CN113372604A - Method for preparing thermosetting epoxy resin microporous foam with assistance of ultrasound - Google Patents
Method for preparing thermosetting epoxy resin microporous foam with assistance of ultrasound Download PDFInfo
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- CN113372604A CN113372604A CN202110861532.4A CN202110861532A CN113372604A CN 113372604 A CN113372604 A CN 113372604A CN 202110861532 A CN202110861532 A CN 202110861532A CN 113372604 A CN113372604 A CN 113372604A
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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
- C08J2205/00—Foams characterised by their properties
- C08J2205/04—Foams characterised by their properties characterised by the foam pores
- C08J2205/044—Micropores, i.e. average diameter being between 0,1 micrometer and 0,1 millimeter
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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
- C08J2363/02—Polyglycidyl ethers of bis-phenols
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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
- C08J2463/00—Characterised by the use of epoxy resins; Derivatives of epoxy resins
- C08J2463/02—Polyglycidyl ethers of bis-phenols
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids
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Abstract
The invention provides a method for preparing thermosetting epoxy resin microporous foam by ultrasonic assistance, and relates to the technical field of supercritical carbon dioxide foaming processes. The method of the invention comprises the following steps: carrying out supercritical carbon dioxide saturated adsorption on the thermosetting epoxy resin sheet; and foaming the thermosetting epoxy resin with saturated adsorption under an ultrasonic condition to obtain the thermosetting epoxy resin microporous foam. According to the invention, through the energy released in the cavitation effect of the ultrasonic wave, the fluidity of the carbon dioxide fluid in the epoxy resin is promoted, and the uniform distribution of gas in a thermosetting resin system is promoted, so that the foaming performance of the epoxy resin is obviously improved, and a uniform and compact foam structure with small pores can be formed.
Description
Technical Field
The invention relates to the technical field of supercritical carbon dioxide foaming processes, in particular to a method for preparing thermosetting epoxy resin microporous foam by ultrasonic assistance.
Background
The supercritical carbon dioxide foaming molding is a physical foaming molding technology and a microcellular foaming molding technology, has the advantages of environmental protection, good solubility, low viscosity, large diffusion coefficient, no toxicity, realization of complex structure and the like, can effectively improve internal stress distribution, provides toughness of a foam material to a higher degree, and is used as a method for producing a solvent-free functional polymer microcellular structure in a multi-field range.
The epoxy resin has the advantages of high mechanical strength, low shrinkage after curing, stable size, excellent corrosion resistance, good heat resistance, high electrical insulation performance and the like, plays a vital role in the fields of aerospace, ship transportation, machine manufacturing and the like, and has good application prospect.
The traditional epoxy resin foam material is prepared by foaming supercritical carbon dioxide, and has the problems that the solubility of supercritical carbon dioxide fluid in thermosetting epoxy resin is low, gas is difficult to form stable fine bubbles with obvious pore walls in a polymer matrix by using small gas molecular clusters, a cross-linked network structure is formed after curing, the carbon dioxide fluid is difficult to mix and diffuse due to high viscosity, and the mechanical property of the foam material is greatly reduced due to large pores and unstable pores formed under high-temperature foaming after pressure maintaining in a reaction kettle.
Disclosure of Invention
The invention aims to provide an ultrasonic-assisted method for preparing thermosetting epoxy resin microporous foam, which can form uniform and fine microporous foam in thermosetting epoxy resin and is beneficial to improving the mechanical property of an epoxy resin foam material.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a method for preparing thermosetting epoxy resin microporous foam by ultrasonic assistance, which comprises the following steps:
carrying out supercritical carbon dioxide saturated adsorption on the thermosetting epoxy resin sheet;
and foaming the thermosetting epoxy resin with saturated adsorption under an ultrasonic condition to obtain the thermosetting epoxy resin microporous foam.
Preferably, the foaming temperature is 100-120 ℃; the foaming time is 6-30 s.
Preferably, the ultrasound is continuous ultrasound or pulsed ultrasound.
Preferably, the power of the ultrasound is 75W-450W.
Preferably, when pulsed ultrasound is employed, the duty cycle is 50%.
Preferably, the pulse width of the pulse ultrasound is 1-5 s.
Preferably, the temperature of the supercritical carbon dioxide saturated adsorption is 45-55 ℃, the pressure is 15-20 MPa, and the heat preservation and pressure maintaining time is 48-72 h.
Preferably, the preparation method of the thermosetting epoxy resin sheet comprises the following steps:
mixing bisphenol A epoxy resin, hyperbranched epoxy resin, 2-ethyl-4-methylimidazole and a modifier in dichloromethane, and drying in vacuum to obtain modified epoxy resin powder; pressing the modified epoxy resin powder to obtain a thermosetting epoxy resin sheet; the modifier is polyether amine or polyether amine-silane coupling agent M2070-KH 560;
or the modified epoxy resin is sequentially subjected to rotary evaporation and vacuum drying to obtain modified epoxy resin powder; and pressing the modified epoxy resin powder to obtain the thermosetting epoxy resin sheet.
Preferably, the preparation method of the polyether amine-silane coupling agent M2070-KH560 comprises the following steps: mixing polyether amine M2070 and a silane coupling agent KH560 in ethanol, reacting the obtained mixture at 60 ℃ for 12h, and drying to obtain the polyether amine-silane coupling agent M2070-KH 560; the mass ratio of the polyether amine M2070 to the silane coupling agent KH560 is 10 (1-3).
Preferably, the mass ratio of the bisphenol A epoxy resin, the hyperbranched epoxy resin, the 2-ethyl-4-methylimidazole and the modifier is 18:2:1: 0.98.
The invention provides a method for preparing thermosetting epoxy resin microporous foam by ultrasonic assistance, which comprises the following steps: carrying out supercritical carbon dioxide saturated adsorption on the thermosetting epoxy resin sheet; and foaming the thermosetting epoxy resin with saturated adsorption under an ultrasonic condition to obtain the thermosetting epoxy resin microporous foam.
According to the invention, through the energy released in the cavitation effect of the ultrasonic wave, the fluidity of the carbon dioxide fluid in the epoxy resin is promoted, and the uniform distribution of gas in a thermosetting resin system is promoted, so that the foaming performance of the epoxy resin is obviously improved, and a uniform and compact foam structure with small pores can be formed.
The invention improves the foaming performance of the epoxy resin through ultrasonic assistance, does not change the components of the epoxy resin due to the ultrasonic physical effect, and can only improve the foaming performance of the supercritical carbon dioxide fluid and ensure that the other performances are not changed in the foaming process of the supercritical carbon dioxide fluid.
In addition, the ultrasonic-assisted production effect is excellent, the condition is highlighted, and the high foaming performance is achieved without adding other modified fillers.
Drawings
FIG. 1 is an SEM photograph of a cross section of a microcellular foam obtained in comparative example 1, example 1-1, and example 1-2;
FIG. 2 is an SEM photograph of a cross section of the microcellular foam obtained in comparative example 2, example 2-1, and example 2-2;
FIG. 3 is an SEM photograph of a cross section of the microcellular foam materials obtained in comparative example 3, example 3-1 and example 3-2;
FIG. 4 is an SEM photograph of a cross section of the microcellular foam materials obtained in comparative example 4, example 4-1 and example 4-2.
Detailed Description
The invention provides a method for preparing thermosetting epoxy resin microporous foam by ultrasonic assistance, which comprises the following steps:
carrying out supercritical carbon dioxide saturated adsorption on the thermosetting epoxy resin sheet;
and foaming the thermosetting epoxy resin with saturated adsorption under an ultrasonic condition to obtain the thermosetting epoxy resin microporous foam.
In the present invention, the starting materials used are all commercially available products well known in the art, unless otherwise specified.
The source of the thermosetting epoxy resin is not particularly required in the present invention, and any thermosetting epoxy resin requiring foaming is well known in the art. In the present invention, the thermosetting epoxy resin sheet is preferably prepared, the thermosetting epoxy resin is preferably prepared by two methods, and the first preparation method preferably includes the steps of:
mixing bisphenol A epoxy resin, hyperbranched epoxy resin, 2-ethyl-4-methylimidazole and a modifier in dichloromethane, and drying in vacuum to obtain modified epoxy resin powder;
pressing the modified epoxy resin powder to obtain a thermosetting epoxy resin sheet;
the modifier is polyether amine or polyether amine-silane coupling agent M2070-KH560
Bisphenol A epoxy resin, hyperbranched epoxy resin, 2-ethyl-4-methylimidazole and a modifier are mixed in dichloromethane and dried in vacuum to obtain modified epoxy resin powder.
In the present invention, the bisphenol a type epoxy resin is preferably E12; the hyperbranched epoxy resin is preferably E102.
In the present invention, when the modifying agent is a polyetheramine-silane coupling agent M2070-KH560, the preparation method of the polyetheramine-silane coupling agent M2070-KH560 preferably comprises: mixing polyether amine M2070 and a silane coupling agent KH560 in ethanol, reacting the obtained mixture at 60 ℃ for 12h, and drying to obtain the polyether amine-silane coupling agent M2070-KH 560; the mass ratio of the polyether amine M2070 to the silane coupling agent KH560 is 10 (1-3), preferably 10: (1.5-2.5).
In the present invention, the mass ratio of the bisphenol a type epoxy resin, the hyperbranched epoxy resin, the 2-ethyl-4-methylimidazole and the modifier is preferably 18:2:1: 0.98.
The invention has no special requirements on the mixing process of the bisphenol A epoxy resin, the hyperbranched epoxy resin, the 2-ethyl-4-methylimidazole and the modifier in the dichloromethane, and can be obtained by uniformly mixing all the substances. The invention has no special requirements on the vacuum drying condition, and can completely remove the dichloromethane. After vacuum drying, the present invention preferably further comprises processing the obtained dried product into powder to obtain epoxy resin powder. The present invention does not require any particular treatment, and any treatment that is known in the art can be used to form a powder.
The invention takes bisphenol A epoxy resin and hyperbranched epoxy resin as basic materials, takes polyetheramine or polyetheramine-silane coupling agent KH560 as a modifier, and takes 2-ethyl-4-methylimidazole as a curing agent. The hyperbranched epoxy resin has the outstanding advantages of more epoxy groups, good compatibility with bisphenol A epoxy resin, obvious toughening effect and the like; the polyether amine and the polyether amine-KH 560 have the reaction capability with an epoxy resin matrix, and can react with active groups such as epoxy groups, hydroxyl groups, carboxyl groups and the like to improve the crosslinking structure of epoxy. Therefore, the hyperbranched epoxy resin and the modifier modified bisphenol A epoxy resin can act on the cross-linking structure and the matrix viscoelasticity of the cured product and can generate effects on supercritical CO2The foaming stage provides sufficient segmental motion and adequate matrix strength for gas diffusion and cell growth to allow cell expansion while being constrained so that cell coalescence does not occur.
After the modified epoxy resin powder is obtained, the modified epoxy resin powder is pressed to obtain the thermosetting epoxy resin sheet.
The conditions for said pressing are not particularly critical in the present invention, and the pressing conditions known in the art may be used. In the examples of the present invention, the pressing was performed in a press vulcanizer with a pressure of 20MPa and a time of 2 h.
In the present invention, the second preparation method of the thermosetting epoxy resin sheet preferably includes the steps of: carrying out rotary evaporation and vacuum drying on the modified epoxy resin in sequence to obtain modified epoxy resin powder; and pressing the modified epoxy resin powder to obtain the thermosetting epoxy resin sheet.
In the present invention, the modified epoxy resin is preferably a bisphenol a type epoxy resin; in the invention, the rotary evaporation is preferably carried out for 3h at 60 ℃, and the solvent is rapidly removed by using the rotary evaporation. The invention has no special requirements on the vacuum drying conditions, and the vacuum drying conditions well known in the field can be adopted; the invention utilizes vacuum drying to remove residual solvent.
After the modified epoxy resin powder is obtained, the modified epoxy resin powder is pressed to obtain the thermosetting epoxy resin sheet. The conditions for said pressing are not particularly critical in the present invention, and the pressing conditions known in the art may be used.
After the thermosetting epoxy resin sheet is obtained, the invention carries out supercritical carbon dioxide saturated adsorption on the thermosetting epoxy resin sheet.
The invention has no special requirement on the process of the supercritical carbon dioxide saturated adsorption, and adopts the adsorption process well known in the field, specifically, the thermosetting epoxy resin sheet is placed in a high-pressure reaction kettle and CO is injected into the high-pressure reaction kettle2Controlling the pressure in the kettle by gas, preserving heat and pressure for a period of time, and then quickly releasing pressure. In the invention, the temperature of the supercritical carbon dioxide saturated adsorption is preferably 45-55 ℃, more preferably 50 ℃, and the pressure is preferably 15-20 MPa, more preferably 20 MPa; the heat preservation and pressure maintaining time is preferably 48-72 h, and more preferably 55-65 h; the rate of pressure release is preferably <2 s.
After the adsorption saturation, the thermosetting epoxy resin with the adsorption saturation is foamed under the ultrasonic condition to obtain the thermosetting epoxy resin microporous foam.
In the present invention, the ultrasound is preferably continuous ultrasound or pulsed ultrasound, more preferably pulsed ultrasound; the power of the ultrasonic wave is preferably 75-450W, more preferably 150-375W, and further preferably 187.5-300W.
When pulse ultrasound is adopted, the duty ratio of the pulse ultrasound is preferably 50%, and the pulse width of the pulse ultrasound is preferably 1-5 s, more preferably 3-5 s, and most preferably 3 s. In the present invention, the pulse width of the pulsed ultrasound refers to the duration of the ultrasound within each pulse period. In the invention, when the duty ratio of the pulse ultrasound is 50% and the pulse width is 3s, the pulse ultrasound is switched on for 3s and switched off for 3 s.
In the invention, the foaming temperature is preferably 100-120 ℃, and more preferably 110 ℃; the foaming time is preferably 6 to 30s, more preferably 10 to 20s, and further preferably 15 s.
When pulsed ultrasound is used, the time for foaming according to the invention refers to the sum of the ultrasound on and off times.
In the foaming stage, the foam holes are nucleated and grow, and the fluidity of carbon dioxide fluid in the epoxy resin is promoted by introducing ultrasonic waves and utilizing the energy released in the cavitation effect of the ultrasonic waves, so that the gas is uniformly distributed in a thermosetting resin system, the foaming performance of the epoxy resin is obviously improved, and a uniform and compact foam structure with small pores can be formed.
The method for preparing thermosetting epoxy resin microcellular foam by ultrasound assistance provided by the present invention is described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.
Examples 1 to 1
Dissolving 18g of epoxy resin (E12), 2g of hyperbranched epoxy resin (E102), 1g of polyetheramine (M2070) and 0.98g of diethyl tetramethyl imidazole (2E4MZ) in dichloromethane, uniformly stirring at constant temperature until the mixture is completely mixed, and then placing the mixture in a vacuum oven for drying until the dichloromethane is completely removed; and then processing the dried product into powder, placing the powder into a flat vulcanizing instrument, pressing and molding the powder under the conditions of 20Mpa and 2 hours, placing the sheet into a high-pressure reaction kettle, performing supercritical carbon dioxide saturated adsorption at the adsorption temperature of 50 ℃, the pressure of 20Mpa, the adsorption time of 72 hours and the pressure relief rate of 2s, and then performing continuous ultrasonic foaming under the condition of 100 ℃ with the ultrasonic power of 450W and the foaming time of 15s to obtain the thermosetting epoxy resin microporous foam.
Examples 1 to 2
The only difference from example 1-1 was that continuous ultrasound was changed to pulsed ultrasound, the ultrasound pulse width was 3s, and the duty ratio was 50%.
Comparative example 1
The difference from example 1-1 is that no ultrasound was applied.
Example 2-1
Dissolving 18g of epoxy resin (E12), 2g of hyperbranched epoxy resin (E102), 1g of polyetheramine (M2070) and 0.98g of diethyl tetramethyl imidazole (2E4MZ) in dichloromethane, uniformly stirring at constant temperature until the mixture is completely mixed, and then placing the mixture in a vacuum oven for drying until the dichloromethane is completely removed; and then processing the dried product into powder, placing the powder into a flat vulcanizing instrument, pressing and molding the powder under the conditions of 20Mpa and 2 hours, placing the sheet into a high-pressure reaction kettle, performing supercritical carbon dioxide saturated adsorption at the adsorption temperature of 50 ℃, the pressure of 20Mpa, the adsorption time of 72 hours and the pressure relief rate of 2s, and then performing continuous ultrasonic foaming under the condition of 110 ℃ with the ultrasonic power of 450W and the foaming time of 15s to obtain the thermosetting epoxy resin microporous foam.
Examples 2 to 2
The only difference from example 2-1 was that continuous ultrasound was changed to pulsed ultrasound, the ultrasound pulse width was 3s, and the duty ratio was 50%.
Comparative example 2
The only difference from example 2-1 is that no ultrasound was applied.
Example 3-1
Reacting polyether amine (M2070) and a silane coupling agent KH560 in a mass ratio of 10:1 in ethanol at 60 ℃ for 12h, and removing the solvent to obtain a polyether amine-silane coupling agent (M2070-KH 560);
dissolving 18g of epoxy resin (E12), 2g of hyperbranched epoxy resin (E102), 1g of polyetheramine-silane coupling agent (M2070-KH560) and 0.98g of diethyl tetramethylimidazole (2E4MZ) in dichloromethane, uniformly stirring at constant temperature until the epoxy resin, the hyperbranched epoxy resin and the diethyl tetramethylimidazole are completely mixed, and then placing the mixture in a vacuum oven for drying until the dichloromethane is completely removed; and then processing the dried product into powder, putting the powder into a flat vulcanizing instrument for compression molding, putting the sheet into a high-pressure reaction kettle for supercritical carbon dioxide saturated adsorption, wherein the adsorption temperature is 50 ℃, the pressure is 20Mpa, the adsorption time is 72 hours, the pressure relief rate is less than 2s, and then carrying out continuous ultrasonic assisted foaming at the temperature of 110 ℃, the ultrasonic power is 450W, and the foaming time is 15s, so as to obtain the thermosetting epoxy resin microcellular foam.
Examples 3 to 2
The only difference from example 3-1 was that continuous ultrasound was changed to pulsed ultrasound, the ultrasound pulse width was 3s, and the duty ratio was 50%.
Comparative example 3
The only difference from example 3-1 is that no ultrasound was applied.
Example 4-1
Reacting polyether amine (M2070) and a silane coupling agent KH560 in a mass ratio of 10:1 in ethanol at 60 ℃ for 12h, and removing the solvent to obtain a polyether amine-silane coupling agent (M2070-KH 560);
dissolving 18g of epoxy resin (E12), 2g of hyperbranched epoxy resin (E102), 1g of polyetheramine-silane coupling agent (M2070-KH-560) and 0.98g of diethyl tetramethylimidazole (2E4MZ) in dichloromethane, uniformly stirring at constant temperature until the epoxy resin, the hyperbranched epoxy resin and the diethyl tetramethylimidazole are completely mixed, and then placing the mixture in a vacuum oven for drying until the dichloromethane is completely removed; and then processing the dried product into powder, putting the powder into a flat vulcanizing instrument for compression molding, putting the sheet into a high-pressure reaction kettle for supercritical carbon dioxide saturated adsorption, wherein the adsorption temperature is 50 ℃, the pressure is 20Mpa, the adsorption time is 72 hours, the pressure relief rate is less than 2s, and then carrying out continuous ultrasonic assisted foaming at the temperature of 120 ℃, the ultrasonic power is 450W, and the foaming time is 15s, so as to obtain the thermosetting epoxy resin microcellular foam.
Example 4 to 2
The only difference from example 4-1 was that continuous ultrasound was changed to pulsed ultrasound, the ultrasound pulse width was 3s, and the duty ratio was 50%.
Comparative example 4
The only difference from example 4-1 is that no ultrasound was applied.
Structural characterization:
the thermosetting epoxy resin microporous foams prepared in the examples and the comparative examples were quenched and fractured in liquid nitrogen, metal spraying was performed, and the cell structure of the foams was observed by using a scanning electron microscope (FEI corporation) to obtain SEM photographs of the sections of the foams, wherein the acceleration voltage was 10KV, and the results are shown in FIGS. 1 to 4.
As can be seen from fig. 1, comparative example 1, in which no ultrasonic assistance was applied, cells collapsed and no complete cells were present; in the embodiment 1-1, the cellular foam material obtained by applying continuous ultrasound has uniform cells, the diameter of the cells is 1-10 μm, and the whole cellular foam material has a small and dense cellular structure; in the embodiment 1-2, the microcellular foam material obtained by applying pulse ultrasound has uniform cells with the diameter of 1-5 μm, and the whole material has a compact and uniform cell structure.
As can be seen from fig. 2, comparative example 2 has no ultrasonic assistance applied, the cell diameter is large, and most of the cells collapse; in the embodiment 2-1, the cellular structure of the microporous foam material obtained by applying continuous ultrasound is more compact, and the pore diameter is smaller and reaches 1-10 mu m; example 2-2 is more dense and uniform in cell structure than example 2-1.
In FIG. 3, 3 represents comparative example 3, 3-1 represents example 3-1, 3-2 represents example 3-2. As can be seen from FIG. 3, in comparative example 3, no ultrasonic assistance is applied, and the pore diameter of the cell is large and reaches 10-20 μm; example 3-1 continuous ultrasound was applied, the cell structure was more compact, the pore size was smaller, reaching 1-5 μm; example 3-2 is more dense and uniform in cell structure than example 3-1.
In FIG. 4, 4 represents comparative example 4, 4-1 represents example 4-1, 4-2 represents example 4-2. As can be seen from FIG. 4, comparative example 4 has no ultrasonic assistance, the cell diameter is large and reaches 20 μm, the distribution is not uniform and the number of cells is small; example 4-1 continuous ultrasound was applied, the cell structure was more compact, the pore size was smaller, reaching 1-10 μm; example 4-2 is more dense and uniform in cell structure than example 4-1.
As can be seen from the above examples and comparative examples, the present invention provides an ultrasound-assisted method for preparing a thermosetting epoxy resin microcellular foam, by which uniform and fine microcellular foams can be formed in a thermosetting epoxy resin, particularly when pulsed ultrasound is used, with the best foaming effect.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. An ultrasonic-assisted method for preparing thermosetting epoxy resin microporous foam comprises the following steps:
carrying out supercritical carbon dioxide saturated adsorption on the thermosetting epoxy resin sheet;
and foaming the thermosetting epoxy resin with saturated adsorption under an ultrasonic condition to obtain the thermosetting epoxy resin microporous foam.
2. The method according to claim 1, wherein the foaming temperature is 100-120 ℃; the foaming time is 6-30 s.
3. The method according to claim 1 or 2, wherein the ultrasound is continuous ultrasound or pulsed ultrasound.
4. The method of claim 3, wherein the power of the ultrasound is 75W to 450W.
5. A method according to claim 3, wherein the duty cycle is 50% when pulsed ultrasound is employed.
6. The method according to claim 5, wherein the pulse width of the pulsed ultrasound is 1-5 s.
7. The method according to claim 1, wherein the temperature of the supercritical carbon dioxide saturated adsorption is 45-55 ℃, the pressure is 15-20 MPa, and the holding time is 48-72 h.
8. The method of claim 1, wherein the thermosetting epoxy resin sheet is prepared by a method comprising:
mixing bisphenol A epoxy resin, hyperbranched epoxy resin, 2-ethyl-4-methylimidazole and a modifier in dichloromethane, and drying in vacuum to obtain modified epoxy resin powder; pressing the modified epoxy resin powder to obtain a thermosetting epoxy resin sheet; the modifier is polyether amine or polyether amine-silane coupling agent M2070-KH 560;
or the modified epoxy resin is sequentially subjected to rotary evaporation and vacuum drying to obtain modified epoxy resin powder; and pressing the modified epoxy resin powder to obtain the thermosetting epoxy resin sheet.
9. The method of claim 8, wherein the polyetheramine-silane coupling agent M2070-KH560 is prepared by a method comprising: mixing polyether amine M2070 and a silane coupling agent KH560 in ethanol, reacting the obtained mixture at 60 ℃ for 12h, and drying to obtain the polyether amine-silane coupling agent M2070-KH 560; the mass ratio of the polyether amine M2070 to the silane coupling agent KH560 is 10 (1-3).
10. The method according to claim 8 or 9, wherein the mass ratio of the bisphenol a epoxy resin, the hyperbranched epoxy resin, the 2-ethyl-4-methylimidazole and the modifier is 18:2:1: 0.98.
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