtained in example 5, at a magnification of 1000;

FIG. 5 is an SEM topography of the polyimide film/silica composite A6 obtained in example 6, at a magnification of 3000;

FIG. 6 is an SEM topography of the polyimide film/silica composite A7 obtained in example 7, at a magnification of 3000;

FIG. 7 is an SEM topography of a polyimide fiber/silica composite D1 obtained in comparative example 1, wherein the magnification is 200000 times;

FIG. 8 is an SEM topography of polyimide fiber/silica composite D2 obtained in comparative example 2, at a magnification of 3000 times;

FIG. 9 is an SEM topography of polyimide fiber/silica composite D2 obtained in comparative example 3, at a magnification of 1000;

Fig. 10a is an X-ray diffraction pattern of a polyimide fiber as a raw material, a polyimide fiber when the temperature is increased to 100 c, a polyimide fiber when the temperature is increased to 200 c, and a polyimide fiber when the temperature is increased to 300 c in step (3) of example 1.

FIG. 10b is SEM images of the surface of the polyimide fibers at a temperature of 100 deg.C, the polyimide fibers at a temperature of 200 deg.C and the polyimide fibers at a temperature of 300 deg.C in step (3) of example 1.

FIG. 11a is an X-ray diffraction pattern of a polyimide film as a raw material, a polyimide film when the temperature is raised to 100 ℃, a polyimide film when the temperature is raised to 200 ℃ and a polyimide film when the temperature is raised to 300 ℃ in step (3) of example 2.

FIG. 11b is SEM images of the surface of the polyimide film at a temperature of 100 deg.C, the polyimide film at a temperature of 200 deg.C and the polyimide film at a temperature of 300 deg.C in step (3) of example 1.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

In the present invention, the "polyimide/silica composite" refers to a composite containing polyimide and silica, and the silica is attached to at least a part of the surface of the polyimide.

the first aspect of the invention provides a preparation method of a polyimide/silicon dioxide composite material, which comprises the following steps:

(1) Contacting the polyimide substrate with alkali liquor to obtain a polyimide substrate treated by the alkali liquor;

(2) Placing a dispersion liquid containing a silicon source in a reactor, placing a polyimide substrate treated by alkali liquor above the dispersion liquid, sealing the reactor, raising the temperature of the dispersion liquid to 160 ℃ with the reaction temperature being 100 ℃, preferably raising the temperature of the dispersion liquid to 150 ℃ with the reaction temperature being 110 ℃, and keeping the temperature at the reaction temperature for 2-24 hours, preferably 3-20 hours, more preferably 10-20 hours;

(3) And (3) carrying out heat treatment on the polyimide substrate obtained in the step (2).

According to the method, in the step (1), the polyimide substrate is contacted with alkali liquor, so that the alkali liquor etches the surface of the polyimide substrate, an active group-COO-is generated on the surface of the polyimide substrate and is used as a growth point of a hydrolysis condensation reaction of a silicon dioxide precursor, and silicon dioxide cannot grow on the surface of the substrate which is not etched. The polyimide substrate can be soaked in the alkali liquor, so that the surface of the polyimide substrate is etched by the alkali liquor.

According to the method of the present invention, in the step (1), the contacting is performed under conditions that allow the reactive group-COO-to be formed on the surface of the polyimide base. Preferably, the concentration of the alkali solution is 0.5-10mol/L, so that the active group-COO-can not be formed on the surface of the polyimide matrix, and the mechanical property of the polyimide matrix can not be significantly affected, and specifically, the concentration of the alkali solution can be 0.5mol/L, 1mol/L, 1.5mol/L, 2mol/L, 2.5mol/L, 3mol/L, 3.5mol/L, 4mol/L, 4.5mol/L, 5mol/L, 5.5mol/L, 6mol/L, 6.5mol/L, 7mol/L, 7.5mol/L, 8mol/L, 8.5mol/L, 9mol/L, 9.5mol/L or 10 mol/L. More preferably, the concentration of the alkali liquor is 4-7 mol/L. The alkali in the alkali solution can be an alkali capable of etching to form-COO-groups on the surface of the polyimide group, such as: alkali metal hydroxides, specific examples of which may include, but are not limited to: sodium hydroxide and/or potassium hydroxide. In particular, the lye may be an aqueous solution of sodium hydroxide and/or potassium hydroxide.

In step (1), the contacting may be carried out at a temperature of 0 to 60 ℃, for example: the contacting is carried out at a temperature of 5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃ or 60 ℃. Preferably, in step (1), the contacting is carried out at a temperature of 10-50 ℃. The duration of the contact may be selected according to the temperature of the contact. In general, the duration of the contact may be from 1 to 20min, for example: 1min, 2min, 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, 19min or 20 min. Preferably, the duration of said contact is between 2 and 10 min.

according to the method of the invention, the purpose of the step (2) is to generate a silicon-containing atmosphere in the container, so that silanol and siloxane in the silicon-containing atmosphere are adsorbed and reacted on the surface of the polyimide base body to generate a silicon dioxide precursor, and then the self-growth and self-deposition of silicon dioxide are completed on the surface of the base body.

In the step (2), the dispersion liquid can be silica sol and/or hydrolysate containing siloxane. The siloxane is preferably at least one of ethyl orthosilicate, methyl orthosilicate, methyltriethoxysilane and methyltrimethoxysilane.

in the step (2), the hydrolysis liquid containing siloxane contains siloxane, water, alcohol and catalyst. The alcohol may be C₁-C₆Alcohol of (2), preferably C₁-C₆More preferably C₁-C₄The aliphatic alcohol of (3) is more preferably at least one of methanol, ethanol, propanol and butanol. The catalyst may be an acid or a base, preferably an acid, more preferably at least one of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, formic acid, and acetic acid, and further preferably hydrochloric acid and/or sulfuric acid. In the hydrolysate containing siloxane, the molar ratio of siloxane, alcohol and water can be 1: (1-8): (1-10), preferably 1: (3-5): (4-7).The catalyst is preferably used in an amount such that the pH of the dispersion is from 0 to 5, more preferably such that the pH of the dispersion is from 1 to 4.

the siloxane-containing hydrolysate can be prepared by a method comprising the following steps: the siloxane is mixed with alcohol and water, and the catalyst is added to the mixture.

In the step (2), the volume of the dispersion is preferably 0.05 to 0.08 of the total volume of the reactor from the viewpoint of improving the safety of the reactor under the condition that the amount of the silicon source used is ensured to satisfy the use requirement.

in the step (2), the polyimide substrate is preferably placed 2 to 10cm above the dispersion, more preferably 2.5 to 8cm above the dispersion, and further preferably 3 to 5cm above the dispersion.

In the step (2), after the reactor is closed, the temperature of the dispersion is preferably gradually raised to the reaction temperature to form a more uniform silica layer on the surface of the polyimide base. Preferably, after closing the reactor, the temperature of the dispersion is raised to the reaction temperature at a rate of 1-3 ℃/min.

in the step (2), from the viewpoint of further improving the uniformity of the silica layer formed on the surface of the polyimide base, it is preferable to stir the dispersion at an ambient temperature (usually 15 to 40 ℃, preferably 20 to 30 ℃) for 20 to 60 minutes before raising the temperature of the dispersion to the reaction temperature.

In the step (2), the reaction temperature may be specifically 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃, 150 ℃, 155 ℃ or 160 ℃. In the step (2), the dispersion may be maintained at the reaction temperature for 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, or 24 hours.

According to the method of the present invention, the polyimide substrate is subjected to heat treatment at a high temperature in step (3) in order to cyclize the alkali-etched polyimide again.

In the step (3), the heat treatment is carried out under conditions such that the polyimide substrate can be cyclized, and the heat treatment may be carried out at a temperature of, for example, 200 ℃ and 360 ℃. Preferably, the heat treatment is carried out at a temperature of 280-350 ℃, for example: 280 ℃, 285 ℃, 290 ℃, 295 ℃, 300 ℃, 305 ℃, 310 ℃, 315 ℃, 320 ℃, 325 ℃, 330 ℃, 335 ℃, 340 ℃, 345 ℃ or 350 ℃. The duration of the heat treatment can be selected according to the temperature of the heat treatment and can be between 0.5 and 2h, for example: 0.5h, 1h, 1.5h or 2 h. Preferably, the duration of the heat treatment is 1-2 h. In the step (3), the temperature of the polyimide substrate obtained in the step (2) is preferably gradually raised to the heat treatment temperature. More preferably, the polyimide substrate obtained in step (2) is raised to the heat treatment temperature at a rate of 0.5 to 5 ℃/min. Further preferably, the polyimide substrate obtained in the step (2) is raised to the heat treatment temperature at a rate of 1.5 to 3 ℃/min.

According to the method of the present invention, the polyimide substrate is preferably a polyimide material having a large specific surface area, but a polyimide material having a small specific surface area is also applicable. According to the method of the present invention, the polyimide substrate may be at least one of a polyimide fiber, a polyimide film, a polyimide nanofiber membrane, and a polyimide felt, and the polyimide of the present invention has no particular requirement on the chemical structure of the polyimide, and may be one or a combination of two or more of an aliphatic polyimide, a semi-aromatic polyimide, and an aromatic polyimide.

According to the method of the present invention, the polyimide substrate may be washed by a conventional method before use to purify the surface of the substrate, for example: the polyimide substrate surface may be washed with water. From the viewpoint of further improving the washing effect, the washing is preferably ultrasonic cleaning.

The second aspect of the present invention provides a polyimide/silica composite material produced by the production method according to the first aspect of the present invention.

The composite material according to the present invention comprises a polyimide substrate and silica particles attached to the surface of the polyimide substrate.

According to the composite material of the present invention, the silica particles preferably have a particle size of 50 to 500 nm. The particle size of the silica particles is measured by a scanning electron microscope or an atomic force microscope.

In the prior art, a silicon dioxide precursor is added into a polyamic acid solution to prepare a polyamic acid/silicon dioxide precursor composite material, and then hydrolysis of the silicon dioxide precursor and imidization of the polyamic acid are performed. Compared with the prior art, the invention has the following advantages and characteristics:

(1) In the invention, after the polyimide substrate material in any form is etched by alkali liquor, the surface of the polyimide substrate material is provided with a group-COO-with higher activity, in the heat treatment process, a silicon source volatilizes, and because the silicon hydroxyl group and the carbonyl group after the opening of the imine ring form a hydrogen bond to interact with an organic phase, the self-growth and self-deposition of silicon dioxide on the polyimide substrate are realized, and the silicon dioxide precursor does not need to be doped in the polyamic acid solution to influence the substrate performance. And the generated silicon dioxide particles or deposition layers are uniform and compact, and the deposition amount of the silicon dioxide on the surface of the matrix can be regulated and controlled by controlling the using amount of the silicon source and the acting time of steam.

(2) The polyimide substrate etched by the alkali liquor is subjected to high-temperature hot cyclization again, various performances such as mechanical strength and the like of the substrate are recovered, a compact silicon dioxide protective layer is formed on the surface of the polyimide material, and the polymer material is not changed in property and simultaneously forms a compact protective layer, so that atomic oxygen cannot penetrate through the protective layer to enter the surface of the polymer to react with carbon elements, and the improvement of the atomic oxygen resistance of the polyimide is facilitated.

(3) The preparation method provided by the invention does not need complex preparation process and post-treatment steps, has wide application range, and can meet the modification requirements of polyimide materials with different chemical structures and different physical appearances.

For a better understanding and description of the present invention, reference is made to the following drawings and examples, which together with the description serve to explain the principles of the invention and its practical application, all such modifications as fall within the scope of the claims.

In the following examples and comparative examples, infrared spectroscopic analysis was carried out on an infrared spectrometer available from Nicolet, USA under the model Nwxus 670.

In the following examples and comparative examples, Scanning Electron Microscope (SEM) analysis was performed on a scanning electron microscope of type S-4700449C available from HITACHI, Japan.

In the following examples and comparative examples, Atomic Force Microscope (AFM) analysis was performed on an AFM5500 model number available from Chiese chemical industries, Inc. (TCI).

In the following examples and comparative examples, X-ray diffraction (XRD) analysis was carried out on an X-ray diffractometer, model Bruker D8 Advance, from Bruker, Germany.