Preparation method and application of high-temperature-resistant polyimide resin

Abstract

The invention provides a preparation method and application of high-temperature-resistant polyimide resin, and the preparation method comprises the following steps: weighing the following raw materials: polyimide resin, a modified silicon-based filler, a reactive diluent and an anti-aging agent according to a corresponding weight ratio, sequentially adding the weighed polyimide resin, reactive diluent and anti-aging agent into a mixing kettle, and uniformly mixing at room temperature and normal pressure to obtain the high-temperature-resistant polyimide resin. Adding the modified silicon-based filler into the mixed material, uniformly mixing in vacuum at 120-150 DEG C to obtain a high-temperature-resistant polyimide resin precursor, and heating and curing along with the high-temperature-resistant polyimide resin precursor to obtain the high-temperature-resistant polyimide resin. By adding the modified silicon-based filler, the high-temperature-resistant polyimide resin with the glass transition temperature higher than 376 DEG C, the initial decomposition temperature higher than 516 DEG C, the heat conductivity coefficient larger than 0.42 W / (m * DEG C) and the thermal expansion coefficient smaller than 32 PPM / DEG C is obtained, and the heat resistance of the high-temperature-resistant polyimide resin meets the manufacturing requirements of high-temperature parts of spacecraft engines.

Description

Technical Field

[0001] The invention relates to the technical field of polyimide resin preparation, in particular to a preparation method and application of a high-temperature-resistant polyimide resin. Background Art

[0002] High temperature resistant insulation materials are the key research and development core of high-performance engines, especially motors in some special application environments, which have higher requirements for high temperature insulation materials. Polyimide resin is one of the organic polymer materials with the best comprehensive performance. Due to its rigid aromatic heterocyclic structure, this material is one of the polymer materials with the best heat resistance. Polyimide composite materials have been successfully used in the cold end of high-performance aerospace engines due to their temperature resistance of more than 230°C, such as outer casings, intermediate casings, blades, appropriate nozzle adjustment plates, and projectiles, which have a significant effect on reducing structural weight and improving engine thrust-to-weight ratio.

[0003] However, since this type of composite material will decompose at 500°C or above, and the operating temperature of engine components is generally much higher than that of aircraft components, it cannot provide long-term stable and safe protection for the power unit. Its application range is limited to the cold end and peripheral components of the engine, and it cannot be used for the preparation of high-temperature components. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the deficiencies in the prior art, the present invention provides a preparation method and application of a high-temperature-resistant polyimide resin to solve the problems raised in the above background technology.

[0006] (II) Technical solution

[0007] To achieve the above object, the present invention is implemented by the following technical scheme: A method for preparing a high temperature resistant polyimide resin comprises the following steps:

[0008] S1. Preparation of silicon-based fillers:

[0009] S1-1, weigh the thermal conductive filler and silica sol in a weight ratio of 3-5:100 respectively;

[0010] S1-2, placing the raw materials weighed in step S1-1 in a mixing kettle, and ultrasonically mixing for 20 to 25 minutes to obtain a mixed suspension;

[0011] S1-3, freeze-drying the mixed suspension in step S1-2 to obtain a silicon-based filler;

[0012] Among them, the freeze-drying temperature is -20 to -30°C, the vacuum degree is 1.3 to 5 Pa, and the drying time is 30 to 50 minutes;

[0013] S2. Preparation of modified silicon-based filler:

[0014] S2-1, immerse the silicon-based filler in a 5% to 10% concentration coupling agent solution for 1 to 2 hours;

[0015] S2-2, taking out the impregnated material in step S2-1, drying it, and crushing it to obtain a modified silicon-based filler;

[0016] S3. Weigh the following raw materials according to the corresponding weight ratio:

[0017] Polyimide resin 70%~85%;

[0018] Modified silicon-based filler 4.5% to 13.5%;

[0019] Active diluent 10% to 15%;

[0020] Anti-aging agent 0.5%~1.5%;

[0021] S4, adding the polyimide resin, active diluent and antioxidant weighed in S3 into the mixing kettle in sequence, and mixing evenly at room temperature and pressure;

[0022] The mixing speed is 300-400 r / min, and the mixing time is 15-20 min;

[0023] S5, adding the modified silicon-based filler weighed in S3 to the mixed material in S4, and mixing evenly in vacuum at 120-150° C. to obtain a high-temperature-resistant polyimide resin precursor;

[0024] The mixing speed is 600-800 r / min, the vacuum degree in the equipment is 3-5 Pa, and the mixing time is 30-40 min;

[0025] S6, curing the high-heat-resistant polyimide resin precursor by increasing the temperature to obtain the high-heat-resistant polyimide resin.

[0026] As a further preference, the silica sol in S1-1 is a neutral or alkaline small-pore silica sol, and the thermal conductive filler in S1-1 is one or more of nano-scale flaky carbon powder, alumina, boron nitride, and silicon carbide.

[0027] As a further preference, the coupling agent in S2-1 is one of a silane coupling agent and a titanate coupling agent, wherein the silane coupling agent includes one or more of KH550, KH560, KH570, KH792, DL602, and DL171, and the molecular formula of the titanate coupling agent is (RO)mTi(OX-RY)n, wherein X: one or more of alkoxy, carboxyl, sulfoxy, phosphoryl, phosphite, and pyrophosphoryl; R: the long chain part in the titanate coupling agent molecule, with a carbon number of 12 to 20; Y: one or more of an unsaturated double bond group, an amino group, and a hydroxyl group; n: the number of functional groups contained in the titanate coupling agent molecule, and n is 1 to 3.

[0028] As further preferred, the polyimide resin in S3 is one or more of ethynyl-terminated polyimide oligomer, phenylethynyl-terminated polyimide oligomer, and hydroxyl-terminated polyimide oligomer;

[0029] The polyimide resin structural formula is: ;

[0030] Wherein, n=an integer between 4 and 6; , , Any of the structures; or .

[0031] As a further preference, the active diluent in S3 is a low melting point small molecule containing a nitrogen heterocyclic structure;

[0032] The reactive diluent structural formula is: ,in: or .

[0033] As further preferred, the antioxidant in S3 is one or more of N-phenyl-α-aniline, N-phenyl-β-naphthylamine, and N-phenyl-N'-cyclohexyl-p-phenylenediamine.

[0034] The present invention also provides an application of a high-heat-resistant polyimide resin. The high-heat-resistant polyimide resin prepared by the above method is applied to the manufacture of high-temperature components of a spacecraft engine.

[0035] Beneficial Effects

[0036] The present invention provides a preparation method and application of a high-temperature-resistant polyimide resin, which has the following beneficial effects:

[0037] The present invention uses silica sol as a distribution system, distributes the thermally conductive filler, and then freeze-dries it to evenly distribute the thermally conductive filler in the silica gel skeleton pores and its holes, thereby improving the composite thermal conductivity of the silicon-based filler and the uniformity of the filler's own distribution, thereby avoiding the presence of weak areas in the subsequently prepared polyimide resin due to the uneven structure of the filler itself, resulting in fracture;

[0038] Moreover, the silicon-based filler is modified by impregnating the coupling agent to improve the bonding property of the modified silicon-based filler and the resin, thereby improving the overall mechanical strength and stress resistance of the material. At the same time, the addition of the modified silicon-based filler can prevent the high-temperature resistant polyimide resin from undergoing drastic deformation in the range from creep temperature to decomposition temperature, thereby affecting the normal operation of the spacecraft engine.

[0039] Finally, the small molecules produced by the decomposition of the high-heat-resistant polyimide resin at high temperatures are adsorbed by the micropores in the modified silicon-based filler and flow in the material, filling the cracks produced when the resin is heated to avoid material breakage. At the same time, some of the small molecules produced are captured by the micropores and further cross-linked with the coupling agent under high-temperature conditions to avoid material disintegration, thereby improving the high-temperature resistance of the high-heat-resistant polyimide resin. DETAILED DESCRIPTION

[0040] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below by reference are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0041] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the shown positions or positional relationships, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0042] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0044] The disclosure below provides many different embodiments or examples to implement different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can appreciate the application of other processes and / or the use of other materials.

[0045] The embodiment of the present invention provides a method for preparing a high-temperature-resistant polyimide resin, comprising the following steps:

[0046] S1. Preparation of silicon-based fillers:

[0047] S1-1, weigh the thermal conductive filler and silica sol in a weight ratio of 3-5:100 respectively;

[0048] S1-2, placing the raw materials weighed in step S1-1 in a mixing kettle, and ultrasonically mixing for 20 to 25 minutes to obtain a mixed suspension;

[0049] S1-3, freeze-drying the mixed suspension in step S1-2 to obtain a silicon-based filler;

[0050] Among them, the freeze-drying temperature is -20 to -30°C, the vacuum degree is 1.3 to 5 Pa, and the drying time is 30 to 50 minutes;

[0051] S2. Preparation of modified silicon-based filler:

[0052] S2-1, immerse the silicon-based filler in a 5% to 10% concentration coupling agent solution for 1 to 2 hours;

[0053] S2-2, taking out the impregnated material in step S2-1, drying it, and crushing it to obtain a modified silicon-based filler;

[0054] S3. Weigh the following raw materials according to the corresponding weight ratio:

[0055] Polyimide resin 70%~85%;

[0056] Modified silicon-based filler 4.5% to 13.5%;

[0057] Active diluent 10% to 15%;

[0058] Anti-aging agent 0.5%~1.5%;

[0059] S4, adding the polyimide resin, active diluent and antioxidant weighed in S3 into the mixing kettle in sequence, and mixing evenly at room temperature and pressure;

[0060] The mixing speed is 300-400 r / min, and the mixing time is 15-20 min;

[0061] S5, adding the modified silicon-based filler weighed in S3 to the mixed material in S4, and mixing evenly in vacuum at 120-150° C. to obtain a high-temperature-resistant polyimide resin precursor;

[0062] The mixing speed is 600-800 r / min, the vacuum degree in the equipment is 3-5 Pa, and the mixing time is 30-40 min;

[0063] S6, curing the high-heat-resistant polyimide resin precursor by heating to obtain the high-heat-resistant polyimide resin;

[0064] The temperature rise curing is a staged temperature rise, and the specific temperature and constant temperature time are: 300℃ / 1h, 320℃ / 1h, 340℃ / 1h, 360℃ / 1h, 380℃ / 2h.

[0065] This embodiment also provides an application of a high-heat-resistant polyimide resin, in which the high-heat-resistant polyimide resin prepared by the above method is applied to the manufacture of high-temperature components of spacecraft engines.

[0066] In order to further understand the present invention, the preparation method of the high temperature resistant polyimide resin provided by the present invention is described below in conjunction with examples, and the protection scope of the present invention is not limited by the following examples.

[0067] Example 1

[0068] A high temperature resistant polyimide resin:

[0069] Raw materials (by weight):

[0070] Polyimide resin 70%~85%;

[0071] Modified silicon-based filler 4.5% to 13.5%;

[0072] Active diluent 10% to 15%;

[0073] Anti-aging agent 0.5%~1.5%;

[0074] The silica sol is a neutral or alkaline small-pore silica sol, and the thermal conductive filler is one or more of nano-scale flaky carbon powder, alumina, boron nitride, and silicon carbide;

[0075] The coupling agent is one of a silane coupling agent and a titanate coupling agent, wherein the silane coupling agent includes one or more of KH550, KH560, KH570, KH792, DL602, and DL171, and the molecular formula of the titanate coupling agent is (RO)mTi(OX-RY)n, wherein X is one or more of an alkoxy group, a carboxyl group, a sulfoxy group, a phosphoryl group, a phosphite group, and a pyrophosphoryl group; R is a long chain part in the titanate coupling agent molecule, and the number of carbon atoms is 12 to 20; Y is one or more of an unsaturated double bond group, an amino group, and a hydroxyl group; n is the number of functional groups contained in the titanate coupling agent molecule, and n is 1 to 3;

[0076] The polyimide resin is one or more of ethynyl-terminated polyimide oligomer, phenylethynyl-terminated polyimide oligomer, and hydroxyl-terminated polyimide oligomer;

[0077] The polyimide resin structural formula is: ;

[0078] Wherein, n=an integer between 4 and 6; , , Any of the structures; or ;

[0079] The active diluent is a low melting point small molecule containing a nitrogen heterocyclic structure;

[0080] The reactive diluent structural formula is: ,in: or ;

[0081] The antioxidant is one or more of N-phenyl-α-aniline, N-phenyl-β-naphthylamine and N-phenyl-N'-cyclohexyl-p-phenylenediamine.

[0082] The detailed components of each control experimental group are shown in the following table:

[0083] Continuing from the above table:

[0084] Comparative Example 1

[0085] Preparation method of polyimide resin:

[0086] S1. Preparation of silicon-based fillers:

[0087] S1-1, weigh the thermal conductive filler and silica sol in a weight ratio of 3-5:100 respectively;

[0088] S1-2, placing the raw materials weighed in step S1-1 in a mixing kettle, and ultrasonically mixing for 20 to 25 minutes to obtain a mixed suspension;

[0089] S1-3, freeze-drying the mixed suspension in step S1-2 to obtain a silicon-based filler;

[0090] Among them, the freeze-drying temperature is -20 to -30°C, the vacuum degree is 1.3 to 5 Pa, and the drying time is 30 to 50 minutes;

[0091] S2. Preparation of modified silicon-based filler:

[0092] S2-1, immerse the silicon-based filler in a 5% to 10% concentration coupling agent solution for 1 to 2 hours;

[0093] S2-2, taking out the impregnated material in step S2-1, drying it, and crushing it to obtain a modified silicon-based filler;

[0094] S3, weigh the following raw materials: polyimide resin, modified silicon-based filler, active diluent and antioxidant;

[0095] S4, adding the polyimide resin, active diluent and antioxidant weighed in S3 into the mixing kettle in sequence, and mixing evenly at room temperature and pressure;

[0096] The mixing speed is 300-400 r / min, and the mixing time is 15-20 min;

[0097] S5, adding the modified silicon-based filler weighed in S3 to the mixed material in S4, and mixing evenly in vacuum at 120-150° C. to obtain a high-temperature-resistant polyimide resin precursor;

[0098] The mixing speed is 600-800 r / min, the vacuum degree in the equipment is 3-5 Pa, and the mixing time is 30-40 min;

[0099] S6, curing the high-heat-resistant polyimide resin precursor by increasing the temperature to obtain the high-heat-resistant polyimide resin.

[0100] The detailed components of each control experimental group are shown in the following table:

[0101] Performance Test:

[0102] Tg and initial thermal decomposition temperature, the resin was injection molded into strips with a length of 20 mm, a width of 5 mm, and a thickness of 1.5 mm, and the single cantilever beam mode was selected to test the grouped samples using a dynamic thermomechanical analyzer.

[0103] For the thermal conductivity measurement, the resin was injection molded into a sample with a length of 40 mm, a width of 40 mm, and a thickness of 5 mm. The sample was measured by the steady-state hot plate method in accordance with the standard ASTM D5470.

[0104] For the determination of thermal expansion coefficient, the resin was injection molded into a specimen with a length of 10 mm, a width of 8 mm, and a thickness of 2 mm, and the sample was measured using a high-temperature horizontal expansion coefficient tester.

[0105] The performance test results of the experimental group and the control group are as follows:

[0106] It should be noted that the control group 3 increased the amount of modified silicon-based filler, and the control group 6 reduced the amount of active diluent, resulting in a significant increase in the viscosity of the resin premix, which could not meet the requirements of the infusion process. The control group 4 added too much antioxidant, which exceeded its solubility and caused frosting. Therefore, the above three groups were unable to undergo relevant performance testing.

[0107] In summary: the present invention uses silica sol as a dispersion system to disperse the thermally conductive filler, and then freeze-drying to evenly embed the thermally conductive filler on the surface of the holes and gaps of the silica skeleton to form a silicon-based filler with a thermally conductive filler inside. The modified silicon-based filler is prepared by impregnating a coupling agent, and the modified silicon-based filler is used as a skeleton to mix and cure with a polyimide resin, an active diluent and an antioxidant. The coupling agent on the surface of the modified silicon-based filler can greatly improve the adhesion between the filler and the resin. The active diluent can reduce the viscosity of the system during mixing and improve the mixing uniformity. It also participates in curing and cross-linking during the later curing, reduces the content of small molecule compounds in the curing system, and improves the high temperature resistance of the material. At the same time, the silica inlaid with thermally conductive fillers in the internal gaps supports the resin system, while improving the thermal conductivity of the resin, avoiding excessive deformation of the resin in the glass transition temperature and initial thermal decomposition range, affecting the normal use of the material, and the capillary phenomenon caused by the micropores of the modified silicon-based filler can adsorb small molecules. During curing, it adsorbs part of the active diluent and cross-links through the coupling agent to increase the cross-linking density of the material. When the material is in a high temperature environment, the small molecules and part of the active diluent generated by the thermal decomposition of the resin are adsorbed into the modified silicon-based filler. The gaps generated by the flow of small molecules and active diluents are filled to avoid rapid decomposition of the material at high temperatures.

[0108] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high temperature resistant polyimide resin, comprising the following steps: S1. Preparation of silicon-based fillers: S1-1, weigh the thermal conductive filler and silica sol in a weight ratio of 3-5:100 respectively; S1-2, placing the raw materials weighed in step S1-1 in a mixing kettle, and ultrasonically mixing for 20 to 25 minutes to obtain a mixed suspension; S1-3, freeze-drying the mixed suspension in step S1-2 to obtain a silicon-based filler; Among them, the freeze-drying temperature is -20 to -30°C, the vacuum degree is 1.3 to 5 Pa, and the drying time is 30 to 50 minutes; S2. Preparation of modified silicon-based filler: S2-1, immerse the silicon-based filler in a 5% to 10% concentration coupling agent solution for 1 to 2 hours; S2-2, taking out the impregnated material in step S2-1, drying it, and crushing it to obtain a modified silicon-based filler; S3. Weigh the following raw materials according to the corresponding weight ratio: Polyimide resin 70%~85%; Modified silicon-based filler 4.5% to 13.5%; Active diluent 10% to 15%; Anti-aging agent 0.5%~1.5%; S4, adding the polyimide resin, active diluent and antioxidant weighed in S3 into the mixing kettle in sequence, and mixing evenly at room temperature and pressure; The mixing speed is 300-400 r / min, and the mixing time is 15-20 min; S5, adding the modified silicon-based filler weighed in S3 to the mixed material in S4, and mixing evenly in vacuum at 120-150° C. to obtain a high-temperature-resistant polyimide resin precursor; The mixing speed is 600-800 r / min, the vacuum degree in the equipment is 3-5 Pa, and the mixing time is 30-40 min; S6, curing the high-heat-resistant polyimide resin precursor by increasing the temperature to obtain the high-heat-resistant polyimide resin.

2. The method for preparing a high temperature resistant polyimide resin according to claim 1, wherein: The silica sol in S1-1 is a neutral or alkaline small-pore silica sol, and the thermal conductive filler in S1-1 is one or more of nano-scale flaky carbon powder, aluminum oxide, boron nitride, and silicon carbide.

3. The method for preparing a high temperature resistant polyimide resin according to claim 1, wherein: The coupling agent in S2-1 is one of a silane coupling agent and a titanate coupling agent, wherein the silane coupling agent includes one or more of KH550, KH560, KH570, KH792, DL602, and DL171, and the molecular formula of the titanate coupling agent is (RO)mTi(OX-RY)n, wherein X is one or more of an alkoxy group, a carboxyl group, a sulfoxy group, a phosphoryl group, a phosphite group, and a pyrophosphoryl group; R is a long chain part in the titanate coupling agent molecule, with a carbon number of 12 to 20; Y is one or more of an unsaturated double bond group, an amino group, and a hydroxyl group; n: the number of functional groups contained in the titanate coupling agent molecule, n is 1 to 3.

4. The method for preparing a high temperature resistant polyimide resin according to claim 1, wherein: The polyimide resin in S3 is one or more of ethynyl-terminated polyimide oligomer, phenylethynyl-terminated polyimide oligomer, and hydroxyl-terminated polyimide oligomer; The polyimide resin structural formula is: ； Wherein, n=an integer between 4 and 6; , , Any of the structures; or .

5. The method for preparing a high temperature resistant polyimide resin according to claim 1, wherein: The active diluent in S3 is a low melting point small molecule containing a nitrogen heterocyclic structure; The reactive diluent structural formula is: ,in: or .

6. The method for preparing a high temperature resistant polyimide resin according to claim 1, characterized in that: The antioxidant in S3 is one or more of N-phenyl-α-aniline, N-phenyl-β-naphthylamine, and N-phenyl-N'-cyclohexyl-p-phenylenediamine.

7. An application of a high temperature resistant polyimide resin, characterized in that: The high-temperature-resistant polyimide resin prepared by the method described in any one of claims 1 to 6 is used in the manufacture of high-temperature components of spacecraft engines.

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