A high-temperature resistant polyimide composite sizing agent and its preparation and usage methods

Abstract

The present invention relates to a high-temperature resistant polyimide composite sizing agent and its preparation and use methods. The high-temperature resistant polyimide composite sizing agent of the present invention comprises polyimide, water, magnetic nanoparticles, a surfactant, and an organic solvent. The present invention uses polyimide resin as the main component of the sizing agent, adds magnetic nanoparticles to the sizing agent, and under the action of an external gradient magnetic field generating device, performs composite sizing treatment on carbon fibers, and realizes controllable sizing content on the fiber surface by in-situ controlling the strength of the gradient magnetic field. The composite sizing agent prepared by the present invention has excellent temperature resistance, low organic solvent content, strong interfacial binding force with polyimide, and good interfacial properties of the composite material.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon fiber sizing agent preparation, and particularly relates to a high-temperature resistant polyimide composite water-soluble emulsion sizing agent and its preparation and use methods. Background Art

[0002] With the development of deep space exploration vehicles, high Mach number aircraft, etc., higher requirements are put forward for the lightweight of materials. Carbon fiber composites have the performance characteristics of high specific strength and specific modulus, and have obvious weight reduction effects, so they are widely used in the aerospace field. Resin matrix composites with higher temperature resistance grades represented by polyimide and bismaleimide can be used as main or secondary load-bearing structural components in high-temperature service environments, so they have been widely used in the structural components of high-temperature resistant and high-load-bearing structures of spacecraft.

[0003] Since the molding temperature of polyimide composites is relatively high, mostly above 300°C, there is currently a lack of suitable high-temperature resistant fiber sizing agents. The sizing agents on the surface of commercial carbon fibers are mostly of the epoxy resin type, which are mainly suitable for epoxy resin matrix composites. However, for high-temperature resistant resin matrices such as polyimide, on the one hand, the reaction activity between the traditional epoxy resin type sizing agent and the resin matrix is poor; on the other hand, the decomposition and aging temperature of ordinary epoxy resin sizing agents is about 200°C. Therefore, during the processing of composites, the decomposition and aging of the sizing agent will generate defects such as voids at the interface, thereby weakening the interface and causing a reduction in the performance of the composites.

[0004] Due to the low activity of polyimide resin, in order to achieve good interfacial properties between the sizing agent and the resin matrix, on the one hand, the main resin components of the sizing agent need to simultaneously meet the structural similarity and excellent heat resistance, and have good process usability; on the other hand, introducing nano-phases into the sizing agent is beneficial to increasing the surface roughness of the fiber, generating good physical meshing effects at the interface between the fiber and the resin, and further enhancing the interfacial bonding strength. Currently, traditional sizing agents cannot meet the above usage requirements, so it is necessary to develop a high-temperature resistant sizing agent suitable for polyimide composites. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the existing technology and provide a preparation and use method of a high-temperature resistant composite sizing agent suitable for polyimide composites.

[0006] The technical solution of the present invention:

[0007] A high-temperature resistant polyimide composite water-based emulsion sizing agent, comprising polyimide, water, magnetic nanoparticles, surfactants and organic solvents.

[0008] Further, in the sizing agent: the content of polyimide resin is 0.5 - 2 wt%; water is the main component with a content of 80 - 90 wt%; the content of magnetic nanoparticles is 0.1 - 1 wt%; the content of surfactant is 0.1 - 1 wt%; the balance is organic solvent.

[0009] In the present invention, polyimide resin is used as the main component of the sizing agent, magnetic nanoparticles are added to the sizing agent, and under the action of an external gradient magnetic field generating device, the carbon fiber is subjected to composite sizing treatment, and the sizing content on the fiber surface is controlled by in-situ controlling the strength of the gradient magnetic field. The prepared composite sizing agent has excellent temperature resistance, low organic solvent content, strong interfacial binding force with polyimide, and good interfacial properties of the composite material.

[0010] A preparation method of a high-temperature resistant polyimide composite water-based emulsion sizing agent is realized through the following steps:

[0011] Step 1: Prepare a polyimide emulsion:

[0012] Dissolve polyimide and surfactant in an organic solvent to form a solution with a mass fraction of 5 - 20%, and drop the solution into deionized water drop by drop while heating. The heating temperature is higher than the boiling point of the organic solvent and lower than the boiling point of water, and continuously stir on a shear emulsifier to form a uniform emulsion. Among them, the mass fraction of polyimide is 0.5 - 2 wt%, the mass fraction of surfactant is 0.1 - 1 wt%, and deionized water accounts for 80 - 90% of the total mass.

[0013] Step 2: Surface treat magnetic nanoparticles:

[0014] Prepare a solution with a concentration of 2 - 10 wt% of silane coupling agent, add magnetic nanoparticles, stir evenly, and dry for later use.

[0015] Step 3: Prepare a polyimide composite emulsion:

[0016] Add the solution containing magnetic nanoparticles obtained in Step 2 to the polyimide emulsion, and perform ultrasonic stirring to obtain a uniformly dispersed sizing agent emulsion, that is, a composite sizing agent. Among them, the mass fraction of polyimide is 0.5 - 2 wt%, and the mass fraction of magnetic nanoparticles is 0.1 - 1 wt%.

[0017] Further, the continuous stirring on the shear emulsifier in Step 1 is carried out on a shear emulsifier at 5000 - 8000 r / min for 15 - 30 min.

[0018] Further, the mass ratio of the coupling agent to the magnetic nanoparticles in Step 2 is 1:1.

[0019] Further, the time of ultrasonic stirring in Step 3 is 1 - 2 h.

[0020] A method for using a high-temperature resistant polyimide composite water-based emulsion sizing agent, which sizes carbon fibers with the composite sizing agent:

[0021] Add the composite sizing agent obtained in the above steps into the sizing tank, and use the sizing device to control the movement of magnetic nanoparticles by applying a gradient magnetic field to size the surface of carbon fibers. The impregnation time is 20 - 40 s, and after high-temperature drying, it is wound up for standby. The sizing amount on the surface of carbon fibers is 0.2 - 1 wt%.

[0022] Subsequently, carbon fiber / polyimide prepregs can be prepared as needed, and polyimide resin composite components can be prepared by compression molding curing or autoclave curing.

[0023] There are no special restrictions on the type of polyimide resin in Step 1. Select a polyimide resin that is soluble in a low-boiling solvent according to the design requirements, such as a polyimide resin capped with phenylacetylene group, allyl norbornene group, ethynyl group, etc., or one or more of them. Specifically, it can be one or more of PMR-15, PMR-II-50, KH-400, KH-500s, etc.

[0024] The organic solvent described in Step 1 is a low-boiling solvent, that is, an organic solvent with a boiling point lower than 100 °C, which is beneficial to removing the solvent by heating, stirring and other methods during the preparation of the sizing agent emulsion, and it is required to meet the dissolution of the used polyimide and form a homogeneous mixed solution with the resin. It can be a single solvent or a mixture of multiple solvents. For example, organic solvents such as N-methylpyrrolidone (NMP), methanol, ethanol, acetone, dioxane, tetrahydrofuran, etc. can be used.

[0025] Preferably, the surfactant in Step 1 is a non-ionic surfactant, selected from one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, polyoxyethylene alkylamine, polyoxyethylene alkylamide, etc. Specifically, it can be one or more of TritonX-100, Tween-60, OP-10, TritonX-305, etc.

[0026] Preferably, the magnetic nanoparticles in Step 2 are nanoparticles with strong magnetism at the nanoscale, including one or a mixture of one or more of ferrite particles such as Fe3O4, Fe2O3, Fe, Mn, Zn, Co, Ni and their alloy particles, iron nitride particles, etc., with a particle size of 50 - 200 nm.

[0027] Preferably, the silane coupling agent in step two is specifically a silane coupling agent of types such as amino silane, anhydride silane, epoxy silane, etc., with active groups such as amino groups and epoxy groups on the surface, which is conducive to forming a strong chemical bonding effect with the main components of the sizing agent.

[0028] In step two, magnetic nanoparticles are treated with a silane coupling agent. After hydrolysis, the silane coupling agent uniformly coats the magnetic nanoparticles to form a typical core-shell structure. At the same time, the polyimide molecular chain contains imide characteristic functional groups, which have a strong affinity for the amino groups in the coupling agent molecule, resulting in chemical bonding effects such as hydrogen bonding. Therefore, the coupling agent in the sizing agent can play a bridging role between the magnetic nanoparticles and the polyimide, effectively improving the dispersion uniformity of the magnetic nanoparticles in the sizing agent solution, and controlling the directional movement of the magnetic nanoparticles and macromolecules through magnetic field changes to control the sizing agent content on the fiber surface.

[0029] The type of carbon fiber in step four is selected according to the structural characteristics and designed load-bearing of the composite material product, such as one or several of T300 grade, T700 grade, T800 grade, T1000 grade, etc.

[0030] The gradient magnetic field generating device in step four is distributed in a room-temperature magnetic field working area with a cylindrical cavity around the fiber sizing tank, which can provide a maximum magnetic field intensity of 1T, and the magnetic field intensity gradient is continuously adjustable within the range of 10 - 100 mT / cm.

[0031] The present invention constructs an axial gradient magnetic field by applying a gradient magnetic field generating device around the sizing tank to control the movement of magnetic nanoparticles, thereby realizing in-situ adjustment of the sizing content on the fiber surface. The main principle is that after applying the gradient magnetic field, the magnetic field intensity decreases from the periphery to the axis along the radial direction. The magnetic particles in the sizing agent will be affected by the magnetization force applied by the magnetic field in the gradient magnetic field and tend to move in the direction of increasing magnetic field under this action, inducing the diffusion movement of the magnetic nanoparticles along the edge of the sizing tank, and changing the concentration of magnetic nanoparticles in the central area of the sizing tank. Moreover, the greater the magnetic field gradient, the greater the magnetic force, and the faster the movement rate of the magnetic particles. By controlling the size of the magnetic field gradient, the movement speed of the magnetic nanoparticles can be changed, thereby controlling the sizing content on the fiber surface.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention proposes a preparation method for a novel high-temperature resistant polyimide composite sizing agent. The main component of the prepared sizing agent is selected as a high-temperature resistant polyimide resin with a relatively high decomposition temperature, which is suitable for high-temperature resistant resin-based composites represented by polyimide. At the same time, magnetic nanoparticles are added as a nano-additive phase in the composite sizing agent, effectively improving the surface roughness of the fiber and enhancing the interfacial meshing strength between the fiber and the resin. The prepared composite material exhibits excellent interfacial properties.

[0034] During the use of the composite sizing agent of the present invention, the directional movement of magnetic nanoparticles in the sizing agent is controlled by applying a gradient magnetic field. The magnetic nanoparticles drive the movement of polyimide macromolecules, thereby achieving uniform and in-situ controllable sizing amount on the fiber surface, and the process method is simple. Brief Description of the Drawings

[0035] Figure 1 It is a flow chart of the preparation and use method of the high-temperature resistant polyimide composite water-soluble emulsion sizing agent of the present invention. Detailed Embodiments

[0036] To make the technical solution of the present invention more clearly understood, the present invention will be described in detail below in conjunction with specific embodiments and the accompanying drawings.

[0037] Example 1: The preparation and use method of the high-temperature resistant polyimide composite water-soluble emulsion sizing agent in this example are as Figure 1 shown, and include the following steps:

[0038] Step 1: Prepare a polyimide emulsion:

[0039] Dissolve PMR-15 polyimide resin and surfactant in an ethanol solvent to form a solution with a mass fraction of 15%. The solution is dropped into water drop by drop while heating. The heating temperature is 80°C, and it is continuously stirred on a shear emulsifier at 5000 - 8000 r / min for 15 - 30 min to form a uniform emulsion. Among them, the mass fraction of polyimide is 0.1 - 2 wt%, the mass fraction of surfactant is 1 wt%, and the mass fraction of deionized water is 90 wt%.

[0040] Step 2: Surface treatment of magnetic nanoparticles:

[0041] Prepare a solution with a concentration of 10 wt% of silane coupling agent, add magnetic nanoparticles, and the mass ratio of the coupling agent to the magnetic nanoparticles is 1:1. After stirring evenly, dry for standby.

[0042] Step 3: Prepare a polyimide composite emulsion:

[0043] Add the magnetic nanoparticles obtained in Step 2 to the polyimide emulsion, and perform ultrasonic stirring for 2 h to obtain a uniformly dispersed sizing agent emulsion. Among them, the mass fraction of polyimide is 1.5 wt%, and the mass fraction of magnetic nanoparticles is 0.5 wt%.

[0044] Step 4: Use the prepared sizing agent to size carbon fibers:

[0045] Add the composite sizing agent obtained in the above steps to the sizing tank. Using the sizing device, control the maximum magnetic field strength around to be 500 mT and the magnetic field strength gradient to be 20 mT / cm through the gradient magnetic field generator, and perform sizing treatment on the surface of T700 carbon fiber. The impregnation time is 20 s. After high-temperature drying, wind it up for standby to obtain a sizing amount of 0.6 wt% on the surface of the carbon fiber.

[0046] Use the sized carbon fiber to prepare T700 carbon fiber / YH-550 polyimide prepreg, and prepare composite specimens through a molding process to obtain a polyimide composite flat plate.

[0047] Implementation effect:

[0048] By testing the interlaminar shear strength of the polyimide composite prepared in this example, the interlaminar shear strength is 103.6 MPa. The interlaminar properties of the polyimide composite prepared using unsized T700 carbon fiber and YH-550 polyimide resin by the existing technology are: the interlaminar shear strength is 80.7 MPa.

[0049] Example 2:

[0050] It is carried out in basically the same manner as in Example 1, except that in step one, KH-400 polyimide resin is used, and the weight fraction of magnetic nanoparticles in the composite sizing agent is 1 wt%.

[0051] Implementation effect: By testing the interlaminar shear strength of the polyimide composite prepared in the present invention, the interlaminar shear strength is 105.7 MPa.

[0052] Example 3:

[0053] It is carried out in basically the same manner as in Example 1, except that during the sizing process, the maximum magnetic field strength gradient around is controlled to be 30 mT / cm.

[0054] Implementation effect: By testing the interlaminar shear strength of the polyimide composite prepared in the present invention, the interlaminar shear strength is 98.7 MPa.

[0055] Example 4:

[0056] It is carried out in basically the same manner as in Example 1, except that during the sizing process, the maximum magnetic field strength gradient around is controlled to be 50 mT / cm.

[0057] Implementation effect: By testing the interlaminar shear strength of the polyimide composite prepared in the present invention, the interlaminar shear strength is 93.5 MPa.

[0058] Example 5:

[0059] It is carried out in basically the same manner as in Example 1, except that the carbon fiber used is T800 carbon fiber.

[0060] Implementation effect: By testing the interlaminar shear strength of the polyimide composite material prepared by the present invention, the interlaminar shear strength is 120.5 MPa. The interlaminar properties of the polyimide composite material prepared using the un-sized T800 carbon fiber by the prior art: the interlaminar shear strength is 106.8 MPa.

[0061] The parts not detailed in the present invention are well-known technologies to those skilled in the art.

[0062] The specific embodiments of the present invention disclosed above are intended to help understand the content of the present invention and implement it accordingly. Those of ordinary skill in the art can understand that various substitutions, changes, and modifications are possible without departing from the spirit and scope of the present invention. The present invention should not be limited to the content disclosed in the embodiments of this specification, and the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A method for using a high-temperature resistant polyimide composite sizing agent, characterized in that, It includes the following steps: 1) Dissolve polyimide and surfactant in an organic solvent to form a solution with a mass fraction of 5-20%. Drop this solution into deionized water drop by drop while heating. The heating temperature is higher than the boiling point of the organic solvent and lower than the boiling point of water. At the same time, continuously stir on a shear emulsifier to form a uniform polyimide emulsion; 2) Prepare a solution with a concentration of 2-10 wt% of a silane coupling agent, add magnetic nanoparticles, and stir well; after hydrolysis of the silane coupling agent, it uniformly coats the magnetic nanoparticles to form a core-shell structure; the silane coupling agent plays a bridging role between the magnetic nanoparticles and polyimide, improving the dispersion uniformity of the magnetic nanoparticles in the sizing agent; 3) Add the solution containing magnetic nanoparticles obtained in step 2) to the polyimide emulsion obtained in step 1), and perform ultrasonic stirring to obtain a sizing agent emulsion with uniform dispersion; The magnetic nanoparticles are used to apply a gradient magnetic field generating device around the sizing tank to construct an axial gradient magnetic field during the sizing process, control the movement of the magnetic nanoparticles, so as to realize in-situ adjustment of the sizing content on the fiber surface; add the composite sizing agent to the sizing tank, use the sizing device, and use the additional gradient magnetic field to control the movement of the magnetic nanoparticles to perform sizing treatment on the surface of the carbon fiber. The impregnation time is 20-40 s, and it is wound up for standby after high-temperature drying; during the sizing process, control the maximum magnetic field strength gradient around to be 30 mT / cm. After applying the gradient magnetic field, the magnetic field strength decreases from the periphery to the axis along the radial direction. The magnetic nanoparticles in the sizing agent are under the action of the magnetization force applied by the magnetic field and tend to move in the direction of increasing magnetic field under this action, inducing the magnetic nanoparticles to diffuse and move along the edge of the sizing tank, changing the concentration of magnetic nanoparticles in the central area of the sizing tank. By controlling the size of the magnetic field gradient, the movement speed of the magnetic nanoparticles is changed, and the magnetic nanoparticles drive the movement of polyimide macromolecules, so as to realize uniform and in-situ controllable sizing amount on the fiber surface; the magnetic nanoparticles, as a nano-additive phase, improve the surface roughness of the fiber and the interfacial meshing strength between the fiber and the resin.

2. The method for using the high-temperature resistant polyimide composite sizing agent according to claim 1, characterized in that In the sizing agent, the content of polyimide resin is 0.5-2 wt%; the content of water is 80-90 wt%; the content of magnetic nanoparticles is 0.1-1 wt%; the content of surfactant is 0.1-1 wt%; the rest is an organic solvent.

3. The usage method of the high-temperature resistant polyimide composite sizing agent according to claim 1, characterized in that The sizing amount on the surface of the carbon fiber is 0.2-1 wt%.

4. The method for using the high-temperature resistant polyimide composite sizing agent according to claim 1, characterized in that, Use the sized carbon fiber to prepare a carbon fiber / polyimide prepreg, and then prepare a polyimide resin composite component by compression molding curing or autoclave curing.

5. A high-temperature resistant polyimide composite sizing agent using the usage method described in claim 1.

6. A method for preparing the high-temperature resistant polyimide composite sizing agent according to claim 5, characterized in that, It includes the following steps: 1) Dissolve polyimide and surfactant in an organic solvent to form a solution with a mass fraction of 5-20%. Drop this solution into deionized water drop by drop while heating. The heating temperature is higher than the boiling point of the organic solvent and lower than the boiling point of water. At the same time, continuously stir on a shear emulsifier to form a uniform polyimide emulsion; 2) Prepare a solution of silane coupling agent with a concentration of 2-10 wt%, add magnetic nanoparticles, and stir well. 3) Add the solution containing magnetic nanoparticles obtained in step 2) to the polyimide emulsion obtained in step 1), and perform ultrasonic stirring to obtain a uniformly dispersed sizing agent emulsion.

7. The method according to claim 6, wherein In step 1), the continuous stirring on the shear emulsifier is carried out on a shear emulsifier at 5000-8000 r / min for 15-30 min.

8. The method according to claim 6, wherein In step 2), the mass ratio of the coupling agent to the magnetic nanoparticles is 1:

1.

9. The method according to claim 6, characterized in that, In step 3), the time of ultrasonic stirring is 1-2 h.

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