CN114605688A - Supercritical epoxy prepreg foamed sheet and preparation method thereof - Google Patents
Supercritical epoxy prepreg foamed sheet and preparation method thereof Download PDFInfo
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- CN114605688A CN114605688A CN202210359678.3A CN202210359678A CN114605688A CN 114605688 A CN114605688 A CN 114605688A CN 202210359678 A CN202210359678 A CN 202210359678A CN 114605688 A CN114605688 A CN 114605688A
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/24—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
- C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
- C08J9/122—Hydrogen, oxygen, CO2, nitrogen or noble gases
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2203/00—Foams characterized by the expanding agent
- C08J2203/06—CO2, N2 or noble gases
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2203/00—Foams characterized by the expanding agent
- C08J2203/08—Supercritical fluid
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2363/00—Characterised by the use of epoxy resins; Derivatives of epoxy resins
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2477/00—Characterised by the use of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Derivatives of such polymers
- C08J2477/10—Polyamides derived from aromatically bound amino and carboxyl groups of amino carboxylic acids or of polyamines and polycarboxylic acids
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K7/00—Use of ingredients characterised by shape
- C08K7/02—Fibres or whiskers
- C08K7/04—Fibres or whiskers inorganic
- C08K7/06—Elements
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K7/00—Use of ingredients characterised by shape
- C08K7/02—Fibres or whiskers
- C08K7/04—Fibres or whiskers inorganic
- C08K7/14—Glass
Abstract
The invention provides an epoxy prepreg foamed sheet, wherein the foaming multiplying power of the foamed sheet is 5-15 times; the diameter of the foam hole of the foamed sheet is 100-300 mu m; the foaming sheet material is obtained by foaming epoxy resin prepreg; the foamed sheet contains reinforcing fibers. The epoxy resin prepreg foamed sheet with the specific structure provided by the invention is a structural core material with excellent performance, has high-temperature resistance, can be equivalent to PMI, and has excellent mechanical properties. The compression performance at normal temperature and high temperature can be better than PMI, and the use requirement of the structural core material loaded at high temperature can be met. In addition, the preparation method provided by the invention only adopts the general epoxy resin prepreg on the market as the raw material, the raw material is easy to obtain, the process is simple, the reaction time is short, the control is easy, the production efficiency is high, the foaming process is green and environment-friendly, the application range is wide, and the industrial scale production and application are favorably realized.
Description
Technical Field
The invention belongs to the technical field of epoxy prepreg foamed plates, relates to an epoxy prepreg foamed plate and a preparation method thereof, and particularly relates to a supercritical epoxy prepreg foamed plate and a preparation method thereof.
Background
The composite material is a new material which is newly developed, and has great promotion effect on the development of scientific technology and various industrial fields. Among them, the sandwich structure composite material is more concerned by various industries. However, the development of the foam core material limits the development of the high-performance sandwich composite material to a certain extent, the foam core materials commonly used at present comprise polyurethanes, hard polyvinyl chloride and methacrylic acid imide, and the development of the high-strength high-performance composite material is limited to a certain extent by the temperature resistance and the strength of the core material.
Therefore, how to develop a new structural foam core material to meet higher requirements of application fields and widen the application depth and width of composite materials has become one of the urgent problems of many research and development manufacturers and front-line researchers.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide an epoxy prepreg foamed sheet and a preparation method thereof, and in particular, to a supercritical epoxy prepreg foamed sheet, the epoxy prepreg foamed sheet provided by the present invention has more excellent mechanical properties and temperature resistance, and is a composite material foam core material with excellent comprehensive properties; and the raw materials are easy to obtain, the process is simple, the control is easy, and the industrial scale production and application are favorably realized.
The invention provides an epoxy prepreg foamed sheet, wherein the foaming multiplying power of the foamed sheet is 5-15 times;
the diameter of the foam hole of the foamed sheet is 100-300 mu m;
the foaming sheet material is obtained by foaming epoxy resin prepreg;
the foamed sheet contains reinforcing fibers.
Preferably, the first and second liquid crystal materials are,
the invention provides an epoxy prepreg foamed sheet, wherein the foaming multiplying power of the foamed sheet is 5-15 times; the diameter of the foam hole of the foamed sheet is 100-300 mu m; the foaming sheet material is obtained by foaming epoxy resin prepreg; the foamed sheet contains reinforcing fibers. Compared with the prior art, the invention starts from another direction by aiming at the restriction of temperature resistance and strength of the core material of the existing polyurethane, hard polyvinyl chloride and methacrylic imide foam core materials which are generally used, and particularly selects the epoxy resin material as the research direction. Although the existing epoxy resin foaming is widely researched, for example, the epoxy resin foam is prepared by a method of using a chemical foaming agent in patent CN105924902B and by a method of combining physical and chemical foaming in patent CN113248873A, the problems of complex formula and difficult control of the foaming process exist; however, patent CN113861490A uses supercritical foaming method based on liquid epoxy resin, but also has the problems of complex formulation and difficult control of reaction process, and is not suitable for industrial production and application. Therefore, it is necessary to find a suitable method to solve the above problems in the technical field of epoxy resin foaming, and to obtain a high-strength and high-performance epoxy resin-based foamed sheet material, which can be further used as a core material of a composite material.
Based on the above, the invention researches and obtains the epoxy resin prepreg foamed sheet material with a specific structure, which is a structural core material with excellent performance, has high-temperature resistance, can be equivalent to PMI, and has excellent mechanical properties. The compression performance at normal temperature and high temperature can be better than PMI, and the use requirement of the structural core material loaded at high temperature can be met. In addition, the epoxy prepreg foaming sheet material provided by the invention only adopts the general epoxy resin prepreg on the market as a raw material, namely the epoxy prepreg foaming sheet material with excellent performance can be obtained.
According to the invention, by utilizing a supercritical method, supercritical gas permeates into the epoxy resin prepreg, and the epoxy resin prepreg is subjected to crosslinking curing at high temperature, so that the pressure is quickly relieved and the foaming is carried out after a certain crosslinking degree is reached to obtain a foaming embryonic plate, and then the foaming embryonic plate is cured at high temperature to obtain the epoxy resin prepreg foaming plate. The preparation method of the epoxy resin foamed sheet provided by the invention has the advantages that the raw materials are easily available, the supercritical fluid foaming mode is adopted, the specific foaming process is combined, the process is simple, the reaction time is short, the control is easy, the production efficiency is high, the prepared epoxy resin-based foamed sheet can be used for a long time at the temperature of-50-200 ℃, the foaming process is green and environment-friendly, the application range is wide, and the industrial scale production and application are favorably realized.
Experimental results show that the preparation method provided by the invention can be combined with the production process of pre-curing, supercritical permeation and heating foaming to realize foaming of the epoxy resin prepreg plate; compared with the industry of liquid epoxy resin foaming, the method is simple, convenient and quick. The prepared foaming plate is large in size, the length and the width of the foaming plate reach 100-1000 mm, and the thickness of the foaming plate reaches 10-100 mm; the diameter of the foam hole is smaller than 100-300 mu m; the foaming rate reaches 5-15 times, compared with the foaming of pure epoxy resin, the prepreg foaming board contains a large amount of glass fibers, the mechanical property is more excellent, the compression strength can be more than 3MPa, and the prepreg foaming board is a composite material foam core material with excellent comprehensive properties.
Detailed Description
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
All of the starting materials of the present invention, without particular limitation as to their source, may be purchased commercially or prepared according to conventional methods well known to those skilled in the art.
All raw materials of the invention have no particular limitation on the purity, and the invention preferably adopts the purity requirement of analytical purity or the purity requirement of the epoxy resin foaming material preparation field.
All the raw materials, the marks and the acronyms thereof belong to the conventional marks and acronyms in the field, each mark and acronym is clear and definite in the field of related application, and the raw materials can be purchased from the market or prepared by a conventional method by the technical staff in the field according to the marks, the acronyms and the corresponding application.
The invention provides an epoxy prepreg foamed sheet, wherein the foaming multiplying power of the foamed sheet is 5-15 times;
the diameter of the foam hole of the foamed sheet is 100-300 mu m;
the foaming sheet material is obtained by foaming epoxy resin prepreg;
the foamed sheet contains reinforcing fibers.
In the present invention, the foaming ratio of the foamed sheet is 5 to 15 times, preferably 7 to 13 times, and more preferably 9 to 11 times.
In the invention, the diameter of the foam hole of the foamed sheet is 100-300 μm, preferably 120-280 μm, more preferably 150-250 μm, and more preferably 180-230 μm.
In the invention, the thickness of the epoxy prepreg foamed sheet is preferably 10-100 mm, more preferably 30-80 mm, and more preferably 50-60 mm.
In the invention, the orientation size of the epoxy prepreg foamed sheet is preferably 100-1000 mm, more preferably 300-800 mm, and more preferably 500-600 mm. Specifically, the orientation dimension is the radial dimension or the transverse dimension.
In the present invention, the cells are preferably of a closed cell structure.
In the present invention, the epoxy prepreg foamed sheet preferably includes a foamed sheet for a composite core material. The invention provides an application of an epoxy prepreg foamed sheet as a composite material core material.
In the present invention, the epoxy resin prepreg preferably includes an epoxy resin prepreg sheet.
In the present invention, after a plurality of epoxy resin prepreg sheets are stacked, an epoxy prepreg foamed sheet is preferably obtained by foaming.
In the invention, the thickness of the epoxy resin prepreg sheet is preferably 0.06-0.2 mm, more preferably 0.09-0.17 mm, and more preferably 0.12-0.14 mm.
In the present invention, the number of the plurality.
In the present invention, the reinforcing fiber preferably includes one or more of a glass fiber, a carbon fiber, and an aramid fiber, and more preferably a glass fiber, a carbon fiber, or an aramid fiber.
In the present invention, the epoxy resin prepreg preferably includes a unidirectional fabric prepreg and/or a fabric prepreg, more preferably a unidirectional fabric prepreg or a fabric prepreg.
In the present invention, the matrix of the epoxy prepreg preferably comprises a thermosetting epoxy resin matrix.
In the present invention, the reinforcing fiber preferably includes a long fiber and/or a continuous fiber, more preferably a long fiber or a continuous fiber.
In the present invention, the epoxy resin prepreg preferably includes a medium-temperature curing epoxy resin prepreg.
In the present invention, the foaming is preferably performed by supercritical fluid foaming.
In the invention, the density of the epoxy prepreg foamed sheet is preferably 50-200 kg/m3More preferably 80 to 170kg/m3More preferably 110 to 140kg/m3。
In the present invention, the epoxy prepreg foamed sheet is preferably a supercritical epoxy prepreg foamed sheet.
The invention provides a preparation method of an epoxy prepreg foamed sheet material, which comprises the following steps:
1) placing a plurality of layers of epoxy resin prepreg sheets in a mold cavity at a first temperature, filling a supercritical fluid, and obtaining a polymer-supercritical fluid homogeneous phase system after balancing;
2) maintaining the pressure stability of the polymer-supercritical fluid homogeneous phase system obtained in the step, heating the temperature of the system to a second temperature, and then releasing pressure and foaming to obtain an epoxy prepreg foaming blank plate;
3) and (3) carrying out post curing on the epoxy prepreg foaming blank obtained in the step to obtain the epoxy prepreg foaming plate.
According to the invention, at a first temperature, a plurality of layers of epoxy resin prepreg sheets are placed in a mold cavity, and supercritical fluid is filled in the mold cavity to achieve balance, so that a polymer-supercritical fluid homogeneous phase system is obtained.
In the invention, the thickness of a single layer of the epoxy resin prepreg sheet is preferably 0.06-0.2 mm, more preferably 0.09-0.17 mm, and more preferably 0.11-0.14 mm.
In the present invention, the number of the plurality of layers is preferably 5 to 10 layers, more preferably 6 to 9 layers, and still more preferably 7 to 8 layers.
In the present invention, the resin content of the epoxy resin prepreg is preferably 30% to 50%, more preferably 34% to 46%, and still more preferably 38% to 42% by mass.
In the invention, the gram weight of the glass fiber unit area of the epoxy resin prepreg sheet is preferably 70-300 g/m2More preferably 120 to 250g/m2More preferably 170 to 200g/m2。
In the present invention, the first temperature is preferably lower than the second temperature.
In the invention, the first temperature is preferably 100-120 ℃, more preferably 104-116 ℃, and more preferably 108-112 ℃.
In the present invention, the supercritical fluid includes supercritical N2And/or supercritical CO2More preferably supercritical N2Or supercritical CO2。
In the present invention, the pressure of the supercritical fluid is preferably 7.2 to 20MPa, more preferably 10 to 17MPa, and still more preferably 13 to 14 MPa.
In the invention, the time for reaching the equilibrium is preferably 30-60 min, more preferably 35-55 min, and more preferably 40-50 min.
The invention further maintains the pressure stability of the polymer-supercritical fluid homogeneous system obtained in the step, and after the temperature of the system is raised to the second temperature, the pressure is released and the foaming is carried out, so that the epoxy prepreg foaming embryonic plate is obtained.
In the invention, the second temperature is preferably 130-160 ℃, more preferably 135-155 ℃, and more preferably 140-150 ℃.
In the invention, the time for raising the temperature is preferably 20-30 min, more preferably 22-28 min, and more preferably 24-26 min.
In the present invention, the temperature is preferably maintained for 5 to 30min, more preferably 10 to 25min, and still more preferably 15 to 20min after the temperature is raised to the second temperature.
In the present invention, the pressure after the pressure release is preferably normal pressure.
In the invention, the pressure relief rate is preferably 10-100 MPa/s, more preferably 30-80 MPa/s, and more preferably 50-60 MPa/s.
Finally, the epoxy prepreg foaming blank obtained in the above steps is subjected to post curing to obtain the epoxy prepreg foaming plate.
In the invention, the post-curing temperature is preferably 120-150 ℃, more preferably 125-145 ℃, and more preferably 130-140 ℃.
In the invention, the post-curing time is preferably 2-6 h, more preferably 2.5-5.5 h, more preferably 3-5 h, and more preferably 3.5-4.5 h.
According to the invention, mature epoxy resin glass fiber prepreg on the market is selected as a base material, a supercritical mode is utilized, pre-curing and supercritical gas permeation are carried out simultaneously, then, the temperature is raised and cured to obtain foaming strength, then, pressure is rapidly released and foaming is carried out to obtain a foam blank, and then, the foam blank is subjected to post-curing to obtain a foam.
The invention is a complete and refined integral preparation process, better ensures the structure and parameters of the epoxy prepreg foamed sheet material, and further improves the comprehensive performance of the epoxy prepreg foamed sheet material, and the preparation method of the epoxy prepreg foamed sheet material can specifically comprise the following steps:
a) placing the epoxy resin prepreg multilayer sheet in a mold cavity at a first temperature, filling a supercritical fluid, and obtaining a polymer-supercritical fluid homogeneous phase system after balancing;
b) maintaining the pressure stability of the polymer-supercritical fluid homogeneous system obtained in the step, heating the temperature of the system to a second temperature, releasing pressure and foaming to obtain an epoxy prepreg foaming blank plate, and performing post curing to obtain the epoxy prepreg foaming plate.
Specifically, the thickness of a single layer of the epoxy prepreg is 0.06-0.2 mm, and the number of layers is 5-10.
Specifically, the resin content of the epoxy prepreg is 30-50%.
Specifically, the glass fiber unit area gram weight of the epoxy prepreg is 70-300 g/m2。
Specifically, the second temperature is higher than the first temperature.
Specifically, the first temperature is 100-120 ℃.
Specifically, the second temperature is 130-160 ℃.
Specifically, the supercritical fluid includes supercritical N2And/or supercritical CO2。
Specifically, the pressure of the supercritical fluid is 7.2-20 MPa.
Specifically, the time for reaching the equilibrium is 30-60 min.
Specifically, the temperature rise time is 20-30 min; and keeping for 5-30 min after heating.
Specifically, the pressure after the pressure relief is normal pressure.
Specifically, the pressure relief rate is 10-100 MPa/s.
Specifically, the post-curing temperature is 120-150 ℃; the time is 2-6 h.
The invention provides a supercritical epoxy prepreg foamed sheet and a preparation method thereof. The epoxy resin prepreg foamed sheet with the specific structure provided by the invention is a structural core material with excellent performance, has high-temperature resistance, can be equivalent to PMI, and has excellent mechanical properties. The compression performance at normal temperature and high temperature can be better than PMI, and the use requirement of the structural core material loaded at high temperature can be met. In addition, the epoxy prepreg foaming sheet material provided by the invention only adopts the general epoxy resin prepreg on the market as a raw material, namely the epoxy prepreg foaming sheet material with excellent performance can be obtained.
According to the invention, by utilizing a supercritical method, supercritical gas permeates into the epoxy resin prepreg, and the epoxy resin prepreg is subjected to crosslinking curing at high temperature, so that the pressure is quickly relieved and the foaming is carried out after a certain crosslinking degree is reached to obtain a foaming embryonic plate, and then the foaming embryonic plate is cured at high temperature to obtain the epoxy resin prepreg foaming plate. The preparation method of the epoxy resin foamed sheet provided by the invention has the advantages that the raw materials are easily available, the supercritical fluid foaming mode is adopted, the specific foaming process is combined, the process is simple, the reaction time is short, the control is easy, the production efficiency is high, the prepared epoxy resin-based foamed sheet can be used for a long time at the temperature of-50-200 ℃, the foaming process is green and environment-friendly, the application range is wide, and the industrial scale production and application are favorably realized.
Experimental results show that the preparation method provided by the invention can be combined with the production process of pre-curing, supercritical permeation and heating foaming to realize foaming of the epoxy resin prepreg plate; compared with the industry of liquid epoxy resin foaming, the method is simple, convenient and quick. The prepared foaming plate is large in size, the length and the width of the foaming plate reach 100-1000 mm, and the thickness of the foaming plate reaches 10-100 mm; the diameter of the foam hole is smaller than 100-300 mu m; the foaming rate reaches 5-15 times, compared with the foaming of pure epoxy resin, the prepreg foaming board contains a large amount of glass fibers, the mechanical property is more excellent, the compression strength can be more than 3MPa, and the prepreg foaming board is a composite material foam core material with excellent comprehensive properties.
For further illustration of the present invention, the following will describe in detail an epoxy prepreg foamed sheet and a method for preparing the same according to the present invention with reference to the following examples, but it should be understood that these examples are carried out on the premise of the technical solution of the present invention, and the detailed embodiments and specific procedures are given, only for further illustration of the features and advantages of the present invention, and not for limitation of the claims of the present invention, and the scope of protection of the present invention is not limited to the following examples.
Example 1
First, a general-purpose epoxy resin prepreg was cut into sheets having an appropriate length and width, and 6 sheets were stacked together in a cavity.
And then keeping the temperature T1 of the die cavity at 100 ℃, replacing air in the die cavity, filling carbon dioxide to a supercritical state, controlling the pressure at 10MPa, maintaining the pressure and permeating for 30min, and entering the next step.
Then, the cavity temperature was raised to T2, T2 was selected at 150 ℃, and the pressure in the cavity was maintained at 12MPa by the booster pump for 30 min.
And finally, releasing the pressure through a pneumatic ball valve, and releasing the pressure in the die cavity from 12MPa to 0 (normal pressure). The pressure relief rate is controlled to be 20-50 MPa/s by adjusting the drift diameter of the pneumatic ball valve. The mold cavity is opened, and the prepared foaming blank is post-cured for 2 hours in an oven at the temperature of 120 ℃.
Example 2
First, a general-purpose epoxy resin prepreg was cut into sheets having an appropriate length and width, and 10 sheets were stacked together in a cavity.
And then keeping the temperature of the die cavity T1 at 120 ℃, replacing air in the die cavity, introducing carbon dioxide to a supercritical state, controlling the pressure at 12MPa, maintaining the pressure and permeating for 50min, and then entering the next step.
Then, the cavity temperature was raised to T2, T2 was selected at 160 ℃, and the pressure in the cavity was maintained at 15MPa by the pressure-increasing pump for 20 min.
And finally, releasing the pressure through a pneumatic ball valve, and releasing the pressure in the die cavity from 15MPa to 0 (normal pressure). The pressure relief rate is controlled to be 20-50 MPa/s by adjusting the drift diameter of the pneumatic ball valve. The mold cavity is opened, and the prepared foaming blank is post-cured for 5 hours in an oven at the temperature of 150 ℃.
Example 3
First, a general-purpose epoxy resin prepreg is cut into sheets having an appropriate length and width, and 8 sheets are stacked together in a cavity.
And then keeping the temperature of the die cavity T1 at 100 ℃, replacing air in the die cavity, filling carbon dioxide to a supercritical state, controlling the pressure at 12MPa, maintaining the pressure and permeating for 30min, and then entering the next step.
Then, the cavity temperature was raised to T2, T2 was selected at 160 ℃, and the pressure in the cavity was maintained at 15MPa by the pressure-increasing pump for 30 min.
And finally, releasing the pressure through a pneumatic ball valve, and releasing the pressure in the die cavity from 15MPa to 0 (normal pressure). The pressure relief rate is controlled to be 20-50 MPa/s by adjusting the drift diameter of the pneumatic ball valve. The mold cavity is opened, and the prepared foaming blank is post-cured for 5 hours in an oven at the temperature of 130 ℃. And finally obtaining the epoxy resin prepreg foamed sheet.
The performance of the epoxy resin prepreg foamed sheet prepared in the embodiment of the invention is detected. See table 1.
TABLE 1 comparison of experimental results for examples and commercial PMIs
| Performance of | Example 1 | Example 2 | Example 3 | Commercially available PMI |
| Density of | 100kg/m3 | 150kg/m3 | 90kg/m3 | 75kg/m3 |
| 5% thermal weight loss temperature | 330℃ | 355℃ | 345℃ | 350℃ |
| Compressive strength | 3.45Mpa | 4.26Mpa | 3.22Mpa | 2.3Mpa |
| Compressive strength at 180 DEG C | 1.12Mpa | 1.54Mpa | 1.38Mpa | 0.8Mpa |
As can be seen from Table 1, the epoxy resin prepreg foamed sheet provided by the invention has high-temperature resistance, can be equivalent to PMI, and has excellent mechanical properties. The compression performance at normal temperature and high temperature can be better than PMI, and the use requirement of the structural core material loaded at high temperature can be met.
The above detailed description of a supercritical epoxy prepreg foamed sheet and a method for making the same provided by the present invention is provided herein with specific examples to explain the principles and embodiments of the present invention, and the above description of the examples is only provided to facilitate the understanding of the method and its core ideas, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any combination of the methods. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The scope of the invention is defined by the claims and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
Claims (10)
1. An epoxy prepreg foamed sheet is characterized in that the foaming ratio of the foamed sheet is 5-15 times;
the diameter of the foam hole of the foamed sheet is 100-300 mu m;
the foaming sheet material is obtained by foaming epoxy resin prepreg;
the foamed sheet contains reinforcing fibers.
2. The epoxy prepreg foamed sheet according to claim 1, wherein the thickness of the epoxy prepreg foamed sheet is 10 to 100 mm;
the oriented size of the epoxy prepreg foamed sheet is 100-1000 mm;
the cells are of a closed cell structure;
the epoxy prepreg foamed sheet comprises a foamed sheet for a composite material core material.
3. The epoxy prepreg foamed sheet according to claim 1, wherein the epoxy resin prepreg comprises an epoxy resin prepreg sheet;
after a plurality of epoxy resin prepreg boards are stacked, foaming to obtain an epoxy prepreg foamed board;
the thickness of each epoxy resin prepreg sheet is 0.06-0.2 mm;
the number of the plurality of the metal sheets is 5-10.
4. The epoxy prepreg foamed sheet according to claim 1, wherein the reinforcing fibers comprise one or more of glass fibers, carbon fibers and aramid fibers;
the epoxy resin prepreg comprises a unidirectional fabric prepreg and/or a fabric prepreg;
the matrix of the epoxy resin prepreg comprises a thermosetting epoxy resin matrix;
the reinforcing fibers include long fibers and/or continuous fibers.
5. The epoxy prepreg foamed sheet according to claim 1, wherein the epoxy resin prepreg comprises a medium-temperature-cured epoxy resin prepreg;
the foaming mode is supercritical fluid foaming;
the density of the epoxy prepreg foamed sheet is 50-200 kg/m3；
The epoxy prepreg foamed sheet is a supercritical epoxy prepreg foamed sheet.
6. The preparation method of the epoxy prepreg foamed sheet is characterized by comprising the following steps:
1) placing a plurality of layers of epoxy resin prepreg sheets in a mold cavity at a first temperature, filling a supercritical fluid, and obtaining a polymer-supercritical fluid homogeneous phase system after balancing;
2) maintaining the pressure stability of the polymer-supercritical fluid homogeneous phase system obtained in the step, heating the temperature of the system to a second temperature, and then releasing pressure and foaming to obtain an epoxy prepreg foaming blank plate;
3) and (3) carrying out post curing on the epoxy prepreg foaming blank obtained in the step to obtain the epoxy prepreg foaming plate.
7. The preparation method according to claim 6, wherein the single-layer thickness of the epoxy resin prepreg sheet is 0.06-0.2 mm;
the number of the layers is 5-10;
the resin mass content of the epoxy resin prepreg is 30-50%;
the glass fiber unit area gram weight of the epoxy resin prepreg sheet is 70-300 g/m2。
8. The method of claim 6, wherein the first temperature is lower than the second temperature;
the first temperature is 100-120 ℃;
the second temperature is 130-160 ℃.
9. The method of claim 6, wherein the supercritical fluid comprises supercritical N2And/or supercritical CO2；
The pressure of the supercritical fluid is 7.2-20 MPa;
the time for reaching the equilibrium is 30-60 min;
the temperature rise time is 20-30 min;
and keeping the temperature for 5-30 min after the temperature is raised to the second temperature.
10. The method according to claim 6, wherein the pressure after the pressure release is normal pressure;
the pressure relief rate is 10-100 MPa/s;
the post-curing temperature is 120-150 ℃;
the post-curing time is 2-6 h.
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