CN113977841B - Polyimide composite foam containing honeycomb core lattice structure and preparation method thereof - Google Patents
Polyimide composite foam containing honeycomb core lattice structure and preparation method thereof Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/02—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles
- B29C44/08—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles using several expanding or moulding steps
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- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/1003—Preparatory processes
- C08G73/1035—Preparatory processes from tetracarboxylic acids or derivatives and diisocyanates
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- 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
- C08J9/02—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by the reacting monomers or modifying agents during the preparation or modification of macromolecules
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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- C08J2379/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen, or carbon only, not provided for in groups C08J2361/00 - C08J2377/00
- C08J2379/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
- C08J2379/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
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Abstract
The invention discloses a polyimide composite foam containing a honeycomb core lattice structure and a preparation method thereof, wherein the preparation method comprises the following steps: s1, calculating the consumption of foaming slurry; according to the overall apparent density of the polyimide composite foam containing the honeycomb core lattice structure and the specification of a mould for preparing the polyimide foam honeycomb core lattice, designing the polyimide foam honeycomb core lattice with higher density and the polyimide composite foam containing the honeycomb core lattice structure with lower overall apparent density, and calculating the total consumption of foaming slurry and the consumption of foaming slurry for preparing the polyimide foam honeycomb core lattice, wherein the difference between the total consumption of foaming slurry and the consumption of foaming slurry for filling the honeycomb core lattice; s2, preparing foaming slurry; s3, preparing polyimide foam honeycomb core lattices by combining the S1-S2; s4, preparing polyimide composite foam containing the honeycomb core lattice structure by combining S1-S3. The invention realizes the effects of improving the flame retardant property, the safety and the mechanical property, simplifying the production process and reducing the production cost.
Description
Technical Field
The invention relates to the technical field of flame retardant materials, in particular to polyimide composite foam containing a honeycomb core lattice structure and a preparation method thereof.
Background
The one-step polyimide foam is prepared by taking anhydride and isocyanate as raw materials. Because of the imide ring structure and the porous structure, the one-step polyimide foam has various outstanding physical and chemical properties such as sound absorption, heat insulation, radiation resistance, high and low temperature resistance, acid and alkali resistance and the like, and meanwhile, compared with other types of polyimide foam, the polyimide foam has the advantages of relatively simple production process, higher yield and lower price, and is widely applied to high-end fields such as aerospace, automobiles, high-speed trains, microelectronics and the like.
Further, in the fields of thermal insulation and sound absorption foam material flame retardance and use safety, the requirement is not strict, and the fully imidized one-step polyimide foam is too high in price to be widely applied to the common technical fields of building, storage and the like, and the one-step polyimide foam has unique technical advantages due to extremely strong formula adjustability and designability. The core of the method is that the formula of the one-step polyimide foam and the foaming molding preparation technology can realize the reduction of the proportion of the anhydride or the derivative thereof to the isocyanate and the reduction of the imidization degree of the material by reducing the consumption of the anhydride or the derivative thereof which takes up higher proportion of the cost of raw materials, and finally ensure the foaming molding of the foam body while ensuring the linear reduction of the production cost, the flame retardance and the use safety of the material, thereby obtaining the foam body with good heat insulation and sound absorption effects. Therefore, the preparation technology advantage of the one-step polyimide foam is beneficial to the preparation and production of the one-step polyimide foam with specific fire-proof grades in different fields, the price of the final product is effectively reduced compared with that of the one-step polyimide foam with complete imidization while the fire-proof grade of the material is not seriously excessive, and the capacity and the application field of the one-step polyimide foam material are greatly improved.
In order to further improve the market competitiveness of the series one-step polyimide foam material and other polymer-based heat insulation and sound absorption foam materials, a new path for further improving the flame retardance, the use safety and the mechanical property of the series one-step polyimide foam material under the condition of not changing the use amount and the imidization degree of anhydride or derivative thereof in the preparation formula of the series one-step polyimide foam material is explored, and the series one-step polyimide foam material has become a main direction of development of the series one-step polyimide foam material. Based on the discovery of these new paths, further adjustments of the one-step polyimide foam formulation, i.e., further reduction of the amount of anhydride or derivative thereof, to achieve further reductions in material costs, can be reversed.
Meanwhile, the one-step polyimide foam is used as a light functional material, and has the problems of easy tearing, easy breaking, low strength and the like under lower density, and the improvement of mechanical properties of the one-step polyimide foam is usually solved by adopting modes of mould pressing, density improvement and the like at present, but the consumption of raw materials and the manufacturing cost are increased sharply.
Currently, scientific researchers and related units at home and abroad mainly increase the flame retardance and the use safety of the one-step polyimide foam by adding various flame retardants.
In the "halogen-free composite flame-retardant polyimide foam material and the preparation method thereof" disclosed in the Chinese patent document CN107286343A, the inventor prepares the graphene phosphoric acid or phosphoric acid graphite flame-retardant material by adding a graphite material and a phosphorus flame retardant and performing high-speed ball milling in a sealed ball milling steel tank so as to improve the flame retardance of the one-step polyimide foam.
In the method for preparing the high-flame-retardance low-density polyimide foam by a one-step method disclosed in the Chinese patent document CN104497255A, the inventor obviously improves the flame retardance of the one-step polyimide foam by adding hydrotalcite and a liquid flame retardant at the same time.
In the "a low-cost flame-retardant polyimide heat-insulating foam and a preparation method and application thereof" disclosed in Chinese patent document CN110922627A, the inventor improves the flame retardance of the material by adding an autonomously synthesized reactive phosphorus flame retardant.
The mode of adding the flame retardant can effectively improve the flame retardance and the use safety of the one-step polyimide foam material, however, the cost of most of the high-efficiency flame retardants is far higher than that of low-price anhydride raw materials such as pyromellitic anhydride and the like at present, and the high-efficiency flame retardant becomes a new core cost factor. Meanwhile, most of high-efficiency flame retardants are liquid, are easy to volatilize in the high-temperature curing process of the one-step polyimide foam, so that the flame retardant effect of the high-efficiency flame retardants is reduced, the environment protection is not facilitated, and the internal agglomeration phenomenon is caused by the excessively high addition amount, so that the mechanical property of the material is seriously influenced.
In Effects of aramid honeycomb core on the flame retardance and mechanical property for isocyanate-based polyimide foams, the authors realize effective improvement of flame retardance and great improvement of mechanical properties of materials by using an aramid honeycomb core lattice to separate the space of the whole one-step polyimide foam. However, the cost of the aramid honeycomb core lattice per se is higher than that of the one-step polyimide foam with low imidization degree, so that the aramid honeycomb core lattice is not suitable for being applied to industrial production. Further, related researchers have conducted the study of space separation of the whole one-step polyimide foam by aluminum honeycomb, but the heat insulation performance of the one-step polyimide foam is greatly lost due to the heat bridge effect of the aluminum honeycomb, so that the heat conductivity coefficient of the one-step polyimide foam is increased from about 0.04W/(m.K) to about 0.5W/(m.K), the heat insulation or heat preservation function is reduced to about 10% of the original heat insulation or heat preservation function, and the heat insulation performance is extremely unfavorable for the application of materials.
Disclosure of Invention
In view of the above, the present invention aims to provide a polyimide composite foam containing a honeycomb core lattice structure and a preparation method thereof, which can solve the technical problems of insufficient flame retardant property and mechanical property, complex production process and high production cost of the flame retardant material in the prior art.
The adopted technical scheme is as follows:
the invention relates to a preparation method of polyimide composite foam containing a honeycomb core lattice structure, which comprises the following steps:
s1, calculating the consumption of foaming slurry: according to the overall apparent density of the polyimide composite foam containing the honeycomb core lattice structure and the specification of a mould for preparing the polyimide foam honeycomb core lattice, designing the polyimide foam honeycomb core lattice with higher density and the polyimide composite foam containing the honeycomb core lattice structure with lower overall apparent density, and calculating the total consumption of foaming slurry and the consumption of foaming slurry for preparing the polyimide foam honeycomb core lattice, wherein the difference between the total consumption of foaming slurry and the consumption of foaming slurry for filling the honeycomb core lattice;
s2, preparing foaming slurry: sequentially weighing polar solvent and aromatic dianhydride, adding into a reaction device connected with a reflux condenser, stirring, heating the system to 40-80 ℃, stopping heating, and then adding fatty alcohol and aromatic dianhydride for esterification reaction until the reaction is finished; cooling to room temperature, sequentially adding a foam stabilizer, a surfactant, a catalyst and deionized water, and uniformly stirring to obtain a foaming base material; pouring the foaming backing material into a foaming slurry mixing container from a reaction device, immediately adding polyisocyanate into the foaming backing material, and mechanically stirring uniformly to obtain foaming slurry;
s3, preparing polyimide foam honeycomb core lattices: according to the consumption of the foaming slurry of the polyimide foam honeycomb core lattice calculated in the step S1 and the total foaming slurry prepared in the step S2, obtaining the calculated amount of the foaming slurry used for preparing the polyimide foam honeycomb core lattice from the total foaming slurry prepared in the step S2, quickly and uniformly pouring the foaming slurry into the bottom of a steel mold with an upper opening and a release agent, taking a steel plate with a ring-shaped uniform distribution steel hexagonal prism structure and the release agent as an upper cover, quickly closing the mold, tightening screws, standing for 10-15min, then placing the mold into an oven with the temperature of 160-240 ℃, curing at high temperature for 2-3h, and cooling and demolding to obtain the polyimide foam honeycomb core lattice;
s4, preparing polyimide composite foam with a honeycomb core lattice structure: continuously using the steel mold with the upper opening and coated with the release agent used in the step S3, and calculating the consumption of the foaming slurry for filling the honeycomb core lattice according to the step S1; and (3) obtaining the calculated amount of foaming slurry for filling the core material cells from the total foaming slurry prepared in the step (S2), quickly and uniformly pouring the foaming slurry into the bottom of the core material cells, then quickly inserting the polyimide foam honeycomb core cells prepared in the step (S3) into a mold, taking a flat steel plate coated with a release agent as an upper cover, quickly closing the mold, screwing up screws, standing for 10-15min, then placing the mold into an oven at 160-240 ℃, curing at high temperature for 2-3h, and cooling and demolding to obtain the polyimide composite foam containing the honeycomb core cell structure.
Further, in the step S2, 20-200 parts of aromatic dianhydride, 5-80 parts of fatty alcohol, 100-195 parts of isocyanate, 50-70 parts of polar solvent, 10-15 parts of foam stabilizer, 10-15 parts of surfactant, 5-10 parts of catalyst and 10-15 parts of deionized water are calculated according to parts by weight.
Further, in step S2, the aromatic dianhydride includes a mixture of one or more of 3,3', 4' -benzophenone tetracarboxylic dianhydride, 4' -oxydiphthalic anhydride, 3', 4' -biphenyl tetracarboxylic dianhydride and pyromellitic dianhydride.
Further, in step S2, the fatty alcohol includes a mixture of one or more of methanol, ethanol, propanol, and isopropanol.
Further, in step S2, the catalyst comprises a mixture of one or more of triethanolamine, stannous octoate, dibutyltin dilaurate, dabco 33-LV.
Further, in the step S2, the isocyanate is polyphenyl polymethylene polyisocyanate with the NCO weight percentage of 30-40%.
The invention discloses polyimide composite foam containing a honeycomb core lattice structure, which is prepared by the preparation method in any scheme.
Further, the wall thickness of the polyimide foam honeycomb core lattice is 2-4mm.
Further, the diameter of the circumcircle of the polyimide foam honeycomb core lattice is 7.2-20.0mm.
Compared with the prior art, the invention has the beneficial effects that:
according to the polyimide composite foam containing the honeycomb core lattice structure, on the premise that the matrix resin component and the density of the whole polyimide foam material by a serialization one-step method are not changed and a flame retardant is not added, the macroscopic unevenness and separation of local density are realized only by introducing the high-density honeycomb core lattice structure with the same component, the dense and self-supporting fireproof heat-insulating carbon layer formed in the combustion process of the high-density honeycomb core lattice structure and the division of flame when the low-density foam filled in the honeycomb core lattice is combusted are relied on, the reduction of the flame aggregation degree is realized, the air convection is prevented, the integral combustion degree, the heat release behavior and the combustion smoke release behavior of the composite foam are finally reduced, the use safety is further improved, the technical foundation for further reducing the production cost of the polyimide foam with specific fireproof grade by one-step method is laid, and the market competitiveness of the polyimide foam material of one-step method is improved.
Meanwhile, the foam mechanical property is further improved by means of special mechanical properties of the honeycomb structure. The invention has simple operation and low preparation requirement, and the product is convenient for industrial production and wide application.
In summary, the invention solves the problems of insufficient flame retardant property and mechanical property, complex production process and high production cost of the flame retardant material in the prior art, and has the beneficial effects of improving the flame retardant property, safety, mechanical property, simplifying the production process and reducing the production cost under the condition of realizing macroscopic non-uniformity and separation of local density by introducing the high-density honeycomb structure with the same components.
Drawings
Fig. 1 is a schematic structural view of a steel mold upper cover with annularly distributed hexagonal prisms used in example 1 of the present invention.
Detailed Description
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown, and in which embodiments of the invention are shown, by way of illustration only, and not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Comparative example 1
Weighing 17.3 g of N, N-dimethylformamide solution, 11.76 g of 3,3', 4' -benzophenone tetracarboxylic dianhydride, adding into a reaction device connected with a reflux condenser, stirring and heating the system to 50 ℃, stopping heating, then adding 2.44 g of methanol and 3,3', 4' -benzophenone tetracarboxylic dianhydride for esterification reaction, obtaining transparent carboxylate solution after reaction, cooling the solution to room temperature, sequentially adding 3.75 g of polyethylene glycol 600, 3.75 g of AK8805 surfactant, 2.4 g of catalyst and 3.6 g of deionized water, stirring uniformly to obtain a foaming base material, pouring the foaming base material into a foaming slurry mixing container, immediately adding 45 g of polymethylene polyphenyl polyisocyanate with the NCO weight part of 31.5%, mechanically stirring at high speed to obtain a foaming slurry, rapidly and uniformly pouring the foaming slurry into a mold bottom with the size of 10cm of an inner cavity of 10 x 10cm, 5cm of a mold release agent, coating a rectangular steel plate with the mold release agent, rapidly and uniformly pouring the foaming slurry into a mold with the mold bottom of a rectangular cover at the temperature of 180 m, rapidly and tightly closing the mold with the temperature of 180 m, cooling to obtain a screw, cooling to obtain a low-density experiment, cooling the screw, and cooling to be 2m after the experiment, cooling to obtain a cooling experiment, and cooling in a 2m, cooling, and cooling to obtain a cooling medium 3 A one-step polyimide foam.
The limiting oxygen index value of the prepared one-step polyimide foam is 22.5%; a compressive strength of 364kPa; the heat conductivity coefficient is 0.051W/(m.K); peak combustion heat release 183kW/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The total release amount of the combustion flue gas is 6.79m 2 /m 2 。
Comparative example 2
This comparative example was different from comparative example 1 in that all the reagents or medicines were used in an amount of 20% by weight of the corresponding reagents or medicines in the comparative example, and the rest of the operations were the same as in example 1, giving a density of 75.+ -. 2kg/m 3 A one-step polyimide foam.
The limiting oxygen index value of the prepared one-step polyimide foam is 24.9%; the compression strength is 290kPa; the heat conductivity coefficient is 0.053W/(m.K); peak combustion heat release 214kW/m 2 The method comprises the steps of carrying out a first treatment on the surface of the Total release amount of combustion flue gas 7.17m 2 /m 2 。
Comparative example 3
This comparative example was different from comparative example 1 in that "3,3', 4' -benzophenone tetracarboxylic dianhydride was used in an amount of 34.27 g, methanol was added in an amount of 7.11 g, and a semitransparent viscous carboxylate solution was obtained after the reaction was completed", and the other operations were the same as in example 1 to obtain a density of 125.+ -. 2kg/m 3 A one-step polyimide foam.
The limiting oxygen index value of the prepared one-step polyimide foam is 22.2%; a compressive strength of 372kPa; the heat conductivity coefficient is 0.049W/(m.K); peak combustion heat release 159kW/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The total release amount of the combustion flue gas is 5.41m 2 /m 2 。
Comparative example 4
This comparative example was different from comparative example 1 in that "3,3', 4' -benzophenone tetracarboxylic dianhydride was used in an amount of 56.78 g and methanol was added in an amount of 11.38 g, and an almost white paste-like carboxylic acid ester solution was obtained after the reaction was completed", and the remaining operations were the same as in example 1 to obtain a density of about 147.+ -. 2kg/m 3 A one-step polyimide foam.
The limiting oxygen index value of the prepared one-step polyimide foam is 30.7%; a compressive strength of 387kPa; the heat conductivity coefficient is 0.047W/(m.K); peak combustion heat release 143kW/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The total release amount of the combustion flue gas is 4.08m 2 /m 2 。
Example 1
Referring to the schematic diagram shown in fig. 1, a die steel upper cover with annular hexagonal prisms is used for manufacturing the high-density polyimide foam honeycomb core lattice, and the size of the inner cavity of the die is 20cm by 5cm. The length of the hexagonal prism inlaid in the steel upper cover of the die is 5cm, and the side length is 9.6mm (namely, the diameter of the circumscribing circle is 19.2 mm). According to the design drawing, first hexagonal prisms are embedded in the right center of a steel plate, then other hexagonal prisms are uniformly and annularly embedded according to the drawing, and the interval (gap) between two adjacent hexagonal prisms is 2mm, namely the wall thickness of the finally prepared honeycomb core lattice is ensured to be 2mm. And (3) after all the complete hexagonal prisms are inlaid according to the drawing, finally inlaying incomplete hexagonal prisms according to the drawing and the actual situation of the boundary.
In this embodiment, after the upper cover with hexagonal prism is placed in the mold, the ratio of the volume of the hexagonal prism to the volume of the remaining space in the mold is 39.9:10.2, that is, the ratio of the volume of the low-density foam filled in the core cell to the volume of the high-density foam in the honeycomb core cell in the finally prepared composite foam.
This example produces a composite foam having a honeycomb cell structure of the same density as comparative example 1, i.e., a composite foam having an overall apparent density of 94.+ -.2 kg/m 3 . In view of the fact that the volume of the cavity of the mold used in this example, i.e., the overall apparent volume of the composite foam, was 4 times that of comparative example 1, the total amount of each reagent and chemical used to prepare the foamed slurry of honeycomb cells and filled cells, respectively, was 4 times that of the corresponding reagent and chemical in comparative example 1. The example sets the density of the prepared foam to 280kg/m 3 The high density polyimide foam honeycomb core cell of (2) is filled with a low density polyimide foam having a density of 46.4kg/m 3 . From the above data, it was further calculated that the mass of the foamed slurry used for preparing the high-density polyimide foam honeycomb core cell should be 2.43 times the mass of the foamed slurry in comparative example 1, and that the mass of the foamed slurry used for filling the honeycomb core cell should be 1.57 times the mass of the foamed slurry in comparative example 1.
According to the slurry preparation process in comparative example 1 and the calculated amounts of various materials, a foaming slurry for preparing a high-density polyimide foam honeycomb core lattice was prepared, the foaming slurry was rapidly and uniformly poured into the bottom of a steel mold with an upper opening and a cavity size of 20cm x 5cm coated with a release agent, then the upper cover with a ring-shaped uniform distribution steel hexagonal prism structure designed and manufactured in this example and coated with a release agent was rapidly closed, screws were screwed, left standing for 15 minutes, then the mold was put into an oven with a temperature of 180 ℃ for curing at a high temperature for 2 hours, and the actual foam density of 277kg/m was obtained after cooling and demolding 3 The polyimide foam honeycomb core lattice is placed for 1-2 days at room temperature for standby. After the honeycomb core cells were available, the foamed slurry for filling the honeycomb core cells was prepared according to the slurry preparation process in comparative example 1 and the above-calculated amounts of the various materials, rapidly and uniformly poured into the bottom of a steel mold having an internal cavity size of 20cm x 5cm, followed by rapid pouringInserting the prepared polyimide foam honeycomb core lattice into a mold, taking a flat plate steel plate coated with a release agent as an upper cover, rapidly closing the mold, screwing up a screw, standing for 15 minutes, then placing the mold into a baking oven at 180 ℃ for high-temperature curing for 2 hours, and cooling and demolding to obtain the actual overall apparent density of 92.5kg/m 3 A polyimide composite foam containing a honeycomb core cell structure.
The limiting oxygen index value of the prepared polyimide composite foam containing the honeycomb core lattice structure is 28.4%; the compressive strength is 421kPa; the heat conductivity coefficient is 0.040W/(m.K); peak combustion heat release 67kW/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The total release amount of the combustion flue gas is 1.02m 2 /m 2 。
Example 2
In this example, the mold designed and manufactured in example 1 was used, and after the upper cover with hexagonal prism was put into the mold, the ratio of the volume of hexagonal prism to the volume of the remaining space in the mold was still 39.9:10.2, i.e. the ratio of the volume of low-density foam filled in the core cell to the volume of high-density foam of the honeycomb core cell in the finally prepared composite foam.
This example produces a composite foam having a honeycomb cell structure of the same density as comparative example 3, i.e., a composite foam having an overall apparent density of 125.+ -. 1kg/m 3 . In view of the fact that the volume of the cavity of the mold used in this example, i.e., the overall apparent volume of the composite foam, is 4 times that of comparative example 3, the total amount of each reagent and chemical used to prepare the foamed slurry of honeycomb cells and filled cells, respectively, was 4 times that of the corresponding reagent and chemical in comparative example 3. The present example sets the density of the prepared foam to 400kg/m 3 The high density polyimide foam honeycomb core cell of (2) is filled with a low density polyimide foam having a density of 54.7kg/m 3 . From the above data, it was further calculated that the mass of the foamed slurry used for preparing the high-density polyimide foam honeycomb cells should be 2.61 times that of the foamed slurry in comparative example 3, and that the mass of the foamed slurry used for filling the honeycomb cells should be 1.39 times that of the foamed slurry in comparative example 3.
The slurry preparation process in comparative example 3 and the calculated amounts of the materials were used to preparePreparing foaming slurry of a high-density polyimide foam honeycomb core lattice, rapidly and uniformly pouring the foaming slurry into the bottom of a steel mold with an upper opening and a cavity with the size of 20cm x 5cm coated with a release agent, rapidly closing a mold, screwing a screw, standing for 15 minutes on an upper cover which is provided with an annular uniform distribution steel hexagonal prism structure and is coated with the release agent and is designed and manufactured in the embodiment, then placing the mold into a baking oven with the temperature of 180 ℃, curing at high temperature for 2 hours, cooling and demolding to obtain the actual foam with the density of 394kg/m 3 The polyimide foam honeycomb core lattice is placed for 1-2 days at room temperature for standby. After the honeycomb core is available, preparing foaming slurry for filling the honeycomb core according to the slurry preparation process in the comparative example 3 and the calculated various material dosages, rapidly and uniformly pouring the foaming slurry into the bottom of a steel mould with an inner cavity size of 20cm x 5cm, then rapidly inserting the prepared polyimide foam honeycomb core into the mould, taking a flat plate steel plate coated with a release agent as an upper cover, rapidly closing the mould, screwing up a screw, standing for 15 minutes, then placing the mould into a drying oven with a temperature of 180 ℃, curing for 2 hours at a high temperature, and cooling and demoulding to obtain the actual whole apparent density of 123.8kg/m 3 A polyimide composite foam containing a honeycomb core cell structure.
The limiting oxygen index value of the prepared polyimide composite foam containing the honeycomb core lattice structure is 29.1 percent; a compressive strength of 464kPa; the heat conductivity coefficient is 0.042W/(m.K); 55kW/m peak heat of combustion release 2 The method comprises the steps of carrying out a first treatment on the surface of the The total release amount of the combustion flue gas is 0.93m 2 /m 2 。
Example 3
In this example, the mold designed and manufactured in example 1 was used, and after the upper cover with hexagonal prism was put into the mold, the ratio of the volume of hexagonal prism to the volume of the remaining space in the mold was still 39.9:10.2, i.e. the ratio of the volume of low-density foam filled in the core cell to the volume of high-density foam of the honeycomb core cell in the finally prepared composite foam.
This example produces a composite foam having a honeycomb cell structure of the same density as comparative example 4, i.e., a composite foam having an overall apparent density of 157.+ -. 3kg/m 3 . In view of the volume of the cavity of the mold used in this example, i.e., the composite foam monolithThe apparent volume is 4 times that of comparative example 4, so the total amount of each reagent and chemical used to prepare the foamed slurry of honeycomb cells and filled cells, respectively, is 4 times that of comparative example 4. The example sets the density of the prepared foam to 450kg/m 3 The high density polyimide foam honeycomb core cell of (2) has a low density polyimide foam density of 82.1kg/m 3 . From the above data, it was further calculated that the mass of the foamed slurry used for preparing the high-density polyimide foam honeycomb cells should be 2.34 times the mass of the foamed slurry in comparative example 4, and that the mass of the foamed slurry used for filling the honeycomb cells should be 1.66 times the mass of the foamed slurry in comparative example 4.
According to the slurry preparation process in comparative example 4 and the calculated amounts of various materials, preparing a foaming slurry for preparing a high-density polyimide foam honeycomb core lattice, rapidly and uniformly pouring the foaming slurry into the bottom of a steel mold with an upper opening and a cavity size of 20cm x 5cm coated with a release agent, rapidly covering an upper cover which is designed and manufactured in the embodiment and has a ring-shaped uniform distribution steel hexagonal prism structure and is coated with the release agent, rapidly closing the mold, screwing down screws, standing for 15 minutes, then placing the mold in an oven with a temperature of 180 ℃, curing at a high temperature for 2 hours, cooling and demolding to obtain the actual foam with a density of 441kg/m 3 The polyimide foam honeycomb core lattice is placed for 1-2 days at room temperature for standby. After the honeycomb core is available, preparing foaming slurry for filling the honeycomb core according to the slurry preparation process in the comparative example 4 and the calculated various material dosages, rapidly and uniformly pouring the foaming slurry into the bottom of a steel mold with the inner cavity size of 20cm x 5cm, then rapidly inserting the prepared polyimide foam honeycomb core into the mold, taking a flat plate steel plate coated with a release agent as an upper cover, rapidly closing the mold, screwing up a screw, standing for 15 minutes, then placing the mold into a baking oven with the temperature of 180 ℃, curing for 2 hours at high temperature, and cooling and demolding to obtain the actual overall apparent density of 153.6kg/m 3 A polyimide composite foam containing a honeycomb core cell structure.
Limiting oxygen finger of prepared polyimide composite foam containing honeycomb core lattice structureThe value is 31.1%; compression strength is 452kPa; the thermal conductivity is 0.039W/(m.K); peak combustion heat release 51kW/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The total release amount of the combustion flue gas is 0.81m 2 /m 2 。
Example 4
The present example was identical to the external dimensions and the internal dimensions of the molds used in examples 1 to 3, i.e., the internal dimensions of the molds were 20cm by 5cm, and the length of the hexagonal prism inlaid in the steel upper cover of the mold with the annularly distributed hexagonal prisms for preparing the high-density polyimide foam honeycomb core lattice was 5cm as well, but the difference was that the side length of the hexagonal prism was changed to 4.8mm (i.e., the diameter of the circumscribed circle was 9.6 mm). The interval (gap) between two adjacent hexagonal prisms is 2mm, namely the wall thickness of the finally prepared honeycomb core lattice is ensured to be 2mm. Other processes for making the mold and the referenced drawings are identical to the molds used in examples 1-3.
In this embodiment, after the upper cover with hexagonal prism is placed in the mold, the ratio of the volume of the hexagonal prism to the volume of the remaining space in the mold is 10.0:5.4, that is, the ratio of the volume of the low-density foam filled in the core cell to the volume of the high-density foam in the honeycomb core cell in the finally prepared composite foam.
The foaming slurry formulation procedure and formulation used to prepare the foam of this example was the same as in example 3.
This example produces a composite foam having a honeycomb cell structure of the same density as comparative example 4, i.e., a composite foam having an overall apparent density of 157.+ -. 3kg/m 3 . In view of the fact that the volume of the cavity of the mold used in this example, i.e., the overall apparent volume of the composite foam, is 4 times that of comparative example 4, the total amount of each reagent and chemical used to prepare the foamed slurry of honeycomb cells and filled cells, respectively, was 4 times that of the corresponding reagent and chemical in comparative example 4. The present example sets the density of the prepared foam to 400kg/m 3 The high density polyimide foam honeycomb core cell of (2) is filled with a low density polyimide foam having a density of 25.8kg/m 3 . From the above data, it was further calculated that the mass of the foamed slurry for preparing the high-density polyimide foam honeycomb core cell should be 3.57 times the mass of the foamed slurry in comparative example 4, and that the mass of the foamed slurry for filling the honeycomb core cell should be foamed in comparative example 4And 0.43 times of the mass of the slurry.
A high density polyimide foam honeycomb core was prepared according to the procedure shown in example 3, and the actual foam density was 395kg/m after cooling and demolding 3 The polyimide foam honeycomb core lattice is placed for 1-2 days at room temperature for standby. After the honeycomb cells are available, a syntactic foam is prepared following the procedure of example 3. Finally, the actual overall apparent density is 154.2kg/m 3 A polyimide composite foam containing a honeycomb core cell structure.
The limiting oxygen index value of the prepared polyimide composite foam containing the honeycomb core lattice structure is 31.5%; compression strength 437kPa; the thermal conductivity is 0.038W/(m.K); 48kW/m peak heat of combustion release 2 The method comprises the steps of carrying out a first treatment on the surface of the The total release amount of the combustion flue gas is 0.77m 2 /m 2 。
The above list of detailed descriptions is only specific to practical embodiments of the present invention, and they are not intended to limit the scope of the present invention, and all equivalent embodiments or modifications that do not depart from the spirit of the present invention should be included in the scope of the present invention.
Claims (10)
1. The preparation method of the polyimide composite foam containing the honeycomb core lattice structure is characterized by comprising the following steps of:
s1, calculating the consumption of foaming slurry: according to the overall apparent density of the polyimide composite foam containing the honeycomb core lattice structure and the specification of a mould for preparing the polyimide foam honeycomb core lattice, designing the polyimide foam honeycomb core lattice with higher density and the polyimide composite foam containing the honeycomb core lattice structure with lower overall apparent density, and calculating the total consumption of foaming slurry and the consumption of foaming slurry for preparing the polyimide foam honeycomb core lattice, wherein the difference between the total consumption of foaming slurry and the consumption of foaming slurry for filling the honeycomb core lattice;
s2, preparing foaming slurry: sequentially weighing polar solvent and aromatic dianhydride, adding into a reaction device connected with a reflux condenser, stirring, heating the system to 40-80 ℃, stopping heating, and then adding fatty alcohol and aromatic dianhydride for esterification reaction until the reaction is finished; cooling to room temperature, sequentially adding a foam stabilizer, a surfactant, a catalyst and deionized water, and uniformly stirring to obtain a foaming base material; pouring the foaming backing material into a foaming slurry mixing container from a reaction device, immediately adding polyisocyanate into the foaming backing material, and mechanically stirring uniformly to obtain foaming slurry;
s3, preparing polyimide foam honeycomb core lattices: according to the consumption of the foaming slurry of the polyimide foam honeycomb core lattice calculated in the step S1 and the total foaming slurry prepared in the step S2, obtaining the calculated amount of the foaming slurry used for preparing the polyimide foam honeycomb core lattice from the total foaming slurry prepared in the step S2, quickly and uniformly pouring the foaming slurry into the bottom of a steel mold with an upper opening and a release agent, taking a steel plate with a ring-shaped uniform distribution steel hexagonal prism structure and the release agent as an upper cover, quickly closing the mold, tightening screws, standing for 10-15min, then placing the mold into an oven with the temperature of 160-240 ℃, curing at high temperature for 2-3h, and cooling and demolding to obtain the polyimide foam honeycomb core lattice;
s4, preparing polyimide composite foam with a honeycomb core lattice structure: continuously using the steel mold with the upper opening and coated with the release agent used in the step S3, and calculating the consumption of the foaming slurry for filling the honeycomb core lattice according to the step S1; and (3) obtaining the calculated amount of foaming slurry for filling the core material cells from the total foaming slurry prepared in the step (S2), quickly and uniformly pouring the foaming slurry into the bottom of the core material cells, then quickly inserting the polyimide foam honeycomb core cells prepared in the step (S3) into a mold, taking a flat steel plate coated with a release agent as an upper cover, quickly closing the mold, screwing up screws, standing for 10-15min, then placing the mold into an oven at 160-240 ℃, curing at high temperature for 2-3h, and cooling and demolding to obtain the polyimide composite foam containing the honeycomb core cell structure.
2. The method for preparing a polyimide composite foam containing a honeycomb core cell structure according to claim 1, wherein in the step S2, 20-200 parts by weight of aromatic dianhydride, 5-80 parts by weight of fatty alcohol, 100-195 parts by weight of isocyanate, 50-70 parts by weight of polar solvent, 10-15 parts by weight of foam stabilizer, 10-15 parts by weight of surfactant, 5-10 parts by weight of catalyst and 10-15 parts by weight of deionized water are calculated.
3. The method for preparing a polyimide composite foam having a honeycomb cell structure according to claim 1, wherein the aromatic dianhydride comprises a mixture of one or more of 3,3', 4' -benzophenone tetracarboxylic dianhydride, 4' -oxydiphthalic anhydride, 3', 4' -biphenyl tetracarboxylic dianhydride and pyromellitic dianhydride in step S2.
4. The method for preparing a polyimide composite foam having a honeycomb cell structure according to claim 1, wherein in step S2, the aliphatic alcohol comprises a mixture of one or more of methanol, ethanol, propanol, and isopropanol.
5. The method for preparing a polyimide composite foam having a honeycomb cell structure according to claim 1, wherein the catalyst comprises a mixture of one or more of triethanolamine, stannous octoate, dibutyltin dilaurate, and Dabco33-LV in step S2.
6. The method for preparing a polyimide composite foam having a honeycomb core structure according to claim 1, wherein in the step S2, the isocyanate is polyphenyl polymethylene polyisocyanate having an NCO weight percentage of 30% to 40%.
7. A polyimide composite foam having a honeycomb cell structure, which is produced by the production method according to any one of claims 1 to 6.
8. The polyimide composite foam having a honeycomb cell structure according to claim 7, wherein the polyimide foam honeycomb cell has a wall thickness of 2 to 4mm.
9. The polyimide composite foam having a honeycomb cell structure according to claim 7, wherein the polyimide foam honeycomb cells have a circumscribed circle diameter of 7.2 to 20.0mm.
10. The polyimide composite foam having a honeycomb cell structure according to claim 7, wherein the polyimide foam honeycomb cell has a density of 250 to 470kg/m3; the polyimide composite foam containing the honeycomb core lattice structure has the overall apparent density of 90-160kg/m < 3 >.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5188879A (en) * | 1991-07-15 | 1993-02-23 | Sorrento Engineering Corporation | Polyimide foam filled structures |
| CN104804190A (en) * | 2015-04-30 | 2015-07-29 | 哈尔滨工程大学 | Flame-retardant polyimide foam material comprising honeycomb core space structure, and preparation method |
| CN104910380A (en) * | 2015-06-02 | 2015-09-16 | 哈尔滨工程大学 | Preparation method of honeycomb-reinforced polyimide foam composite material |
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| KR102355596B1 (en) * | 2016-04-28 | 2022-01-25 | 로저스코포레이션 | Composites, methods of making the same, and articles comprising the composites |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5188879A (en) * | 1991-07-15 | 1993-02-23 | Sorrento Engineering Corporation | Polyimide foam filled structures |
| CN104804190A (en) * | 2015-04-30 | 2015-07-29 | 哈尔滨工程大学 | Flame-retardant polyimide foam material comprising honeycomb core space structure, and preparation method |
| CN104910380A (en) * | 2015-06-02 | 2015-09-16 | 哈尔滨工程大学 | Preparation method of honeycomb-reinforced polyimide foam composite material |
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