阅读说明：本技术 一种聚酰亚胺复合材料及其制备方法 (Polyimide composite material and preparation method thereof ) 是由 孟思益 罗熙雯 王芳 周利庄 于 2021-08-31 设计创作，主要内容包括：本发明涉及聚酰亚胺领域,具体涉及一种聚酰亚胺复合材料及其制备方法。本发明提供一种低热膨胀系数聚酰亚胺复合材料,与传统的石墨填充聚酰亚胺复合材料相比,该材料生产工艺简单,具有较低的热膨胀系数。本发明的技术方案为：一种低热膨胀系数耐高温聚酰亚胺复合材料,是由以下重量百分比的原料组成：聚酰亚胺树脂：54-83；石墨：10-30；碳纤维：5-10；金属纳米纤维：2-6。通过在传统的石墨填充耐高温聚酰亚胺基础上,同时添加碳纤维和金属纳米纤维,不仅可以提高材料的力学性能,还能使材料热膨胀系数降低20％以上,大幅提高了材料在高温下的尺寸稳定性。(The invention relates to the field of polyimide, and particularly relates to a polyimide composite material and a preparation method thereof. Compared with the traditional graphite filled polyimide composite material, the polyimide composite material with the low thermal expansion coefficient provided by the invention has the advantages of simple production process and lower thermal expansion coefficient. The technical scheme of the invention is as follows: a low thermal expansion coefficient high temperature resistant polyimide composite material is composed of the following raw materials by weight percent: polyimide resin: 54-83; graphite: 10-30 parts of; carbon fiber: 5-10; metal nano-fiber: 2-6. On the basis of traditional high-temperature-resistant polyimide filled with graphite, carbon fibers and metal nanofibers are added simultaneously, so that the mechanical property of the material can be improved, the thermal expansion coefficient of the material can be reduced by more than 20%, and the dimensional stability of the material at high temperature is greatly improved.)

1. The polyimide composite material is characterized by comprising the following raw materials in percentage by weight:

polyimide resin: 54-83

Graphite: 10-30

Carbon fiber: 5-10

Metal nano-fiber: 2-6.

2. The polyimide composite material according to claim 1, wherein the polyimide resin is a polyimide resin obtained by polycondensation of pyromellitic anhydride and 4, 4-diaminodiphenyl ether as monomers.

3. The polyimide composite material as claimed in claim 1, wherein the graphite is one or a combination of two of flake graphite with a particle size of 800 mesh or more and amorphous graphite.

4. The polyimide composite material as claimed in claim 1, wherein the carbon fiber has a length of 200-500 μm.

5. The polyimide composite material as claimed in claim 1, wherein the metal nanofibers are one or more of copper nanofibers, aluminum nanofibers or stainless steel nanofibers, have a length of 50-1000 μm, and have a diameter of 50-500 nm.

6. The polyimide composite material as claimed in claim 1, wherein the metal nanofibers have a length of 100-500 μm and a diameter of 50-100 nm.

7. The polyimide composite material according to any one of claims 1 to 6, wherein the raw materials comprise, in parts by weight:

polyimide resin: 67-76

Graphite: 15-20

Carbon fiber: 6-8

Metal nano-fiber: 3-5.

8. The polyimide composite material according to any one of claims 1 to 6, wherein the polyimide composite material is a polyimide composite materialThe thermal expansion coefficient of the polyimide composite material is less than or equal to 36 multiplied by 10^-6/℃。

9. The method for preparing a polyimide composite material according to any one of claims 1 to 8, comprising the steps of:

s1, cleaning the metal nano-fibers in alcohol for 8-12min, and then drying for 2-3 h;

s2, drying the polyimide resin, the graphite and the carbon fiber at the temperature of 150-;

s3, adding the polyimide resin, the graphite, the carbon fiber and the metal nanofiber into a high-speed mixer according to the mass percentage of the formula, and uniformly mixing at normal temperature to obtain a mixed material;

and S4, coating a silicone oil high-temperature release agent on the inner surface of the mold, and carrying out hot-press molding on the mixed material obtained in the step S3.

10. The method as claimed in claim 9, wherein the hot pressing temperature of the hot pressing molding in step S4 is 400-420 ℃, the pressure is 70-100MPa, and the time is 1.5-2.0 h.

Technical Field

The invention relates to the field of polyimide, and particularly relates to a polyimide composite material and a preparation method thereof.

Background

Polyimide resin has excellent heat resistance and mechanical properties, and is always the focus of research on high-temperature resistant composite materials of aero-engines. The polyimide can be used within the range of 280-450 ℃, and the polyimide-based composite material has good mechanical property and electrical property, high specific strength and specific stiffness, excellent thermal stability and chemical stability, small thermal expansion coefficient, strong solvent resistance, high dimensional stability and easy molding of a part with a complex shape, and is a resin-based composite material for a structure widely used by the current aero-engine. The PMDA-ODA type polyimide resin prepared by polycondensation by taking pyromellitic dianhydride (PMDA) and 4, 4-diaminodiphenyl ether (ODA) as monomers has the advantages of large rigidity of molecular structure, regular molecular chain, good symmetry and excellent heat resistance, and can be used for high-temperature resistant parts of aeroengines, such as bushings, bearings and the like, by filling graphite in the PMDA-ODA type polyimide resin, the lubricating and wear-resisting properties of the polyimide resin can be improved.

At present, polyimide resin matrix composite materials used by domestic engines mainly comprise fiber reinforced polyimide and graphite filled polyimide. The graphite filled polyimide (PMDA-ODA) composite material has excellent heat resistance, lubrication, wear resistance and other performances, and the short-term use temperature can reach more than 450 ℃, but the material has large thermal expansion coefficient, poor dimensional stability at high temperature, complex production process and special forming and processing process, so the manufacturing cost is high, and continuous mass production is difficult to realize. The fiber-woven reinforced polyimide composite material has excellent mechanical property, good durability, good heat resistance of a thermosetting polyimide resin matrix, a use temperature of up to 360-370 ℃, low friction factor, extremely low linear expansion coefficient compared with a graphite-filled linear polyimide composite material, and remarkably improved dimensional stability, but the application of the fiber-woven composite material is greatly restricted due to high carbon fiber weaving cost and complex manufacturing process.

Disclosure of Invention

The invention aims to provide a polyimide composite material with a low thermal expansion coefficient, which has a simple production process and a lower thermal expansion coefficient and improves the dimensional stability of the material under a high-temperature working condition compared with the traditional graphite filled polyimide composite material.

In order to solve the above technology, the technical scheme of the invention is as follows:

the low-thermal expansion coefficient high-temperature resistant polyimide composite material is characterized by comprising the following raw materials in percentage by weight:

polyimide resin: 54-83

Graphite: 10-30

Carbon fiber: 5-10

Metal nano-fiber: 2-6.

Further, the polyimide resin is a PMDA-ODA type polyimide resin obtained by polycondensation of pyromellitic dianhydride (PMDA) and 4, 4-diaminodiphenyl ether (ODA) as monomers.

Further, the graphite is one or a combination of two of flake graphite and amorphous graphite with more than 800 meshes, and the graphite is used as a self-lubricating functional filler, so that the heat resistance, the lubricating property and the wear resistance of the composite material can be enhanced.

Further, the length of the carbon fiber is 200-500 μm. The combination of the carbon fiber and the matrix resin can enhance the mechanical property of the composite material, reduce the linear expansion coefficient of the composite material and improve the dimensional stability.

Further, the metal nano fiber is one or more of copper nano fiber, aluminum nano fiber or stainless steel nano fiber, the length of the metal nano fiber is 50-1000 mu m, and the diameter of the metal nano fiber is 50-500 nm. The metal nano-fiber is selected, has small particle size, larger specific surface area and stronger interface bonding force with matrix resin, and can improve the mechanical property of the composite material; meanwhile, the metal nano-fiber has low thermal expansion coefficient and good dispersibility, and can reduce the thermal expansion coefficient when being added into the composite material.

Preferably, the metal nanofiber has a length of 100-500 μm and a diameter of 50-100 nm.

Further, the preparation method of the polyimide composite material comprises the following steps:

s1, washing the metal nano-fibers in alcohol for 8-12min, and then drying for 2-3 h.

S2, drying the polyimide resin, the graphite and the carbon fiber at the temperature of 150-175 ℃ for 3-5 h.

S3, adding the metal nano-fibers, the polyimide resin, the graphite and the carbon fibers obtained after the treatment in the steps S1 and S2 into a high-speed mixer according to the mass percentage of the formula, and uniformly mixing at normal temperature to obtain the mixed material.

And S4, coating a silicone oil high-temperature release agent on the inner surface of the mold, and carrying out hot-press molding on the mixed material obtained in the step S3.

Further, the hot press molding in step S4 is to select a corresponding mold according to a specific prepared component, and hot press mold the mixed material prepared in step S3 to obtain the polyimide composite material.

Further, the hot pressing temperature of the hot pressing molding in the step S4 is 400-420 ℃, the pressure is 70-100MPa, and the time is 1.5-2.0 h.

Preferably, the raw materials by weight percentage are:

polyimide resin: 67-76

Graphite: 15-20

Carbon fiber: 6-8

Metal nano-fiber: 3-5.

Furthermore, the thermal expansion coefficient of the polyimide composite material is less than or equal to 36 multiplied by 10^-6/℃。

Compared with the prior art, the invention has the following beneficial effects:

the short-term use temperature of the traditional graphite filled polyimide (PMDA-ODA) composite material can reach more than 450 ℃, but the thermal expansion coefficient of the material is larger, and the dimensional stability at high temperature is poorer.

The metal nano-fiber is a nano-material with small particle size, large specific surface area, small thermal expansion coefficient, good dispersibility and strong interface bonding force with matrix resin; on the basis of traditional high-temperature-resistant polyimide filled with graphite, carbon fibers and metal nanofibers are added simultaneously, so that the mechanical property of the material can be improved, the thermal expansion coefficient of the material can be reduced by more than 20%, and the dimensional stability of the material at high temperature is greatly improved. The polyimide material with the low thermal expansion coefficient provided by the invention can replace high-temperature resistant materials such as metal, ceramic and the like under specific conditions due to stable size under high-temperature conditions, and can be used as high-temperature resistant lubricating wear-resistant materials such as aircraft engine bearings, bushings and the like.

The traditional manufacturing process of the graphite filled polyimide composite material or the fiber woven reinforced polyimide composite material is complex, the cost is high, the polyimide composite material provided by the invention does not need a special forming or processing process, the preparation process is simple, the manufacturing cost is reduced, and the method is suitable for continuous large-batch production and manufacturing.

Drawings

FIG. 1 is a flow chart of the preparation of a polyimide composite material with low thermal expansion coefficient according to the present invention.

Detailed Description

The invention will be described with reference to specific embodiments. It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

Example 1

The copper nanofibers were washed in alcohol for 10min and then dried for 3 h.

Drying PMDA-ODA type polyimide resin, flake graphite and carbon fiber at 150 ℃ for 5 h.

And (3) adding the raw materials obtained after the treatment in the steps into a high-speed mixer, and uniformly mixing at normal temperature to obtain the mixed material. The weight portions of the raw materials are as follows:

58 parts of PMDA-ODA type polyimide resin

30 parts of flake graphite

10 parts of carbon fiber

And 2 parts of copper nano fibers.

Hot-pressing the material according to the specifically prepared part, wherein the hot-pressing process comprises the following steps:

coating a silicone oil high-temperature release agent on the inner surface of a mould, adding the mixed material into the mould, and performing hot press molding, wherein the mould pressing temperature is 410 ℃, the pressure is 90MPa, and the time is 1.5 h.

Example 2

The aluminum nanofibers were washed in alcohol for 8min and then dried for 3 h.

Drying PMDA-ODA type polyimide resin, flake graphite and carbon fiber at 150 ℃ for 5 h.

And (3) adding the raw materials obtained after the treatment in the steps into a high-speed mixer, and uniformly mixing at normal temperature to obtain the mixed material. The raw materials comprise the following components in parts by weight:

78 parts of PMDA-ODA type polyimide resin

10 parts of flake graphite

8 parts of carbon fiber

4 parts of aluminum nano fiber.

Hot-pressing the material according to the specifically prepared part, wherein the hot-pressing process comprises the following steps:

coating a silicone oil high-temperature release agent on the inner surface of a mould, adding the mixed material into the mould, and performing hot press molding at the mould pressing temperature of 420 ℃, the pressure of 70MPa and the time of 2 h.

Example 3

The stainless steel nanofiber is washed in alcohol for 10min and then dried for 2 h.

Drying PMDA-ODA type polyimide resin, amorphous graphite and carbon fiber at 170 ℃ for 3.5 h.

And (3) adding the raw materials obtained after the treatment in the steps into a high-speed mixer, and uniformly mixing at normal temperature to obtain the mixed material. The raw materials comprise the following components in parts by weight:

71 parts of PMDA-ODA type polyimide resin

Amorphous graphite 15 parts

10 parts of carbon fiber

4 parts of stainless steel nano fiber.

Hot-pressing the material according to the specifically prepared part, wherein the hot-pressing process comprises the following steps:

coating a silicone oil high-temperature release agent on the inner surface of a mould, adding the mixed material into the mould, and performing hot press molding, wherein the mould pressing temperature is 410 ℃, the pressure is 80MPa, and the time is 1.5 h.

Example 4

The copper nanofibers were washed in alcohol for 12min and then dried for 3 h.

The PMDA-ODA type polyimide resin, the flake graphite and the carbon fiber are dried for 3 hours at the temperature of 175 ℃.

And (3) adding the raw materials obtained after the treatment in the steps into a high-speed mixer, and uniformly mixing at normal temperature to obtain the mixed material. The raw materials comprise the following components in parts by weight:

79 parts of PMDA-ODA type polyimide resin

10 parts of flake graphite

5 parts of carbon fiber

6 parts of copper nano fibers.

Hot-pressing the material according to the specifically prepared part, wherein the hot-pressing process comprises the following steps:

coating a silicone oil high-temperature release agent on the inner surface of a mould, and adding the mixed material into the mould, wherein the mould pressing temperature is 400 ℃, the pressure is 70MPa, and the time is 2 hours.

Example 5

The copper nanofibers were washed in alcohol for 12min and then dried for 3 h.

Drying PMDA-ODA type polyimide resin, flake graphite and carbon fiber at 160 ℃ for 4 h.

And (3) adding the raw materials obtained after the treatment in the steps into a high-speed mixer, and uniformly mixing at normal temperature to obtain the mixed material. The raw materials comprise the following components in parts by weight:

69 parts of PMDA-ODA type polyimide resin

15 parts of flake graphite

10 parts of carbon fiber

6 parts of copper nano fibers.

Hot-pressing the material according to the specifically prepared part, wherein the hot-pressing process comprises the following steps:

coating a silicone oil high-temperature release agent on the inner surface of a mould, and adding the mixed material into the mould, wherein the mould pressing temperature is 420 ℃, the pressure is 90MPa, and the time is 2 h.

The carbon fiber length selected in the above embodiment is within 200-500 μm, such as 200 μm, 300 μm, 500 μm.

The metal nanofibers selected in the above embodiments have a length within 50-1000 μm, such as 50 μm, 100 μm, 500 μm, 800 μm, 1000 μm, preferably within 100-500 μm, and a diameter within 50-500nm, such as 50nm, 100nm, 300nm, 500nm, preferably within 50-100 nm.

Comparative example 1

Drying PMDA-ODA type polyimide resin, flake graphite and carbon fiber at 150 ℃ for 5 h.

And (3) adding the raw materials obtained after the treatment in the steps into a high-speed mixer, and uniformly mixing at normal temperature to obtain the mixed material. The raw materials comprise the following components in parts by weight:

69 parts of PMDA-ODA type polyimide resin

15 parts of flake graphite

16 parts of carbon fiber.

Hot-pressing the material according to the specifically prepared part, wherein the hot-pressing process comprises the following steps:

coating a silicone oil high-temperature release agent on the inner surface of a mould, and adding the mixed material into the mould, wherein the mould pressing temperature is 400 ℃, the pressure is 80MPa, and the time is 2 h.

Comparative example 2

Drying PMDA-ODA type polyimide resin and flake graphite at 150 ℃ for 5 h.

And (3) adding the raw materials obtained after the treatment in the steps into a high-speed mixer, and uniformly mixing at normal temperature to obtain the mixed material. The raw materials comprise the following components in parts by weight:

85 parts of PMDA-ODA type polyimide resin

15 parts of flake graphite.

Hot-pressing the material according to the specifically prepared part, wherein the hot-pressing process comprises the following steps:

coating a silicone oil high-temperature release agent on the inner surface of a mould, and adding the mixed material into the mould, wherein the mould pressing temperature is 420 ℃, the pressure is 70MPa, and the time is 2 h.

The products obtained in examples 1 to 6 and comparative examples 1 to 2 were subjected to a performance test and a performance comparison was made.

The tensile strength is measured according to GB/T1040.1-2018 and GB/T1040.2-2006;

the bending strength is determined according to GB/T9341-;

the coefficient of thermal expansion was determined in accordance with GB/T1036-2008.

The performance pair ratios are shown in table 1:

TABLE 1

As can be seen from Table 1, the polyimide composite material with a low thermal expansion coefficient of the invention has excellent mechanical properties, and compared with the traditional graphite-filled polyimide composite material, the thermal expansion coefficient of the polyimide composite material prepared by the technology of the invention is greatly reduced by more than 20%, which greatly improves the dimensional stability of the material in a high-temperature environment. The material can replace high-temperature resistant materials such as metal, ceramic and the like under specific conditions, and can be used for high-temperature resistant, lubricating and wear-resistant materials such as aircraft engine bearings, bushings and the like.

The preparation process of the polyimide material with the low thermal expansion coefficient is simple, a special molding treatment process is not needed, the manufacturing cost is reduced, and the polyimide material is more suitable for continuous mass production.