Bulk-phase high molecular weight modified polyimide composite material and preparation method thereof

Abstract

The invention belongs to the field of resin-based composite materials, and relates to a bulk-phase high-molecular-weight modified polyimide composite material and a preparation method thereof. The composite material resin comprises low-viscosity polyimide resin A and high-molecular-weight polyimide resin B, the low-viscosity polyimide resin A realizes RTM molding of the composite material, and the high-molecular-weight polyimide resin B realizes bulk phase modification of the composite material. The resin A and the resin B respectively have different viscosity matching requirements at the injection temperature and the low-viscosity co-temperature point, so that the purposes of low-resistance injection and interpenetration between the low-viscosity co-temperature point resins to form an interface are achieved. According to the present invention, the bulk phase high molecular weight modification of the composite material can be achieved while the polyimide composite material adopts the RTM low-cost molding process, such that the method is the new way for the high performance of the RTM molding polyimide composite material, and can be used for the lightweight of the high-temperature-resistant components of the aero-engine, the aviation, the aerospace and other advanced equipment.

Description

Technical Field

[0001] The invention belongs to the field of resin-based composite materials and relates to a bulk high molecular weight modified polyimide composite material and a preparation method thereof. Background Art

[0002] The heat resistance of polyimide resin-based composite materials can reach above 280℃, which is the highest grade of composite materials in temperature resistance at present. It has great application value in high-tech fields such as aerospace. As an alternative or supplementary process to hot pressing process, resin transfer molding (RTM) molding process has the advantages of relatively simple process, low production cost, complex components, high component integrity and short process cycle. The key to the RTM molding of polyimide composite materials is that the resin matrix can meet the process requirements of melt viscosity below 1Pa·s. In order to regulate the viscosity of the polyimide resin matrix, it is necessary to use an active end-capping agent (such as phenylacetylene phthalic anhydride PEPA) to end-cap the resin molecular chain to control the molecular weight. For polyimide resins that meet the RTM molding process, the resin molecular weight is usually controlled to a lower value below 1250g / mol, and low molecular weight has an adverse effect on the thermal oxidation stability and toughness of polyimide composites.

[0003] Patent ZL201910982456.5 discloses a method for improving the thermal oxidation stability of RTM-molded polyimide composite materials. In this method, the composite material is surface-modified with a high molecular weight polyimide resin, and the core layer matrix is ​​a low-viscosity resin. In order to further achieve high performance of thermal aging stability and toughness of RTM-molded polyimide composite materials, it is necessary to develop new methods. Summary of the invention

[0004] The purpose of the present invention is to provide a bulk high molecular weight modified polyimide composite material and a preparation method thereof, so as to achieve high performance of RTM molded polyimide composite materials.

[0005] The technical solution of the present invention is:

[0006] A method for preparing a bulk high molecular weight modified polyimide composite material, wherein the composite material is prepared by a resin transfer molding (RTM) process, and the preparation steps are as follows:

[0007] (1) placing a fiber preform in a closed mold, wherein the fiber preform is a fiber product pre-impregnated with a polytetraacetic acid diester diamide or a polyamic acid precursor solution of a polyimide resin B, and heating the mold to an injection temperature point of the injection polyimide resin A;

[0008] (2) melting the polyimide resin A and injecting it into the mold described in step (1);

[0009] (3) heating the mold in step (2) to a low viscosity common temperature point of the viscosity of the polyimide resin A and the polyimide resin B, and keeping the temperature for no less than 30 minutes;

[0010] (4) heating the mold in step (3) to between 350° C. and 400° C. to solidify the composite material;

[0011] (5) After cooling the mold in step (4), demolding is performed to obtain the composite material.

[0012] The viscosity of the polyimide resin A at the injection temperature is not higher than 1 Pa·s.

[0013] The polyimide resin B has a designed molecular weight between 1500 and 50000 g / mol, and at the injection temperature of the polyimide resin A, its viscosity is not less than 3000 Pa·s, preferably not less than 5000 Pa·s.

[0014] The mass fraction of the polyimide resin B in the fiber preform is between 10% and 40%.

[0015] At a temperature point higher than the injection temperature of the polyimide resin A, the polyimide resin A and the polyimide resin B have a low viscosity eutectic point, and the viscosity of both at the low viscosity eutectic point is no higher than 500 Pa·s.

[0016] The polyimide resin A and the polyimide resin B are both thermosetting polyimide resins.

[0017] The molecular chain end of the thermosetting polyimide resin matrix contains one of acetylene, phenylacetylene and norbornene.

[0018] The fibers in the fiber preform are selected from one or more of carbon fibers, glass fibers, quartz fibers, polyimide fibers, and aramid fibers.

[0019] The invention has the advantages that: the invention discloses a bulk phase high molecular weight modified polyimide composite material and a preparation method thereof, and realizes bulk phase high molecular weight modification of RTM molded polyimide composite material by viscosity matching design of high molecular weight modified resin and low viscosity polyimide resin for injection. The two resins have different viscosity matching requirements at injection temperature and low viscosity eutectic point, respectively, so as to realize the purpose of low resistance injection and resin interpenetration to form interface: (1) the viscosity of polyimide resin A at injection temperature is not higher than 1Pa·s, which is convenient for injection; (2) the polyimide resin B precursor solution is pre-impregnated into the fiber preform, and a porous structure is formed after heat treatment, and because it is in an infusible state with a viscosity of not less than 3000Pa·s at injection temperature, the porous structure can be maintained, thereby reducing the flow resistance of resin A; (3) polyimide resins A and B have a low viscosity eutectic point of not higher than 500Pa·s after injection, which is convenient for resins to interpenetrate to form a fusion interface. The invention can realize bulk high molecular weight modification of the composite material while adopting the RTM low-cost molding process for the polyimide composite material, and is a new way to improve the high performance of the RTM molded polyimide composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Ultrasonic nondestructive testing results of polyimide composite materials: a Example 1, b Comparative Example 1

[0021] Green to white, good internal quality; blue to black, with delamination defects. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with specific examples, but the present invention is not limited to the following examples. The methods described are conventional methods unless otherwise specified. The materials described can be obtained from public commercial channels unless otherwise specified.

[0023] A method for preparing a bulk high molecular weight modified polyimide composite material, wherein the composite material is prepared by a resin transfer molding (RTM) process, and the preparation steps are as follows:

[0024] (1) placing a fiber preform in a closed mold, wherein the fiber preform is a fiber product pre-impregnated with a polytetraacetic acid diester diamide or a polyamic acid precursor solution of a polyimide resin B, and heating the mold to an injection temperature point of the injection polyimide resin A;

[0025] (2) melting the polyimide resin A and injecting it into the mold described in step (1);

[0026] (3) heating the mold in step (2) to a low viscosity common temperature point of the viscosity of the polyimide resin A and the polyimide resin B, and keeping the temperature for no less than 30 minutes;

[0027] (4) heating the mold in step (3) to between 350° C. and 400° C. to solidify the composite material;

[0028] (5) After cooling the mold in step (4), demolding is performed to obtain the composite material.

[0029] The viscosity of the polyimide resin A at the injection temperature is not higher than 1 Pa·s.

[0030] The polyimide resin B has a designed molecular weight between 1500 and 50000 g / mol, and at the injection temperature of the polyimide resin A, its viscosity is not less than 3000 Pa·s, preferably not less than 5000 Pa·s.

[0031] The mass fraction of the polyimide resin B in the fiber preform is between 10% and 40%.

[0032] At a temperature point higher than the injection temperature of the polyimide resin A, the polyimide resin A and the polyimide resin B have a low viscosity eutectic point, and the viscosity of both at the low viscosity eutectic point is no higher than 500 Pa·s.

[0033] The polyimide resin A and the polyimide resin B are both thermosetting polyimide resins.

[0034] The molecular chain end of the thermosetting polyimide resin matrix contains one of acetylene, phenylacetylene and norbornene.

[0035] The fibers in the fiber preform are selected from one or more of carbon fibers, glass fibers, quartz fibers, polyimide fibers, and aramid fibers.

[0036] The composite material samples were cut into 150 (length) * 12 (width), placed in 350 ° C air for 200 hours, and the thermal aging weight loss of the samples was tested; the composite material was cut into pieces and the post-impact compression strength was tested according to ASTM D 7136 and ASTM D 7137.

[0037] The specific embodiments are as follows:

[0038] Embodiment 1:

[0039] The bulk high molecular weight modified polyimide composite material in this embodiment is composed as follows:

[0040] (1) The polyimide resin A is a low-viscosity 4-phenylethynylphthalic anhydride-terminated 2,3,3',4'-biphenyltetracarboxylic acid dianhydride type polyimide, and the resin injection temperature is selected to be 280°C, and its viscosity at this temperature is 0.1 Pa·s;

[0041] (2) The fiber preform is a T800 grade carbon fiber product pre-impregnated with a polytetraacetic acid diester diamide precursor solution of polyimide resin B, wherein the mass fraction of resin B is 25%; polyimide resin B is a fluorinated polyimide terminated with 4-phenylethynylphthalic anhydride, having a designed molecular weight of 2000 g / mol and a viscosity of 11000 Pa·s at an injection temperature of 280°C; the low viscosity common temperature point of the polyimide resin A and the polyimide resin B is 325°C, and the viscosities of resin A and resin B at 325°C are 0.1 Pa·s and 180 Pa·s, respectively.

[0042] The bulk high molecular weight modified polyimide composite material is prepared by RTM process, and the preparation steps are as follows:

[0043] (1) placing a fiber preform in a closed mold, and heating the mold to an injection temperature of the polyimide resin A of 280° C.;

[0044] (2) melting the polyimide resin A and injecting it into the mold described in step (2);

[0045] (3) heating the mold in step (2) to 325° C., the low viscosity common temperature point of the viscosity of polyimide resin A and polyimide resin B, and keeping the temperature for 60 min;

[0046] (4) heating the mold in step (3) to 380° C. to solidify the composite material;

[0047] (5) After cooling the mold in step (4), demolding is performed to obtain the composite material.

[0048] After the composite material samples were cut, thermal aging weight loss and post-impact compression strength tests were carried out.

[0049] Embodiment 2:

[0050] Compared with Example 1: the injection temperature of polyimide resin A is selected to be 287° C., and the viscosity of polyimide resin B at the injection temperature is 5000 Pa·s.

[0051] Other information is the same as Example 1.

[0052] Embodiment 3:

[0053] Compared with Example 1: (1) polyimide resin A is a medium-low viscosity 4-phenylethynylphthalic anhydride terminated polyimide, the resin injection temperature point is 280°C, and its viscosity at this temperature point is 1 Pa·s; (2) polyimide resin B is a phenylethynyl terminated biphenyltetracarboxylic dianhydride-p-phenylenediamine / ether diamine type polyimide resin, with a designed molecular weight of 5000 g / mol, and its viscosity at an injection temperature point of 280°C is 3000 Pa·s; the low viscosity common temperature point of the polyimide resin A and the polyimide resin B is 325°C, and the viscosities of the resin A and the resin B at 325°C are 5 Pa·s and 100 Pa·s, respectively.

[0054] Other information is the same as Example 1.

[0055] Embodiment 4:

[0056] Compared with Example 1, the mass fraction of resin B in the fiber preform is 35%.

[0057] Other information is the same as Example 1.

[0058] Comparative Example 1:

[0059] Compared with Example 2, the designed molecular weight of polyimide resin B is 3000 g / mol, and its viscosity at the injection temperature of 280° C. is 800 Pa·s, and its viscosity at 325° C. is 50 Pa·s.

[0060] Other information is the same as Example 2.

[0061] Comparative Example 2:

[0062] Compared with Example 2, the designed molecular weight of polyimide resin B is 10000 g / mol, and its viscosity at an injection temperature of 280° C. and above is higher than 12000 Pa·s, and there is no low-viscosity temperature point with a viscosity lower than 500 Pa·s.

[0063] Other information is the same as Example 2.

[0064] Comparative Example 3:

[0065] Compared with Example 1, the fiber preform is not pre-impregnated with polyimide resin B, and the other implementation processes are the same as those of Example 1.

[0066] The internal states of the composite materials of the embodiments and comparative examples are shown in Table 1. In embodiments 1 to 4, the viscosity of resin A at an injection temperature of 280°C is not higher than 1 Pa·s, the viscosity of resin B at the injection point is above 3000 Pa·s, and resin A and resin B have a low-viscosity point with a viscosity lower than 500 Pa·s at 325°C after injection. The mass fraction of resin B in the fiber preform reaches 35%, and a composite material with sufficient injection, no delamination and excellent internal quality can be obtained ( Figure 1 Left). In Comparative Example 1, the viscosity of resin B at the injection point is 800 Pa·s, and the composite material cannot be injected and has internal defects such as delamination ( Figure 1 Right), which is related to the destruction of the porous structure caused by the melting of resin B and the high viscosity of resin A; in comparative example 2, the viscosity of resin B at 325°C reaches more than 12000Pa·s, there is no low viscosity point, and the composite material has defects such as pores and stratification, which is related to the failure of resin B to form a good interface with resin A. Compared with the composite material prepared by pure low-viscosity thermosetting resin A (molecular weight below 1250g / mol) in comparative example 1, after the bulk phase high molecular weight modification of the composite material using high molecular weight resin B, the thermal weight loss rate of the composite material is reduced by more than 80%, and the compression strength after impact is increased by more than 40%. The above results illustrate that the disclosed bulk phase high molecular weight modified polyimide composite material and its preparation method, through the viscosity matching design of high molecular weight modified resin and injection low viscosity polyimide resin, realizes the bulk phase high molecular weight modification of the composite material while realizing the RTM process molding of the composite material, improves the thermal aging stability and toughness of the composite material, and provides a new way to improve the high performance of RTM molded polyimide composite materials.

[0067] Table 1 Comparison of internal molding quality and performance of composite materials in Examples and Comparative Examples

[0068]

[0069] .

Claims

1. A method for preparing a bulk high molecular weight modified polyimide composite material, characterized in that: The composite material is prepared by resin transfer molding (RTM) process, and the preparation steps are as follows: (1) placing a fiber preform in a closed mold, wherein the fiber preform is a fiber product pre-impregnated with a polytetraacetic acid diester diamide or a polyamic acid precursor solution of a polyimide resin B, and heating the mold to an injection temperature point of the injection polyimide resin A; (2) melting the polyimide resin A and injecting it into the mold described in step (1); (3) heating the mold in step (2) to a low viscosity common temperature point of the viscosity of the polyimide resin A and the polyimide resin B, and keeping the temperature for no less than 30 minutes; (4) heating the mold in step (3) to between 350° C. and 400° C. to solidify the composite material; (5) After cooling the mold in step (4), demolding is performed to obtain the composite material.

2. The method for preparing the bulk high molecular weight modified polyimide composite material according to claim 1, characterized in that: The viscosity of the polyimide resin A at the injection temperature is not higher than 1 Pa·s.

3. The method for preparing the bulk high molecular weight modified polyimide composite material according to claim 1, characterized in that: The designed molecular weight of the polyimide resin B is between 1500 and 50000 g / mol, and at the injection temperature of the polyimide resin A, the viscosity of the polyimide resin B is not less than 3000 Pa·s.

4. The method for preparing the bulk high molecular weight modified polyimide composite material according to claim 3, characterized in that: At the injection temperature of the polyimide resin A, the viscosity of the polyimide resin B is not less than 5000 Pa·s.

5. The method for preparing the bulk high molecular weight modified polyimide composite material according to claim 1, characterized in that: The mass fraction of the polyimide resin B in the fiber preform is between 10% and 40%.

6. The method for preparing the bulk high molecular weight modified polyimide composite material according to claim 1, characterized in that: At a temperature point higher than the injection temperature of the polyimide resin A, the polyimide resin A and the polyimide resin B have a low viscosity eutectic point, and the viscosity of both at the low viscosity eutectic point is no higher than 500 Pa·s.

7. The method for preparing the bulk high molecular weight modified polyimide composite material according to claim 1, characterized in that: The polyimide resin A and the polyimide resin B are both thermosetting polyimide resins.

8. The method for preparing the bulk high molecular weight modified polyimide composite material according to claim 7, characterized in that: The molecular chain end of the thermosetting polyimide resin matrix contains one of acetylene, phenylacetylene and norbornene.

9. The method for preparing the bulk high molecular weight modified polyimide composite material according to claim 1, characterized in that: The fibers in the fiber preform are selected from one or more of carbon fibers, glass fibers, quartz fibers, polyimide fibers, and aramid fibers.

10. A bulk high molecular weight modified polyimide composite material, characterized in that: A polyimide composite material prepared by the method according to any one of claims 1 to 9.

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